Enable Shrink Wrapping for PPC64.

[kbarton]

Summary

This patch will enable the shrink wrapping optimization for PPC64.

The changes in this patch are as follows:

1. Modify the emitPrologue and emitEpilogue methods to work properly when the prologue and epilogue blocks are not the first/last blocks in the function
2. Fix a bug in PPCEarlyReturn optimization caused by an empty entry block in the function
3. Override the runShrinkWrap PredicateFtor (defined in TargetMachine) to check whether shrink wrapping should run:
   • Shrink wrapping will run on PPC64 (Little Endian and Big Endian) unless -enable-shrink-wrap=false is specified on command line

A new test case, ppc-shrink-wrapping.ll was created based on the existing shrink wrapping tests for x86, arm, and arm64.

[hfinkel]

lib/Target/PowerPC/PPCFrameLowering.cpp

1002–1025

Does RB stand for Return Block? Please use a more verbose name.

lib/Target/PowerPC/PPCTargetMachine.cpp

384

Don't add a dependency on EnableShrinkWrapOpt here. We would need to duplicate this checking logic in every target, and that's not a good design. (and the command-line argument itself is an internal detail of ShrinkWrap.cpp). Please have the code in ShrinkWrap.cpp (or Passes.cpp) check this before calling the target specific callback.

[kbarton]

Addressed Hal's comments.

[hfinkel]

lib/Target/PowerPC/PPCTargetMachine.cpp

383

This is also not the right place for this logic. Please address my feedback here:

http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150810/292978.html

and then we can move forward with this.

[kbarton]

lib/Target/PowerPC/PPCTargetMachine.cpp

383

I've made these changed and posted in a new review: http://reviews.llvm.org/D12293

[kbarton]

Changed the interface to override the new TargetFrameLowering::enableShrinkWrapping method defined in http://reviews.llvm.org/D12293.

[hfinkel]

LGTM.

[kbarton]

Committed revision 247237.

[chapuni]

Seems it might trigger crash in CodeGen/PowerPC/remap-crash.ll .
Investigating. I reproduced the crash on i686-linux (compiled with -m32).

See also

• http://bb.pgr.jp/builders/ninja-x64-msvc-RA-centos6
• http://bb.pgr.jp/builders/clang-3stage-i686-linux

FYI, I used the patch to catch crash.

--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -866,6 +866,12 @@ void MachineInstr::addMemOperand(MachineFunction &MF,

 bool MachineInstr::hasPropertyInBundle(unsigned Mask, QueryType Type) const {
   assert(!isBundledWithPred() && "Must be called on bundle header");
+  if (const auto MBB = getParent()) {
+    const auto MF = MBB->getParent();
+    if (MF) {
+      assert(&MF->getSubtarget());
+    }
+  }
   for (MachineBasicBlock::const_instr_iterator MII = this;; ++MII) {
     if (MII->getDesc().getFlags() & Mask) {
       if (Type == AnyInBundle)

[chapuni]

lib/Target/PowerPC/PPCFrameLowering.cpp

1002–1025

It is unsafe if MBBI points end iterator.
Tweaked in r247395. Please reconfirm.

lib/CodeGen/ShrinkWrap.cpp

if (Save && Restore && Save != Restore &&
           break;
         }
       }      
     }
   }
 }
 
 bool ShrinkWrap::runOnMachineFunction(MachineFunction &MF) {
+  // If Shrink wrapping has been explicitly disabled on the command line, do not
+  // run regardless of target-specific overrides 
+  if (EnableShrinkWrapOpt == cl::BOU_FALSE)
+    return false;
+
   if (PredicateFtor && !PredicateFtor(MF)) 
     return false;
-  
   if (MF.empty() || skipOptnoneFunction(*MF.getFunction()))
     return false;
 
   DEBUG(dbgs() << "**** Analysing " << MF.getName() << '\n');
 
   init(MF);
 
   for (MachineBasicBlock &MBB : MF) {

lib/Target/PowerPC/PPCEarlyReturn.cpp

bool processBlock(MachineBasicBlock &ReturnMBB) {
           (I->getOpcode() != PPC::BLR && I->getOpcode() != PPC::BLR8) ||
           I != ReturnMBB.getLastNonDebugInstr())
         return Changed;
 
