[WebAssembly] Implement prolog/epilog insertion and FrameIndex elimination

[dschuff]

Summary

Use the SP32 physical register as the base for FrameIndex lowering. Update it and the __stack_pointer global var in the prolog and epilog. Extend the mapping of virtual registers to wasm locals to include the physical registers.

Rather than modify the target-independent PrologEpilogInserter (which asserts that there are no virtual registers left) Include a slightly-modified copy for Wasm that does not have this assertion and only clears the virtual registers if scavenging was needed (which of course it isn't for wasm).

[dschuff]

Nevermind, this won't work. I'll just make it an MCSymbol in MI too. hold off on the review

[dschuff]

• Use SP32 as phys reg for FI lowering and update printer to handle it. Make prolog/epilog update SP global var

[dschuff]

In this version the SP32 physical register is used as the base for FrameIndex lowering. It and the @SP global var are updated in the prolog and epilog. An alternative would be just to use an arbitrary virtual register (which would be have to be stashed by the prolog e.g. in WebAssemblyRegisterInfo) but using SP seems easier to understand in the IR and not really any different in the final output.

[sunfish]

I'm still reviewing this, but here are a few initial comments.

lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

74

We also need a prologue when MFI->adjustsStack(). Can you assert that doesn't happen for now?

84

Instead of using getNamedGlobal on the Module, which requires a declaration in LLVM IR, we can use MF.createExternalSymbolName (and addExternalSymbol below), which creates an ExternalSymbol, which is a very lightweight thing that doesn't require any up-front setup.

Also, "SP" is in the C/C++ user namespace. What do you think about "__stack_pointer"?

120

Can you assert MFI->getCalleeSavedInfo().empty(), just to double-check ourselves?

155

This code doesn't yet set up FP; can you assert !hasFP(MF) for now?

Can you add TODO comments for:

• Do ".setMIFlag(MachineInstr::FrameSetup)" on emitted instructions
• Emit TargetOpcode::CFI_INSTRUCTION instructions

[dschuff]

• Use SP32 as phys reg for FI lowering and update printer to handle it. Make prolog/epilog update SP global var
• Address first round of comments

lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

84

Done. One consequence is that the MachinePointerInfo no longer has the reference to the stack pointer, but that's probably OK.

155

hasFP() currently includes MFI->hasCalls(), which seems wrong, at least for wasm. I took that out.

Added the former TODO to EmitPrologue and the latter to the top with the other TODOs.

[sunfish]

Looks good.

lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

84

Ah. This might be a job for PseudoSourceValue::ExternalSymbolCallEntry then. In fact, it looks like it would work to just use that right now; the only odd part is the "Call" in the name, which may be an artifact of the fact that the only thing using it right now is doing GOT loads for calls. Perhaps we could rename/generalize it though. In any case, this isn't urgent, so perhaps just add a comment mentioning this.

154

Sounds good.

test/CodeGen/WebAssembly/userstack.ll

9

With ExternalSymbol to get __stack_pointer, we no longer need to declare it at the LLVM IR level.

14

Is this function still needed now that we're using an ExternalSymbol for __stack_pointer?

[dschuff]

• Address final comments

test/CodeGen/WebAssembly/userstack.ll

14

No, in fact it was never actually needed, just leftover.

[dschuff]

• Remove changes to target-independent PEI, add WasmPEI

[dschuff]

Based on the current state of the discussion, either supporting virtual registers after RA or switching to physical registers will be a longer-term proposition. So I've included a modified PEI pass for WebAssembly and reverted the changes to the target-independent one (similarly to NVPTX) to allow us to make progress for now.

[sunfish]

lgtm (with the new changes).

lib/Target/WebAssembly/WebAssembly.h

43

It isn't stated so, but the passes above are ordered in the order that they run (except for Relooper, which is not currently run). Would you mind moving the PEI pass up just below RegColoring?

lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

154

Nit: unnecessary blank line here.

lib/Target/WebAssembly/WebAssemblyPEI.cpp

186

This is one of the changes to the generic PEI, right? Could you add a comment?

[dschuff]

• Address comments on updated CL

lib/Target/WebAssembly/WebAssemblyPEI.cpp

234

Also added comment here, the other "real" diff from generic PEI

lib/Target/WebAssembly/CMakeLists.txt

add_llvm_target(WebAssemblyCodeGen
   WebAssemblyISelDAGToDAG.cpp
   WebAssemblyISelLowering.cpp
   WebAssemblyInstrInfo.cpp
   WebAssemblyLowerBrUnless.cpp
   WebAssemblyMachineFunctionInfo.cpp
   WebAssemblyMCInstLower.cpp
   WebAssemblyOptimizeReturned.cpp
   WebAssemblyPeephole.cpp
+  WebAssemblyPEI.cpp
   WebAssemblyRegisterInfo.cpp
   WebAssemblyRegColoring.cpp
   WebAssemblyRegNumbering.cpp
   WebAssemblyRegStackify.cpp
   WebAssemblySelectionDAGInfo.cpp
   WebAssemblyStoreResults.cpp
   WebAssemblySubtarget.cpp
   WebAssemblyTargetMachine.cpp
   WebAssemblyTargetTransformInfo.cpp
 )
 
 add_dependencies(LLVMWebAssemblyCodeGen intrinsics_gen)
 
 add_subdirectory(InstPrinter)
 add_subdirectory(TargetInfo)
 add_subdirectory(MCTargetDesc)

lib/Target/WebAssembly/WebAssembly.h

 
 FunctionPass *createWebAssemblyISelDag(WebAssemblyTargetMachine &TM,
                                        CodeGenOpt::Level OptLevel);
 FunctionPass *createWebAssemblyArgumentMove();
 
 FunctionPass *createWebAssemblyStoreResults();
 FunctionPass *createWebAssemblyRegStackify();
 FunctionPass *createWebAssemblyRegColoring();
+FunctionPass *createWebAssemblyPEI();
 FunctionPass *createWebAssemblyCFGStackify();
 FunctionPass *createWebAssemblyLowerBrUnless();
 FunctionPass *createWebAssemblyRegNumbering();
 FunctionPass *createWebAssemblyPeephole();
 
 FunctionPass *createWebAssemblyRelooper();
 
 } // end namespace llvm
 
 #endif

lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "wasm-frame-info"
 
 // TODO: Implement a red zone?
+// TODO: wasm64
+// TODO: Prolog/epilog should be stackified too. This pass runs after register
+//       stackification, so we'll have to do it manually.
+// TODO: Emit TargetOpcode::CFI_INSTRUCTION instructions
 
 /// Return true if the specified function should have a dedicated frame pointer
 /// register.
 bool WebAssemblyFrameLowering::hasFP(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   const auto *RegInfo =
       MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo();
-  return MFI->hasCalls() || MFI->hasVarSizedObjects() ||
-         MFI->isFrameAddressTaken() || MFI->hasStackMap() ||
-         MFI->hasPatchPoint() || RegInfo->needsStackRealignment(MF);
+  return MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken() ||
+         MFI->hasStackMap() || MFI->hasPatchPoint() ||
+         RegInfo->needsStackRealignment(MF);
 }
 
 /// 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 WebAssemblyFrameLowering::hasReservedCallFrame(
     const MachineFunction &MF) const {
   return !MF.getFrameInfo()->hasVarSizedObjects();
 }
 
 void WebAssemblyFrameLowering::eliminateCallFramePseudoInstr(
     MachineFunction & /*MF*/, MachineBasicBlock & /*MBB*/,
     MachineBasicBlock::iterator /*I*/) const {
   llvm_unreachable("TODO: implement eliminateCallFramePseudoInstr");
 }
 
