[ARM][Thumb] Command-line option to ensure AAPCS compliant Frame Records

[pratlucas]

Summary

Currently the a AAPCS compliant frame record is not always created for
functions when it should. Although a consistent frame record might not
be required in some cases, there are still scenarios where applications
may want to make use of the call hierarchy made available trough it.

In order to enable the use of AAPCS compliant frame records whilst keep
backwards compatibility, this patch introduces a new command-line option
(-mframe-chain=[none|aapcs|aapcs+leaf]) for Aarch32 and Thumb backends.
The option allows users to explicitly select when to use it, and is also
useful to ensure the extra overhead introduced by the frame records is
only introduced when necessary, in particular for Thumb targets.

[pratlucas]

Addressing linting messages.

[efriedma]

We probably want testcases for accessing various parts of the stack frame with FP stored in r11; for example, can we correctly access arguments passed on the stack if there's stack realignment?

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

263

It seems sort of fragile to assume the entry block doesn't contain any tPUSH instructions; we can use them in places other than the prologue. Can we use the FrameSetup flag?

[pratlucas]

Adding frame access test coverage, adding check for FrameSetup flag and adjusting calculation of FP value.

[pratlucas]

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

263

This approach is fragile indeed, I guess the fact that high reg spills are less usual has helpep it go unnoticed for so long.
I've added the checks for the FrameSetup flag to make sure it doesn't run over into unrelated instructions.

[efriedma]

llvm/test/CodeGen/Thumb/frame-access.ll

44

ldr r0, [r11, #8] is not a valid Thumb1 instruction.

[pratlucas]

Fix incorrect use of r11 on load/store instructions.

[efriedma]

llvm/lib/Target/ARM/ARMFrameLowering.cpp

2226

How do you end up with tSTRi with a frameindex operand? SelectionDAG won't generate that, I think.

2492

Should requiresAAPCSFrameRecord() be orthogonal to DisableFramePointerElim()? I mean, we have a complete set of flags controlling frame pointer elimination; the only part that's "new" here is that the frame pointer is stored in r11, instead of r7.

2699

Rearrange this to check ExtraCSSpill first, so we don't run canSpillOnFrameIndexAccess() if it isn't necessary?

llvm/test/CodeGen/Thumb/frame-access.ll

77

Can we use sp-relative accesses here? If we're not doing dynamic allocations, it should be a fixed offset.

103

I don't think "add r11, sp, #0" corresponds to a legal Thumb1 instruction? (Does -verify-machine-instrs catch this?)

[pratlucas]

llvm/lib/Target/ARM/ARMFrameLowering.cpp

2226

Indeed I didn't hit any case where tSTRi was emitted during my tests, but I included it here to be on the safe side given the contents of the comment on line 2050. I'm happy to remove it if it's indeed not necessary.

2492

For cases where a function's codegen requires the use of a frame pointer, we want an AAPCS compliant frame record to be generated even when the frame pointer elimination is enabled. For that reason we need the two options to be orthogonal on some level.
I've updated this check to be more strict and only consider requiresAAPCSFrameRecord() when the function has a frame pointer.

llvm/test/CodeGen/Thumb/frame-access.ll

77

The current criteria for the Arm and Thumb backends is that fixed frame indices are always accessed through FP whenever it is available (See ARMFrameLowering.cpp).
I guess that could be changed, but I feel it would fall outside the scope of this patch.

[pratlucas]

Addressing review comments.

[efriedma]

llvm/lib/Target/ARM/ARMFrameLowering.cpp

2245

Should this also check hasFP?

2492

For cases where a function's codegen requires the use of a frame pointer, we want an AAPCS compliant frame record to be generated even when the frame pointer elimination is enabled.

That's... hmm. Feels a little weird, but I guess it makes sense.

The hasFP(MF) here is redundant; this is already inside an if (HasFP) { block.

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

1189

Are we actually guaranteed to have any unused return registers at this point? The calling convention uses r0-r3 to return values.

llvm/test/CodeGen/Thumb/frame-access.ll

77

This patch does make it much more likely that fp-relative accesses are going to be out of range, but sure, I guess we can treat it as a separate issue.

[pratlucas]

Avoiding unecessary uses of FP and addressing review comments.

[pratlucas]

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

1189

Although unlikely in thumb1, we could run out of return registers here indeed (the calling convention only uses r2 and r3 to return 128-bit containerized vectors).
I've updated the code to make use of a scratch register if that ever happens. This required D126285, a minor NFC change so it could work correctly.

llvm/test/CodeGen/Thumb/frame-access.ll

77

That's a good point. I've pondered over this for a bit and realized that this is not the intended behaviour - we want FP and the frame record to be compliant with AAPCS in the scenarios where they're supposed to be generated and not to make its use more likely.
I've updated the code to match this. The expected behaviour when using the new option should be:

• r11 is set as the frame pointer - It should be reserved and not used as a general purpose register
• For a function, an AAPCS compliant frame record should be created and r11 should point to its location on the stack if:
  • Frame pointer elimination is disabled for the function (leaf vs non-leaf)
  • Codegen requires the use of FP

[efriedma]

llvm/lib/Target/ARM/ARMFrameLowering.cpp

1045

I guess this is related to this patch because it involves the interaction of PACBTI with -mframe_chain ? (Without this patch, PACBTI doesn't exist on any targets where the frame pointer is in r11.) I'm fine leaving it to a followup, though.

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

1118

*intermediate.

llvm/lib/Target/ARM/ThumbRegisterInfo.cpp

541–555

Do we need to do something different here if FrameReg is r11?

[pratlucas]

Addressing comments.

[pratlucas]

llvm/lib/Target/ARM/ARMFrameLowering.cpp

1045

Sounds good. I'm going to address that on a followup patch.

[efriedma]

llvm/test/CodeGen/Thumb/frame-access.ll

335

This sequence requires, in general, scavenging two registers. I'm not sure we can do that in general? I think we normally only have one emergency spill slot.

Maybe we can save a register using add instead of mov; something like ldr r0, .LCPI0_0; add r0, r11; ldr r0, [r0].

[pratlucas]

Avoid scavenging extra register when accessing const pool.

[pratlucas]

llvm/test/CodeGen/Thumb/frame-access.ll

335

That's true. Loads aren't affected as they reuse the destination register, but stores would indeed require the scaveging of two registers.
I've updaded the code to use the add approach instead.

[efriedma]

LGTM

The Thumb1 changes here are complicated, so I'm not sure we found all the issues, but you fixed all the issues I spotted.

[pratlucas]

Fixing assertion failure caused by incorrect use of tSTRr.

[RKSimon]

@pratlucas I'm seeing errors on my EXPENSIVE_CHECKS builds - please can you take a look?

Command Output (stdout):
--
$ ":" "RUN: at line 1"
$ "e:\llvm\ninja\bin\llc.exe" "-mtriple" "thumb-arm-none-eabi" "-filetype" "asm" "-o" "-" "E:\llvm\llvm-project\llvm\test\CodeGen\Thumb\frame-chain.ll" "-frame-pointer=all"
# command stderr:

# After Prologue/Epilogue Insertion & Frame Finalization
# Machine code for function required_fp: NoPHIs, TracksLiveness, NoVRegs, TiedOpsRewritten, TracksDebugUserValues
Frame Objects:
  fi#0: size=4, align=4, at location [SP-20]
  fi#1: size=4, align=4, at location [SP-24]
  fi#2: size=4, align=8, at location [SP-32]
  fi#3: size=8, align=8, at location [SP-40]
  fi#4: variable sized, align=1, at location [SP-40]
  fi#5: size=4, align=4, at location [SP-4]
  fi#6: size=4, align=4, at location [SP-8]
  fi#7: size=4, align=4, at location [SP-12]
  fi#8: size=4, align=4, at location [SP-16]
Function Live Ins: $r0, $r1

bb.0 (%ir-block.2):
  liveins: $r0, $r1, $r4, $lr
  frame-setup tPUSH 14, $noreg, killed $r4, killed $r6, killed $r7, killed $lr, implicit-def $sp, implicit $sp
  frame-setup CFI_INSTRUCTION def_cfa_offset 16
  frame-setup CFI_INSTRUCTION offset $lr, -4
  frame-setup CFI_INSTRUCTION offset $r7, -8
  frame-setup CFI_INSTRUCTION offset $r6, -12
  frame-setup CFI_INSTRUCTION offset $r4, -16
  $r7 = frame-setup tADDrSPi $sp, 2, 14, $noreg
  frame-setup CFI_INSTRUCTION def_cfa $r7, 8
  $sp = frame-setup tSUBspi $sp(tied-def 0), 6, 14, $noreg
  $r6 = tMOVr $sp, 14, $noreg
  $r2 = tMOVr killed $r6, 14, $noreg
  tSTRi killed renamable $r1, renamable $r2, 4, 14, $noreg :: (store (s32) into %ir.4)
  tSTRi renamable $r0, renamable $r2, 5, 14, $noreg :: (store (s32) into %ir.3)
  renamable $r1 = COPY $sp
  tSTRi killed renamable $r1, renamable $r2, 2, 14, $noreg :: (store (s32) into %ir.5, align 8)
  renamable $r1, dead $cpsr = tLSLri renamable $r0, 2, 14, $noreg
  renamable $r1, dead $cpsr = nuw tADDi3 killed renamable $r1, 7, 14, $noreg
  renamable $r3, dead $cpsr = tMOVi8 7, 14, $noreg
  renamable $r1, dead $cpsr = tBIC killed renamable $r1(tied-def 0), killed renamable $r3, 14, $noreg
  renamable $r3 = COPY $sp
  renamable $r1, dead $cpsr = tSUBrr killed renamable $r3, killed renamable $r1, 14, $noreg
  $sp = COPY killed renamable $r1
  renamable $r1, dead $cpsr = tMOVi8 0, 14, $noreg
  tSTRi killed renamable $r1, $r6, 1, 14, $noreg :: (store (s32) into %ir.6 + 4, basealign 8)
  tSTRi killed renamable $r0, killed renamable $r2, 0, 14, $noreg :: (store (s32) into %ir.6, align 8)
  $r4, $cpsr = frame-destroy tSUBi3 killed $r7, 7, 14, $noreg
  $r4, $cpsr = frame-destroy tSUBi8 $r4(tied-def 0), 1, 14, $noreg
  $sp = frame-destroy tMOVr $r4, 14, $noreg
  frame-destroy tPOP 14, $noreg, def $r4, def $r6, def $r7, implicit-def $sp, implicit $sp
  frame-destroy tPOP 14, $noreg, def $r0, implicit-def $sp, implicit $sp
  $lr = frame-destroy tMOVr killed $r0, 14, $noreg
  tBX_RET 14, $noreg

# End machine code for function required_fp.

*** Bad machine code: Non-flag-setting Thumb1 mov is v6-only ***
- function:    required_fp
- basic block: %bb.0  (0x166ad7b18e8)
- instruction: $r2 = tMOVr killed $r6, 14, $noreg
LLVM ERROR: Found 1 machine code errors.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace

[pratlucas]

The newly added frame-chain.ll test uncovered an issue with an invalid use of the tMOVr instruction, which is only available from V6 onwards. The failure was captured by a buildbot with expensive checks enabled.
The issue is unrelated to the codegen changes from this patch, and still happens when compiling the same IR code if the changes are reverted.
Given the above, I've updated the test to use thumbv6m while the issue is not resolved: rGcbcce82ef6b5.

[RKSimon]

Cheers! Are you looking at a fix or please can you raise a ticket?

[pratlucas]

@RKSimon I was writting my comment above just before I saw your message, lucky they went in in the correct order :)
I'm tracking down the source of the invalid tMOVr and I'll raise a ticket with the details.

[pratlucas]

Fixing use-after-poison issue detected by ASAN buildbot.

When popping LR on thumb it's value is popped into PC and used as a return.
The original return instruction gets erased, invalidating the MachineInstr
iterator. This change makes sure we don't try to access the iterator in these
conditions.

[efriedma]

LGTM with one minor comment (feel free to ignore if you disagree)

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

958

Maybe consider making this an MachineBasicBlock::iterator&, so MI isn't a dangling pointer? Not that the result is really any different from what you're doing here, but maybe less confusing.

[pratlucas]

Updating method to use MAchineBasickBlock::iterator&.

clang/include/clang/Driver/Options.td

def ForceAAPCSBitfieldLoad : Flag<["-"], "faapcs-bitfield-load">, Group<m_arm_Features_Group>,
   HelpText<"Follows the AAPCS standard that all volatile bit-field write generates at least one load. (ARM only).">,
   MarshallingInfoFlag<CodeGenOpts<"ForceAAPCSBitfieldLoad">>;
 defm aapcs_bitfield_width : BoolOption<"f", "aapcs-bitfield-width",
   CodeGenOpts<"AAPCSBitfieldWidth">, DefaultTrue,
   NegFlag<SetFalse, [], "Do not follow">, PosFlag<SetTrue, [], "Follow">,
   BothFlags<[NoXarchOption, CC1Option], " the AAPCS standard requirement stating that"
             " volatile bit-field width is dictated by the field container type. (ARM only).">>,
   Group<m_arm_Features_Group>;
-
+def mframe_chain : Joined<["-"], "mframe-chain=">,
+  Group<m_arm_Features_Group>, Values<"none,aapcs,aapcs+leaf">,
+  HelpText<"Select the frame chain model used to emit frame records (Arm only).">;
 def mgeneral_regs_only : Flag<["-"], "mgeneral-regs-only">, Group<m_Group>,
   HelpText<"Generate code which only uses the general purpose registers (AArch64/x86 only)">;
 def mfix_cmse_cve_2021_35465 : Flag<["-"], "mfix-cmse-cve-2021-35465">,
   Group<m_arm_Features_Group>,
   HelpText<"Work around VLLDM erratum CVE-2021-35465 (ARM only)">;
 def mno_fix_cmse_cve_2021_35465 : Flag<["-"], "mno-fix-cmse-cve-2021-35465">,
   Group<m_arm_Features_Group>,
   HelpText<"Don't work around VLLDM erratum CVE-2021-35465 (ARM only)">;

clang/lib/Driver/ToolChains/Arch/ARM.cpp

if (!((llvm::ARM::parseArchVersion(ArchSuffix) >= 8) &&
       // feature.
       if (!Args.hasArg(options::OPT_fno_integrated_as)) {
         Features.push_back("-sha2");
         Features.push_back("-aes");
       }
     }
   }
 
+  // Propagate frame-chain model selection
+  if (Arg *A = Args.getLastArg(options::OPT_mframe_chain)) {
+    StringRef FrameChainOption = A->getValue();
+    if (FrameChainOption.startswith("aapcs"))
+      Features.push_back("+aapcs-frame-chain");
+    if (FrameChainOption == "aapcs+leaf")
+      Features.push_back("+aapcs-frame-chain-leaf");
+  }
+
   // CMSE: Check for target 8M (for -mcmse to be applicable) is performed later.
   if (Args.getLastArg(options::OPT_mcmse))
     Features.push_back("+8msecext");
 
   if (Arg *A = Args.getLastArg(options::OPT_mfix_cmse_cve_2021_35465,
                                options::OPT_mno_fix_cmse_cve_2021_35465)) {
     if (!Args.getLastArg(options::OPT_mcmse))
       D.Diag(diag::err_opt_not_valid_without_opt)

llvm/lib/Target/ARM/ARM.td

def FeatureNoBTIAtReturnTwice : SubtargetFeature<"no-bti-at-return-twice",
                                                  "NoBTIAtReturnTwice", "true",
                                                  "Don't place a BTI instruction "
                                                  "after a return-twice">;
 
 def FeatureFixCortexA57AES1742098 : SubtargetFeature<"fix-cortex-a57-aes-1742098",
   "FixCortexA57AES1742098", "true",
   "Work around Cortex-A57 Erratum 1742098 / Cortex-A72 Erratum 1655431 (AES)">;
 
+def FeatureAAPCSFrameChain : SubtargetFeature<"aapcs-frame-chain",
+                                              "CreateAAPCSFrameChain", "true",
+                                              "Create an AAPCS compliant frame chain">;
+
+def FeatureAAPCSFrameChainLeaf : SubtargetFeature<"aapcs-frame-chain-leaf",
+                                                  "CreateAAPCSFrameChainLeaf", "true",
+                                                  "Create an AAPCS compliant frame chain "
+                                                  "for leaf functions",
+                                                  [FeatureAAPCSFrameChain]>;
+
 //===----------------------------------------------------------------------===//
 // ARM architecture class
 //
 