       SmallVector<MachineBasicBlock*, 8> PredToRemove;
       for (MachineBasicBlock::pred_iterator PI = ReturnMBB.pred_begin(),
            PIE = ReturnMBB.pred_end(); PI != PIE; ++PI) {
         bool OtherReference = false, BlockChanged = false;
+
+        if ((*PI)->empty())
+          continue;
+        
         for (MachineBasicBlock::iterator J = (*PI)->getLastNonDebugInstr();;) {
+          if (J == (*PI)->end())
+            break;
+
           MachineInstrBuilder MIB;
           if (J->getOpcode() == PPC::B) {
             if (J->getOperand(0).getMBB() == &ReturnMBB) {
               // This is an unconditional branch to the return. Replace the
               // branch with a blr.
               MIB =
                 BuildMI(**PI, J, J->getDebugLoc(), TII->get(I->getOpcode()));
               MIB.copyImplicitOps(I);

lib/Target/PowerPC/PPCFrameLowering.cpp

for (MachineBasicBlock::iterator MBBI = BI->end(); MBBI != BI->begin(); ) {
 
         }
       }
     }
 }
 
 void PPCFrameLowering::emitPrologue(MachineFunction &MF,
                                     MachineBasicBlock &MBB) const {
-  assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
   MachineBasicBlock::iterator MBBI = MBB.begin();
   MachineFrameInfo *MFI = MF.getFrameInfo();
   const PPCInstrInfo &TII =
       *static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
   const PPCRegisterInfo *RegInfo =
       static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
 
   MachineModuleInfo &MMI = MF.getMMI();
void PPCFrameLowering::emitPrologue(MachineFunction &MF,
   if (!isSVR4ABI)
     for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) {
       if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) {
         HandleVRSaveUpdate(MBBI, TII);
         break;
       }
     }
 
-  // Move MBBI back to the beginning of the function.
+  // Move MBBI back to the beginning of the prologue block.
   MBBI = MBB.begin();
 
   // Work out frame sizes.
   unsigned FrameSize = determineFrameLayout(MF);
   int NegFrameSize = -FrameSize;
   if (!isInt<32>(NegFrameSize))
     llvm_unreachable("Unhandled stack size!");
 
for (unsigned I = 0, E = CSI.size(); I != E; ++I) {
           nullptr, MRI->getDwarfRegNum(Reg, true), Offset));
       BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(CFIIndex);
     }
   }
 }
 
 void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
                                     MachineBasicBlock &MBB) const {
-  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
-  assert(MBBI != MBB.end() && "Returning block has no terminator");
+  MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
+  DebugLoc dl;
+
+  if (MBBI != MBB.end())
+    dl = MBBI->getDebugLoc();
+  
   const PPCInstrInfo &TII =
       *static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
   const PPCRegisterInfo *RegInfo =
       static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
 
-  unsigned RetOpcode = MBBI->getOpcode();
-  DebugLoc dl;
-
-  assert((RetOpcode == PPC::BLR ||
-          RetOpcode == PPC::BLR8 ||
-          RetOpcode == PPC::TCRETURNri ||
-          RetOpcode == PPC::TCRETURNdi ||
-          RetOpcode == PPC::TCRETURNai ||
-          RetOpcode == PPC::TCRETURNri8 ||
-          RetOpcode == PPC::TCRETURNdi8 ||
-          RetOpcode == PPC::TCRETURNai8) &&
-         "Can only insert epilog into returning blocks");
-
   // Get alignment info so we know how to restore the SP.
   const MachineFrameInfo *MFI = MF.getFrameInfo();
 
   // Get the number of bytes allocated from the FrameInfo.
   int FrameSize = MFI->getStackSize();
 
   // Get processor type.
   bool isPPC64 = Subtarget.isPPC64();
void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
   int PBPOffset = 0;
   if (FI->usesPICBase()) {
     MachineFrameInfo *FFI = MF.getFrameInfo();
     int PBPIndex = FI->getPICBasePointerSaveIndex();
     assert(PBPIndex && "No PIC Base Pointer Save Slot!");
     PBPOffset = FFI->getObjectOffset(PBPIndex);
   }
 