-void WebAssemblyFrameLowering::emitPrologue(MachineFunction & /*MF*/,
-                                            MachineBasicBlock & /*MBB*/) const {
-  llvm_unreachable("TODO: implement emitPrologue");
+void WebAssemblyFrameLowering::emitPrologue(MachineFunction &MF,
+                                            MachineBasicBlock &MBB) const {
+  // TODO: Do ".setMIFlag(MachineInstr::FrameSetup)" on emitted instructions
+  auto *MFI = MF.getFrameInfo();
+  assert(MFI->getCalleeSavedInfo().empty() &&
+         "WebAssembly should not have callee-saved registers");
+  assert(!hasFP(MF) && "Functions needing frame pointers not yet supported");
+  assert(!MFI->adjustsStack() && "Dynamic stack adjustmet not yet supported");
+  uint64_t StackSize = MFI->getStackSize();
+  if (!StackSize)
+    return;
+
+  const auto *TII = MF.getSubtarget().getInstrInfo();
+  auto &MRI = MF.getRegInfo();
+  auto InsertPt = MBB.begin();
+  DebugLoc DL;
+
+  // Get the current stacktop
+  // TODO: To support dynamic alloc, also copy to FP
+  unsigned SPReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+  auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer");
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), SPReg)
+      .addExternalSymbol(SPSymbol);
+  // This MachinePointerInfo should reference __stack_pointer as well but
+  // doesn't because MachinePointerInfo() takes a GV which we don't have for
+  // __stack_pointer. TODO: check if PseudoSourceValue::ExternalSymbolCallEntry
+  // is appropriate instead. (likewise for EmitEpologue below)
+  auto *LoadMMO = new MachineMemOperand(MachinePointerInfo(),
+                                        MachineMemOperand::MOLoad, 4, 4);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::LOAD_I32), SPReg)
+      .addImm(0)
+      .addReg(SPReg)
+      .addMemOperand(LoadMMO);
+  // Subtract the frame size
+  unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+      .addImm(StackSize);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::SUB_I32), WebAssembly::SP32)
+      .addReg(SPReg)
+      .addReg(OffsetReg);
+  // The SP32 register now has the new stacktop. Also write it back to memory.
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+      .addExternalSymbol(SPSymbol);
+  auto *MMO = new MachineMemOperand(MachinePointerInfo(),
+                                    MachineMemOperand::MOStore, 4, 4);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::STORE_I32), WebAssembly::SP32)
+      .addImm(0)
+      .addReg(OffsetReg)
+      .addReg(WebAssembly::SP32)
+      .addMemOperand(MMO);
 }
 
-void WebAssemblyFrameLowering::emitEpilogue(MachineFunction & /*MF*/,
-                                            MachineBasicBlock & /*MBB*/) const {
-  llvm_unreachable("TODO: implement emitEpilogue");
+void WebAssemblyFrameLowering::emitEpilogue(MachineFunction &MF,
+                                            MachineBasicBlock &MBB) const {
+  uint64_t StackSize = MF.getFrameInfo()->getStackSize();
+  if (!StackSize)
+    return;
+  const auto *TII = MF.getSubtarget().getInstrInfo();
+  auto &MRI = MF.getRegInfo();
+  unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+  auto InsertPt = MBB.getFirstTerminator();
+  DebugLoc DL;
+
+  if (InsertPt != MBB.end()) {
+    DL = InsertPt->getDebugLoc();
+  }
+
+  // Restore the stack pointer. Without FP its value is just SP32 - stacksize
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+      .addImm(StackSize);
+  auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer");
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::ADD_I32), WebAssembly::SP32)
+      .addReg(WebAssembly::SP32)
+      .addReg(OffsetReg);
+  // Re-use OffsetReg to hold the address of the stacktop
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+      .addExternalSymbol(SPSymbol);
+  auto *MMO = new MachineMemOperand(MachinePointerInfo(),
+                                    MachineMemOperand::MOStore, 4, 4);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::STORE_I32), WebAssembly::SP32)
+      .addImm(0)
+      .addReg(OffsetReg)
+      .addReg(WebAssembly::SP32)
+      .addMemOperand(MMO);
 }

lib/Target/WebAssembly/WebAssemblyISelLowering.h

private:
   SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                                bool IsVarArg,
                                const SmallVectorImpl<ISD::InputArg> &Ins,
                                SDLoc DL, SelectionDAG &DAG,
                                SmallVectorImpl<SDValue> &InVals) const override;
 
   // Custom lowering hooks.
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
+  SDValue LowerFrameIndex(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerExternalSymbol(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerBR_JT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerJumpTable(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerVASTART(SDValue Op, SelectionDAG &DAG) const;
 };
 
 namespace WebAssembly {
 FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                          const TargetLibraryInfo *libInfo);
 } // end namespace WebAssembly
 
 } // end namespace llvm
 
 #endif

lib/Target/WebAssembly/WebAssemblyISelLowering.cpp

WebAssemblyTargetLowering::WebAssemblyTargetLowering(
   for (auto T : {MVT::i1, MVT::i8, MVT::i16, MVT::i32})
     setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);
 
   // Dynamic stack allocation: use the default expansion.
   setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVTPtr, Expand);
 
+  setOperationAction(ISD::FrameIndex, MVT::i32, Custom);
+
   // Expand these forms; we pattern-match the forms that we can handle in isel.
   for (auto T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
     for (auto Op : {ISD::BR_CC, ISD::SELECT_CC})
       setOperationAction(Op, T, Expand);
 
   // We have custom switch handling.
   setOperationAction(ISD::BR_JT, MVT::Other, Custom);
 

 //===----------------------------------------------------------------------===//
 
 SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
                                                   SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
   default:
     llvm_unreachable("unimplemented operation lowering");
     return SDValue();
+  case ISD::FrameIndex:
+    return LowerFrameIndex(Op, DAG);
   case ISD::GlobalAddress:
     return LowerGlobalAddress(Op, DAG);
   case ISD::ExternalSymbol:
     return LowerExternalSymbol(Op, DAG);
   case ISD::JumpTable:
     return LowerJumpTable(Op, DAG);
   case ISD::BR_JT:
     return LowerBR_JT(Op, DAG);
   case ISD::VASTART:
     return LowerVASTART(Op, DAG);
   }
 }
 
+SDValue WebAssemblyTargetLowering::LowerFrameIndex(SDValue Op,
+                                                   SelectionDAG &DAG) const {
+  int FI = cast<FrameIndexSDNode>(Op)->getIndex();
+  return DAG.getTargetFrameIndex(FI, Op.getValueType());
+}
+
 SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
                                                       SelectionDAG &DAG) const {
   SDLoc DL(Op);
   const auto *GA = cast<GlobalAddressSDNode>(Op);
   EVT VT = Op.getValueType();
   assert(GA->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
   if (GA->getAddressSpace() != 0)
     fail(DL, DAG, "WebAssembly only expects the 0 address space");

lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h

 /// \brief This file declares WebAssembly-specific per-machine-function
 /// information.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMACHINEFUNCTIONINFO_H
 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMACHINEFUNCTIONINFO_H
 
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 
 namespace llvm {
 
 /// This class is derived from MachineFunctionInfo and contains private
 /// WebAssembly-specific information for each MachineFunction.
 class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
   MachineFunction &MF;
 
   std::vector<MVT> Params;
 
   /// A mapping from CodeGen vreg index to WebAssembly register number.
   std::vector<unsigned> WARegs;
 
   /// A mapping from CodeGen vreg index to a boolean value indicating whether
   /// the given register is considered to be "stackified", meaning it has been
   /// determined or made to meet the stack requirements:
   ///   - single use (per path)
   ///   - single def (per path)
   ///   - defined and used in LIFO order with other stack registers
   BitVector VRegStackified;
 
+  // One entry for each possible target reg. we expect it to be small.
+  std::vector<unsigned> PhysRegs;
+
 public:
-  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {}
+  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {
+    PhysRegs.resize(WebAssembly::NUM_TARGET_REGS, -1U);
+  }
   ~WebAssemblyFunctionInfo() override;
 
   void addParam(MVT VT) { Params.push_back(VT); }
   const std::vector<MVT> &getParams() const { return Params; }
 
   static const unsigned UnusedReg = -1u;
 
   void stackifyVReg(unsigned VReg) {
     if (TargetRegisterInfo::virtReg2Index(VReg) >= VRegStackified.size())
       VRegStackified.resize(TargetRegisterInfo::virtReg2Index(VReg) + 1);
     VRegStackified.set(TargetRegisterInfo::virtReg2Index(VReg));
   }
   bool isVRegStackified(unsigned VReg) const {
     if (TargetRegisterInfo::virtReg2Index(VReg) >= VRegStackified.size())
       return false;
     return VRegStackified.test(TargetRegisterInfo::virtReg2Index(VReg));
   }
 