 // A-series ISA
 def FeatureAClass : SubtargetFeature<"aclass", "ARMProcClass", "AClass",
                                      "Is application profile ('A' series)">;
 

llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp

 //===-- ARMBaseRegisterInfo.cpp - ARM Register Information ----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the base ARM implementation of TargetRegisterInfo class.
ARMBaseRegisterInfo::ARMBaseRegisterInfo()
     : ARMGenRegisterInfo(ARM::LR, 0, 0, ARM::PC) {
   ARM_MC::initLLVMToCVRegMapping(this);
 }
 
 const MCPhysReg*
 ARMBaseRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
   const ARMSubtarget &STI = MF->getSubtarget<ARMSubtarget>();
   bool UseSplitPush = STI.splitFramePushPop(*MF);
-  const MCPhysReg *RegList =
-      STI.isTargetDarwin()
-          ? CSR_iOS_SaveList
-          : (UseSplitPush ? CSR_AAPCS_SplitPush_SaveList : CSR_AAPCS_SaveList);
-
   const Function &F = MF->getFunction();
+
   if (F.getCallingConv() == CallingConv::GHC) {
     // GHC set of callee saved regs is empty as all those regs are
     // used for passing STG regs around
     return CSR_NoRegs_SaveList;
   } else if (STI.splitFramePointerPush(*MF)) {
     return CSR_Win_SplitFP_SaveList;
   } else if (F.getCallingConv() == CallingConv::CFGuard_Check) {
     return CSR_Win_AAPCS_CFGuard_Check_SaveList;
   } else if (F.getCallingConv() == CallingConv::SwiftTail) {
     return STI.isTargetDarwin()
                ? CSR_iOS_SwiftTail_SaveList
-               : (UseSplitPush ? CSR_AAPCS_SplitPush_SwiftTail_SaveList
+               : (UseSplitPush ? CSR_ATPCS_SplitPush_SwiftTail_SaveList
                                : CSR_AAPCS_SwiftTail_SaveList);
   } else if (F.hasFnAttribute("interrupt")) {
     if (STI.isMClass()) {
       // M-class CPUs have hardware which saves the registers needed to allow a
       // function conforming to the AAPCS to function as a handler.
-      return UseSplitPush ? CSR_AAPCS_SplitPush_SaveList : CSR_AAPCS_SaveList;
+      return UseSplitPush ? CSR_ATPCS_SplitPush_SaveList : CSR_AAPCS_SaveList;
     } else if (F.getFnAttribute("interrupt").getValueAsString() == "FIQ") {
       // Fast interrupt mode gives the handler a private copy of R8-R14, so less
       // need to be saved to restore user-mode state.
       return CSR_FIQ_SaveList;
     } else {
       // Generally only R13-R14 (i.e. SP, LR) are automatically preserved by
       // exception handling.
       return CSR_GenericInt_SaveList;
     }
   }
 
   if (STI.getTargetLowering()->supportSwiftError() &&
       F.getAttributes().hasAttrSomewhere(Attribute::SwiftError)) {
     if (STI.isTargetDarwin())
       return CSR_iOS_SwiftError_SaveList;
 
-    return UseSplitPush ? CSR_AAPCS_SplitPush_SwiftError_SaveList :
+    return UseSplitPush ? CSR_ATPCS_SplitPush_SwiftError_SaveList :
       CSR_AAPCS_SwiftError_SaveList;
   }
 
   if (STI.isTargetDarwin() && F.getCallingConv() == CallingConv::CXX_FAST_TLS)
     return MF->getInfo<ARMFunctionInfo>()->isSplitCSR()
                ? CSR_iOS_CXX_TLS_PE_SaveList
                : CSR_iOS_CXX_TLS_SaveList;
-  return RegList;
+
+  if (STI.isTargetDarwin())
+    return CSR_iOS_SaveList;
+
+  if (UseSplitPush)
+    return STI.createAAPCSFrameChain() ? CSR_AAPCS_SplitPush_SaveList
+                                       : CSR_ATPCS_SplitPush_SaveList;
+
+  return CSR_AAPCS_SaveList;
 }
 
 const MCPhysReg *ARMBaseRegisterInfo::getCalleeSavedRegsViaCopy(
     const MachineFunction *MF) const {
   assert(MF && "Invalid MachineFunction pointer.");
   if (MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS &&
       MF->getInfo<ARMFunctionInfo>()->isSplitCSR())
     return CSR_iOS_CXX_TLS_ViaCopy_SaveList;

 
 bool ARMBaseRegisterInfo::isInlineAsmReadOnlyReg(const MachineFunction &MF,
                                                  unsigned PhysReg) const {
   const ARMSubtarget &STI = MF.getSubtarget<ARMSubtarget>();
   const ARMFrameLowering *TFI = getFrameLowering(MF);
 
   BitVector Reserved(getNumRegs());
   markSuperRegs(Reserved, ARM::PC);
-  if (TFI->hasFP(MF))
+  if (TFI->isFPReserved(MF))
     markSuperRegs(Reserved, STI.getFramePointerReg());
   if (hasBasePointer(MF))
     markSuperRegs(Reserved, BasePtr);
   assert(checkAllSuperRegsMarked(Reserved));
   return Reserved.test(PhysReg);
 }
 
 const TargetRegisterClass *

llvm/lib/Target/ARM/ARMCallingConv.td

 def CSR_AAPCS_SwiftError : CalleeSavedRegs<(sub CSR_AAPCS, R8)>;
 
 // R10 is used to pass swiftself, remove it from CSR.
 def CSR_AAPCS_SwiftTail : CalleeSavedRegs<(sub CSR_AAPCS, R10)>;
 
 // The order of callee-saved registers needs to match the order we actually push
 // them in FrameLowering, because this order is what's used by
 // PrologEpilogInserter to allocate frame index slots. So when R7 is the frame
-// pointer, we use this AAPCS alternative.
-def CSR_AAPCS_SplitPush : CalleeSavedRegs<(add LR, R7, R6, R5, R4,
+// pointer, we use this ATPCS alternative.
+def CSR_ATPCS_SplitPush : CalleeSavedRegs<(add LR, R7, R6, R5, R4,
                                                R11, R10, R9, R8,
                                                (sequence "D%u", 15, 8))>;
 
 def CSR_Win_SplitFP : CalleeSavedRegs<(add R10, R9, R8, R7, R6, R5, R4,
                                                (sequence "D%u", 15, 8),
                                                LR, R11)>;
 
 // R8 is used to pass swifterror, remove it from CSR.
-def CSR_AAPCS_SplitPush_SwiftError : CalleeSavedRegs<(sub CSR_AAPCS_SplitPush,
+def CSR_ATPCS_SplitPush_SwiftError : CalleeSavedRegs<(sub CSR_ATPCS_SplitPush,
                                                       R8)>;
 
 // R10 is used to pass swifterror, remove it from CSR.
-def CSR_AAPCS_SplitPush_SwiftTail : CalleeSavedRegs<(sub CSR_AAPCS_SplitPush,
+def CSR_ATPCS_SplitPush_SwiftTail : CalleeSavedRegs<(sub CSR_ATPCS_SplitPush,
                                                      R10)>;
 
+// When enforcing an AAPCS compliant frame chain, R11 is used as the frame
+// pointer even for Thumb targets, where split pushes are necessary.
+// This AAPCS alternative makes sure the frame index slots match the push
+// order in that case.
+def CSR_AAPCS_SplitPush : CalleeSavedRegs<(add LR, R11,
+                                               R7, R6, R5, R4,
+                                               R10, R9, R8,
+                                               (sequence "D%u", 15, 8))>;
+
 // Constructors and destructors return 'this' in the ARM C++ ABI; since 'this'
 // and the pointer return value are both passed in R0 in these cases, this can
 // be partially modelled by treating R0 as a callee-saved register
 // Only the resulting RegMask is used; the SaveList is ignored
 def CSR_AAPCS_ThisReturn : CalleeSavedRegs<(add LR, R11, R10, R9, R8, R7, R6,
                                             R5, R4, (sequence "D%u", 15, 8),
                                             R0)>;
 

llvm/lib/Target/ARM/ARMFrameLowering.h

restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
                               MutableArrayRef<CalleeSavedInfo> CSI,
                               const TargetRegisterInfo *TRI) const override;
 
   bool keepFramePointer(const MachineFunction &MF) const override;
 
   bool enableCalleeSaveSkip(const MachineFunction &MF) const override;
 
   bool hasFP(const MachineFunction &MF) const override;
+  bool isFPReserved(const MachineFunction &MF) const;
   bool hasReservedCallFrame(const MachineFunction &MF) const override;
   bool canSimplifyCallFramePseudos(const MachineFunction &MF) const override;
   StackOffset getFrameIndexReference(const MachineFunction &MF, int FI,
                                      Register &FrameReg) const override;
   int ResolveFrameIndexReference(const MachineFunction &MF, int FI,
                                  Register &FrameReg, int SPAdj) const;
 
   void getCalleeSaves(const MachineFunction &MF,

llvm/lib/Target/ARM/ARMFrameLowering.cpp

 // | arguments passed on the stack     |
 // |                                   |
 // |-----------------------------------| <- (sp at function entry)
 // |                                   |
 // | varargs from registers            |
 // |                                   |
 // |-----------------------------------|
 // |                                   |
-// | prev_fp, prev_lr                  |
+// | prev_lr                           |
+// | prev_fp                           |
 // | (a.k.a. "frame record")           |
 // |                                   |
 // |- - - - - - - - - - - - - - - - - -| <- fp (r7 or r11)
 // |                                   |
 // | callee-saved gpr registers        |
 // |                                   |
 // |-----------------------------------|
 // |                                   |
bool ARMFrameLowering::hasFP(const MachineFunction &MF) const {
   if (MF.getTarget().Options.DisableFramePointerElim(MF))
     return true;
 
   // Frame pointer required for use within this function.
   return (RegInfo->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
           MFI.isFrameAddressTaken());
 }
 
+/// isFPReserved - Return true if the frame pointer register should be
+/// considered a reserved register on the scope of the specified function.
+bool ARMFrameLowering::isFPReserved(const MachineFunction &MF) const {
+  return hasFP(MF) || MF.getSubtarget<ARMSubtarget>().createAAPCSFrameChain();
+}
+
 /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
 /// not required, we reserve argument space for call sites in the function
 /// immediately on entry to the current function.  This eliminates the need for
 /// add/sub sp brackets around call sites.  Returns true if the call frame is
 /// included as part of the stack frame.
 bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   unsigned CFSize = MFI.getMaxCallFrameSize();
void ARMFrameLowering::emitPrologue(MachineFunction &MF,
   }
 
   // Set FP to point to the stack slot that contains the previous FP.
   // For iOS, FP is R7, which has now been stored in spill area 1.
   // Otherwise, if this is not iOS, all the callee-saved registers go
   // into spill area 1, including the FP in R11.  In either case, it
   // is in area one and the adjustment needs to take place just after
   // that push.
+  // FIXME: The above is not necessary true when PACBTI is enabled.
+  // AAPCS requires use of R11, and PACBTI gets in the way of regular pushes,
+  // so FP ends up on area two.
   MachineBasicBlock::iterator AfterPush;
   if (HasFP) {
     AfterPush = std::next(GPRCS1Push);
     unsigned PushSize = sizeOfSPAdjustment(*GPRCS1Push);
     int FPOffset = PushSize + FramePtrOffsetInPush;
     if (STI.splitFramePointerPush(MF)) {
       AfterPush = std::next(GPRCS2Push);
       emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, AfterPush, dl, TII,
bool ARMFrameLowering::enableShrinkWrapping(const MachineFunction &MF) const {
   // generated. A follow-up patch will fix this in a more performant manner.
   if (MF.getInfo<ARMFunctionInfo>()->shouldSignReturnAddress(
           true /* SpillsLR */))
     return false;
 
   return true;
 }
 
+static bool requiresAAPCSFrameRecord(const MachineFunction &MF) {
+  const auto &Subtarget = MF.getSubtarget<ARMSubtarget>();
+  return Subtarget.createAAPCSFrameChainLeaf() ||
+         (Subtarget.createAAPCSFrameChain() && MF.getFrameInfo().hasCalls());
+}
+
+// Thumb1 may require a spill when storing to a frame index through FP, for
+// cases where FP is a high register (R11). This scans the function for cases
+// where this may happen.
+static bool canSpillOnFrameIndexAccess(const MachineFunction &MF,
+                                       const TargetFrameLowering &TFI) {
+  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
+  if (!AFI->isThumb1OnlyFunction())
+    return false;
+
+  for (const auto &MBB : MF)
+    for (const auto &MI : MBB)
+      if (MI.getOpcode() == ARM::tSTRspi || MI.getOpcode() == ARM::tSTRi)
+        for (const auto &Op : MI.operands())
+          if (Op.isFI()) {
+            Register Reg;
+            TFI.getFrameIndexReference(MF, Op.getIndex(), Reg);
+            if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::SP)
+              return true;
+          }
+  return false;
+}
+
 void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                             BitVector &SavedRegs,
                                             RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
   // This tells PEI to spill the FP as if it is any other callee-save register
   // to take advantage the eliminateFrameIndex machinery. This also ensures it
   // is spilled in the order specified by getCalleeSavedRegs() to make it easier
   // to combine multiple loads / stores.
-  bool CanEliminateFrame = true;
+  bool CanEliminateFrame = !(requiresAAPCSFrameRecord(MF) && hasFP(MF));
   bool CS1Spilled = false;
   bool LRSpilled = false;
   unsigned NumGPRSpills = 0;
   unsigned NumFPRSpills = 0;
   SmallVector<unsigned, 4> UnspilledCS1GPRs;
   SmallVector<unsigned, 4> UnspilledCS2GPRs;
   const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
       MF.getSubtarget().getRegisterInfo());
if (AFI->isThumb1OnlyFunction()) {
     // immediate. tSTRi, which is used for bp- and fp-relative accesses, has
     // a 5-bit unsigned immediate.
     //
     // We could try to check if the function actually contains a tSTRspi
     // that might need the spill slot, but it's not really important.
     // Functions with VLAs or extremely large call frames are rare, and
     // if a function is allocating more than 1KB of stack, an extra 4-byte
     // slot probably isn't relevant.
+    //
+    // A special case is the scenario where r11 is used as FP, where accesses
+    // to a frame index will require its value to be moved into a low reg.
+    // This is handled later on, once we are able to determine if we have any
+    // fp-relative accesses.
     if (RegInfo->hasBasePointer(MF))
       EstimatedRSStackSizeLimit = (1U << 5) * 4;
     else
       EstimatedRSStackSizeLimit = (1U << 8) * 4;
     EstimatedRSFixedSizeLimit = (1U << 5) * 4;
   } else {
     EstimatedRSStackSizeLimit =
         estimateRSStackSizeLimit(MF, this, HasNonSPFrameIndex);
void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
   if (BigFrameOffsets ||
       !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
     AFI->setHasStackFrame(true);
 
     if (HasFP) {
       SavedRegs.set(FramePtr);
       // If the frame pointer is required by the ABI, also spill LR so that we
       // emit a complete frame record.
-      if (MF.getTarget().Options.DisableFramePointerElim(MF) && !LRSpilled) {
+      if ((requiresAAPCSFrameRecord(MF) ||
+           MF.getTarget().Options.DisableFramePointerElim(MF)) &&
+          !LRSpilled) {
         SavedRegs.set(ARM::LR);
         LRSpilled = true;
         NumGPRSpills++;
         auto LRPos = llvm::find(UnspilledCS1GPRs, ARM::LR);
         if (LRPos != UnspilledCS1GPRs.end())
           UnspilledCS1GPRs.erase(LRPos);
       }
       auto FPPos = llvm::find(UnspilledCS1GPRs, FramePtr);
if (AFI->isThumb1OnlyFunction()) {
           LLVM_DEBUG(
               dbgs()
               << printReg(Reg, TRI)
               << " is non-saved low register, adding to AvailableRegs\n");
         }
       }
 
       // r7 can be used if it is not being used as the frame pointer.
-      if (!HasFP) {
+      if (!HasFP || FramePtr != ARM::R7) {
         if (SavedRegs.test(ARM::R7)) {
           --RegDeficit;
           LLVM_DEBUG(dbgs() << "%r7 is saved low register, RegDeficit = "
                             << RegDeficit << "\n");
         } else {
           AvailableRegs.push_back(ARM::R7);
           LLVM_DEBUG(
               dbgs()
if (TargetAlign >= Align(8) && (NumGPRSpills & 1)) {
           ExtraCSSpill = true;
       }
     }
 
