Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1361 insertions, 0 deletions

diff --git a/js/src/jit/arm/Trampoline-arm.cpp b/js/src/jit/arm/Trampoline-arm.cpp
new file mode 100644
index 0000000000..bd4f88a766
--- /dev/null
+++ b/js/src/jit/arm/Trampoline-arm.cpp
@@ -0,0 +1,1361 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jit/arm/SharedICHelpers-arm.h"
+#include "jit/Bailouts.h"
+#include "jit/BaselineFrame.h"
+#include "jit/CalleeToken.h"
+#include "jit/JitFrames.h"
+#include "jit/JitRuntime.h"
+#include "jit/JitSpewer.h"
+#ifdef JS_ION_PERF
+#  include "jit/PerfSpewer.h"
+#endif
+#include "jit/VMFunctions.h"
+#include "vm/JitActivation.h"  // js::jit::JitActivation
+#include "vm/JSContext.h"
+#include "vm/Realm.h"
+
+#include "jit/MacroAssembler-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+static const FloatRegisterSet NonVolatileFloatRegs = FloatRegisterSet(
+    (1ULL << FloatRegisters::d8) | (1ULL << FloatRegisters::d9) |
+    (1ULL << FloatRegisters::d10) | (1ULL << FloatRegisters::d11) |
+    (1ULL << FloatRegisters::d12) | (1ULL << FloatRegisters::d13) |
+    (1ULL << FloatRegisters::d14) | (1ULL << FloatRegisters::d15));
+
+static void GenerateReturn(MacroAssembler& masm, int returnCode) {
+  // Restore non-volatile floating point registers.
+  masm.transferMultipleByRuns(NonVolatileFloatRegs, IsLoad, StackPointer, IA);
+
+  // Get rid of padding word.
+  masm.addPtr(Imm32(sizeof(void*)), sp);
+
+  // Set up return value
+  masm.ma_mov(Imm32(returnCode), r0);
+
+  // Pop and return
+  masm.startDataTransferM(IsLoad, sp, IA, WriteBack);
+  masm.transferReg(r4);
+  masm.transferReg(r5);
+  masm.transferReg(r6);
+  masm.transferReg(r7);
+  masm.transferReg(r8);
+  masm.transferReg(r9);
+  masm.transferReg(r10);
+  masm.transferReg(r11);
+  // r12 isn't saved, so it shouldn't be restored.
+  masm.transferReg(pc);
+  masm.finishDataTransfer();
+  masm.flushBuffer();
+}
+
+struct EnterJITStack {
+  double d8;
+  double d9;
+  double d10;
+  double d11;
+  double d12;
+  double d13;
+  double d14;
+  double d15;
+
+  // Padding.
+  void* padding;
+
+  // Non-volatile registers.
+  void* r4;
+  void* r5;
+  void* r6;
+  void* r7;
+  void* r8;
+  void* r9;
+  void* r10;
+  void* r11;
+  // The abi does not expect r12 (ip) to be preserved
+  void* lr;
+
+  // Arguments.
+  // code == r0
+  // argc == r1
+  // argv == r2
+  // frame == r3
+  CalleeToken token;
+  JSObject* scopeChain;
+  size_t numStackValues;
+  Value* vp;
+};
+
+/*
+ * This method generates a trampoline for a c++ function with the following
+ * signature:
+ *   void enter(void* code, int argc, Value* argv, InterpreterFrame* fp,
+ *              CalleeToken calleeToken, JSObject* scopeChain, Value* vp)
+ *   ...using standard EABI calling convention
+ */
+void JitRuntime::generateEnterJIT(JSContext* cx, MacroAssembler& masm) {
+  enterJITOffset_ = startTrampolineCode(masm);
+
+  const Address slot_token(sp, offsetof(EnterJITStack, token));
+  const Address slot_vp(sp, offsetof(EnterJITStack, vp));
+
+  static_assert(OsrFrameReg == r3);
+
+  Assembler* aasm = &masm;
+
+  // Save non-volatile registers. These must be saved by the trampoline,
+  // rather than the JIT'd code, because they are scanned by the conservative
+  // scanner.
+  masm.startDataTransferM(IsStore, sp, DB, WriteBack);
+  masm.transferReg(r4);   // [sp,0]
+  masm.transferReg(r5);   // [sp,4]
+  masm.transferReg(r6);   // [sp,8]
+  masm.transferReg(r7);   // [sp,12]
+  masm.transferReg(r8);   // [sp,16]
+  masm.transferReg(r9);   // [sp,20]
+  masm.transferReg(r10);  // [sp,24]
+  masm.transferReg(r11);  // [sp,28]
+  // The abi does not expect r12 (ip) to be preserved
+  masm.transferReg(lr);  // [sp,32]
+  // The 5th argument is located at [sp, 36]
+  masm.finishDataTransfer();
+
+  // Add padding word.