   void initWARegs();
   void setWAReg(unsigned VReg, unsigned WAReg) {
     assert(WAReg != UnusedReg);
     assert(TargetRegisterInfo::virtReg2Index(VReg) < WARegs.size());
     WARegs[TargetRegisterInfo::virtReg2Index(VReg)] = WAReg;
   }
-  unsigned getWAReg(unsigned VReg) const {
-    assert(TargetRegisterInfo::virtReg2Index(VReg) < WARegs.size());
-    return WARegs[TargetRegisterInfo::virtReg2Index(VReg)];
+  unsigned getWAReg(unsigned Reg) const {
+    if (TargetRegisterInfo::isVirtualRegister(Reg)) {
+      assert(TargetRegisterInfo::virtReg2Index(Reg) < WARegs.size());
+      return WARegs[TargetRegisterInfo::virtReg2Index(Reg)];
+    }
+    return PhysRegs[Reg];
   }
   // If new virtual registers are created after initWARegs has been called,
   // this function can be used to add WebAssembly register mappings for them.
   void addWAReg(unsigned VReg, unsigned WAReg) {
     assert(VReg = WARegs.size());
     WARegs.push_back(WAReg);
   }
+
+  void addPReg(unsigned PReg, unsigned WAReg) {
+    assert(PReg < WebAssembly::NUM_TARGET_REGS);
+    assert(WAReg < -1U);
+    PhysRegs[PReg] = WAReg;
+  }
 };
 