+  bool IsReturnBlock = MBBI->isReturn();
+  
+  if (IsReturnBlock) {
+    unsigned RetOpcode = MBBI->getOpcode();
     bool UsesTCRet =  RetOpcode == PPC::TCRETURNri ||
                       RetOpcode == PPC::TCRETURNdi ||
                       RetOpcode == PPC::TCRETURNai ||
                       RetOpcode == PPC::TCRETURNri8 ||
                       RetOpcode == PPC::TCRETURNdi8 ||
                       RetOpcode == PPC::TCRETURNai8;
 
     if (UsesTCRet) {
       int MaxTCRetDelta = FI->getTailCallSPDelta();
       MachineOperand &StackAdjust = MBBI->getOperand(1);
       assert(StackAdjust.isImm() && "Expecting immediate value.");
       // Adjust stack pointer.
       int StackAdj = StackAdjust.getImm();
       int Delta = StackAdj - MaxTCRetDelta;
       assert((Delta >= 0) && "Delta must be positive");
       if (MaxTCRetDelta>0)
         FrameSize += (StackAdj +Delta);
       else
         FrameSize += StackAdj;
     }
+  }
 
   // Frames of 32KB & larger require special handling because they cannot be
   // indexed into with a simple LD/LWZ immediate offset operand.
   bool isLargeFrame = !isInt<16>(FrameSize);
 
   if (FrameSize) {
     // In the prologue, the loaded (or persistent) stack pointer value is offset
     // by the STDU/STDUX/STWU/STWUX instruction.  Add this offset back now.
for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
       BuildMI(MBB, MBBI, dl, TII.get(PPC::MTOCRF8), MustSaveCRs[i])
         .addReg(TempReg, getKillRegState(i == e-1));
 
   if (MustSaveLR)
     BuildMI(MBB, MBBI, dl, MTLRInst).addReg(ScratchReg);
 
   // Callee pop calling convention. Pop parameter/linkage area. Used for tail
   // call optimization
+  if (IsReturnBlock) {
+    unsigned RetOpcode = MBBI->getOpcode();
     if (MF.getTarget().Options.GuaranteedTailCallOpt &&
         (RetOpcode == PPC::BLR || RetOpcode == PPC::BLR8) &&
         MF.getFunction()->getCallingConv() == CallingConv::Fast) {
       PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
       unsigned CallerAllocatedAmt = FI->getMinReservedArea();
 
       if (CallerAllocatedAmt && isInt<16>(CallerAllocatedAmt)) {
         BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
           .addReg(SPReg).addImm(CallerAllocatedAmt);
       } else {
         BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
           .addImm(CallerAllocatedAmt >> 16);
         BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
           .addReg(ScratchReg, RegState::Kill)
           .addImm(CallerAllocatedAmt & 0xFFFF);
         BuildMI(MBB, MBBI, dl, AddInst)
           .addReg(SPReg)
           .addReg(FPReg)
           .addReg(ScratchReg);
       }
     } else if (RetOpcode == PPC::TCRETURNdi) {
       MBBI = MBB.getLastNonDebugInstr();
       MachineOperand &JumpTarget = MBBI->getOperand(0);
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILB)).
         addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset());
     } else if (RetOpcode == PPC::TCRETURNri) {
       MBBI = MBB.getLastNonDebugInstr();
       assert(MBBI->getOperand(0).isReg() && "Expecting register operand.");
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBCTR));
     } else if (RetOpcode == PPC::TCRETURNai) {
       MBBI = MBB.getLastNonDebugInstr();
       MachineOperand &JumpTarget = MBBI->getOperand(0);
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBA)).addImm(JumpTarget.getImm());
     } else if (RetOpcode == PPC::TCRETURNdi8) {
       MBBI = MBB.getLastNonDebugInstr();
       MachineOperand &JumpTarget = MBBI->getOperand(0);
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILB8)).
         addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset());
     } else if (RetOpcode == PPC::TCRETURNri8) {
       MBBI = MBB.getLastNonDebugInstr();
       assert(MBBI->getOperand(0).isReg() && "Expecting register operand.");
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBCTR8));
     } else if (RetOpcode == PPC::TCRETURNai8) {
       MBBI = MBB.getLastNonDebugInstr();
       MachineOperand &JumpTarget = MBBI->getOperand(0);
       BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBA8)).addImm(JumpTarget.getImm());
     }
   }
+}
 