     // Estimate if we might need to scavenge a register at some point in order
     // to materialize a stack offset. If so, either spill one additional
     // callee-saved register or reserve a special spill slot to facilitate
     // register scavenging. Thumb1 needs a spill slot for stack pointer
-    // adjustments also, even when the frame itself is small.
-    if (BigFrameOffsets && !ExtraCSSpill) {
+    // adjustments and for frame index accesses when FP is high register,
+    // even when the frame itself is small.
+    if (!ExtraCSSpill &&
+        (BigFrameOffsets || canSpillOnFrameIndexAccess(MF, *this))) {
       // If any non-reserved CS register isn't spilled, just spill one or two
       // extra. That should take care of it!
       unsigned NumExtras = TargetAlign.value() / 4;
       SmallVector<unsigned, 2> Extras;
       while (NumExtras && !UnspilledCS1GPRs.empty()) {
         unsigned Reg = UnspilledCS1GPRs.pop_back_val();
         if (!MRI.isReserved(Reg) &&
             (!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg))) {

llvm/lib/Target/ARM/ARMMachineFunctionInfo.h

class ARMFunctionInfo : public MachineFunctionInfo {
   /// Some may be spilled after the stack has been realigned.
   unsigned GPRCS1Offset = 0;
   unsigned GPRCS2Offset = 0;
   unsigned DPRCSOffset = 0;
 
   /// GPRCS1Size, GPRCS2Size, DPRCSSize - Sizes of callee saved register spills
   /// areas.
   unsigned FPCXTSaveSize = 0;
+  unsigned FRSaveSize = 0;
   unsigned GPRCS1Size = 0;
   unsigned GPRCS2Size = 0;
   unsigned DPRCSAlignGapSize = 0;
   unsigned DPRCSSize = 0;
 
   /// NumAlignedDPRCS2Regs - The number of callee-saved DPRs that are saved in
   /// the aligned portion of the stack frame.  This is always a contiguous
   /// sequence of D-registers starting from d8.
public:
   unsigned getGPRCalleeSavedArea2Offset() const { return GPRCS2Offset; }
   unsigned getDPRCalleeSavedAreaOffset()  const { return DPRCSOffset; }
 
   void setGPRCalleeSavedArea1Offset(unsigned o) { GPRCS1Offset = o; }
   void setGPRCalleeSavedArea2Offset(unsigned o) { GPRCS2Offset = o; }
   void setDPRCalleeSavedAreaOffset(unsigned o)  { DPRCSOffset = o; }
 
   unsigned getFPCXTSaveAreaSize() const       { return FPCXTSaveSize; }
+  unsigned getFrameRecordSavedAreaSize() const { return FRSaveSize; }
   unsigned getGPRCalleeSavedArea1Size() const { return GPRCS1Size; }
   unsigned getGPRCalleeSavedArea2Size() const { return GPRCS2Size; }
   unsigned getDPRCalleeSavedGapSize() const   { return DPRCSAlignGapSize; }
   unsigned getDPRCalleeSavedAreaSize()  const { return DPRCSSize; }
 
   void setFPCXTSaveAreaSize(unsigned s)       { FPCXTSaveSize = s; }
+  void setFrameRecordSavedAreaSize(unsigned s) { FRSaveSize = s; }
   void setGPRCalleeSavedArea1Size(unsigned s) { GPRCS1Size = s; }
   void setGPRCalleeSavedArea2Size(unsigned s) { GPRCS2Size = s; }
   void setDPRCalleeSavedGapSize(unsigned s)   { DPRCSAlignGapSize = s; }
   void setDPRCalleeSavedAreaSize(unsigned s)  { DPRCSSize = s; }
 
   unsigned getArgumentStackSize() const { return ArgumentStackSize; }
   void setArgumentStackSize(unsigned size) { ArgumentStackSize = size; }
 

llvm/lib/Target/ARM/ARMSubtarget.h

#include "ARMGenSubtargetInfo.inc"
   bool isRClass() const { return ARMProcClass == RClass; }
   bool isAClass() const { return ARMProcClass == AClass; }
 
   bool isR9Reserved() const {
     return isTargetMachO() ? (ReserveR9 || !HasV6Ops) : ReserveR9;
   }
 
   MCPhysReg getFramePointerReg() const {
-    if (isTargetDarwin() || (!isTargetWindows() && isThumb()))
+    if (isTargetDarwin() ||
+        (!isTargetWindows() && isThumb() && !createAAPCSFrameChain()))
       return ARM::R7;
     return ARM::R11;
   }
 
   /// Returns true if the frame setup is split into two separate pushes (first
   /// r0-r7,lr then r8-r11), principally so that the frame pointer is adjacent
   /// to lr. This is always required on Thumb1-only targets, as the push and
   /// pop instructions can't access the high registers.

llvm/lib/Target/ARM/Thumb1FrameLowering.cpp

 //===- Thumb1FrameLowering.cpp - Thumb1 Frame Information -----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the Thumb1 implementation of TargetFrameLowering class.
void Thumb1FrameLowering::emitPrologue(MachineFunction &MF,
   int CFAOffset = 0;
 
   // Thumb add/sub sp, imm8 instructions implicitly multiply the offset by 4.
   NumBytes = (NumBytes + 3) & ~3;
   MFI.setStackSize(NumBytes);
 
   // Determine the sizes of each callee-save spill areas and record which frame
   // belongs to which callee-save spill areas.
-  unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
+  unsigned FRSize = 0, GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
   int FramePtrSpillFI = 0;
 
   if (ArgRegsSaveSize) {
     emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -ArgRegsSaveSize,
                                  ARM::NoRegister, MachineInstr::FrameSetup);
     CFAOffset += ArgRegsSaveSize;
     unsigned CFIIndex =
         MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset));
if (NumBytes - ArgRegsSaveSize != 0) {
           MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset));
       BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(CFIIndex)
           .setMIFlags(MachineInstr::FrameSetup);
     }
     return;
   }
 
+  bool HasFrameRecordArea = hasFP(MF) && ARM::hGPRRegClass.contains(FramePtr);
+
   for (const CalleeSavedInfo &I : CSI) {
     Register Reg = I.getReg();
     int FI = I.getFrameIdx();
+    if (Reg == FramePtr)
+      FramePtrSpillFI = FI;
     switch (Reg) {
+    case ARM::R11:
+      if (HasFrameRecordArea) {
+        FRSize += 4;
+        break;
+      }
+      LLVM_FALLTHROUGH;
     case ARM::R8:
     case ARM::R9:
     case ARM::R10:
-    case ARM::R11:
       if (STI.splitFramePushPop(MF)) {
         GPRCS2Size += 4;
         break;
       }
       LLVM_FALLTHROUGH;
+    case ARM::LR:
+      if (HasFrameRecordArea) {
+        FRSize += 4;
+        break;
+      }
+      LLVM_FALLTHROUGH;
     case ARM::R4:
     case ARM::R5:
     case ARM::R6:
     case ARM::R7:
-    case ARM::LR:
-      if (Reg == FramePtr)
-        FramePtrSpillFI = FI;
       GPRCS1Size += 4;
       break;
     default:
       DPRCSSize += 8;
     }
   }
 
+  MachineBasicBlock::iterator FRPush, GPRCS1Push, GPRCS2Push;
+  if (HasFrameRecordArea) {
+    // Skip Frame Record setup:
+    //   push {lr}
+    //   mov lr, r11
+    //   push {lr}
+    std::advance(MBBI, 2);
+    FRPush = MBBI++;
+  }
+
   if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) {
+    GPRCS1Push = MBBI;
     ++MBBI;
   }
 
+  // Find last push instruction for GPRCS2 - spilling of high registers
+  // (r8-r11) could consist of multiple tPUSH and tMOVr instructions.
+  while (true) {
+    MachineBasicBlock::iterator OldMBBI = MBBI;
+    // Skip a run of tMOVr instructions
+    while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tMOVr &&
+           MBBI->getFlag(MachineInstr::FrameSetup))
+      MBBI++;
+    if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH &&
+        MBBI->getFlag(MachineInstr::FrameSetup)) {
+      GPRCS2Push = MBBI;
+      MBBI++;
+    } else {
+      // We have reached an instruction which is not a push, so the previous
+      // run of tMOVr instructions (which may have been empty) was not part of
+      // the prologue. Reset MBBI back to the last PUSH of the prologue.
+      MBBI = OldMBBI;
+      break;
+    }
+  }
+
   // Determine starting offsets of spill areas.
-  unsigned DPRCSOffset  = NumBytes - ArgRegsSaveSize - (GPRCS1Size + GPRCS2Size + DPRCSSize);
+  unsigned DPRCSOffset = NumBytes - ArgRegsSaveSize -
+                         (FRSize + GPRCS1Size + GPRCS2Size + DPRCSSize);
   unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
   unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
   bool HasFP = hasFP(MF);
   if (HasFP)
     AFI->setFramePtrSpillOffset(MFI.getObjectOffset(FramePtrSpillFI) +
                                 NumBytes);
+  if (HasFrameRecordArea)
+    AFI->setFrameRecordSavedAreaSize(FRSize);
   AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
   AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
   AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
   NumBytes = DPRCSOffset;
 
   int FramePtrOffsetInBlock = 0;
   unsigned adjustedGPRCS1Size = GPRCS1Size;
   if (GPRCS1Size > 0 && GPRCS2Size == 0 &&
-      tryFoldSPUpdateIntoPushPop(STI, MF, &*std::prev(MBBI), NumBytes)) {
+      tryFoldSPUpdateIntoPushPop(STI, MF, &*(GPRCS1Push), NumBytes)) {
     FramePtrOffsetInBlock = NumBytes;
     adjustedGPRCS1Size += NumBytes;
     NumBytes = 0;
   }
+  CFAOffset += adjustedGPRCS1Size;
 
+  // Adjust FP so it point to the stack slot that contains the previous FP.
+  if (HasFP) {
+    MachineBasicBlock::iterator AfterPush =
+        HasFrameRecordArea ? std::next(FRPush) : std::next(GPRCS1Push);
+    if (HasFrameRecordArea) {
+      // We have just finished pushing the previous FP into the stack,
+      // so simply capture the SP value as the new Frame Pointer.
+      BuildMI(MBB, AfterPush, dl, TII.get(ARM::tMOVr), FramePtr)
+          .addReg(ARM::SP)
+          .setMIFlags(MachineInstr::FrameSetup)
+          .add(predOps(ARMCC::AL));
+    } else {
+      FramePtrOffsetInBlock +=
+          MFI.getObjectOffset(FramePtrSpillFI) + GPRCS1Size + ArgRegsSaveSize;
+      BuildMI(MBB, AfterPush, dl, TII.get(ARM::tADDrSPi), FramePtr)
+          .addReg(ARM::SP)
+          .addImm(FramePtrOffsetInBlock / 4)
+          .setMIFlags(MachineInstr::FrameSetup)
+          .add(predOps(ARMCC::AL));
+    }
+
+    if(FramePtrOffsetInBlock) {
+      unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfa(
+          nullptr, MRI->getDwarfRegNum(FramePtr, true), (CFAOffset - FramePtrOffsetInBlock)));
+      BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex)
+          .setMIFlags(MachineInstr::FrameSetup);
+    } else {
+      unsigned CFIIndex =
+          MF.addFrameInst(MCCFIInstruction::createDefCfaRegister(
+              nullptr, MRI->getDwarfRegNum(FramePtr, true)));
+      BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex)
+          .setMIFlags(MachineInstr::FrameSetup);
+    }
+    if (NumBytes > 508)
+      // If offset is > 508 then sp cannot be adjusted in a single instruction,
+      // try restoring from fp instead.
+      AFI->setShouldRestoreSPFromFP(true);
+  }
+
+  // Emit call frame information for the callee-saved low registers.
+  if (GPRCS1Size > 0) {
+    MachineBasicBlock::iterator Pos = std::next(GPRCS1Push);
     if (adjustedGPRCS1Size) {
-    CFAOffset += adjustedGPRCS1Size;
       unsigned CFIIndex =
           MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset));
-    BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+      BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(CFIIndex)
           .setMIFlags(MachineInstr::FrameSetup);
     }
     for (const CalleeSavedInfo &I : CSI) {
       Register Reg = I.getReg();
       int FI = I.getFrameIdx();
       switch (Reg) {
       case ARM::R8:
       case ARM::R9:
       case ARM::R10:
       case ARM::R11:
       case ARM::R12:
         if (STI.splitFramePushPop(MF))
           break;
         LLVM_FALLTHROUGH;
       case ARM::R0:
       case ARM::R1:
       case ARM::R2:
       case ARM::R3:
       case ARM::R4:
       case ARM::R5:
       case ARM::R6:
       case ARM::R7:
       case ARM::LR:
         unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
             nullptr, MRI->getDwarfRegNum(Reg, true), MFI.getObjectOffset(FI)));
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
             .addCFIIndex(CFIIndex)
             .setMIFlags(MachineInstr::FrameSetup);
         break;
       }
     }
-
-  // Adjust FP so it point to the stack slot that contains the previous FP.
-  if (HasFP) {
-    FramePtrOffsetInBlock +=
-        MFI.getObjectOffset(FramePtrSpillFI) + GPRCS1Size + ArgRegsSaveSize;
-    BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
-        .addReg(ARM::SP)
-        .addImm(FramePtrOffsetInBlock / 4)
-        .setMIFlags(MachineInstr::FrameSetup)
-        .add(predOps(ARMCC::AL));
-    if(FramePtrOffsetInBlock) {
-      CFAOffset -= FramePtrOffsetInBlock;
-      unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfa(
-          nullptr, MRI->getDwarfRegNum(FramePtr, true), CFAOffset));
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
-          .addCFIIndex(CFIIndex)
-          .setMIFlags(MachineInstr::FrameSetup);
-    } else {
-      unsigned CFIIndex =
-          MF.addFrameInst(MCCFIInstruction::createDefCfaRegister(
-              nullptr, MRI->getDwarfRegNum(FramePtr, true)));
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
-          .addCFIIndex(CFIIndex)
-          .setMIFlags(MachineInstr::FrameSetup);
-    }
-    if (NumBytes > 508)
-      // If offset is > 508 then sp cannot be adjusted in a single instruction,
-      // try restoring from fp instead.
-      AFI->setShouldRestoreSPFromFP(true);
-  }
-
-  // Skip past the spilling of r8-r11, which could consist of multiple tPUSH
-  // and tMOVr instructions. We don't need to add any call frame information
-  // in-between these instructions, because they do not modify the high
-  // registers.
-  while (true) {
-    MachineBasicBlock::iterator OldMBBI = MBBI;
-    // Skip a run of tMOVr instructions
-    while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tMOVr)
-      MBBI++;
-    if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) {
-      MBBI++;
-    } else {
-      // We have reached an instruction which is not a push, so the previous
-      // run of tMOVr instructions (which may have been empty) was not part of
-      // the prologue. Reset MBBI back to the last PUSH of the prologue.
-      MBBI = OldMBBI;
-      break;
-    }
   }
 
   // Emit call frame information for the callee-saved high registers.
+  if (GPRCS2Size > 0) {
+    MachineBasicBlock::iterator Pos = std::next(GPRCS2Push);
     for (auto &I : CSI) {
       Register Reg = I.getReg();
       int FI = I.getFrameIdx();
       switch (Reg) {
       case ARM::R8:
       case ARM::R9:
       case ARM::R10:
       case ARM::R11:
       case ARM::R12: {
         unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
             nullptr, MRI->getDwarfRegNum(Reg, true), MFI.getObjectOffset(FI)));
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
             .addCFIIndex(CFIIndex)
             .setMIFlags(MachineInstr::FrameSetup);
         break;
       }
       default:
         break;
       }
     }
+  }
 
   if (NumBytes) {
     // Insert it after all the callee-save spills.
     //
     // For a large stack frame, we might need a scratch register to store
     // the size of the frame.  We know all callee-save registers are free
     // at this point in the prologue, so pick one.
     unsigned ScratchRegister = ARM::NoRegister;
if (MBBI != MBB.begin()) {
       do
         --MBBI;
       while (MBBI != MBB.begin() && MBBI->getFlag(MachineInstr::FrameDestroy));
       if (!MBBI->getFlag(MachineInstr::FrameDestroy))
         ++MBBI;
     }
 