 } // end namespace llvm
 
 #endif

lib/Target/WebAssembly/WebAssemblyPEI.cpp

+//===-- WebAssemblyPEI.cpp - Insert Prolog/Epilog code in function --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass is responsible for finalizing the functions frame layout, saving
+// callee saved registers, and for emitting prolog & epilog code for the
+// function.
+//
+// This pass must be run after register allocation.  After this pass is
+// executed, it is illegal to construct MO_FrameIndex operands.
+//
+// This is a copy of lib/CodeGen/PrologEpilogInserter.cpp except that it does
+// not assert that all virtual registers are gone (because WebAssembly currently
+// uses virtual rather than physical registers), and only runs
+// MRI.clearVirtRegs() if scavenging happened (which it never does). It also
+// uses a different class name so it can be registered via INITIALIZE_PASS.
+// It is otherwise unmodified, so any changes to the target-independent PEI
+// can be easily applied.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/IndexedMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/CodeGen/StackProtector.h"
+#include "llvm/CodeGen/WinEHFuncInfo.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetFrameLowering.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include <climits>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "pei"
+namespace llvm {
+void initializeWasmPEIPass(PassRegistry&);
+}
+namespace {
+class WasmPEI : public MachineFunctionPass {
+public:
+  static char ID;
+  WasmPEI() : MachineFunctionPass(ID) {
+    initializeWasmPEIPass(*PassRegistry::getPassRegistry());
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
+  /// frame indexes with appropriate references.
+  ///
+  bool runOnMachineFunction(MachineFunction &Fn) override;
+
+private:
+  RegScavenger *RS;
+
+  // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
+  // stack frame indexes.
+  unsigned MinCSFrameIndex, MaxCSFrameIndex;
+
+  // Save and Restore blocks of the current function. Typically there is a
+  // single save block, unless Windows EH funclets are involved.
+  SmallVector<MachineBasicBlock *, 1> SaveBlocks;
+  SmallVector<MachineBasicBlock *, 4> RestoreBlocks;
+
+  // Flag to control whether to use the register scavenger to resolve
+  // frame index materialization registers. Set according to
+  // TRI->requiresFrameIndexScavenging() for the current function.
+  bool FrameIndexVirtualScavenging;
+
+  void calculateSets(MachineFunction &Fn);
+  void calculateCallsInformation(MachineFunction &Fn);
+  void assignCalleeSavedSpillSlots(MachineFunction &Fn,
+                                   const BitVector &SavedRegs);
+  void insertCSRSpillsAndRestores(MachineFunction &Fn);
+  void calculateFrameObjectOffsets(MachineFunction &Fn);
+  void replaceFrameIndices(MachineFunction &Fn);
+  void replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
+                           int &SPAdj);
+  void scavengeFrameVirtualRegs(MachineFunction &Fn);
+  void insertPrologEpilogCode(MachineFunction &Fn);
+};
+} // namespace
+
+char WasmPEI::ID = 0;
+
+namespace llvm {
+FunctionPass *createWebAssemblyPEI() {
+  return new WasmPEI();
+}
+}
+
+static cl::opt<unsigned>
+WarnStackSize("wasm-warn-stack-size", cl::Hidden, cl::init((unsigned)-1),
+              cl::desc("Warn for stack size bigger than the given"
+                       " number"));
+
+INITIALIZE_PASS_BEGIN(WasmPEI, "wasmprologepilog",
+                "Wasm Prologue/Epilogue Insertion", false, false)
+INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
+INITIALIZE_PASS_DEPENDENCY(StackProtector)
+INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
+INITIALIZE_PASS_END(WasmPEI, "wasmprologepilog",
+                    "Wasm Prologue/Epilogue Insertion & Frame Finalization",
+                    false, false)
+
+STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged");
+STATISTIC(NumBytesStackSpace,
+          "Number of bytes used for stack in all functions");
+
+void WasmPEI::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesCFG();
+  AU.addPreserved<MachineLoopInfo>();
+  AU.addPreserved<MachineDominatorTree>();
+  AU.addRequired<StackProtector>();
+  AU.addRequired<TargetPassConfig>();
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+/// Compute the set of return blocks
+void WasmPEI::calculateSets(MachineFunction &Fn) {
+  const MachineFrameInfo *MFI = Fn.getFrameInfo();
+
+  // Even when we do not change any CSR, we still want to insert the
+  // prologue and epilogue of the function.
+  // So set the save points for those.
+
+  // Use the points found by shrink-wrapping, if any.
+  if (MFI->getSavePoint()) {
+    SaveBlocks.push_back(MFI->getSavePoint());
+    assert(MFI->getRestorePoint() && "Both restore and save must be set");
+    MachineBasicBlock *RestoreBlock = MFI->getRestorePoint();
+    // If RestoreBlock does not have any successor and is not a return block
+    // then the end point is unreachable and we do not need to insert any
+    // epilogue.
+    if (!RestoreBlock->succ_empty() || RestoreBlock->isReturnBlock())
+      RestoreBlocks.push_back(RestoreBlock);
+    return;
+  }
+
+  // Save refs to entry and return blocks.
+  SaveBlocks.push_back(&Fn.front());
+  for (MachineBasicBlock &MBB : Fn) {
+    if (MBB.isEHFuncletEntry())
+      SaveBlocks.push_back(&MBB);
+    if (MBB.isReturnBlock())
+      RestoreBlocks.push_back(&MBB);
+  }
+}
+
+/// StackObjSet - A set of stack object indexes
+typedef SmallSetVector<int, 8> StackObjSet;
+
+/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
+/// frame indexes with appropriate references.
+///
+bool WasmPEI::runOnMachineFunction(MachineFunction &Fn) {
+  const Function* F = Fn.getFunction();
+  const TargetRegisterInfo *TRI = Fn.getSubtarget().getRegisterInfo();
+  const TargetFrameLowering *TFI = Fn.getSubtarget().getFrameLowering();
+
+  // LOCALMOD: assert removed from target-independent PEI
+  //assert(!Fn.getRegInfo().getNumVirtRegs() && "Regalloc must assign all vregs");
+
+  RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : nullptr;
+  FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
+
+  // Calculate the MaxCallFrameSize and AdjustsStack variables for the
+  // function's frame information. Also eliminates call frame pseudo
+  // instructions.
+  calculateCallsInformation(Fn);
+
+  // Determine which of the registers in the callee save list should be saved.
+  BitVector SavedRegs;
+  TFI->determineCalleeSaves(Fn, SavedRegs, RS);
+
+  // Insert spill code for any callee saved registers that are modified.
+  assignCalleeSavedSpillSlots(Fn, SavedRegs);
+
+  // Determine placement of CSR spill/restore code:
+  // place all spills in the entry block, all restores in return blocks.
+  calculateSets(Fn);
+
+  // Add the code to save and restore the callee saved registers.
+  if (!F->hasFnAttribute(Attribute::Naked))
+    insertCSRSpillsAndRestores(Fn);
+
+  // Allow the target machine to make final modifications to the function
+  // before the frame layout is finalized.
+  TFI->processFunctionBeforeFrameFinalized(Fn, RS);
+
+  // Calculate actual frame offsets for all abstract stack objects...
+  calculateFrameObjectOffsets(Fn);
+
+  // Add prolog and epilog code to the function.  This function is required
+  // to align the stack frame as necessary for any stack variables or
+  // called functions.  Because of this, calculateCalleeSavedRegisters()
+  // must be called before this function in order to set the AdjustsStack
+  // and MaxCallFrameSize variables.
+  if (!F->hasFnAttribute(Attribute::Naked))
+    insertPrologEpilogCode(Fn);
+
+  // Replace all MO_FrameIndex operands with physical register references
+  // and actual offsets.
+  //
+  replaceFrameIndices(Fn);
+
+  // If register scavenging is needed, as we've enabled doing it as a
+  // post-pass, scavenge the virtual registers that frame index elimination
+  // inserted.
+  if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging) {
+    scavengeFrameVirtualRegs(Fn);
+    // Clear any vregs created by virtual scavenging.
+    // LOCALMOD: made this call conditional with scavengeFrameVirtualregs()
+    Fn.getRegInfo().clearVirtRegs();
+  }
+
+  // Warn on stack size when we exceeds the given limit.
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+  uint64_t StackSize = MFI->getStackSize();
+  if (WarnStackSize.getNumOccurrences() > 0 && WarnStackSize < StackSize) {
+    DiagnosticInfoStackSize DiagStackSize(*F, StackSize);
+    F->getContext().diagnose(DiagStackSize);
+  }
+
+  delete RS;
+  SaveBlocks.clear();
+  RestoreBlocks.clear();
+  return true;
+}
+
+/// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
+/// variables for the function's frame information and eliminate call frame
+/// pseudo instructions.
+void WasmPEI::calculateCallsInformation(MachineFunction &Fn) {
+  const TargetInstrInfo &TII = *Fn.getSubtarget().getInstrInfo();
+  const TargetFrameLowering *TFI = Fn.getSubtarget().getFrameLowering();
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+
+  unsigned MaxCallFrameSize = 0;
+  bool AdjustsStack = MFI->adjustsStack();
+
+  // Get the function call frame set-up and tear-down instruction opcode
+  unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
+  unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
+
+  // Early exit for targets which have no call frame setup/destroy pseudo
+  // instructions.
+  if (FrameSetupOpcode == ~0u && FrameDestroyOpcode == ~0u)
+    return;
+
+  std::vector<MachineBasicBlock::iterator> FrameSDOps;
+  for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
+    for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
+      if (I->getOpcode() == FrameSetupOpcode ||
+          I->getOpcode() == FrameDestroyOpcode) {
+        assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
+               " instructions should have a single immediate argument!");
+        unsigned Size = I->getOperand(0).getImm();
+        if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
+        AdjustsStack = true;
+        FrameSDOps.push_back(I);
+      } else if (I->isInlineAsm()) {
+        // Some inline asm's need a stack frame, as indicated by operand 1.
+        unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
+        if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
+          AdjustsStack = true;
+      }
+
+  MFI->setAdjustsStack(AdjustsStack);
+  MFI->setMaxCallFrameSize(MaxCallFrameSize);
+
+  for (std::vector<MachineBasicBlock::iterator>::iterator
+         i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
+    MachineBasicBlock::iterator I = *i;
+
+    // If call frames are not being included as part of the stack frame, and
+    // the target doesn't indicate otherwise, remove the call frame pseudos
+    // here. The sub/add sp instruction pairs are still inserted, but we don't
+    // need to track the SP adjustment for frame index elimination.
+    if (TFI->canSimplifyCallFramePseudos(Fn))
+      TFI->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
+  }
+}
+
+void WasmPEI::assignCalleeSavedSpillSlots(MachineFunction &F,
+                                      const BitVector &SavedRegs) {
+  // These are used to keep track the callee-save area. Initialize them.
+  MinCSFrameIndex = INT_MAX;
+  MaxCSFrameIndex = 0;
+
+  if (SavedRegs.empty())
+    return;
+
+  const TargetRegisterInfo *RegInfo = F.getSubtarget().getRegisterInfo();
+  const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&F);
+
+  std::vector<CalleeSavedInfo> CSI;
+  for (unsigned i = 0; CSRegs[i]; ++i) {
+    unsigned Reg = CSRegs[i];
+    if (SavedRegs.test(Reg))
+      CSI.push_back(CalleeSavedInfo(Reg));
+  }
+
+  const TargetFrameLowering *TFI = F.getSubtarget().getFrameLowering();
+  MachineFrameInfo *MFI = F.getFrameInfo();
+  if (!TFI->assignCalleeSavedSpillSlots(F, RegInfo, CSI)) {
+    // If target doesn't implement this, use generic code.
+
+    if (CSI.empty())
+      return; // Early exit if no callee saved registers are modified!
+
+    unsigned NumFixedSpillSlots;
+    const TargetFrameLowering::SpillSlot *FixedSpillSlots =
+        TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
+
+    // Now that we know which registers need to be saved and restored, allocate
+    // stack slots for them.
+    for (std::vector<CalleeSavedInfo>::iterator I = CSI.begin(), E = CSI.end();
+         I != E; ++I) {
+      unsigned Reg = I->getReg();
+      const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
+
+      int FrameIdx;
+      if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
+        I->setFrameIdx(FrameIdx);
+        continue;
+      }
+
+      // Check to see if this physreg must be spilled to a particular stack slot
+      // on this target.
+      const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
+      while (FixedSlot != FixedSpillSlots + NumFixedSpillSlots &&
+             FixedSlot->Reg != Reg)
+        ++FixedSlot;
+
+      if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
+        // Nope, just spill it anywhere convenient.
+        unsigned Align = RC->getAlignment();
+        unsigned StackAlign = TFI->getStackAlignment();
+
+        // We may not be able to satisfy the desired alignment specification of
+        // the TargetRegisterClass if the stack alignment is smaller. Use the
+        // min.
+        Align = std::min(Align, StackAlign);
+        FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
+        if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