 void PPCFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                             BitVector &SavedRegs,
                                             RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 
   const PPCRegisterInfo *RegInfo =
       static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());

lib/Target/PowerPC/PPCTargetMachine.cpp

public:
   void addIRPasses() override;
   bool addPreISel() override;
   bool addILPOpts() override;
   bool addInstSelector() override;
   void addMachineSSAOptimization() override;
   void addPreRegAlloc() override;
   void addPreSched2() override;
   void addPreEmitPass() override;
+
+  //  FunctionPass *createShrinkWrapPass() override;
+  bool runShrinkWrap(const MachineFunction &Fn) const;
 };
 } // namespace
 
 TargetPassConfig *PPCTargetMachine::createPassConfig(PassManagerBase &PM) {
   return new PPCPassConfig(this, PM);
 }
 
 void PPCPassConfig::addIRPasses() {
void PPCPassConfig::addPreEmitPass() {
   // Must run branch selection immediately preceding the asm printer.
   addPass(createPPCBranchSelectionPass(), false);
 }
 
 TargetIRAnalysis PPCTargetMachine::getTargetIRAnalysis() {
   return TargetIRAnalysis(
       [this](Function &F) { return TargetTransformInfo(PPCTTIImpl(this, F)); });
 }
+
+bool PPCPassConfig::runShrinkWrap(const MachineFunction &Fn) const {
+  return (Fn.getSubtarget<PPCSubtarget>().isSVR4ABI() &&
+          Fn.getSubtarget<PPCSubtarget>().isPPC64());
+}