     // Move SP to start of FP callee save spill area.
-    NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
+    NumBytes -= (AFI->getFrameRecordSavedAreaSize() +
+                 AFI->getGPRCalleeSavedArea1Size() +
                  AFI->getGPRCalleeSavedArea2Size() +
                  AFI->getDPRCalleeSavedAreaSize() +
                  ArgRegsSaveSize);
 
     if (AFI->shouldRestoreSPFromFP()) {
       NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
       // Reset SP based on frame pointer only if the stack frame extends beyond
       // frame pointer stack slot, the target is ELF and the function has FP, or
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
         .addReg(PopReg, RegState::Define)
         .addReg(TemporaryReg, RegState::Kill)
         .add(predOps(ARMCC::AL))
         .setMIFlag(MachineInstr::FrameDestroy);
 
   return true;
 }
 
-using ARMRegSet = std::bitset<ARM::NUM_TARGET_REGS>;
-
-// Return the first iteraror after CurrentReg which is present in EnabledRegs,
-// or OrderEnd if no further registers are in that set. This does not advance
-// the iterator fiorst, so returns CurrentReg if it is in EnabledRegs.
-static const unsigned *findNextOrderedReg(const unsigned *CurrentReg,
-                                          const ARMRegSet &EnabledRegs,
-                                          const unsigned *OrderEnd) {
-  while (CurrentReg != OrderEnd && !EnabledRegs[*CurrentReg])
-    ++CurrentReg;
-  return CurrentReg;
-}
-
-bool Thumb1FrameLowering::spillCalleeSavedRegisters(
-    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
-    ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
-  if (CSI.empty())
-    return false;
-
-  DebugLoc DL;
-  const TargetInstrInfo &TII = *STI.getInstrInfo();
-  MachineFunction &MF = *MBB.getParent();
-  const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
-      MF.getSubtarget().getRegisterInfo());
-
-  ARMRegSet LoRegsToSave; // r0-r7, lr
-  ARMRegSet HiRegsToSave; // r8-r11
-  ARMRegSet CopyRegs;     // Registers which can be used after pushing
-                          // LoRegs for saving HiRegs.
-
-  for (const CalleeSavedInfo &I : llvm::reverse(CSI)) {
-    Register Reg = I.getReg();
-
+static const SmallVector<Register> OrderedLowRegs = {ARM::R4, ARM::R5, ARM::R6,
+                                                     ARM::R7, ARM::LR};
+static const SmallVector<Register> OrderedHighRegs = {ARM::R8, ARM::R9,
+                                                      ARM::R10, ARM::R11};
+static const SmallVector<Register> OrderedCopyRegs = {
+    ARM::R0, ARM::R1, ARM::R2, ARM::R3, ARM::R4,
+    ARM::R5, ARM::R6, ARM::R7, ARM::LR};
+
+static void splitLowAndHighRegs(const std::set<Register> &Regs,
+                                std::set<Register> &LowRegs,
+                                std::set<Register> &HighRegs) {
+  for (Register Reg : Regs) {
     if (ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) {
-      LoRegsToSave[Reg] = true;
+      LowRegs.insert(Reg);
     } else if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::LR) {
-      HiRegsToSave[Reg] = true;
+      HighRegs.insert(Reg);
     } else {
       llvm_unreachable("callee-saved register of unexpected class");
     }
-
-    if ((ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) &&
-        !MF.getRegInfo().isLiveIn(Reg) &&
-        !(hasFP(MF) && Reg == RegInfo->getFrameRegister(MF)))
-      CopyRegs[Reg] = true;
-  }
+  }
 
-  // Unused argument registers can be used for the high register saving.
-  for (unsigned ArgReg : {ARM::R0, ARM::R1, ARM::R2, ARM::R3})
-    if (!MF.getRegInfo().isLiveIn(ArgReg))
-      CopyRegs[ArgReg] = true;
+template <typename It>
+It getNextOrderedReg(It OrderedStartIt, It OrderedEndIt,
+                     const std::set<Register> &RegSet) {
+  return std::find_if(OrderedStartIt, OrderedEndIt,
+                      [&](Register Reg) { return RegSet.count(Reg); });
+}
 
-  // Push the low registers and lr
+static void pushRegsToStack(MachineBasicBlock &MBB,
+                            MachineBasicBlock::iterator MI,
+                            const TargetInstrInfo &TII,
+                            const std::set<Register> &RegsToSave,
+                            const std::set<Register> &CopyRegs) {
+  MachineFunction &MF = *MBB.getParent();
   const MachineRegisterInfo &MRI = MF.getRegInfo();
-  if (!LoRegsToSave.none()) {
+  DebugLoc DL;
+
+  std::set<Register> LowRegs, HighRegs;
+  splitLowAndHighRegs(RegsToSave, LowRegs, HighRegs);
+
+  // Push low regs first
+  if (!LowRegs.empty()) {
     MachineInstrBuilder MIB =
         BuildMI(MBB, MI, DL, TII.get(ARM::tPUSH)).add(predOps(ARMCC::AL));
-    for (unsigned Reg : {ARM::R4, ARM::R5, ARM::R6, ARM::R7, ARM::LR}) {
-      if (LoRegsToSave[Reg]) {
+    for (unsigned Reg : OrderedLowRegs) {
+      if (LowRegs.count(Reg)) {
         bool isKill = !MRI.isLiveIn(Reg);
         if (isKill && !MRI.isReserved(Reg))
           MBB.addLiveIn(Reg);
 
         MIB.addReg(Reg, getKillRegState(isKill));
       }
     }
     MIB.setMIFlags(MachineInstr::FrameSetup);
   }
 
-  // Push the high registers. There are no store instructions that can access
-  // these registers directly, so we have to move them to low registers, and
-  // push them. This might take multiple pushes, as it is possible for there to
+  // Now push the high registers
+  // There are no store instructions that can access high registers directly,
+  // so we have to move them to low registers, and push them.
+  // This might take multiple pushes, as it is possible for there to
   // be fewer low registers available than high registers which need saving.
 
-  // These are in reverse order so that in the case where we need to use
+  // Find the first register to save.
+  // Registers must be processed in reverse order so that in case we need to use
   // multiple PUSH instructions, the order of the registers on the stack still
   // matches the unwind info. They need to be swicthed back to ascending order
   // before adding to the PUSH instruction.
-  static const unsigned AllCopyRegs[] = {ARM::LR, ARM::R7, ARM::R6,
-                                         ARM::R5, ARM::R4, ARM::R3,
-                                         ARM::R2, ARM::R1, ARM::R0};
-  static const unsigned AllHighRegs[] = {ARM::R11, ARM::R10, ARM::R9, ARM::R8};
+  auto HiRegToSave = getNextOrderedReg(OrderedHighRegs.rbegin(),
+                                       OrderedHighRegs.rend(),
+                                       HighRegs);
 
-  const unsigned *AllCopyRegsEnd = std::end(AllCopyRegs);
-  const unsigned *AllHighRegsEnd = std::end(AllHighRegs);
-
-  // Find the first register to save.
-  const unsigned *HiRegToSave = findNextOrderedReg(
-      std::begin(AllHighRegs), HiRegsToSave, AllHighRegsEnd);
-
-  while (HiRegToSave != AllHighRegsEnd) {
+  while (HiRegToSave != OrderedHighRegs.rend()) {
     // Find the first low register to use.
-    const unsigned *CopyReg =
-        findNextOrderedReg(std::begin(AllCopyRegs), CopyRegs, AllCopyRegsEnd);
+    auto CopyRegIt = getNextOrderedReg(OrderedCopyRegs.rbegin(),
+                                       OrderedCopyRegs.rend(),
+                                       CopyRegs);
 
     // Create the PUSH, but don't insert it yet (the MOVs need to come first).
     MachineInstrBuilder PushMIB = BuildMI(MF, DL, TII.get(ARM::tPUSH))
                                       .add(predOps(ARMCC::AL))
                                       .setMIFlags(MachineInstr::FrameSetup);
 
     SmallVector<unsigned, 4> RegsToPush;
-    while (HiRegToSave != AllHighRegsEnd && CopyReg != AllCopyRegsEnd) {
-      if (HiRegsToSave[*HiRegToSave]) {
+    while (HiRegToSave != OrderedHighRegs.rend() &&
+           CopyRegIt != OrderedCopyRegs.rend()) {
+      if (HighRegs.count(*HiRegToSave)) {
         bool isKill = !MRI.isLiveIn(*HiRegToSave);
         if (isKill && !MRI.isReserved(*HiRegToSave))
           MBB.addLiveIn(*HiRegToSave);
 
         // Emit a MOV from the high reg to the low reg.
         BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr))
-            .addReg(*CopyReg, RegState::Define)
+            .addReg(*CopyRegIt, RegState::Define)
             .addReg(*HiRegToSave, getKillRegState(isKill))
             .add(predOps(ARMCC::AL))
             .setMIFlags(MachineInstr::FrameSetup);
 
         // Record the register that must be added to the PUSH.
-        RegsToPush.push_back(*CopyReg);
+        RegsToPush.push_back(*CopyRegIt);
 
-        CopyReg = findNextOrderedReg(++CopyReg, CopyRegs, AllCopyRegsEnd);
-        HiRegToSave =
-            findNextOrderedReg(++HiRegToSave, HiRegsToSave, AllHighRegsEnd);
+        CopyRegIt = getNextOrderedReg(std::next(CopyRegIt),
+                                      OrderedCopyRegs.rend(),
+                                      CopyRegs);
+        HiRegToSave = getNextOrderedReg(std::next(HiRegToSave),
+                                        OrderedHighRegs.rend(),
+                                        HighRegs);
       }
     }
 
     // Add the low registers to the PUSH, in ascending order.
     for (unsigned Reg : llvm::reverse(RegsToPush))
       PushMIB.addReg(Reg, RegState::Kill);
 
     // Insert the PUSH instruction after the MOVs.
     MBB.insert(MI, PushMIB);
   }
-
-  return true;
 }
 
-bool Thumb1FrameLowering::restoreCalleeSavedRegisters(
-    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
-    MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
-  if (CSI.empty())
-    return false;
-
+static void popRegsFromStack(MachineBasicBlock &MBB,
+                             MachineBasicBlock::iterator MI,
+                             const TargetInstrInfo &TII,
+                             const std::set<Register> &RegsToRestore,
+                             const std::set<Register> &AvailableCopyRegs,
+                             bool IsVarArg, bool HasV5Ops) {
   MachineFunction &MF = *MBB.getParent();
   ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
-  const TargetInstrInfo &TII = *STI.getInstrInfo();
-  const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
-      MF.getSubtarget().getRegisterInfo());
-
-  bool isVarArg = AFI->getArgRegsSaveSize() > 0;
   DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
 
-  ARMRegSet LoRegsToRestore;
-  ARMRegSet HiRegsToRestore;
-  // Low registers (r0-r7) which can be used to restore the high registers.
-  ARMRegSet CopyRegs;
-
-  for (CalleeSavedInfo I : CSI) {
-    Register Reg = I.getReg();
+  std::set<Register> LowRegs, HighRegs;
+  splitLowAndHighRegs(RegsToRestore, LowRegs, HighRegs);
 
-    if (ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) {
-      LoRegsToRestore[Reg] = true;
-    } else if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::LR) {
-      HiRegsToRestore[Reg] = true;
-    } else {
-      llvm_unreachable("callee-saved register of unexpected class");
-    }
-
-    // If this is a low register not used as the frame pointer, we may want to
-    // use it for restoring the high registers.
-    if ((ARM::tGPRRegClass.contains(Reg)) &&
-        !(hasFP(MF) && Reg == RegInfo->getFrameRegister(MF)))
-      CopyRegs[Reg] = true;
-  }
-
-  // If this is a return block, we may be able to use some unused return value
-  // registers for restoring the high regs.
-  auto Terminator = MBB.getFirstTerminator();
-  if (Terminator != MBB.end() && Terminator->getOpcode() == ARM::tBX_RET) {
-    CopyRegs[ARM::R0] = true;
-    CopyRegs[ARM::R1] = true;
-    CopyRegs[ARM::R2] = true;
-    CopyRegs[ARM::R3] = true;
-    for (auto Op : Terminator->implicit_operands()) {
-      if (Op.isReg())
-        CopyRegs[Op.getReg()] = false;
-    }
-  }
-
-  static const unsigned AllCopyRegs[] = {ARM::R0, ARM::R1, ARM::R2, ARM::R3,
-                                         ARM::R4, ARM::R5, ARM::R6, ARM::R7};
-  static const unsigned AllHighRegs[] = {ARM::R8, ARM::R9, ARM::R10, ARM::R11};
-
-  const unsigned *AllCopyRegsEnd = std::end(AllCopyRegs);
-  const unsigned *AllHighRegsEnd = std::end(AllHighRegs);
+  // Pop the high registers first
+  // There are no store instructions that can access high registers directly,
+  // so we have to pop into low registers and them move to  the high registers.
+  // This might take multiple pops, as it is possible for there to
+  // be fewer low registers available than high registers which need restoring.
 
   // Find the first register to restore.
-  auto HiRegToRestore = findNextOrderedReg(std::begin(AllHighRegs),
-                                           HiRegsToRestore, AllHighRegsEnd);
+  auto HiRegToRestore = getNextOrderedReg(OrderedHighRegs.begin(),
+                                          OrderedHighRegs.end(),
+                                          HighRegs);
+
+  std::set<Register> CopyRegs = AvailableCopyRegs;
+  Register LowScratchReg;
+  if (!HighRegs.empty() && CopyRegs.empty()) {
+    // No copy regs are available to pop high regs. Let's make use of a return
+    // register and the scratch register (IP/R12) to copy things around.
+    LowScratchReg = ARM::R0;
+    BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr))
+        .addReg(ARM::R12, RegState::Define)
+        .addReg(LowScratchReg, RegState::Kill)
+        .add(predOps(ARMCC::AL))
+        .setMIFlag(MachineInstr::FrameDestroy);
+    CopyRegs.insert(LowScratchReg);
+  }
 
-  while (HiRegToRestore != AllHighRegsEnd) {
-    assert(!CopyRegs.none());
+  while (HiRegToRestore != OrderedHighRegs.end()) {
+    assert(!CopyRegs.empty());
     // Find the first low register to use.
-    auto CopyReg =
-        findNextOrderedReg(std::begin(AllCopyRegs), CopyRegs, AllCopyRegsEnd);
+    auto CopyReg = getNextOrderedReg(OrderedCopyRegs.begin(),
+                                     OrderedCopyRegs.end(),
+                                     CopyRegs);
 
     // Create the POP instruction.
     MachineInstrBuilder PopMIB = BuildMI(MBB, MI, DL, TII.get(ARM::tPOP))
                                      .add(predOps(ARMCC::AL))
                                      .setMIFlag(MachineInstr::FrameDestroy);
 
-    while (HiRegToRestore != AllHighRegsEnd && CopyReg != AllCopyRegsEnd) {
+    while (HiRegToRestore != OrderedHighRegs.end() &&
+           CopyReg != OrderedCopyRegs.end()) {
       // Add the low register to the POP.
       PopMIB.addReg(*CopyReg, RegState::Define);
 
       // Create the MOV from low to high register.
       BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr))
           .addReg(*HiRegToRestore, RegState::Define)
           .addReg(*CopyReg, RegState::Kill)
           .add(predOps(ARMCC::AL))
           .setMIFlag(MachineInstr::FrameDestroy);
 
-      CopyReg = findNextOrderedReg(++CopyReg, CopyRegs, AllCopyRegsEnd);
-      HiRegToRestore =
-          findNextOrderedReg(++HiRegToRestore, HiRegsToRestore, AllHighRegsEnd);
+      CopyReg = getNextOrderedReg(std::next(CopyReg),
+                                  OrderedCopyRegs.end(),
+                                  CopyRegs);
+      HiRegToRestore = getNextOrderedReg(std::next(HiRegToRestore),
+                                         OrderedHighRegs.end(),
+                                         HighRegs);
     }
   }
 
+  // Restore low register used as scratch if necessary
+  if (LowScratchReg.isValid()) {
+    BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr))
+        .addReg(LowScratchReg, RegState::Define)
+        .addReg(ARM::R12, RegState::Kill)
+        .add(predOps(ARMCC::AL))
+        .setMIFlag(MachineInstr::FrameDestroy);
+  }
+
+  // Now pop the low registers
+  if (!LowRegs.empty()) {
     MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP))
                                   .add(predOps(ARMCC::AL))
                                   .setMIFlag(MachineInstr::FrameDestroy);
 
     bool NeedsPop = false;
-  for (CalleeSavedInfo &Info : llvm::reverse(CSI)) {
-    Register Reg = Info.getReg();
-
-    // High registers (excluding lr) have already been dealt with
-    if (!(ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR))
+    for (Register Reg : OrderedLowRegs) {
+      if (!LowRegs.count(Reg))
         continue;
 
       if (Reg == ARM::LR) {
-      Info.setRestored(false);
         if (!MBB.succ_empty() ||
             MI->getOpcode() == ARM::TCRETURNdi ||
             MI->getOpcode() == ARM::TCRETURNri)
           // LR may only be popped into PC, as part of return sequence.
           // If this isn't the return sequence, we'll need emitPopSpecialFixUp
           // to restore LR the hard way.
           // FIXME: if we don't pass any stack arguments it would be actually
           // advantageous *and* correct to do the conversion to an ordinary call
           // instruction here.
           continue;
         // Special epilogue for vararg functions. See emitEpilogue
-      if (isVarArg)
+        if (IsVarArg)
           continue;
         // ARMv4T requires BX, see emitEpilogue
-      if (!STI.hasV5TOps())
+        if (!HasV5Ops)
           continue;
 