+        if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
+      } else {
+        // Spill it to the stack where we must.
+        FrameIdx =
+            MFI->CreateFixedSpillStackObject(RC->getSize(), FixedSlot->Offset);
+      }
+
+      I->setFrameIdx(FrameIdx);
+    }
+  }
+
+  MFI->setCalleeSavedInfo(CSI);
+}
+
+/// Helper function to update the liveness information for the callee-saved
+/// registers.
+static void updateLiveness(MachineFunction &MF) {
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  // Visited will contain all the basic blocks that are in the region
+  // where the callee saved registers are alive:
+  // - Anything that is not Save or Restore -> LiveThrough.
+  // - Save -> LiveIn.
+  // - Restore -> LiveOut.
+  // The live-out is not attached to the block, so no need to keep
+  // Restore in this set.
+  SmallPtrSet<MachineBasicBlock *, 8> Visited;
+  SmallVector<MachineBasicBlock *, 8> WorkList;
+  MachineBasicBlock *Entry = &MF.front();
+  MachineBasicBlock *Save = MFI->getSavePoint();
+
+  if (!Save)
+    Save = Entry;
+
+  if (Entry != Save) {
+    WorkList.push_back(Entry);
+    Visited.insert(Entry);
+  }
+  Visited.insert(Save);
+
+  MachineBasicBlock *Restore = MFI->getRestorePoint();
+  if (Restore)
+    // By construction Restore cannot be visited, otherwise it
+    // means there exists a path to Restore that does not go
+    // through Save.
+    WorkList.push_back(Restore);
+
+  while (!WorkList.empty()) {
+    const MachineBasicBlock *CurBB = WorkList.pop_back_val();
+    // By construction, the region that is after the save point is
+    // dominated by the Save and post-dominated by the Restore.
+    if (CurBB == Save && Save != Restore)
+      continue;
+    // Enqueue all the successors not already visited.
+    // Those are by construction either before Save or after Restore.
+    for (MachineBasicBlock *SuccBB : CurBB->successors())
+      if (Visited.insert(SuccBB).second)
+        WorkList.push_back(SuccBB);
+  }
+
+  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
+
+  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
+    for (MachineBasicBlock *MBB : Visited) {
+      MCPhysReg Reg = CSI[i].getReg();
+      // Add the callee-saved register as live-in.
+      // It's killed at the spill.
+      if (!MBB->isLiveIn(Reg))
+        MBB->addLiveIn(Reg);
+    }
+  }
+}
+
+/// insertCSRSpillsAndRestores - Insert spill and restore code for
+/// callee saved registers used in the function.
+///
+void WasmPEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
+  // Get callee saved register information.
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
+
+  MFI->setCalleeSavedInfoValid(true);
+
+  // Early exit if no callee saved registers are modified!
+  if (CSI.empty())
+    return;
+
+  const TargetInstrInfo &TII = *Fn.getSubtarget().getInstrInfo();
+  const TargetFrameLowering *TFI = Fn.getSubtarget().getFrameLowering();
+  const TargetRegisterInfo *TRI = Fn.getSubtarget().getRegisterInfo();
+  MachineBasicBlock::iterator I;
+
+  // Spill using target interface.
+  for (MachineBasicBlock *SaveBlock : SaveBlocks) {
+    I = SaveBlock->begin();
+    if (!TFI->spillCalleeSavedRegisters(*SaveBlock, I, CSI, TRI)) {
+      for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
+        // Insert the spill to the stack frame.
+        unsigned Reg = CSI[i].getReg();
+        const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
+        TII.storeRegToStackSlot(*SaveBlock, I, Reg, true, CSI[i].getFrameIdx(),
+                                RC, TRI);
+      }
+    }
+    // Update the live-in information of all the blocks up to the save point.
+    updateLiveness(Fn);
+  }
+
+  // Restore using target interface.
+  for (MachineBasicBlock *MBB : RestoreBlocks) {
+    I = MBB->end();
+
+    // Skip over all terminator instructions, which are part of the return
+    // sequence.
+    MachineBasicBlock::iterator I2 = I;
+    while (I2 != MBB->begin() && (--I2)->isTerminator())
+      I = I2;
+
+    bool AtStart = I == MBB->begin();
+    MachineBasicBlock::iterator BeforeI = I;
+    if (!AtStart)
+      --BeforeI;
+
+    // Restore all registers immediately before the return and any
+    // terminators that precede it.
+    if (!TFI->restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
+      for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
+        unsigned Reg = CSI[i].getReg();
+        const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
+        TII.loadRegFromStackSlot(*MBB, I, Reg, CSI[i].getFrameIdx(), RC, TRI);
+        assert(I != MBB->begin() &&
+               "loadRegFromStackSlot didn't insert any code!");
+        // Insert in reverse order.  loadRegFromStackSlot can insert
+        // multiple instructions.
+        if (AtStart)
+          I = MBB->begin();
+        else {
+          I = BeforeI;
+          ++I;
+        }
+      }
+    }
+  }
+}
+
+/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
+static inline void
+AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
+                  bool StackGrowsDown, int64_t &Offset,
+                  unsigned &MaxAlign, unsigned Skew) {
+  // If the stack grows down, add the object size to find the lowest address.
+  if (StackGrowsDown)
+    Offset += MFI->getObjectSize(FrameIdx);
+
+  unsigned Align = MFI->getObjectAlignment(FrameIdx);
+
+  // If the alignment of this object is greater than that of the stack, then
+  // increase the stack alignment to match.
+  MaxAlign = std::max(MaxAlign, Align);
+
+  // Adjust to alignment boundary.
+  Offset = RoundUpToAlignment(Offset, Align, Skew);
+
+  if (StackGrowsDown) {
+    DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
+    MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
+  } else {
+    DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
+    MFI->setObjectOffset(FrameIdx, Offset);
+    Offset += MFI->getObjectSize(FrameIdx);
+  }
+}
+
+/// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
+/// those required to be close to the Stack Protector) to stack offsets.
+static void
+AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
+                      SmallSet<int, 16> &ProtectedObjs,
+                      MachineFrameInfo *MFI, bool StackGrowsDown,
+                      int64_t &Offset, unsigned &MaxAlign, unsigned Skew) {
+
+  for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
+        E = UnassignedObjs.end(); I != E; ++I) {
+    int i = *I;
+    AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign, Skew);
+    ProtectedObjs.insert(i);
+  }
+}
+
+/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
+/// abstract stack objects.
+///
+void WasmPEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
+  const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
+  StackProtector *SP = &getAnalysis<StackProtector>();
+
+  bool StackGrowsDown =
+    TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
+
+  // Loop over all of the stack objects, assigning sequential addresses...
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+
+  // Start at the beginning of the local area.
+  // The Offset is the distance from the stack top in the direction
+  // of stack growth -- so it's always nonnegative.
+  int LocalAreaOffset = TFI.getOffsetOfLocalArea();
+  if (StackGrowsDown)
+    LocalAreaOffset = -LocalAreaOffset;
+  assert(LocalAreaOffset >= 0
+         && "Local area offset should be in direction of stack growth");
+  int64_t Offset = LocalAreaOffset;
+
+  // Skew to be applied to alignment.
+  unsigned Skew = TFI.getStackAlignmentSkew(Fn);
+
+  // If there are fixed sized objects that are preallocated in the local area,
+  // non-fixed objects can't be allocated right at the start of local area.
+  // We currently don't support filling in holes in between fixed sized
+  // objects, so we adjust 'Offset' to point to the end of last fixed sized
+  // preallocated object.
+  for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
+    int64_t FixedOff;
+    if (StackGrowsDown) {
+      // The maximum distance from the stack pointer is at lower address of
+      // the object -- which is given by offset. For down growing stack
+      // the offset is negative, so we negate the offset to get the distance.
+      FixedOff = -MFI->getObjectOffset(i);
+    } else {
+      // The maximum distance from the start pointer is at the upper
+      // address of the object.
+      FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
+    }
+    if (FixedOff > Offset) Offset = FixedOff;
+  }
+
+  // First assign frame offsets to stack objects that are used to spill
+  // callee saved registers.
+  if (StackGrowsDown) {
+    for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
+      // If the stack grows down, we need to add the size to find the lowest
+      // address of the object.
+      Offset += MFI->getObjectSize(i);
+
+      unsigned Align = MFI->getObjectAlignment(i);
+      // Adjust to alignment boundary
+      Offset = RoundUpToAlignment(Offset, Align, Skew);
+
+      MFI->setObjectOffset(i, -Offset);        // Set the computed offset
+    }
+  } else {
+    int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
+    for (int i = MaxCSFI; i >= MinCSFI ; --i) {
+      unsigned Align = MFI->getObjectAlignment(i);
+      // Adjust to alignment boundary
+      Offset = RoundUpToAlignment(Offset, Align, Skew);
+
+      MFI->setObjectOffset(i, Offset);
+      Offset += MFI->getObjectSize(i);
+    }
+  }
+
+  unsigned MaxAlign = MFI->getMaxAlignment();
+
+  // Make sure the special register scavenging spill slot is closest to the
+  // incoming stack pointer if a frame pointer is required and is closer
+  // to the incoming rather than the final stack pointer.
+  const TargetRegisterInfo *RegInfo = Fn.getSubtarget().getRegisterInfo();
+  bool EarlyScavengingSlots = (TFI.hasFP(Fn) &&
+                               TFI.isFPCloseToIncomingSP() &&
+                               RegInfo->useFPForScavengingIndex(Fn) &&
+                               !RegInfo->needsStackRealignment(Fn));
+  if (RS && EarlyScavengingSlots) {
+    SmallVector<int, 2> SFIs;
+    RS->getScavengingFrameIndices(SFIs);
+    for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
+           IE = SFIs.end(); I != IE; ++I)
+      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew);
+  }
+
+  // FIXME: Once this is working, then enable flag will change to a target
+  // check for whether the frame is large enough to want to use virtual
+  // frame index registers. Functions which don't want/need this optimization
+  // will continue to use the existing code path.
+  if (MFI->getUseLocalStackAllocationBlock()) {
+    unsigned Align = MFI->getLocalFrameMaxAlign();
+
+    // Adjust to alignment boundary.
+    Offset = RoundUpToAlignment(Offset, Align, Skew);
+
+    DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
+
+    // Resolve offsets for objects in the local block.
+    for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
+      std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
+      int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
+      DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
+            FIOffset << "]\n");
+      MFI->setObjectOffset(Entry.first, FIOffset);
+    }
+    // Allocate the local block
+    Offset += MFI->getLocalFrameSize();
+
+    MaxAlign = std::max(Align, MaxAlign);
+  }
+
+  // Make sure that the stack protector comes before the local variables on the
+  // stack.
+  SmallSet<int, 16> ProtectedObjs;
+  if (MFI->getStackProtectorIndex() >= 0) {
+    StackObjSet LargeArrayObjs;
+    StackObjSet SmallArrayObjs;
+    StackObjSet AddrOfObjs;
+
+    AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
+                      Offset, MaxAlign, Skew);
+
+    // Assign large stack objects first.
+    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+      if (MFI->isObjectPreAllocated(i) &&
+          MFI->getUseLocalStackAllocationBlock())
+        continue;
+      if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
+        continue;
+      if (RS && RS->isScavengingFrameIndex((int)i))
+        continue;
+      if (MFI->isDeadObjectIndex(i))
+        continue;
+      if (MFI->getStackProtectorIndex() == (int)i)
+        continue;
+
+      switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
+      case StackProtector::SSPLK_None:
+        continue;
+      case StackProtector::SSPLK_SmallArray:
+        SmallArrayObjs.insert(i);
+        continue;
+      case StackProtector::SSPLK_AddrOf:
+        AddrOfObjs.insert(i);
+        continue;
+      case StackProtector::SSPLK_LargeArray:
+        LargeArrayObjs.insert(i);
+        continue;
+      }
+      llvm_unreachable("Unexpected SSPLayoutKind.");
+    }
+
+    AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
+                          Offset, MaxAlign, Skew);
+    AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
+                          Offset, MaxAlign, Skew);
+    AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
+                          Offset, MaxAlign, Skew);
+  }
+
+  // Then assign frame offsets to stack objects that are not used to spill
+  // callee saved registers.
+  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+    if (MFI->isObjectPreAllocated(i) &&
+        MFI->getUseLocalStackAllocationBlock())
+      continue;
+    if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
+      continue;
+    if (RS && RS->isScavengingFrameIndex((int)i))
+      continue;
+    if (MFI->isDeadObjectIndex(i))