test/CodeGen/PowerPC/ppc-shrink-wrapping.ll

+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 %s -o - | FileCheck %s --check-prefix=CHECK --check-prefix=ENABLE
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 %s -o - -enable-shrink-wrap=false |  FileCheck %s --check-prefix=CHECK --check-prefix=DISABLE
+;
+; Note: Lots of tests use inline asm instead of regular calls.
+; This allows to have a better control on what the allocation will do.
+; Otherwise, we may have spill right in the entry block, defeating
+; shrink-wrapping. Moreover, some of the inline asm statement (nop)
+; are here to ensure that the related paths do not end up as critical
+; edges.
+
+
+; Initial motivating example: Simple diamond with a call just on one side.
+; CHECK-LABEL: foo:
+;
+; Compare the arguments and return
+; No prologue needed.
+; ENABLE: cmpw 0, 3, 4
+; ENABLE-NEXT: bgelr 0
+;
+; Prologue code.
+;  At a minimum, we save/restore the link register. Other registers may be saved
+;  as well. 
+; CHECK: mflr 
+;
+; Compare the arguments and jump to exit.
+; After the prologue is set.
+; DISABLE: cmpw 0, 3, 4
+; DISABLE-NEXT: bge 0, .[[EXIT_LABEL:LBB[0-9_]+]]
+;
+; Store %a on the stack
+; CHECK: stw 3, {{[0-9]+([0-9]+)}}
+; Set the alloca address in the second argument.
+; CHECK-NEXT: addi 4, 1, {{[0-9]+}}
+; Set the first argument to zero.
+; CHECK-NEXT: li 3, 0
+; CHECK-NEXT: bl doSomething
+;
+; With shrink-wrapping, epilogue is just after the call.
+; Restore the link register and return.
+; Note that there could be other epilog code before the link register is 
+; restored but we will not check for it here.
+; ENABLE: mtlr
+; ENABLE-NEXT: blr
+;
+; DISABLE: [[EXIT_LABEL]]:
+;
+; Without shrink-wrapping, epilogue is in the exit block.
+; Epilogue code. (What we pop does not matter.)
+; DISABLE: mtlr 0
+; DISABLE-NEXT: blr
+;
+
+define i32 @foo(i32 %a, i32 %b) {
+  %tmp = alloca i32, align 4
+  %tmp2 = icmp slt i32 %a, %b
+  br i1 %tmp2, label %true, label %false
+
+true:
+  store i32 %a, i32* %tmp, align 4
+  %tmp4 = call i32 @doSomething(i32 0, i32* %tmp)
+  br label %false
+
+false:
+  %tmp.0 = phi i32 [ %tmp4, %true ], [ %a, %0 ]
+  ret i32 %tmp.0
+}
+
+; Function Attrs: optsize
+declare i32 @doSomething(i32, i32*)
+
+
+
+; Check that we do not perform the restore inside the loop whereas the save
+; is outside.
+; CHECK-LABEL: freqSaveAndRestoreOutsideLoop:
+;
+; Shrink-wrapping allows to skip the prologue in the else case.
+; ENABLE: cmplwi 0, 3, 0
+; ENABLE: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Prologue code.
+; Make sure we save the link register
+; CHECK: mflr 0
+;
+; DISABLE: cmplwi 0, 3, 0
+; DISABLE: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Loop preheader
+; CHECK-DAG: li [[SUM:[0-9]+]], 0
+; CHECK-DAG: li [[IV:[0-9]+]], 10
+; 
+; Loop body
+; CHECK: .[[LOOP:LBB[0-9_]+]]: # %for.body
+; CHECK: bl something
+; CHECK-DAG: addi [[IV]], [[IV]], -1
+; CHECK-DAG: add [[SUM]], 3, [[SUM]] 
+; CHECK-NEXT: cmplwi [[IV]], 0
+; CHECK-NEXT: bne 0, .[[LOOP]]
+;
+; Next BB.
+; CHECK: slwi 3, [[SUM]], 3
+;
+; Jump to epilogue.
+; DISABLE: b .[[EPILOG_BB:LBB[0-9_]+]]
+;
+; DISABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; DISABLE: slwi 3, 4, 1
+; DISABLE: .[[EPILOG_BB]]: # %if.end
+;
+; Epilogue code.
+; CHECK: mtlr 0
+; CHECK-NEXT: blr
+;
+; ENABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; ENABLE: slwi 3, 4, 1
+; ENABLE-NEXT: blr
+define i32 @freqSaveAndRestoreOutsideLoop(i32 %cond, i32 %N) {
+entry:
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %if.else, label %for.preheader
+
+for.preheader:
+  tail call void asm "nop", ""()
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.05 = phi i32 [ %inc, %for.body ], [ 0, %for.preheader ]