         // CMSE entry functions must return via BXNS, see emitEpilogue.
         if (AFI->isCmseNSEntryFunction())
           continue;
 
         // Pop LR into PC.
         Reg = ARM::PC;
         (*MIB).setDesc(TII.get(ARM::tPOP_RET));
         if (MI != MBB.end())
           MIB.copyImplicitOps(*MI);
         MI = MBB.erase(MI);
       }
       MIB.addReg(Reg, getDefRegState(true));
       NeedsPop = true;
     }
 
     // It's illegal to emit pop instruction without operands.
     if (NeedsPop)
       MBB.insert(MI, &*MIB);
     else
       MF.deleteMachineInstr(MIB);
+  }
+}
+
+bool Thumb1FrameLowering::spillCalleeSavedRegisters(
+    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+    ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
+  if (CSI.empty())
+    return false;
+
+  const TargetInstrInfo &TII = *STI.getInstrInfo();
+  MachineFunction &MF = *MBB.getParent();
+  const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
+      MF.getSubtarget().getRegisterInfo());
+  Register FPReg = RegInfo->getFrameRegister(MF);
+
+  // In case FP is a high reg, we need a separate push sequence to generate
+  // a correct Frame Record
+  bool NeedsFrameRecordPush = hasFP(MF) && ARM::hGPRRegClass.contains(FPReg);
+
+  std::set<Register> FrameRecord;
+  std::set<Register> SpilledGPRs;
+  for (const CalleeSavedInfo &I : CSI) {
+    Register Reg = I.getReg();
+    if (NeedsFrameRecordPush && (Reg == FPReg || Reg == ARM::LR))
+      FrameRecord.insert(Reg);
+    else
+      SpilledGPRs.insert(Reg);
+  }
+
+  pushRegsToStack(MBB, MI, TII, FrameRecord, {ARM::LR});
+
+  // Determine intermediate registers which can be used for pushing high regs:
+  // - Spilled low regs
+  // - Unused argument registers
+  std::set<Register> CopyRegs;
+  for (Register Reg : SpilledGPRs)
+    if ((ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) &&
+        !MF.getRegInfo().isLiveIn(Reg) && !(hasFP(MF) && Reg == FPReg))
+      CopyRegs.insert(Reg);
+  for (unsigned ArgReg : {ARM::R0, ARM::R1, ARM::R2, ARM::R3})
+    if (!MF.getRegInfo().isLiveIn(ArgReg))
+      CopyRegs.insert(ArgReg);
+
+  pushRegsToStack(MBB, MI, TII, SpilledGPRs, CopyRegs);
+
+  return true;
+}
+
+bool Thumb1FrameLowering::restoreCalleeSavedRegisters(
+    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+    MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
+  if (CSI.empty())
+    return false;
+
+  MachineFunction &MF = *MBB.getParent();
+  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
+  const TargetInstrInfo &TII = *STI.getInstrInfo();
+  const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
+      MF.getSubtarget().getRegisterInfo());
+  bool IsVarArg = AFI->getArgRegsSaveSize() > 0;
+  Register FPReg = RegInfo->getFrameRegister(MF);
+
+  // In case FP is a high reg, we need a separate pop sequence to generate
+  // a correct Frame Record
+  bool NeedsFrameRecordPop = hasFP(MF) && ARM::hGPRRegClass.contains(FPReg);
+
+  std::set<Register> FrameRecord;
+  std::set<Register> SpilledGPRs;
+  for (CalleeSavedInfo &I : CSI) {
+    Register Reg = I.getReg();
+    if (NeedsFrameRecordPop && (Reg == FPReg || Reg == ARM::LR))
+      FrameRecord.insert(Reg);
+    else
+      SpilledGPRs.insert(Reg);
+
+    if (Reg == ARM::LR)
+      I.setRestored(false);
+  }
+
+  // Determine intermidiate registers which can be used for popping high regs:
+  // - Spilled low regs
+  // - Unused return registers
+  std::set<Register> CopyRegs;
+  std::set<Register> UnusedReturnRegs;
+  for (Register Reg : SpilledGPRs)
+    if ((ARM::tGPRRegClass.contains(Reg)) && !(hasFP(MF) && Reg == FPReg))
+      CopyRegs.insert(Reg);
+  auto Terminator = MBB.getFirstTerminator();
+  if (Terminator != MBB.end() && Terminator->getOpcode() == ARM::tBX_RET) {
+    UnusedReturnRegs.insert(ARM::R0);
+    UnusedReturnRegs.insert(ARM::R1);
+    UnusedReturnRegs.insert(ARM::R2);
+    UnusedReturnRegs.insert(ARM::R3);
+    for (auto Op : Terminator->implicit_operands()) {
+      if (Op.isReg())
+        UnusedReturnRegs.erase(Op.getReg());
+    }
+  }
+  CopyRegs.insert(UnusedReturnRegs.begin(), UnusedReturnRegs.end());
+
+  popRegsFromStack(MBB, MI, TII, SpilledGPRs, CopyRegs, IsVarArg,
+                   STI.hasV5TOps());
+  // Only unused return registers can be used as copy regs at this point
+  popRegsFromStack(MBB, MI, TII, FrameRecord, UnusedReturnRegs, IsVarArg,
+                   STI.hasV5TOps());
 
   return true;
 }

llvm/lib/Target/ARM/ThumbRegisterInfo.cpp

 //===-- ThumbRegisterInfo.cpp - Thumb-1 Register Information -------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the Thumb-1 implementation of the TargetRegisterInfo

 }
 
 bool ThumbRegisterInfo::rewriteFrameIndex(MachineBasicBlock::iterator II,
                                           unsigned FrameRegIdx,
                                           Register FrameReg, int &Offset,
                                           const ARMBaseInstrInfo &TII) const {
   MachineInstr &MI = *II;
   MachineBasicBlock &MBB = *MI.getParent();
+  MachineFunction &MF = *MBB.getParent();
   assert(MBB.getParent()->getSubtarget<ARMSubtarget>().isThumb1Only() &&
          "This isn't needed for thumb2!");
   DebugLoc dl = MI.getDebugLoc();
   MachineInstrBuilder MIB(*MBB.getParent(), &MI);
   unsigned Opcode = MI.getOpcode();
   const MCInstrDesc &Desc = MI.getDesc();
   unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
 
if (Opcode == ARM::tADDframe) {
 
     // Common case: small offset, fits into instruction.
     MachineOperand &ImmOp = MI.getOperand(ImmIdx);
     int ImmedOffset = Offset / Scale;
     unsigned Mask = (1 << NumBits) - 1;
 
     if ((unsigned)Offset <= Mask * Scale) {
       // Replace the FrameIndex with the frame register (e.g., sp).
-      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
+      Register DestReg = FrameReg;
+
+      // In case FrameReg is a high register, move it to a low reg to ensure it
+      // can be used as an operand.
+      if (ARM::hGPRRegClass.contains(FrameReg) && FrameReg != ARM::SP) {
+        DestReg = MF.getRegInfo().createVirtualRegister(&ARM::tGPRRegClass);
+        BuildMI(MBB, II, dl, TII.get(ARM::tMOVr), DestReg)
+            .addReg(FrameReg)
+            .add(predOps(ARMCC::AL));
+      }
+
+      MI.getOperand(FrameRegIdx).ChangeToRegister(DestReg, false);
       ImmOp.ChangeToImmediate(ImmedOffset);
 
       // If we're using a register where sp was stored, convert the instruction
       // to the non-SP version.
       unsigned NewOpc = convertToNonSPOpcode(Opcode);
       if (NewOpc != Opcode && FrameReg != ARM::SP)
         MI.setDesc(TII.get(NewOpc));
 
if (Opcode == ARM::tLDRspi) {
       }
     } else {
       emitThumbRegPlusImmediate(MBB, II, dl, TmpReg, FrameReg, Offset, TII,
                                 *this);
     }
 
     MI.setDesc(TII.get(UseRR ? ARM::tLDRr : ARM::tLDRi));
     MI.getOperand(FIOperandNum).ChangeToRegister(TmpReg, false, false, true);
-    if (UseRR)
+    if (UseRR) {
+      if (!ARM::hGPRRegClass.contains(FrameReg)) {
         // Use [reg, reg] addrmode. Replace the immediate operand w/ the frame
         // register. The offset is already handled in the vreg value.
         MI.getOperand(FIOperandNum+1).ChangeToRegister(FrameReg, false, false,
                                                        false);
+      } else {
+        // If FrameReg is a high register, add the reg values in a separate
+        // instruction as the load won't be able to access it.
+        BuildMI(MBB, II, dl, TII.get(ARM::tADDhirr), TmpReg)
+            .addReg(TmpReg)
+            .addReg(FrameReg)
+            .add(predOps(ARMCC::AL));
+      }
+    }
   } else if (MI.mayStore()) {
       VReg = MF.getRegInfo().createVirtualRegister(&ARM::tGPRRegClass);
       bool UseRR = false;
 
       if (Opcode == ARM::tSTRspi) {
         if (FrameReg == ARM::SP || STI.genExecuteOnly())
           emitThumbRegPlusImmInReg(MBB, II, dl, VReg, FrameReg,
                                    Offset, false, TII, *this);
         else {
           emitLoadConstPool(MBB, II, dl, VReg, 0, Offset);
           UseRR = true;
         }
       } else
         emitThumbRegPlusImmediate(MBB, II, dl, VReg, FrameReg, Offset, TII,
                                   *this);
       MI.setDesc(TII.get(UseRR ? ARM::tSTRr : ARM::tSTRi));
       MI.getOperand(FIOperandNum).ChangeToRegister(VReg, false, false, true);
-      if (UseRR)
+      if (UseRR) {
+        if (!ARM::hGPRRegClass.contains(FrameReg)) {
           // Use [reg, reg] addrmode. Replace the immediate operand w/ the frame
           // register. The offset is already handled in the vreg value.
           MI.getOperand(FIOperandNum+1).ChangeToRegister(FrameReg, false, false,
                                                          false);
         } else {
+          // If FrameReg is a high register, add the reg values in a separate
+          // instruction as the load won't be able to access it.
+          BuildMI(MBB, II, dl, TII.get(ARM::tADDhirr), VReg)
+              .addReg(VReg)
+              .addReg(FrameReg)
+              .add(predOps(ARMCC::AL));
+          }
+      }
+  } else {
     llvm_unreachable("Unexpected opcode!");
   }
 
   // Add predicate back if it's needed.
   if (MI.isPredicable())
     MIB.add(predOps(ARMCC::AL));
 }
 

llvm/test/CodeGen/ARM/frame-chain-reserved-fp.ll

+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-NONE
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none 2>&1 | FileCheck %s --check-prefix=RESERVED-NONE
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+
+declare void @leaf(i32 %input)
+
+define void @reserved_r7(i32 %input) {
+; RESERVED-NONE-NOT: error: write to reserved register 'R7'
+; RESERVED-R11-NOT: error: write to reserved register 'R7'
+  %1 = call i32 asm sideeffect "mov $0, $1", "={r7},r"(i32 %input)
+  ret void
+}
+
+define void @reserved_r11(i32 %input) {
+; RESERVED-NONE-NOT: error: write to reserved register 'R11'
+; RESERVED-R11: error: write to reserved register 'R11'
+  %1 = call i32 asm sideeffect "mov $0, $1", "={r11},r"(i32 %input)
+  ret void
+}