+      continue;
+    if (MFI->getStackProtectorIndex() == (int)i)
+      continue;
+    if (ProtectedObjs.count(i))
+      continue;
+
+    AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign, Skew);
+  }
+
+  // Make sure the special register scavenging spill slot is closest to the
+  // stack pointer.
+  if (RS && !EarlyScavengingSlots) {
+    SmallVector<int, 2> SFIs;
+    RS->getScavengingFrameIndices(SFIs);
+    for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
+           IE = SFIs.end(); I != IE; ++I)
+      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew);
+  }
+
+  if (!TFI.targetHandlesStackFrameRounding()) {
+    // If we have reserved argument space for call sites in the function
+    // immediately on entry to the current function, count it as part of the
+    // overall stack size.
+    if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
+      Offset += MFI->getMaxCallFrameSize();
+
+    // Round up the size to a multiple of the alignment.  If the function has
+    // any calls or alloca's, align to the target's StackAlignment value to
+    // ensure that the callee's frame or the alloca data is suitably aligned;
+    // otherwise, for leaf functions, align to the TransientStackAlignment
+    // value.
+    unsigned StackAlign;
+    if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
+        (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
+      StackAlign = TFI.getStackAlignment();
+    else
+      StackAlign = TFI.getTransientStackAlignment();
+
+    // If the frame pointer is eliminated, all frame offsets will be relative to
+    // SP not FP. Align to MaxAlign so this works.
+    StackAlign = std::max(StackAlign, MaxAlign);
+    Offset = RoundUpToAlignment(Offset, StackAlign, Skew);
+  }
+
+  // Update frame info to pretend that this is part of the stack...
+  int64_t StackSize = Offset - LocalAreaOffset;
+  MFI->setStackSize(StackSize);
+  NumBytesStackSpace += StackSize;
+}
+
+/// insertPrologEpilogCode - Scan the function for modified callee saved
+/// registers, insert spill code for these callee saved registers, then add
+/// prolog and epilog code to the function.
+///
+void WasmPEI::insertPrologEpilogCode(MachineFunction &Fn) {
+  const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
+
+  // Add prologue to the function...
+  for (MachineBasicBlock *SaveBlock : SaveBlocks)
+    TFI.emitPrologue(Fn, *SaveBlock);
+
+  // Add epilogue to restore the callee-save registers in each exiting block.
+  for (MachineBasicBlock *RestoreBlock : RestoreBlocks)
+    TFI.emitEpilogue(Fn, *RestoreBlock);
+
+  for (MachineBasicBlock *SaveBlock : SaveBlocks)
+    TFI.inlineStackProbe(Fn, *SaveBlock);
+
+  // Emit additional code that is required to support segmented stacks, if
+  // we've been asked for it.  This, when linked with a runtime with support
+  // for segmented stacks (libgcc is one), will result in allocating stack
+  // space in small chunks instead of one large contiguous block.
+  if (Fn.shouldSplitStack()) {
+    for (MachineBasicBlock *SaveBlock : SaveBlocks)
+      TFI.adjustForSegmentedStacks(Fn, *SaveBlock);
+  }
+
+  // Emit additional code that is required to explicitly handle the stack in
+  // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The
+  // approach is rather similar to that of Segmented Stacks, but it uses a
+  // different conditional check and another BIF for allocating more stack
+  // space.
+  if (Fn.getFunction()->getCallingConv() == CallingConv::HiPE)
+    for (MachineBasicBlock *SaveBlock : SaveBlocks)
+      TFI.adjustForHiPEPrologue(Fn, *SaveBlock);
+}
+
+/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
+/// register references and actual offsets.
+///
+void WasmPEI::replaceFrameIndices(MachineFunction &Fn) {
+  const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
+  if (!TFI.needsFrameIndexResolution(Fn)) return;
+
+  // Store SPAdj at exit of a basic block.
+  SmallVector<int, 8> SPState;
+  SPState.resize(Fn.getNumBlockIDs());
+  SmallPtrSet<MachineBasicBlock*, 8> Reachable;
+
+  // Iterate over the reachable blocks in DFS order.
+  for (auto DFI = df_ext_begin(&Fn, Reachable), DFE = df_ext_end(&Fn, Reachable);
+       DFI != DFE; ++DFI) {
+    int SPAdj = 0;
+    // Check the exit state of the DFS stack predecessor.
+    if (DFI.getPathLength() >= 2) {
+      MachineBasicBlock *StackPred = DFI.getPath(DFI.getPathLength() - 2);
+      assert(Reachable.count(StackPred) &&
+             "DFS stack predecessor is already visited.\n");
+      SPAdj = SPState[StackPred->getNumber()];
+    }
+    MachineBasicBlock *BB = *DFI;
+    replaceFrameIndices(BB, Fn, SPAdj);
+    SPState[BB->getNumber()] = SPAdj;
+  }
+
+  // Handle the unreachable blocks.
+  for (auto &BB : Fn) {
+    if (Reachable.count(&BB))
+      // Already handled in DFS traversal.
+      continue;
+    int SPAdj = 0;
+    replaceFrameIndices(&BB, Fn, SPAdj);
+  }
+}
+
+void WasmPEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
+                              int &SPAdj) {
+  assert(Fn.getSubtarget().getRegisterInfo() &&
+         "getRegisterInfo() must be implemented!");
+  const TargetInstrInfo &TII = *Fn.getSubtarget().getInstrInfo();
+  const TargetRegisterInfo &TRI = *Fn.getSubtarget().getRegisterInfo();
+  const TargetFrameLowering *TFI = Fn.getSubtarget().getFrameLowering();
+  unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
+  unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
+
+  if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
+
+  bool InsideCallSequence = false;
+
+  for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
+
+    if (I->getOpcode() == FrameSetupOpcode ||
+        I->getOpcode() == FrameDestroyOpcode) {
+      InsideCallSequence = (I->getOpcode() == FrameSetupOpcode);
+      SPAdj += TII.getSPAdjust(I);
+
+      MachineBasicBlock::iterator PrevI = BB->end();
+      if (I != BB->begin()) PrevI = std::prev(I);
+      TFI->eliminateCallFramePseudoInstr(Fn, *BB, I);
+
+      // Visit the instructions created by eliminateCallFramePseudoInstr().
+      if (PrevI == BB->end())
+        I = BB->begin();     // The replaced instr was the first in the block.
+      else
+        I = std::next(PrevI);
+      continue;
+    }
+
+    MachineInstr *MI = I;
+    bool DoIncr = true;
+    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+      if (!MI->getOperand(i).isFI())
+        continue;
+
+      // Frame indices in debug values are encoded in a target independent
+      // way with simply the frame index and offset rather than any
+      // target-specific addressing mode.
+      if (MI->isDebugValue()) {
+        assert(i == 0 && "Frame indices can only appear as the first "
+                         "operand of a DBG_VALUE machine instruction");
+        unsigned Reg;
+        MachineOperand &Offset = MI->getOperand(1);
+        Offset.setImm(Offset.getImm() +
+                      TFI->getFrameIndexReference(
+                          Fn, MI->getOperand(0).getIndex(), Reg));
+        MI->getOperand(0).ChangeToRegister(Reg, false /*isDef*/);
+        continue;
+      }
+
+      // TODO: This code should be commoned with the code for
+      // PATCHPOINT. There's no good reason for the difference in
+      // implementation other than historical accident.  The only
+      // remaining difference is the unconditional use of the stack
+      // pointer as the base register.
+      if (MI->getOpcode() == TargetOpcode::STATEPOINT) {
+        assert((!MI->isDebugValue() || i == 0) &&
+               "Frame indicies can only appear as the first operand of a "
+               "DBG_VALUE machine instruction");
+        unsigned Reg;
+        MachineOperand &Offset = MI->getOperand(i + 1);
+        const unsigned refOffset =
+          TFI->getFrameIndexReferenceFromSP(Fn, MI->getOperand(i).getIndex(),
+                                            Reg);
+
+        Offset.setImm(Offset.getImm() + refOffset);
+        MI->getOperand(i).ChangeToRegister(Reg, false /*isDef*/);
+        continue;
+      }
+
+      // Some instructions (e.g. inline asm instructions) can have
+      // multiple frame indices and/or cause eliminateFrameIndex
+      // to insert more than one instruction. We need the register
+      // scavenger to go through all of these instructions so that
+      // it can update its register information. We keep the
+      // iterator at the point before insertion so that we can
+      // revisit them in full.
+      bool AtBeginning = (I == BB->begin());
+      if (!AtBeginning) --I;
+
+      // If this instruction has a FrameIndex operand, we need to
+      // use that target machine register info object to eliminate
+      // it.
+      TRI.eliminateFrameIndex(MI, SPAdj, i,
+                              FrameIndexVirtualScavenging ?  nullptr : RS);
+
+      // Reset the iterator if we were at the beginning of the BB.
+      if (AtBeginning) {
+        I = BB->begin();
+        DoIncr = false;
+      }
+
+      MI = nullptr;
+      break;
+    }
+
+    // If we are looking at a call sequence, we need to keep track of
+    // the SP adjustment made by each instruction in the sequence.
+    // This includes both the frame setup/destroy pseudos (handled above),
+    // as well as other instructions that have side effects w.r.t the SP.
+    // Note that this must come after eliminateFrameIndex, because 
+    // if I itself referred to a frame index, we shouldn't count its own
+    // adjustment.
+    if (MI && InsideCallSequence)
+      SPAdj += TII.getSPAdjust(MI);
+
+    if (DoIncr && I != BB->end()) ++I;
+
+    // Update register states.
+    if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
+  }
+}
+
+/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
+/// with physical registers. Use the register scavenger to find an
+/// appropriate register to use.
+///
+/// FIXME: Iterating over the instruction stream is unnecessary. We can simply
+/// iterate over the vreg use list, which at this point only contains machine
+/// operands for which eliminateFrameIndex need a new scratch reg.
+void
+WasmPEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
+  // Run through the instructions and find any virtual registers.
+  for (MachineFunction::iterator BB = Fn.begin(),
+       E = Fn.end(); BB != E; ++BB) {
+    RS->enterBasicBlock(&*BB);
+
+    int SPAdj = 0;
+
+    // The instruction stream may change in the loop, so check BB->end()
+    // directly.
+    for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
+      // We might end up here again with a NULL iterator if we scavenged a
+      // register for which we inserted spill code for definition by what was
+      // originally the first instruction in BB.
+      if (I == MachineBasicBlock::iterator(nullptr))
+        I = BB->begin();
+
+      MachineInstr *MI = I;
+      MachineBasicBlock::iterator J = std::next(I);
+      MachineBasicBlock::iterator P =
+                         I == BB->begin() ? MachineBasicBlock::iterator(nullptr)
+                                          : std::prev(I);
+
+      // RS should process this instruction before we might scavenge at this
+      // location. This is because we might be replacing a virtual register
+      // defined by this instruction, and if so, registers killed by this
+      // instruction are available, and defined registers are not.
+      RS->forward(I);
+
+      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+        if (MI->getOperand(i).isReg()) {
+          MachineOperand &MO = MI->getOperand(i);
+          unsigned Reg = MO.getReg();
+          if (Reg == 0)
+            continue;
+          if (!TargetRegisterInfo::isVirtualRegister(Reg))
+            continue;
+
+          // When we first encounter a new virtual register, it
+          // must be a definition.
+          assert(MI->getOperand(i).isDef() &&
+                 "frame index virtual missing def!");
+          // Scavenge a new scratch register
+          const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
+          unsigned ScratchReg = RS->scavengeRegister(RC, J, SPAdj);
+
+          ++NumScavengedRegs;
+
+          // Replace this reference to the virtual register with the
+          // scratch register.
+          assert (ScratchReg && "Missing scratch register!");
+          Fn.getRegInfo().replaceRegWith(Reg, ScratchReg);
+          
+          // Because this instruction was processed by the RS before this
+          // register was allocated, make sure that the RS now records the
+          // register as being used.
+          RS->setRegUsed(ScratchReg);
+        }
+      }
+
+      // If the scavenger needed to use one of its spill slots, the
+      // spill code will have been inserted in between I and J. This is a
+      // problem because we need the spill code before I: Move I to just
+      // prior to J.
+      if (I != std::prev(J)) {
+        BB->splice(J, &*BB, I);
+
+        // Before we move I, we need to prepare the RS to visit I again.
+        // Specifically, RS will assert if it sees uses of registers that
+        // it believes are undefined. Because we have already processed
+        // register kills in I, when it visits I again, it will believe that
+        // those registers are undefined. To avoid this situation, unprocess
+        // the instruction I.
+        assert(RS->getCurrentPosition() == I &&
+          "The register scavenger has an unexpected position");
+        I = P;
+        RS->unprocess(P);
+      } else
+        ++I;
+    }
+  }
+}