+  %sum.04 = phi i32 [ %add, %for.body ], [ 0, %for.preheader ]
+  %call = tail call i32 bitcast (i32 (...)* @something to i32 ()*)()
+  %add = add nsw i32 %call, %sum.04
+  %inc = add nuw nsw i32 %i.05, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  %shl = shl i32 %add, 3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %mul = shl nsw i32 %N, 1
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %for.end
+  %sum.1 = phi i32 [ %shl, %for.end ], [ %mul, %if.else ]
+  ret i32 %sum.1
+}
+
+declare i32 @something(...)
+
+; Check that we do not perform the shrink-wrapping inside the loop even
+; though that would be legal. The cost model must prevent that.
+; CHECK-LABEL: freqSaveAndRestoreOutsideLoop2:
+; Prologue code.
+; Make sure we save the link register before the call
+; CHECK: mflr 0
+;
+; Loop preheader
+; CHECK-DAG: li [[SUM:[0-9]+]], 0
+; CHECK-DAG: li [[IV:[0-9]+]], 10
+; 
+; Loop body
+; CHECK: .[[LOOP:LBB[0-9_]+]]: # %for.body
+; CHECK: bl something
+; CHECK-DAG: addi [[IV]], [[IV]], -1
+; CHECK-DAG: add [[SUM]], 3, [[SUM]] 
+; CHECK-NEXT: cmplwi [[IV]], 0
+; CHECK-NEXT: bne 0, .[[LOOP]]
+;
+; Next BB
+; CHECK: %for.exit
+; CHECK: mtlr 0
+; CHECK-NEXT: blr
+define i32 @freqSaveAndRestoreOutsideLoop2(i32 %cond) {
+entry:
+  br label %for.preheader
+
+for.preheader:
+  tail call void asm "nop", ""()
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %i.04 = phi i32 [ 0, %for.preheader ], [ %inc, %for.body ]
+  %sum.03 = phi i32 [ 0, %for.preheader ], [ %add, %for.body ]
+  %call = tail call i32 bitcast (i32 (...)* @something to i32 ()*)()
+  %add = add nsw i32 %call, %sum.03
+  %inc = add nuw nsw i32 %i.04, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.exit, label %for.body
+
+for.exit:
+  tail call void asm "nop", ""()
+  br label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret i32 %add
+}
+
+
+; Check with a more complex case that we do not have save within the loop and
+; restore outside.
+; CHECK-LABEL: loopInfoSaveOutsideLoop:
+;
+; ENABLE: cmplwi 0, 3, 0
+; ENABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Prologue code.
+; Make sure we save the link register 
+; CHECK: mflr 0
+;
+; DISABLE: cmplwi 0, 3, 0
+; DISABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Loop preheader
+; CHECK-DAG: li [[SUM:[0-9]+]], 0
+; CHECK-DAG: li [[IV:[0-9]+]], 10
+; 
+; Loop body
+; CHECK: .[[LOOP:LBB[0-9_]+]]: # %for.body
+; CHECK: bl something
+; CHECK-DAG: addi [[IV]], [[IV]], -1
+; CHECK-DAG: add [[SUM]], 3, [[SUM]] 
+; CHECK-NEXT: cmplwi [[IV]], 0
+; CHECK-NEXT: bne 0, .[[LOOP]]
+; 
+; Next BB
+; CHECK: bl somethingElse 
+; CHECK: slwi 3, [[SUM]], 3
+;
+; Jump to epilogue
+; DISABLE: b .[[EPILOG_BB:LBB[0-9_]+]]
+;
+; DISABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; DISABLE: slwi 3, 4, 1
+;
+; DISABLE: .[[EPILOG_BB]]: # %if.end
+; Epilog code
+; CHECK: mtlr 0
+; CHECK-NEXT: blr
+; 
+; ENABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; ENABLE: slwi 3, 4, 1
+; ENABLE-NEXT: blr
+define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) {
+entry:
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %if.else, label %for.preheader
+
+for.preheader:
+  tail call void asm "nop", ""()
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.05 = phi i32 [ %inc, %for.body ], [ 0, %for.preheader ]
+  %sum.04 = phi i32 [ %add, %for.body ], [ 0, %for.preheader ]
+  %call = tail call i32 bitcast (i32 (...)* @something to i32 ()*)()
+  %add = add nsw i32 %call, %sum.04
+  %inc = add nuw nsw i32 %i.05, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  tail call void bitcast (void (...)* @somethingElse to void ()*)()