llvm/test/CodeGen/ARM/frame-chain.ll

+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all | FileCheck %s --check-prefixes=FP,LEAF-FP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-FP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-FP-AAPCS
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf | FileCheck %s --check-prefixes=FP,LEAF-NOFP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-NOFP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-NOFP-AAPCS
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none | FileCheck %s --check-prefixes=NOFP,LEAF-NOFP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=NOFP-AAPCS,LEAF-NOFP
+; RUN: llc -mtriple arm-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=NOFP-AAPCS,LEAF-NOFP-AAPCS
+
+define dso_local noundef i32 @leaf(i32 noundef %0) {
+; LEAF-FP-LABEL: leaf:
+; LEAF-FP:       @ %bb.0:
+; LEAF-FP-NEXT:    .pad #4
+; LEAF-FP-NEXT:    sub sp, sp, #4
+; LEAF-FP-NEXT:    str r0, [sp]
+; LEAF-FP-NEXT:    add r0, r0, #4
+; LEAF-FP-NEXT:    add sp, sp, #4
+; LEAF-FP-NEXT:    mov pc, lr
+;
+; LEAF-FP-AAPCS-LABEL: leaf:
+; LEAF-FP-AAPCS:       @ %bb.0:
+; LEAF-FP-AAPCS-NEXT:    .save {r11, lr}
+; LEAF-FP-AAPCS-NEXT:    push {r11, lr}
+; LEAF-FP-AAPCS-NEXT:    .setfp r11, sp
+; LEAF-FP-AAPCS-NEXT:    mov r11, sp
+; LEAF-FP-AAPCS-NEXT:    push {r0}
+; LEAF-FP-AAPCS-NEXT:    add r0, r0, #4
+; LEAF-FP-AAPCS-NEXT:    mov sp, r11
+; LEAF-FP-AAPCS-NEXT:    pop {r11, lr}
+; LEAF-FP-AAPCS-NEXT:    mov pc, lr
+;
+; LEAF-NOFP-LABEL: leaf:
+; LEAF-NOFP:       @ %bb.0:
+; LEAF-NOFP-NEXT:    .pad #4
+; LEAF-NOFP-NEXT:    sub sp, sp, #4
+; LEAF-NOFP-NEXT:    str r0, [sp]
+; LEAF-NOFP-NEXT:    add r0, r0, #4
+; LEAF-NOFP-NEXT:    add sp, sp, #4
+; LEAF-NOFP-NEXT:    mov pc, lr
+;
+; LEAF-NOFP-AAPCS-LABEL: leaf:
+; LEAF-NOFP-AAPCS:       @ %bb.0:
+; LEAF-NOFP-AAPCS-NEXT:    .pad #4
+; LEAF-NOFP-AAPCS-NEXT:    sub sp, sp, #4
+; LEAF-NOFP-AAPCS-NEXT:    str r0, [sp]
+; LEAF-NOFP-AAPCS-NEXT:    add r0, r0, #4
+; LEAF-NOFP-AAPCS-NEXT:    add sp, sp, #4
+; LEAF-NOFP-AAPCS-NEXT:    mov pc, lr
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = add nsw i32 %3, 4
+  ret i32 %4
+}
+
+define dso_local noundef i32 @non_leaf(i32 noundef %0) {
+; FP-LABEL: non_leaf:
+; FP:       @ %bb.0:
+; FP-NEXT:    .save {r11, lr}
+; FP-NEXT:    push {r11, lr}
+; FP-NEXT:    .setfp r11, sp
+; FP-NEXT:    mov r11, sp
+; FP-NEXT:    .pad #8
+; FP-NEXT:    sub sp, sp, #8
+; FP-NEXT:    str r0, [sp, #4]
+; FP-NEXT:    bl leaf
+; FP-NEXT:    add r0, r0, #1
+; FP-NEXT:    mov sp, r11
+; FP-NEXT:    pop {r11, lr}
+; FP-NEXT:    mov pc, lr
+;
+; FP-AAPCS-LABEL: non_leaf:
+; FP-AAPCS:       @ %bb.0:
+; FP-AAPCS-NEXT:    .save {r11, lr}
+; FP-AAPCS-NEXT:    push {r11, lr}
+; FP-AAPCS-NEXT:    .setfp r11, sp
+; FP-AAPCS-NEXT:    mov r11, sp
+; FP-AAPCS-NEXT:    .pad #8
+; FP-AAPCS-NEXT:    sub sp, sp, #8
+; FP-AAPCS-NEXT:    str r0, [sp, #4]
+; FP-AAPCS-NEXT:    bl leaf
+; FP-AAPCS-NEXT:    add r0, r0, #1
+; FP-AAPCS-NEXT:    mov sp, r11
+; FP-AAPCS-NEXT:    pop {r11, lr}
+; FP-AAPCS-NEXT:    mov pc, lr
+;
+; NOFP-LABEL: non_leaf:
+; NOFP:       @ %bb.0:
+; NOFP-NEXT:    .save {r11, lr}
+; NOFP-NEXT:    push {r11, lr}
+; NOFP-NEXT:    .pad #8
+; NOFP-NEXT:    sub sp, sp, #8
+; NOFP-NEXT:    str r0, [sp, #4]
+; NOFP-NEXT:    bl leaf
+; NOFP-NEXT:    add r0, r0, #1
+; NOFP-NEXT:    add sp, sp, #8
+; NOFP-NEXT:    pop {r11, lr}
+; NOFP-NEXT:    mov pc, lr
+;
+; NOFP-AAPCS-LABEL: non_leaf:
+; NOFP-AAPCS:       @ %bb.0:
+; NOFP-AAPCS-NEXT:    .save {r11, lr}
+; NOFP-AAPCS-NEXT:    push {r11, lr}
+; NOFP-AAPCS-NEXT:    .pad #8
+; NOFP-AAPCS-NEXT:    sub sp, sp, #8
+; NOFP-AAPCS-NEXT:    str r0, [sp, #4]
+; NOFP-AAPCS-NEXT:    bl leaf
+; NOFP-AAPCS-NEXT:    add r0, r0, #1
+; NOFP-AAPCS-NEXT:    add sp, sp, #8
+; NOFP-AAPCS-NEXT:    pop {r11, lr}
+; NOFP-AAPCS-NEXT:    mov pc, lr
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = call noundef i32 @leaf(i32 noundef %3)
+  %5 = add nsw i32 %4, 1
+  ret i32 %5
+}
+
+declare i8* @llvm.stacksave()
+define dso_local void @required_fp(i32 %0, i32 %1) {
+; LEAF-FP-LABEL: required_fp:
+; LEAF-FP:       @ %bb.0:
+; LEAF-FP-NEXT:    .save {r4, r5, r11, lr}
+; LEAF-FP-NEXT:    push {r4, r5, r11, lr}
+; LEAF-FP-NEXT:    .setfp r11, sp, #8
+; LEAF-FP-NEXT:    add r11, sp, #8
+; LEAF-FP-NEXT:    .pad #24
+; LEAF-FP-NEXT:    sub sp, sp, #24
+; LEAF-FP-NEXT:    str r1, [r11, #-16]
+; LEAF-FP-NEXT:    mov r1, #7
+; LEAF-FP-NEXT:    add r1, r1, r0, lsl #2
+; LEAF-FP-NEXT:    str r0, [r11, #-12]
+; LEAF-FP-NEXT:    bic r1, r1, #7
+; LEAF-FP-NEXT:    str sp, [r11, #-24]
+; LEAF-FP-NEXT:    sub sp, sp, r1
+; LEAF-FP-NEXT:    mov r1, #0
+; LEAF-FP-NEXT:    str r0, [r11, #-32]
+; LEAF-FP-NEXT:    str r1, [r11, #-28]
+; LEAF-FP-NEXT:    sub sp, r11, #8
+; LEAF-FP-NEXT:    pop {r4, r5, r11, lr}
+; LEAF-FP-NEXT:    mov pc, lr
+;
+; LEAF-FP-AAPCS-LABEL: required_fp:
+; LEAF-FP-AAPCS:       @ %bb.0:
+; LEAF-FP-AAPCS-NEXT:    .save {r4, r5, r11, lr}
+; LEAF-FP-AAPCS-NEXT:    push {r4, r5, r11, lr}
+; LEAF-FP-AAPCS-NEXT:    .setfp r11, sp, #8
+; LEAF-FP-AAPCS-NEXT:    add r11, sp, #8
+; LEAF-FP-AAPCS-NEXT:    .pad #24
+; LEAF-FP-AAPCS-NEXT:    sub sp, sp, #24
+; LEAF-FP-AAPCS-NEXT:    str r1, [r11, #-16]
+; LEAF-FP-AAPCS-NEXT:    mov r1, #7
+; LEAF-FP-AAPCS-NEXT:    add r1, r1, r0, lsl #2
+; LEAF-FP-AAPCS-NEXT:    str r0, [r11, #-12]
+; LEAF-FP-AAPCS-NEXT:    bic r1, r1, #7
+; LEAF-FP-AAPCS-NEXT:    str sp, [r11, #-24]
+; LEAF-FP-AAPCS-NEXT:    sub sp, sp, r1
+; LEAF-FP-AAPCS-NEXT:    mov r1, #0
+; LEAF-FP-AAPCS-NEXT:    str r0, [r11, #-32]
+; LEAF-FP-AAPCS-NEXT:    str r1, [r11, #-28]
+; LEAF-FP-AAPCS-NEXT:    sub sp, r11, #8
+; LEAF-FP-AAPCS-NEXT:    pop {r4, r5, r11, lr}
+; LEAF-FP-AAPCS-NEXT:    mov pc, lr
+;
+; LEAF-NOFP-LABEL: required_fp:
+; LEAF-NOFP:       @ %bb.0:
+; LEAF-NOFP-NEXT:    .save {r4, r5, r11}
+; LEAF-NOFP-NEXT:    push {r4, r5, r11}
+; LEAF-NOFP-NEXT:    .setfp r11, sp, #8
+; LEAF-NOFP-NEXT:    add r11, sp, #8
+; LEAF-NOFP-NEXT:    .pad #20
+; LEAF-NOFP-NEXT:    sub sp, sp, #20
+; LEAF-NOFP-NEXT:    str r1, [r11, #-16]
+; LEAF-NOFP-NEXT:    mov r1, #7
+; LEAF-NOFP-NEXT:    add r1, r1, r0, lsl #2
+; LEAF-NOFP-NEXT:    str r0, [r11, #-12]
+; LEAF-NOFP-NEXT:    bic r1, r1, #7
+; LEAF-NOFP-NEXT:    str sp, [r11, #-20]
+; LEAF-NOFP-NEXT:    sub sp, sp, r1
+; LEAF-NOFP-NEXT:    mov r1, #0
+; LEAF-NOFP-NEXT:    str r0, [r11, #-28]
+; LEAF-NOFP-NEXT:    str r1, [r11, #-24]
+; LEAF-NOFP-NEXT:    sub sp, r11, #8
+; LEAF-NOFP-NEXT:    pop {r4, r5, r11}
+; LEAF-NOFP-NEXT:    mov pc, lr
+;
+; LEAF-NOFP-AAPCS-LABEL: required_fp:
+; LEAF-NOFP-AAPCS:       @ %bb.0:
+; LEAF-NOFP-AAPCS-NEXT:    .save {r4, r5, r11, lr}
+; LEAF-NOFP-AAPCS-NEXT:    push {r4, r5, r11, lr}
+; LEAF-NOFP-AAPCS-NEXT:    .setfp r11, sp, #8
+; LEAF-NOFP-AAPCS-NEXT:    add r11, sp, #8
+; LEAF-NOFP-AAPCS-NEXT:    .pad #24
+; LEAF-NOFP-AAPCS-NEXT:    sub sp, sp, #24
+; LEAF-NOFP-AAPCS-NEXT:    str r1, [r11, #-16]
+; LEAF-NOFP-AAPCS-NEXT:    mov r1, #7
+; LEAF-NOFP-AAPCS-NEXT:    add r1, r1, r0, lsl #2
+; LEAF-NOFP-AAPCS-NEXT:    str r0, [r11, #-12]
+; LEAF-NOFP-AAPCS-NEXT:    bic r1, r1, #7
+; LEAF-NOFP-AAPCS-NEXT:    str sp, [r11, #-24]
+; LEAF-NOFP-AAPCS-NEXT:    sub sp, sp, r1
+; LEAF-NOFP-AAPCS-NEXT:    mov r1, #0
+; LEAF-NOFP-AAPCS-NEXT:    str r0, [r11, #-32]
+; LEAF-NOFP-AAPCS-NEXT:    str r1, [r11, #-28]
+; LEAF-NOFP-AAPCS-NEXT:    sub sp, r11, #8
+; LEAF-NOFP-AAPCS-NEXT:    pop {r4, r5, r11, lr}
+; LEAF-NOFP-AAPCS-NEXT:    mov pc, lr
+  %3 = alloca i32, align 4
+  %4 = alloca i32, align 4
+  %5 = alloca i8*, align 8
+  %6 = alloca i64, align 8
+  store i32 %0, i32* %3, align 4
+  store i32 %1, i32* %4, align 4
+  %7 = load i32, i32* %3, align 4
+  %8 = zext i32 %7 to i64
+  %9 = call i8* @llvm.stacksave()
+  store i8* %9, i8** %5, align 8
+  %10 = alloca i32, i64 %8, align 4
+  store i64 %8, i64* %6, align 8
+  ret void
+}

llvm/test/CodeGen/Thumb/frame-access.ll

-; RUN: llc -mtriple=thumbv6m-eabi -frame-pointer=none %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv6m-eabi -frame-pointer=none %s -o - --verify-machineinstrs | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP,CHECK-ATPCS
+; RUN: llc -mtriple=thumbv6m-eabi -frame-pointer=all %s -o - --verify-machineinstrs | FileCheck %s --check-prefixes=CHECK,CHECK-FP-ATPCS,CHECK-ATPCS
+; RUN: llc -mtriple=thumbv6m-eabi -frame-pointer=none -mattr=+aapcs-frame-chain-leaf %s -o - --verify-machineinstrs | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP,CHECK-AAPCS
+; RUN: llc -mtriple=thumbv6m-eabi -frame-pointer=all -mattr=+aapcs-frame-chain-leaf %s -o - --verify-machineinstrs | FileCheck %s --check-prefixes=CHECK,CHECK-FP-AAPCS,CHECK-AAPCS
 
 ; struct S { int x[128]; } s;
 ; int f(int *, int, int, int, struct S);
 ; int g(int *, int, int, int, int, int);
 ; int h(int *, int *, int *);
 ; int u(int *, int *, int *, struct S, struct S);
 
 %struct.S = type { [128 x i32] }
 %struct.__va_list = type { i8* }
 
 @s = common dso_local global %struct.S zeroinitializer, align 4
 
 declare void @llvm.va_start(i8*)
+declare dso_local i32 @i(i32) local_unnamed_addr
 declare dso_local i32 @g(i32*, i32, i32, i32, i32, i32) local_unnamed_addr
 declare dso_local i32 @f(i32*, i32, i32, i32, %struct.S* byval(%struct.S) align 4) local_unnamed_addr
 declare dso_local i32 @h(i32*, i32*, i32*) local_unnamed_addr
 declare dso_local i32 @u(i32*, i32*, i32*, %struct.S* byval(%struct.S) align 4, %struct.S* byval(%struct.S) align 4) local_unnamed_addr
 
 ;
 ; Test access to arguments, passed on stack (including varargs)
 ;
 
-; Usual case, access via SP
+; Usual case, access via SP if FP is not available
 ; int test_args_sp(int a, int b, int c, int d, int e) {
 ;   int v[4];
 ;   return g(v, a, b, c, d, e);
 ; }
 define dso_local i32 @test_args_sp(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) local_unnamed_addr {
 entry:
   %v = alloca [4 x i32], align 4
   %0 = bitcast [4 x i32]* %v to i8*
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %call = call i32 @g(i32* nonnull %arraydecay, i32 %a, i32 %b, i32 %c, i32 %d, i32 %e)
   ret i32 %call
 }
 ; CHECK-LABEL: test_args_sp
 ; Load `e`
-; CHECK:       ldr    r0, [sp, #32]
+; CHECK-NOFP: ldr    r0, [sp, #32]
+; CHECK-FP-ATPCS: ldr  r0, [r7, #8]
+; CHECK-FP-AAPCS: mov    r0, r11
+; CHECK-FP-AAPCS: ldr    r0, [r0, #8]
 ; CHECK-NEXT:  str    r3, [sp]
 ; Pass `e` on stack
 ; CHECK-NEXT:  str    r0, [sp, #4]
 ; CHECK:       bl    g
 
 ; int test_varargs_sp(int a, ...) {
 ;   int v[4];
 ;   __builtin_va_list ap;
entry:
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %call = call i32 @g(i32* nonnull %arraydecay, i32 %a, i32 0, i32 0, i32 0, i32 0)
   ret i32 %call
 }
 ; CHECK-LABEL: test_varargs_sp
 ; Three incoming varargs in registers
 ; CHECK:       sub sp, #12
 ; CHECK:       sub sp, #28
-; Incoming arguments area is accessed via SP
-; CHECK:       add r0, sp, #36
-; CHECK:       stm r0!, {r1, r2, r3}
+; Incoming arguments area is accessed via SP if FP is not available
+; CHECK-NOFP:  add r0, sp, #36
+; CHECK-NOFP:  stm r0!, {r1, r2, r3}
+; CHECK-FP-ATPCS: mov r0, r7
+; CHECK-FP-ATPCS: adds r0, #8
+; CHECK-FP-ATPCS: stm r0!, {r1, r2, r3}
+; CHECK-FP-AAPCS: mov r0, r11
+; CHECK-FP-AAPCS: str r1, [r0, #8]
+; CHECK-FP-AAPCS: mov r0, r11
+; CHECK-FP-AAPCS: str r2, [r0, #12]
+; CHECK-FP-AAPCS: mov r0, r11
+; CHECK-FP-AAPCS: str r3, [r0, #16]
 
 ; Re-aligned stack, access via FP
 ; int test_args_realign(int a, int b, int c, int d, int e) {
 ;   __attribute__((aligned(16))) int v[4];
 ;   return g(v, a, b, c, d, e);
 ; }
 ; Function Attrs: nounwind
 define dso_local i32 @test_args_realign(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) local_unnamed_addr  {
 entry:
   %v = alloca [4 x i32], align 16
   %0 = bitcast [4 x i32]* %v to i8*
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %call = call i32 @g(i32* nonnull %arraydecay, i32 %a, i32 %b, i32 %c, i32 %d, i32 %e)
   ret i32 %call
 }
 ; CHECK-LABEL: test_args_realign
 ; Setup frame pointer
-; CHECK:       add r7, sp, #8
+; CHECK-ATPCS: add r7, sp, #8
+; CHECK-AAPCS: mov r11, sp
 ; Align stack
 ; CHECK:       mov  r4, sp
 ; CHECK-NEXT:  lsrs r4, r4, #4
 ; CHECK-NEXT:  lsls r4, r4, #4
 ; CHECK-NEXT:  mov  sp, r4
 ; Load `e` via FP
-; CHECK:       ldr r0, [r7, #8]
+; CHECK-ATPCS: ldr r0, [r7, #8]
+; CHECK-AAPCS: mov r0, r11
+; CHECK-AAPCS: ldr r0, [r0, #8]
 ; CHECK-NEXT:  str r3, [sp]
 ; Pass `e` as argument
 ; CHECK-NEXT:  str r0, [sp, #4]
 ; CHECK:       bl    g
 