lib/Target/WebAssembly/WebAssemblyPeephole.cpp

for (auto &MI : MBB)
       case WebAssembly::STORE_F64:
       case WebAssembly::STORE_I32:
       case WebAssembly::STORE_I64: {
         // Store instructions return their value operand. If we ended up using
         // the same register for both, replace it with a dead def so that it
         // can use $discard instead.
         MachineOperand &MO = MI.getOperand(0);
         unsigned OldReg = MO.getReg();
-        if (OldReg == MI.getOperand(3).getReg()) {
+        // TODO: Handle SP/physregs
+        if (OldReg == MI.getOperand(3).getReg()
+            && TargetRegisterInfo::isVirtualRegister(MI.getOperand(3).getReg())) {
           Changed = true;
           unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
           MO.setReg(NewReg);
           MO.setIsDead();
           MFI.stackifyVReg(NewReg);
           MFI.addWAReg(NewReg, WebAssemblyFunctionInfo::UnusedReg);
         }
       }
       }
 
   return Changed;
 }

lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp

 //===----------------------------------------------------------------------===//
 
 #include "WebAssembly.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblySubtarget.h"
 #include "llvm/ADT/SCCIterator.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 

 
 bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
   DEBUG(dbgs() << "********** Register Numbering **********\n"
                   "********** Function: "
                << MF.getName() << '\n');
 
   WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
   MachineRegisterInfo &MRI = MF.getRegInfo();
+  const MachineFrameInfo &FrameInfo = *MF.getFrameInfo();
 
   MFI.initWARegs();
 