+  %shl = shl i32 %add, 3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %mul = shl nsw i32 %N, 1
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %for.end
+  %sum.1 = phi i32 [ %shl, %for.end ], [ %mul, %if.else ]
+  ret i32 %sum.1
+}
+
+declare void @somethingElse(...)
+
+; Check with a more complex case that we do not have restore within the loop and
+; save outside.
+; CHECK-LABEL: loopInfoRestoreOutsideLoop:
+;
+; ENABLE: cmplwi 0, 3, 0
+; ENABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Prologue code.
+; Make sure we save the link register
+; CHECK: mflr 0
+;
+; DISABLE: cmplwi 0, 3, 0
+; DISABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; CHECK: bl somethingElse
+;
+; Loop preheader
+; CHECK-DAG: li [[SUM:[0-9]+]], 0
+; CHECK-DAG: li [[IV:[0-9]+]], 10
+; 
+; Loop body
+; CHECK: .[[LOOP:LBB[0-9_]+]]: # %for.body
+; CHECK: bl something
+; CHECK-DAG: addi [[IV]], [[IV]], -1
+; CHECK-DAG: add [[SUM]], 3, [[SUM]] 
+; CHECK-NEXT: cmplwi [[IV]], 0
+; CHECK-NEXT: bne 0, .[[LOOP]]
+;
+; Next BB. 
+; slwi 3, [[SUM]], 3
+;
+; DISABLE: b .[[EPILOG_BB:LBB[0-9_]+]]
+;
+; DISABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; DISABLE: slwi 3, 4, 1
+; DISABLE: .[[EPILOG_BB]]: # %if.end
+;
+; Epilogue code.
+; CHECK: mtlr 0
+; CHECK-NEXT: blr
+;
+; ENABLE: .[[ELSE_LABEL]]: # %if.else
+; Shift second argument by one and store into returned register.
+; ENABLE: slwi 3, 4, 1
+; ENABLE-NEXT: blr
+define i32 @loopInfoRestoreOutsideLoop(i32 %cond, i32 %N) #0 {
+entry:
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %if.else, label %if.then
+
+if.then:                                          ; preds = %entry
+  tail call void bitcast (void (...)* @somethingElse to void ()*)()
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %if.then
+  %i.05 = phi i32 [ 0, %if.then ], [ %inc, %for.body ]
+  %sum.04 = phi i32 [ 0, %if.then ], [ %add, %for.body ]
+  %call = tail call i32 bitcast (i32 (...)* @something to i32 ()*)()
+  %add = add nsw i32 %call, %sum.04
+  %inc = add nuw nsw i32 %i.05, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  %shl = shl i32 %add, 3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %mul = shl nsw i32 %N, 1
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %for.end
+  %sum.1 = phi i32 [ %shl, %for.end ], [ %mul, %if.else ]
+  ret i32 %sum.1
+}
+
+; Check that we handle function with no frame information correctly.
+; CHECK-LABEL: emptyFrame:
+; CHECK: # %entry
+; CHECK-NEXT: li 3, 0
+; CHECK-NEXT: blr
+define i32 @emptyFrame() {
+entry:
+  ret i32 0
+}
+
+
+; Check that we handle inline asm correctly.
+; CHECK-LABEL: inlineAsm:
+;
+; ENABLE: cmplwi 0, 3, 0
+; ENABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Prologue code.
+; Make sure we save the CSR used in the inline asm: r14
+; ENABLE-DAG: li [[IV:[0-9]+]], 10
+; ENABLE-DAG: std 14, -[[STACK_OFFSET:[0-9]+]](1) # 8-byte Folded Spill
+;
+; DISABLE: std 14, -[[STACK_OFFSET:[0-9]+]](1) # 8-byte Folded Spill
+; DISABLE: cmplwi 0, 3, 0
+; DISABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+; DISABLE: li [[IV:[0-9]+]], 10
+;
+; CHECK: nop
+; CHECK: mtctr [[IV]]
+;
+; CHECK: .[[LOOP_LABEL:LBB[0-9_]+]]: # %for.body
+; Inline asm statement.
+; CHECK: addi 14, 14, 1
+; CHECK: bdnz .[[LOOP_LABEL]]
+;
+; Epilogue code.
+; CHECK: li 3, 0
+; CHECK-DAG: ld 14, -[[STACK_OFFSET]](1) # 8-byte Folded Reload
+; CHECK: nop
+; CHECK: blr
+;
+; CHECK: [[ELSE_LABEL]]
+; CHECK-NEXT: slwi 3, 4, 1
+; DISABLE: ld 14, -[[STACK_OFFSET]](1) # 8-byte Folded Reload
+; CHECK-NEXT blr
+; 
+define i32 @inlineAsm(i32 %cond, i32 %N) {
+entry:
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %if.else, label %for.preheader
+
+for.preheader:
+  tail call void asm "nop", ""()
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.03 = phi i32 [ %inc, %for.body ], [ 0, %for.preheader ]
+  tail call void asm "addi 14, 14, 1", "~{r14}"()
+  %inc = add nuw nsw i32 %i.03, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.exit, label %for.body
+
+for.exit:
+  tail call void asm "nop", ""()
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %mul = shl nsw i32 %N, 1
+  br label %if.end
+
+if.end:                                           ; preds = %for.body, %if.else
+  %sum.0 = phi i32 [ %mul, %if.else ], [ 0, %for.exit ]
+  ret i32 %sum.0
+}
+
+
+; Check that we handle calls to variadic functions correctly.
+; CHECK-LABEL: callVariadicFunc:
+;
+; ENABLE: cmplwi 0, 3, 0
+; ENABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Prologue code.
+; CHECK: mflr 0
+; 
+; DISABLE: cmplwi 0, 3, 0
+; DISABLE-NEXT: beq 0, .[[ELSE_LABEL:LBB[0-9_]+]]
+;
+; Setup of the varags.
+; CHECK: mr 4, 3
+; CHECK-NEXT: mr 5, 3
+; CHECK-NEXT: mr 6, 3
+; CHECK-NEXT: mr 7, 3
+; CHECK-NEXT: mr 8, 3
+; CHECK-NEXT: mr 9, 3
+; CHECK-NEXT: bl someVariadicFunc
+; CHECK: slwi 3, 3, 3
+; DISABLE: b .[[EPILOGUE_BB:LBB[0-9_]+]]
+;
+; ENABLE: mtlr 0
+; ENABLE-NEXT: blr
+;
+; CHECK: .[[ELSE_LABEL]]: # %if.else
+; CHECK-NEXT: slwi 3, 4, 1
+; 
+; DISABLE: .[[EPILOGUE_BB]]: # %if.end
+; DISABLE: mtlr
+; CHECK: blr
+define i32 @callVariadicFunc(i32 %cond, i32 %N) {
+entry:
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %if.else, label %if.then
+
+if.then:                                          ; preds = %entry
+  %call = tail call i32 (i32, ...) @someVariadicFunc(i32 %N, i32 %N, i32 %N, i32 %N, i32 %N, i32 %N, i32 %N)
+  %shl = shl i32 %call, 3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %mul = shl nsw i32 %N, 1
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %sum.0 = phi i32 [ %shl, %if.then ], [ %mul, %if.else ]
+  ret i32 %sum.0
+}
+
+declare i32 @someVariadicFunc(i32, ...)
+
+
+
+; Make sure we do not insert unreachable code after noreturn function.
+; Although this is not incorrect to insert such code, it is useless
+; and it hurts the binary size.
+;
+; CHECK-LABEL: noreturn:
+; DISABLE: mflr 0
+;
+; CHECK: cmplwi 3, 0
+; CHECK-NEXT: bne 0, .[[ABORT:LBB[0-9_]+]]
+;
+; CHECK: li 3, 42
+;
+; DISABLE: mtlr 0
+;
+; CHECK-NEXT: blr
+;
+; CHECK: .[[ABORT]]: # %if.abort
+;
+; ENABLE: mflr 0
+;
+; CHECK: bl abort
+; ENABLE-NOT: mtlr 0
+define i32 @noreturn(i8 signext %bad_thing) {
+entry:
+  %tobool = icmp eq i8 %bad_thing, 0
+  br i1 %tobool, label %if.end, label %if.abort
+
+if.abort:
+  tail call void @abort() #0
+  unreachable
+
+if.end:
+  ret i32 42
+}
+
+declare void @abort() #0
+
+attributes #0 = { noreturn nounwind }
+
+
+; Make sure that we handle infinite loops properly When checking that the Save
+; and Restore blocks are control flow equivalent, the loop searches for the
+; immediate (post) dominator for the (restore) save blocks. When either the Save
+; or Restore block is located in an infinite loop the only immediate (post)
+; dominator is itself. In this case, we cannot perform shrink wrapping, but we
+; should return gracefully and continue compilation.
+; The only condition for this test is the compilation finishes correctly.
+; 
+; CHECK-LABEL: infiniteloop
+; CHECK: blr
+define void @infiniteloop() {
+entry:
+  br i1 undef, label %if.then, label %if.end
+
+if.then:
+  %ptr = alloca i32, i32 4
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %sum.03 = phi i32 [ 0, %if.then ], [ %add, %for.body ]
+  %call = tail call i32 bitcast (i32 (...)* @something to i32 ()*)()
+  %add = add nsw i32 %call, %sum.03
+  store i32 %add, i32* %ptr
+  br label %for.body
+
+if.end:
+  ret void
+}