 ; int test_varargs_realign(int a, ...) {
 ;   __attribute__((aligned(16))) int v[4];
 ;   __builtin_va_list ap;
entry:
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %call = call i32 @g(i32* nonnull %arraydecay, i32 %a, i32 0, i32 0, i32 0, i32 0)
   ret i32 %call
 }
 ; CHECK-LABEL: test_varargs_realign
 ; Three incoming register varargs
 ; CHECK:       sub sp, #12
 ; Setup frame pointer
-; CHECK:       add r7, sp, #8
+; CHECK-ATPCS: add r7, sp, #8
+; CHECK-AAPCS: mov r11, sp
 ; Align stack
 ; CHECK:       mov  r4, sp
 ; CHECK-NEXT:  lsrs r4, r4, #4
 ; CHECK-NEXT:  lsls r4, r4, #4
 ; CHECK-NEXT:  mov  sp, r4
 ; Incoming register varargs stored via FP
-; CHECK:      mov r0, r7
-; CHECK-NEXT: adds r0, #8
-; CHECK-NEXT: stm r0!, {r1, r2, r3}
+; CHECK-ATPCS: mov r0, r7
+; CHECK-ATPCS-NEXT: adds r0, #8
+; CHECK-ATPCS-NEXT: stm r0!, {r1, r2, r3}
+; CHECK-AAPCS: mov r0, r11
+; CHECK-AAPCS: str r1, [r0, #8]
+; CHECK-AAPCS: mov r0, r11
+; CHECK-AAPCS: str r2, [r0, #12]
+; CHECK-AAPCS: mov r0, r11
+; CHECK-AAPCS: str r3, [r0, #16]
 ; VLAs present, access via FP
 ; int test_args_vla(int a, int b, int c, int d, int e) {
 ;   int v[a];
 ;   return g(v, a, b, c, d, e);
 ; }
 define dso_local i32 @test_args_vla(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) local_unnamed_addr  {
 entry:
   %vla = alloca i32, i32 %a, align 4
   %call = call i32 @g(i32* nonnull %vla, i32 %a, i32 %b, i32 %c, i32 %d, i32 %e)
   ret i32 %call
 }
 ; CHECK-LABEL: test_args_vla
 ; Setup frame pointer
-; CHECK:       add r7, sp, #12
+; CHECK-ATPCS: add r7, sp, #12
+; CHECK-AAPCS: mov r11, sp
 ; Allocate outgoing stack arguments space
-; CHECK:       sub sp, #4
+; CHECK:       sub sp, #8
 ; Load `e` via FP
-; CHECK:       ldr r5, [r7, #8]
+; CHECK-ATPCS: ldr r5, [r7, #8]
+; CHECK-AAPCS: mov r5, r11
+; CHECK-AAPCS: ldr r5, [r5, #8]
 ; Pass `d` and `e` as arguments
 ; CHECK-NEXT:  str r3, [sp]
 ; CHECK-NEXT:  str r5, [sp, #4]
 ; CHECK:       bl  g
 
 ; int test_varargs_vla(int a, ...) {
 ;   int v[a];
 ;   __builtin_va_list ap;
 ;   __builtin_va_start(ap, a);
 ;   return g(v, a, 0, 0, 0, 0);
 ; }
 define dso_local i32 @test_varargs_vla(i32 %a, ...) local_unnamed_addr  {
 entry:
   %ap = alloca %struct.__va_list, align 4
   %vla = alloca i32, i32 %a, align 4
   %0 = bitcast %struct.__va_list* %ap to i8*
   call void @llvm.va_start(i8* nonnull %0)
   %call = call i32 @g(i32* nonnull %vla, i32 %a, i32 0, i32 0, i32 0, i32 0)
   ret i32 %call
 }
 ; CHECK-LABEL: test_varargs_vla
 ; Three incoming register varargs
 ; CHECK:       sub sp, #12
 ; Setup frame pointer
-; CHECK:       add r7, sp, #8
+; CHECK-ATPCS: add r7, sp, #8
+; CHECK-AAPCS: mov r11, sp
 ; Register varargs stored via FP
-; CHECK-DAG:  str r3, [r7, #16]
-; CHECK-DAG:  str r2, [r7, #12]
-; CHECK-DAG:  str r1, [r7, #8]
+; CHECK-ATPCS-DAG:  str r3, [r7, #16]
+; CHECK-ATPCS-DAG:  str r2, [r7, #12]
+; CHECK-ATPCS-DAG:  str r1, [r7, #8]
+; CHECK-AAPCS-DAG:  mov r5, r11
+; CHECK-AAPCS-DAG:  str r1, [r5, #8]
+; CHECK-AAPCS-DAG:  mov r1, r11
+; CHECK-AAPCS-DAG:  str r3, [r1, #16]
+; CHECK-AAPCS-DAG:  mov r1, r11
+; CHECK-AAPCS-DAG:  str r2, [r1, #12]
 
 ; Moving SP, access via SP
 ; int test_args_moving_sp(int a, int b, int c, int d, int e) {
 ;   int v[4];
 ;   return f(v, a, b + c + d, e, s) + h(v, v+1, v+2);
 ; }
 define dso_local i32 @test_args_moving_sp(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) local_unnamed_addr  {
 entry:
   %v = alloca [4 x i32], align 4
   %0 = bitcast [4 x i32]* %v to i8*
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %add = add nsw i32 %c, %b
   %add1 = add nsw i32 %add, %d
   %call = call i32 @f(i32* nonnull %arraydecay, i32 %a, i32 %add1, i32 %e, %struct.S* byval(%struct.S) nonnull align 4 @s)
   %add.ptr = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 1
   %add.ptr5 = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 2
   %call6 = call i32 @h(i32* nonnull %arraydecay, i32* nonnull %add.ptr, i32* nonnull %add.ptr5)
   %add7 = add nsw i32 %call6, %call
   ret i32 %add7
 }
 ; CHECK-LABEL: test_args_moving_sp
-; 20 bytes callee-saved area
-; CHECK:       push {r4, r5, r6, r7, lr}
-; 20 bytes locals
-; CHECK:       sub sp, #20
+; 20 bytes callee-saved area without FP
+; CHECK-NOFP: push {r4, r5, r6, r7, lr}
+; 20 bytes callee-saved area for ATPCS
+; CHECK-FP-ATPCS: push {r4, r5, r6, r7, lr}
+; 24 bytes callee-saved area for AAPCS as codegen prefers an even number of GPRs spilled
+; CHECK-FP-AAPCS: push {lr}
+; CHECK-FP-AAPCS: mov lr, r11
+; CHECK-FP-AAPCS: push {lr}
+; CHECK-FP-AAPCS: push {r4, r5, r6, r7}
+; 20 bytes locals without FP
+; CHECK-NOFP:       sub sp, #20
+; 28 bytes locals with FP for ATPCS
+; CHECK-FP-ATPCS:       sub sp, #28
+; 24 bytes locals with FP for AAPCS
+; CHECK-FP-AAPCS:       sub sp, #24
 ; Setup base pointer
 ; CHECK:       mov r6, sp
 ; Allocate outgoing arguments space
 ; CHECK:       sub sp, #508
 ; CHECK:       sub sp, #4
-; Load `e` via BP, 40 = 20 + 20
-; CHECK:       ldr r3, [r6, #40]
+; Load `e` via BP if FP is not present (40 = 20 + 20)
+; CHECK-NOFP:  ldr r3, [r6, #40]
+; Load `e` via FP otherwise
+; CHECK-FP-ATPCS: ldr r3, [r7, #8]
+; CHECK-FP-AAPCS: mov r0, r11
+; CHECK-FP-AAPCS: ldr r3, [r0, #8]
 ; CHECK:       bl  f
 ; Stack restored before next call
 ; CHECK-NEXT:  add sp, #508
 ; CHECK-NEXT:  add sp, #4
 ; CHECK:       bl  h
 
 ; int test_varargs_moving_sp(int a, ...) {
 ;   int v[4];
entry:
   %add.ptr5 = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 2
   %call6 = call i32 @h(i32* nonnull %arraydecay, i32* nonnull %add.ptr, i32* nonnull %add.ptr5)
   %add = add nsw i32 %call6, %call
   ret i32 %add
 }
 ; CHECK-LABEL: test_varargs_moving_sp
 ; Three incoming register varargs
 ; CHECK:       sub sp, #12
-; 16 bytes callee-saves
-; CHECK:       push {r4, r5, r6, lr}
-; 20 bytes locals
-; CHECK:       sub sp, #20
-; Incoming varargs stored via BP, 36 = 20 + 16
-; CHECK:       mov r0, r6
-; CHECK-NEXT:  adds r0, #36
-; CHECK-NEXT:  stm r0!, {r1, r2, r3}
+; 16 bytes callee-saves without FP
+; CHECK-NOFP: push {r4, r5, r6, lr}
+; 24 bytes callee-saves with FP
+; CHECK-FP-ATPCS: push {r4, r5, r6, r7, lr}
+; CHECK-FP-AAPCS: push {lr}
+; CHECK-FP-AAPCS: mov lr, r11
+; CHECK-FP-AAPCS: push {lr}
+; CHECK-FP-AAPCS: push {r4, r5, r6, r7}
+; Locals area
+; CHECK-NOFP:       sub sp, #20
+; CHECK-FP-ATPCS:   sub sp, #24
+; CHECK-FP-AAPCS:   sub sp, #20
+; Incoming varargs stored via BP if FP is not present (36 = 20 + 16)
+; CHECK-NOFP:      mov r0, r6
+; CHECK-NOFP-NEXT: adds r0, #36
+; CHECK-NOFP-NEXT: stm r0!, {r1, r2, r3}
+; Incoming varargs stored via FP otherwise
+; CHECK-FP-ATPCS:      mov r0, r7
+; CHECK-FP-ATPCS-NEXT: adds r0, #8
+; CHECK-FP-ATPCS-NEXT: stm r0!, {r1, r2, r3}
+; CHECK-FP-AAPCS:      mov r0, r11
+; CHECK-FP-AAPCS-NEXT: str r1, [r0, #8]
+; CHECK-FP-AAPCS-NEXT: mov r0, r11
+; CHECK-FP-AAPCS-NEXT: str r2, [r0, #12]
+; CHECK-FP-AAPCS-NEXT: mov r0, r11
+; CHECK-FP-AAPCS-NEXT: str r3, [r0, #16]
+
+; struct S { int x[128]; } s;
+; int test(S a, int b) {
+;   return i(b);
+; }
+define dso_local i32 @test_args_large_offset(%struct.S* byval(%struct.S) align 4 %0, i32 %1) local_unnamed_addr {
+  %3 = alloca i32, align 4
+  store i32 %1, i32* %3, align 4
+  %4 = load i32, i32* %3, align 4
+  %5 = call i32 @i(i32 %4)
+  ret i32 %5
+}
+; CHECK-LABEL: test_args_large_offset
+; Without FP: Access to large offset is made using SP
+; CHECK-NOFP:     ldr r0, [sp, #520]
+; With FP: Access to large offset is made through a const pool using FP
+; CHECK-FP:       ldr r0, .LCPI0_0
+; CHECK-FP-ATPCS: ldr r0, [r0, r7]
+; CHECK-FP-AAPCS: add r0, r11
+; CHECK-FP-AAPCS: ldr r0, [r0]
+; CHECK: bl i
 
 ;
 ; Access to locals
 ;
 
 ; Usual case, access via SP.
 ; int test_local(int n) {
 ;   int v[4];
entry:
   %4 = load i32, i32* %x, align 4
   %5 = load i32, i32* %y, align 4
   %6 = load i32, i32* %z, align 4
   %call1 = call i32 @g(i32* nonnull %arraydecay, i32 %4, i32 %5, i32 %6, i32 0, i32 0)
   ret i32 %call1
 }
 ; CHECK-LABEL: test_local_realign
 ; Setup frame pointer
-; CHECK:       add r7, sp, #8
+; CHECK-ATPCS: add r7, sp, #8
+; CHECK-AAPCS: mov r11, sp
 ; Re-align stack
 ; CHECK:       mov r4, sp
 ; CHECK-NEXT:  lsrs r4, r4, #4
 ; CHECK-NEXT:  lsls r4, r4, #4
 ; CHECK-NEXT:  mov  sp, r4
 ; Arguments to `h` computed relative to SP
 ; CHECK:       add r0, sp, #28
 ; CHECK-NEXT:  add r1, sp, #24
entry:
   %3 = load i32, i32* %x, align 4
   %4 = load i32, i32* %y, align 4
   %5 = load i32, i32* %z, align 4
   %call1 = call i32 @g(i32* nonnull %vla, i32 %3, i32 %4, i32 %5, i32 0, i32 0)
   ret i32 %call1
 }
 ; CHECK-LABEL: test_local_vla
 ; Setup frame pointer
-; CHECK:       add  r7, sp, #12
+; CHECK-ATPCS: add r7, sp, #12
+; CHECK-AAPCS: mov r11, sp
+; Locas area
+; CHECK-ATPCS: sub sp, #12
+; CHECK-AAPCS: sub sp, #16
 ; Setup base pointer
 ; CHECK:       mov  r6, sp
-; CHECK:       mov  r5, r6
+; CHECK-ATPCS: mov  r5, r6
+; CHECK-AAPCS: adds  r5, r6, #4
 ; Arguments to `h` compute relative to BP
 ; CHECK:       adds r0, r6, #7
-; CHECK-NEXT:  adds r0, #1
-; CHECK-NEXT:  adds r1, r6, #4
-; CHECK-NEXT:  mov  r2, r6
+; CHECK-ATPCS-NEXT:  adds r0, #1
+; CHECK-ATPCS-NEXT:  adds r1, r6, #4
+; CHECK-ATPCS-NEXT:  mov  r2, r6
+; CHECK-AAPCS-NEXT:  adds r0, #5
+; CHECK-AAPCS-NEXT:  adds r1, r6, #7
+; CHECK-AAPCS-NEXT:  adds r1, #1
+; CHECK-AAPCS-NEXT:  adds r2, r6, #4
 ; CHECK-NEXT:  bl   h
 ; Load `x`, `y`, `z` via BP (r5 should still have the value of r6 from the move
 ; above)
 ; CHECK:       ldr r3, [r5]
 ; CHECK-NEXT:  ldr r2, [r5, #4]
 ; CHECK-NEXT:  ldr r1, [r5, #8]
 ; CHECK:       bl  g
 
entry:
   %arraydecay = getelementptr inbounds [4 x i32], [4 x i32]* %v, i32 0, i32 0
   %call = call i32 @u(i32* nonnull %arraydecay, i32* nonnull %x, i32* nonnull %y, %struct.S* byval(%struct.S) nonnull align 4 @s, %struct.S* byval(%struct.S) nonnull align 4 @s)
   %call2 = call i32 @u(i32* nonnull %arraydecay, i32* nonnull %y, i32* nonnull %z, %struct.S* byval(%struct.S) nonnull align 4 @s, %struct.S* byval(%struct.S) nonnull align 4 @s)
   %add = add nsw i32 %call2, %call
   ret i32 %add
 }
 ; CHECK-LABEL: test_local_moving_sp
 ; Locals area
-; CHECK:      sub sp, #36
+; CHECK-NOFP: sub sp, #36
+; CHECK-FP-ATPCS: sub sp, #44
+; CHECK-FP-AAPCS: sub sp, #40
 ; Setup BP
 ; CHECK:      mov r6, sp
 ; Outoging arguments
 ; CHECK:      sub sp, #508
 ; CHECK-NEXT: sub sp, #508
 ; CHECK-NEXT: sub sp, #8
 ; Argument addresses computed relative to BP
-; CHECK:      adds r4, r6, #7
-; CHECK-NEXT: adds r4, #13
-; CHECK:      adds r1, r6, #7
-; CHECK-NEXT: adds r1, #9
-; CHECK:      adds r5, r6, #7
-; CHECK-NEXT: adds r5, #5
+; CHECK-NOFP:      adds r4, r6, #7
+; CHECK-NOFP-NEXT: adds r4, #13
+; CHECK-NOFP:      adds r1, r6, #7
+; CHECK-NOFP-NEXT: adds r1, #9
+; CHECK-NOFP:      adds r5, r6, #7
+; CHECK-NOFP-NEXT: adds r5, #5
+; CHECK-FP-ATPCS:      adds r0, r6, #7
+; CHECK-FP-ATPCS-NEXT: adds r0, #21
+; CHECK-FP-ATPCS:      adds r1, r6, #7
+; CHECK-FP-ATPCS-NEXT: adds r1, #17
+; CHECK-FP-ATPCS:      adds r5, r6, #7
+; CHECK-FP-ATPCS-NEXT: adds r5, #13
+; CHECK-FP-AAPCS:      adds r4, r6, #7
+; CHECK-FP-AAPCS-NEXT: adds r4, #17
+; CHECK-FP-AAPCS:      adds r1, r6, #7
+; CHECK-FP-AAPCS-NEXT: adds r1, #13
+; CHECK-FP-AAPCS:      adds r5, r6, #7
+; CHECK-FP-AAPCS-NEXT: adds r5, #9
 ; CHECK:      bl   u
 ; Stack restored before next call
 ; CHECK:      add  sp, #508
 ; CHECK-NEXT: add  sp, #508
 ; CHECK-NEXT: add  sp, #8
 ; CHECK:      bl   u

llvm/test/CodeGen/Thumb/frame-chain-reserved-fp.ll

+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=all 2>&1 | FileCheck %s --check-prefix=RESERVED-R7
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-NONE
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=none 2>&1 | FileCheck %s --check-prefix=RESERVED-NONE
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+; RUN: not llc -mtriple thumbv6m-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain-leaf 2>&1 | FileCheck %s --check-prefix=RESERVED-R11
+
+declare void @leaf(i32 %input)
+
+define void @reserved_r7(i32 %input) {
+; RESERVED-NONE-NOT: error: write to reserved register 'R7'
+; RESERVED-R7: error: write to reserved register 'R7'
+; RESERVED-R11-NOT: error: write to reserved register 'R7'
+  %1 = call i32 asm sideeffect "mov $0, $1", "={r7},r"(i32 %input)
+  ret void
+}
+
+define void @reserved_r11(i32 %input) {
+; RESERVED-NONE-NOT: error: write to reserved register 'R11'
+; RESERVED-R7-NOT: error: write to reserved register 'R11'
+; RESERVED-R11: error: write to reserved register 'R11'
+  %1 = call i32 asm sideeffect "mov $0, $1", "={r11},r"(i32 %input)
+  ret void
+}