   // WebAssembly argument registers are in the same index space as local
   // variables. Assign the numbers for them first.
   MachineBasicBlock &EntryMBB = MF.front();
   for (MachineInstr &MI : EntryMBB) {
     switch (MI.getOpcode()) {
if (MFI.isVRegStackified(VReg)) {
       continue;
     }
     // Skip unused registers.
     if (MRI.use_empty(VReg))
       continue;
     if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg)
       MFI.setWAReg(VReg, NumArgRegs + CurReg++);
   }
+  // Allocate locals for used physical registers
+  if (FrameInfo.getStackSize() > 0)
+    MFI.addPReg(WebAssembly::SP32, CurReg++);
 
   return true;
 }

lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp

WebAssemblyRegisterInfo::getReservedRegs(const MachineFunction & /*MF*/) const {
   BitVector Reserved(getNumRegs());
   for (auto Reg : {WebAssembly::SP32, WebAssembly::SP64, WebAssembly::FP32,
                    WebAssembly::FP64})
     Reserved.set(Reg);
   return Reserved;
 }
 
 void WebAssemblyRegisterInfo::eliminateFrameIndex(
-    MachineBasicBlock::iterator /*II*/, int /*SPAdj*/,
-    unsigned /*FIOperandNum*/, RegScavenger * /*RS*/) const {
-  llvm_unreachable(
-      "TODO: implement WebAssemblyRegisterInfo::eliminateFrameIndex");
+    MachineBasicBlock::iterator II, int SPAdj,
+    unsigned FIOperandNum, RegScavenger * /*RS*/) const {
+  assert(SPAdj == 0);
+  MachineInstr &MI = *II;
+
+  MachineBasicBlock &MBB = *MI.getParent();
+  MachineFunction &MF = *MBB.getParent();
+  int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
+  const MachineFrameInfo& MFI = *MF.getFrameInfo();
+  int FrameOffset = MFI.getStackSize() + MFI.getObjectOffset(FrameIndex);
+
+  if (MI.mayLoadOrStore()) {
+    // If this is a load or store, make it relative to SP and fold the frame
+    // offset directly in
+    assert(MI.getOperand(1).getImm() == 0 &&
+           "Can't eliminate FI yet if offset is already set");
+    MI.getOperand(1).setImm(FrameOffset);
+    MI.getOperand(2).ChangeToRegister(WebAssembly::SP32, /*IsDef=*/false);
+  } else {
+    // Otherwise create an i32.add SP, offset and make it the operand
+    auto &MRI = MF.getRegInfo();
+    const auto *TII = MF.getSubtarget().getInstrInfo();
+
+    unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+    BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(WebAssembly::CONST_I32), OffsetReg)
+        .addImm(FrameOffset);
+    BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(WebAssembly::ADD_I32), OffsetReg)
+        .addReg(WebAssembly::SP32)
+        .addReg(OffsetReg);
+    MI.getOperand(FIOperandNum).ChangeToRegister(OffsetReg, /*IsDef=*/false);
+  }
 }
 
 unsigned
 WebAssemblyRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
   static const unsigned Regs[2][2] = {
       /*            !isArch64Bit       isArch64Bit      */
       /* !hasFP */ {WebAssembly::SP32, WebAssembly::SP64},
       /*  hasFP */ {WebAssembly::FP32, WebAssembly::FP64}};

lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

void WebAssemblyPassConfig::addPreRegAlloc() {
   addPass(createWebAssemblyRegStackify());
 }
 
 void WebAssemblyPassConfig::addPostRegAlloc() {
   // TODO: The following CodeGen passes don't currently support code containing
   // virtual registers. Consider removing their restrictions and re-enabling
   // them.
   //
-  // Fails with: Regalloc must assign all vregs.
+  // We use our own PrologEpilogInserter which is very slightly modified to
+  // tolerate virtual registers.
   disablePass(&PrologEpilogCodeInserterID);
   // Fails with: should be run after register allocation.
   disablePass(&MachineCopyPropagationID);
 
   // Run the register coloring pass to reduce the total number of registers.
   addPass(createWebAssemblyRegColoring());
 
   TargetPassConfig::addPostRegAlloc();
+
+  // Run WebAssembly's version of the PrologEpilogInserter. Target-independent
+  // PEI runs after PostRegAlloc and after ShrinkWrap. Putting it here will run
+  // PEI before ShrinkWrap but otherwise in the same position in the order.
+  addPass(createWebAssemblyPEI());
 }
 
 void WebAssemblyPassConfig::addPreEmitPass() {
   TargetPassConfig::addPreEmitPass();
     
   // Put the CFG in structured form; insert BLOCK and LOOP markers.
   addPass(createWebAssemblyCFGStackify());
 

test/CodeGen/WebAssembly/userstack.ll

+; RUN: llc < %s -asm-verbose=false | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -fast-isel | FileCheck %s
+
+
+target datalayout = "e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; CHECK-LABEL: alloca32:
+define void @alloca32() {
+ ; CHECK: i32.const [[L1:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.load [[L1]]=, 0([[L1]])
+ ; CHECK-NEXT: i32.const [[L2:.+]]=, 16
+ ; CHECK-NEXT: i32.sub [[SP:.+]]=, [[L1]], [[L2]]
+ %retval = alloca i32
+ ; CHECK: i32.const $push[[L3:.+]]=, 0
+ ; CHECK: i32.store {{.*}}=, 12([[SP]]), $pop[[L3]]
+ store i32 0, i32* %retval
+ ; CHECK: i32.const [[L4:.+]]=, 16
+ ; CHECK-NEXT: i32.add [[SP]]=, [[SP]], [[L4]]
+ ; CHECK-NEXT: i32.const [[L5:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.store [[SP]]=, 0([[L5]]), [[SP]]
+ ret void
+}
+
+; CHECK-LABEL: alloca3264:
+define void @alloca3264() {
+ ; CHECK: i32.const [[L1:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.load [[L1]]=, 0([[L1]])
+ ; CHECK-NEXT: i32.const [[L2:.+]]=, 16
+ ; CHECK-NEXT: i32.sub [[SP:.+]]=, [[L1]], [[L2]]
+ %r1 = alloca i32
+ %r2 = alloca double
+ ; CHECK: i32.const $push[[L3:.+]]=, 0
+ ; CHECK: i32.store {{.*}}=, 12([[SP]]), $pop[[L3]]
+ store i32 0, i32* %r1
+ ; CHECK: i64.const $push[[L4:.+]]=, 0
+ ; CHECK: i64.store {{.*}}=, 0([[SP]]), $pop[[L4]]
+ store double 0.0, double* %r2
+ ; CHECK: i32.const [[L4:.+]]=, 16
+ ; CHECK-NEXT: i32.add [[SP]]=, [[SP]], [[L4]]
+ ; CHECK-NEXT: i32.const [[L5:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.store [[SP]]=, 0([[L5]]), [[SP]]
+ ret void
+}
+
+define void @allocarray() {
+ ; CHECK: i32.const [[L1:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.load [[L1]]=, 0([[L1]])
+ ; CHECK-NEXT: i32.const [[L2:.+]]=, 32
+ ; CHECK-NEXT: i32.sub [[SP:.+]]=, [[L1]], [[L2]]
+ %r = alloca [5 x i32]
+ ; CHECK: i32.const $push[[L3:.+]]=, 1
+ ; CHECK: i32.store {{.*}}=, 12([[SP]]), $pop[[L3]]
+ %p = getelementptr [5 x i32], [5 x i32]* %r, i32 0, i32 0
+ store i32 1, i32* %p
+ ; CHECK: i32.const $push[[L4:.+]]=, 4
+ ; CHECK: i32.const [[L5:.+]]=, 12
+ ; CHECK: i32.add [[L5]]=, [[SP]], [[L5]]
+ ; CHECK: i32.add $push[[L6:.+]]=, [[L5]], $pop[[L4]]
+ ; CHECK: i32.store {{.*}}=, 0($pop[[L6]]), ${{.+}}
+ %p2 = getelementptr [5 x i32], [5 x i32]* %r, i32 0, i32 1
+ store i32 1, i32* %p2
+ ; CHECK: i32.const [[L7:.+]]=, 32
+ ; CHECK-NEXT: i32.add [[SP]]=, [[SP]], [[L7]]
+ ; CHECK-NEXT: i32.const [[L8:.+]]=, __stack_pointer
+ ; CHECK-NEXT: i32.store [[SP]]=, 0([[L7]]), [[SP]]
+ ret void
+}
+
+; TODO: test aligned alloc