llvm/test/CodeGen/Thumb/frame-chain.ll

+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=all | FileCheck %s --check-prefixes=FP,LEAF-FP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-FP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=all -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-FP-AAPCS
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf | FileCheck %s --check-prefixes=FP,LEAF-NOFP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-NOFP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=non-leaf -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=FP-AAPCS,LEAF-NOFP-AAPCS
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=none | FileCheck %s --check-prefixes=NOFP,LEAF-NOFP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain | FileCheck %s --check-prefixes=NOFP-AAPCS,LEAF-NOFP
+; RUN: llc -mtriple thumb-arm-none-eabi -filetype asm -o - %s -frame-pointer=none -mattr=+aapcs-frame-chain-leaf | FileCheck %s --check-prefixes=NOFP-AAPCS,LEAF-NOFP-AAPCS
+
+define dso_local noundef i32 @leaf(i32 noundef %0) {
+; LEAF-FP-LABEL: leaf:
+; LEAF-FP:       @ %bb.0:
+; LEAF-FP-NEXT:    .pad #4
+; LEAF-FP-NEXT:    sub sp, #4
+; LEAF-FP-NEXT:    str r0, [sp]
+; LEAF-FP-NEXT:    adds r0, r0, #4
+; LEAF-FP-NEXT:    add sp, #4
+; LEAF-FP-NEXT:    bx lr
+;
+; LEAF-FP-AAPCS-LABEL: leaf:
+; LEAF-FP-AAPCS:       @ %bb.0:
+; LEAF-FP-AAPCS-NEXT:    .save {lr}
+; LEAF-FP-AAPCS-NEXT:    push {lr}
+; LEAF-FP-AAPCS-NEXT:    mov lr, r11
+; LEAF-FP-AAPCS-NEXT:    .save {r11}
+; LEAF-FP-AAPCS-NEXT:    push {lr}
+; LEAF-FP-AAPCS-NEXT:    .setfp r11, sp
+; LEAF-FP-AAPCS-NEXT:    mov r11, sp
+; LEAF-FP-AAPCS-NEXT:    .pad #4
+; LEAF-FP-AAPCS-NEXT:    sub sp, #4
+; LEAF-FP-AAPCS-NEXT:    str r0, [sp]
+; LEAF-FP-AAPCS-NEXT:    adds r0, r0, #4
+; LEAF-FP-AAPCS-NEXT:    add sp, #4
+; LEAF-FP-AAPCS-NEXT:    pop {r1}
+; LEAF-FP-AAPCS-NEXT:    mov r11, r1
+; LEAF-FP-AAPCS-NEXT:    pop {r1}
+; LEAF-FP-AAPCS-NEXT:    bx r1
+;
+; LEAF-NOFP-LABEL: leaf:
+; LEAF-NOFP:       @ %bb.0:
+; LEAF-NOFP-NEXT:    .pad #4
+; LEAF-NOFP-NEXT:    sub sp, #4
+; LEAF-NOFP-NEXT:    str r0, [sp]
+; LEAF-NOFP-NEXT:    adds r0, r0, #4
+; LEAF-NOFP-NEXT:    add sp, #4
+; LEAF-NOFP-NEXT:    bx lr
+;
+; LEAF-NOFP-AAPCS-LABEL: leaf:
+; LEAF-NOFP-AAPCS:       @ %bb.0:
+; LEAF-NOFP-AAPCS-NEXT:    .pad #4
+; LEAF-NOFP-AAPCS-NEXT:    sub sp, #4
+; LEAF-NOFP-AAPCS-NEXT:    str r0, [sp]
+; LEAF-NOFP-AAPCS-NEXT:    adds r0, r0, #4
+; LEAF-NOFP-AAPCS-NEXT:    add sp, #4
+; LEAF-NOFP-AAPCS-NEXT:    bx lr
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = add nsw i32 %3, 4
+  ret i32 %4
+}
+
+define dso_local noundef i32 @non_leaf(i32 noundef %0) {
+; FP-LABEL: non_leaf:
+; FP:       @ %bb.0:
+; FP-NEXT:    .save {r7, lr}
+; FP-NEXT:    push {r7, lr}
+; FP-NEXT:    .setfp r7, sp
+; FP-NEXT:    add r7, sp, #0
+; FP-NEXT:    .pad #8
+; FP-NEXT:    sub sp, #8
+; FP-NEXT:    str r0, [sp, #4]
+; FP-NEXT:    bl leaf
+; FP-NEXT:    adds r0, r0, #1
+; FP-NEXT:    add sp, #8
+; FP-NEXT:    pop {r7}
+; FP-NEXT:    pop {r1}
+; FP-NEXT:    bx r1
+;
+; FP-AAPCS-LABEL: non_leaf:
+; FP-AAPCS:       @ %bb.0:
+; FP-AAPCS-NEXT:    .save {lr}
+; FP-AAPCS-NEXT:    push {lr}
+; FP-AAPCS-NEXT:    mov lr, r11
+; FP-AAPCS-NEXT:    .save {r11}
+; FP-AAPCS-NEXT:    push {lr}
+; FP-AAPCS-NEXT:    .setfp r11, sp
+; FP-AAPCS-NEXT:    mov r11, sp
+; FP-AAPCS-NEXT:    .pad #8
+; FP-AAPCS-NEXT:    sub sp, #8
+; FP-AAPCS-NEXT:    str r0, [sp, #4]
+; FP-AAPCS-NEXT:    bl leaf
+; FP-AAPCS-NEXT:    adds r0, r0, #1
+; FP-AAPCS-NEXT:    add sp, #8
+; FP-AAPCS-NEXT:    pop {r1}
+; FP-AAPCS-NEXT:    mov r11, r1
+; FP-AAPCS-NEXT:    pop {r1}
+; FP-AAPCS-NEXT:    bx r1
+;
+; NOFP-LABEL: non_leaf:
+; NOFP:       @ %bb.0:
+; NOFP-NEXT:    .save {r7, lr}
+; NOFP-NEXT:    push {r7, lr}
+; NOFP-NEXT:    .pad #8
+; NOFP-NEXT:    sub sp, #8
+; NOFP-NEXT:    str r0, [sp, #4]
+; NOFP-NEXT:    bl leaf
+; NOFP-NEXT:    adds r0, r0, #1
+; NOFP-NEXT:    add sp, #8
+; NOFP-NEXT:    pop {r7}
+; NOFP-NEXT:    pop {r1}
+; NOFP-NEXT:    bx r1
+;
+; NOFP-AAPCS-LABEL: non_leaf:
+; NOFP-AAPCS:       @ %bb.0:
+; NOFP-AAPCS-NEXT:    .save {r7, lr}
+; NOFP-AAPCS-NEXT:    push {r7, lr}
+; NOFP-AAPCS-NEXT:    .pad #8
+; NOFP-AAPCS-NEXT:    sub sp, #8
+; NOFP-AAPCS-NEXT:    str r0, [sp, #4]
+; NOFP-AAPCS-NEXT:    bl leaf
+; NOFP-AAPCS-NEXT:    adds r0, r0, #1
+; NOFP-AAPCS-NEXT:    add sp, #8
+; NOFP-AAPCS-NEXT:    pop {r7}
+; NOFP-AAPCS-NEXT:    pop {r1}
+; NOFP-AAPCS-NEXT:    bx r1
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = call noundef i32 @leaf(i32 noundef %3)
+  %5 = add nsw i32 %4, 1
+  ret i32 %5
+}
+
+declare i8* @llvm.stacksave()
+define dso_local void @required_fp(i32 %0, i32 %1) {
+; FP-LABEL: required_fp:
+; FP:       @ %bb.0:
+; FP-NEXT:    .save {r4, r6, r7, lr}
+; FP-NEXT:    push {r4, r6, r7, lr}
+; FP-NEXT:    .setfp r7, sp, #8
+; FP-NEXT:    add r7, sp, #8
+; FP-NEXT:    .pad #24
+; FP-NEXT:    sub sp, #24
+; FP-NEXT:    mov r6, sp
+; FP-NEXT:    mov r2, r6
+; FP-NEXT:    str r1, [r2, #16]
+; FP-NEXT:    str r0, [r2, #20]
+; FP-NEXT:    mov r1, sp
+; FP-NEXT:    str r1, [r2, #8]
+; FP-NEXT:    lsls r1, r0, #2
+; FP-NEXT:    adds r1, r1, #7
+; FP-NEXT:    movs r3, #7
+; FP-NEXT:    bics r1, r3
+; FP-NEXT:    mov r3, sp
+; FP-NEXT:    subs r1, r3, r1
+; FP-NEXT:    mov sp, r1
+; FP-NEXT:    movs r1, #0
+; FP-NEXT:    str r1, [r6, #4]
+; FP-NEXT:    str r0, [r2]
+; FP-NEXT:    subs r4, r7, #7
+; FP-NEXT:    subs r4, #1
+; FP-NEXT:    mov sp, r4
+; FP-NEXT:    pop {r4, r6, r7}
+; FP-NEXT:    pop {r0}
+; FP-NEXT:    bx r0
+;
+; FP-AAPCS-LABEL: required_fp:
+; FP-AAPCS:       @ %bb.0:
+; FP-AAPCS-NEXT:    .save {lr}
+; FP-AAPCS-NEXT:    push {lr}
+; FP-AAPCS-NEXT:    mov lr, r11
+; FP-AAPCS-NEXT:    .save {r11}
+; FP-AAPCS-NEXT:    push {lr}
+; FP-AAPCS-NEXT:    .setfp r11, sp
+; FP-AAPCS-NEXT:    mov r11, sp
+; FP-AAPCS-NEXT:    .save {r4, r6}
+; FP-AAPCS-NEXT:    push {r4, r6}
+; FP-AAPCS-NEXT:    .pad #24
+; FP-AAPCS-NEXT:    sub sp, #24
+; FP-AAPCS-NEXT:    mov r6, sp
+; FP-AAPCS-NEXT:    mov r2, r6
+; FP-AAPCS-NEXT:    str r1, [r2, #16]
+; FP-AAPCS-NEXT:    str r0, [r2, #20]
+; FP-AAPCS-NEXT:    mov r1, sp
+; FP-AAPCS-NEXT:    str r1, [r2, #8]
+; FP-AAPCS-NEXT:    lsls r1, r0, #2
+; FP-AAPCS-NEXT:    adds r1, r1, #7
+; FP-AAPCS-NEXT:    movs r3, #7
+; FP-AAPCS-NEXT:    bics r1, r3
+; FP-AAPCS-NEXT:    mov r3, sp
+; FP-AAPCS-NEXT:    subs r1, r3, r1
+; FP-AAPCS-NEXT:    mov sp, r1
+; FP-AAPCS-NEXT:    movs r1, #0
+; FP-AAPCS-NEXT:    str r1, [r6, #4]
+; FP-AAPCS-NEXT:    str r0, [r2]
+; FP-AAPCS-NEXT:    mov r4, r11
+; FP-AAPCS-NEXT:    subs r4, #8
+; FP-AAPCS-NEXT:    mov sp, r4
+; FP-AAPCS-NEXT:    pop {r4, r6}
+; FP-AAPCS-NEXT:    pop {r0}
+; FP-AAPCS-NEXT:    mov r11, r0
+; FP-AAPCS-NEXT:    pop {r0}
+; FP-AAPCS-NEXT:    bx r0
+;
+; NOFP-LABEL: required_fp:
+; NOFP:       @ %bb.0:
+; NOFP-NEXT:    .save {r4, r6, r7, lr}
+; NOFP-NEXT:    push {r4, r6, r7, lr}
+; NOFP-NEXT:    .setfp r7, sp, #8
+; NOFP-NEXT:    add r7, sp, #8
+; NOFP-NEXT:    .pad #24
+; NOFP-NEXT:    sub sp, #24
+; NOFP-NEXT:    mov r6, sp
+; NOFP-NEXT:    mov r2, r6
+; NOFP-NEXT:    str r1, [r2, #16]
+; NOFP-NEXT:    str r0, [r2, #20]
+; NOFP-NEXT:    mov r1, sp
+; NOFP-NEXT:    str r1, [r2, #8]
+; NOFP-NEXT:    lsls r1, r0, #2
+; NOFP-NEXT:    adds r1, r1, #7
+; NOFP-NEXT:    movs r3, #7
+; NOFP-NEXT:    bics r1, r3
+; NOFP-NEXT:    mov r3, sp
+; NOFP-NEXT:    subs r1, r3, r1
+; NOFP-NEXT:    mov sp, r1
+; NOFP-NEXT:    movs r1, #0
+; NOFP-NEXT:    str r1, [r6, #4]
+; NOFP-NEXT:    str r0, [r2]
+; NOFP-NEXT:    subs r4, r7, #7
+; NOFP-NEXT:    subs r4, #1
+; NOFP-NEXT:    mov sp, r4
+; NOFP-NEXT:    pop {r4, r6, r7}
+; NOFP-NEXT:    pop {r0}
+; NOFP-NEXT:    bx r0
+;
+; NOFP-AAPCS-LABEL: required_fp:
+; NOFP-AAPCS:       @ %bb.0:
+; NOFP-AAPCS-NEXT:    .save {lr}
+; NOFP-AAPCS-NEXT:    push {lr}
+; NOFP-AAPCS-NEXT:    mov lr, r11
+; NOFP-AAPCS-NEXT:    .save {r11}
+; NOFP-AAPCS-NEXT:    push {lr}
+; NOFP-AAPCS-NEXT:    .setfp r11, sp
+; NOFP-AAPCS-NEXT:    mov r11, sp
+; NOFP-AAPCS-NEXT:    .save {r4, r6}
+; NOFP-AAPCS-NEXT:    push {r4, r6}
+; NOFP-AAPCS-NEXT:    .pad #24
+; NOFP-AAPCS-NEXT:    sub sp, #24
+; NOFP-AAPCS-NEXT:    mov r6, sp
+; NOFP-AAPCS-NEXT:    mov r2, r6
+; NOFP-AAPCS-NEXT:    str r1, [r2, #16]
+; NOFP-AAPCS-NEXT:    str r0, [r2, #20]
+; NOFP-AAPCS-NEXT:    mov r1, sp
+; NOFP-AAPCS-NEXT:    str r1, [r2, #8]
+; NOFP-AAPCS-NEXT:    lsls r1, r0, #2
+; NOFP-AAPCS-NEXT:    adds r1, r1, #7
+; NOFP-AAPCS-NEXT:    movs r3, #7
+; NOFP-AAPCS-NEXT:    bics r1, r3
+; NOFP-AAPCS-NEXT:    mov r3, sp
+; NOFP-AAPCS-NEXT:    subs r1, r3, r1
+; NOFP-AAPCS-NEXT:    mov sp, r1
+; NOFP-AAPCS-NEXT:    movs r1, #0
+; NOFP-AAPCS-NEXT:    str r1, [r6, #4]
+; NOFP-AAPCS-NEXT:    str r0, [r2]
+; NOFP-AAPCS-NEXT:    mov r4, r11
+; NOFP-AAPCS-NEXT:    subs r4, #8
+; NOFP-AAPCS-NEXT:    mov sp, r4
+; NOFP-AAPCS-NEXT:    pop {r4, r6}
+; NOFP-AAPCS-NEXT:    pop {r0}
+; NOFP-AAPCS-NEXT:    mov r11, r0
+; NOFP-AAPCS-NEXT:    pop {r0}
+; NOFP-AAPCS-NEXT:    bx r0
+  %3 = alloca i32, align 4
+  %4 = alloca i32, align 4
+  %5 = alloca i8*, align 8
+  %6 = alloca i64, align 8
+  store i32 %0, i32* %3, align 4
+  store i32 %1, i32* %4, align 4
+  %7 = load i32, i32* %3, align 4
+  %8 = zext i32 %7 to i64
+  %9 = call i8* @llvm.stacksave()
+  store i8* %9, i8** %5, align 8
+  %10 = alloca i32, i64 %8, align 4
+  store i64 %8, i64* %6, align 8
+  ret void
+}