+  masm.subPtr(Imm32(sizeof(void*)), sp);
+
+  // Push the float registers.
+  masm.transferMultipleByRuns(NonVolatileFloatRegs, IsStore, sp, DB);
+
+  // Save stack pointer into r8
+  masm.movePtr(sp, r8);
+
+  // Load calleeToken into r9.
+  masm.loadPtr(slot_token, r9);
+
+  // Save stack pointer.
+  masm.movePtr(sp, r11);
+
+  // Load the number of actual arguments into r10.
+  masm.loadPtr(slot_vp, r10);
+  masm.unboxInt32(Address(r10, 0), r10);
+
+  {
+    Label noNewTarget;
+    masm.branchTest32(Assembler::Zero, r9,
+                      Imm32(CalleeToken_FunctionConstructing), &noNewTarget);
+
+    masm.add32(Imm32(1), r1);
+
+    masm.bind(&noNewTarget);
+  }
+
+  // Guarantee stack alignment of Jit frames.
+  //
+  // This code moves the stack pointer to the location where it should be when
+  // we enter the Jit frame.  It moves the stack pointer such that we have
+  // enough space reserved for pushing the arguments, and the JitFrameLayout.
+  // The stack pointer is also aligned on the alignment expected by the Jit
+  // frames.
+  //
+  // At the end the register r4, is a pointer to the stack where the first
+  // argument is expected by the Jit frame.
+  //
+  aasm->as_sub(r4, sp, O2RegImmShift(r1, LSL, 3));  // r4 = sp - argc*8
+  aasm->as_bic(r4, r4, Imm8(JitStackAlignment - 1));
+  // r4 is now the aligned on the bottom of the list of arguments.
+  static_assert(
+      sizeof(JitFrameLayout) % JitStackAlignment == 0,
+      "No need to consider the JitFrameLayout for aligning the stack");
+  // sp' = ~(JitStackAlignment - 1) & (sp - argc * sizeof(Value))
+  //       - sizeof(JitFrameLayout)
+  aasm->as_sub(sp, r4, Imm8(sizeof(JitFrameLayout)));
+
+  // Get a copy of the number of args to use as a decrement counter, also set
+  // the zero condition code.
+  aasm->as_mov(r5, O2Reg(r1), SetCC);
+
+  // Loop over arguments, copying them from an unknown buffer onto the Ion
+  // stack so they can be accessed from JIT'ed code.
+  {
+    Label header, footer;
+    // If there aren't any arguments, don't do anything.
+    aasm->as_b(&footer, Assembler::Zero);
+    // Get the top of the loop.
+    masm.bind(&header);
+    aasm->as_sub(r5, r5, Imm8(1), SetCC);
+    // We could be more awesome, and unroll this, using a loadm
+    // (particularly since the offset is effectively 0) but that seems more
+    // error prone, and complex.
+    // BIG FAT WARNING: this loads both r6 and r7.
+    aasm->as_extdtr(IsLoad, 64, true, PostIndex, r6,
+                    EDtrAddr(r2, EDtrOffImm(8)));
+    aasm->as_extdtr(IsStore, 64, true, PostIndex, r6,
+                    EDtrAddr(r4, EDtrOffImm(8)));
+    aasm->as_b(&header, Assembler::NonZero);
+    masm.bind(&footer);
+  }
+
+  masm.ma_sub(r8, sp, r8);
+  masm.makeFrameDescriptor(r8, FrameType::CppToJSJit, JitFrameLayout::Size());
+
+  masm.startDataTransferM(IsStore, sp, IB, NoWriteBack);
+  // [sp]    = return address (written later)
+  masm.transferReg(r8);   // [sp',4] = descriptor, argc*8+20
+  masm.transferReg(r9);   // [sp',8]  = callee token
+  masm.transferReg(r10);  // [sp',12]  = actual arguments
+  masm.finishDataTransfer();
+
+  Label returnLabel;
+  {
+    // Handle Interpreter -> Baseline OSR.
+    AllocatableGeneralRegisterSet regs(GeneralRegisterSet::All());
+    regs.take(JSReturnOperand);
+    regs.takeUnchecked(OsrFrameReg);
+    regs.take(r11);
+    regs.take(ReturnReg);
+
+    const Address slot_numStackValues(r11,
+                                      offsetof(EnterJITStack, numStackValues));
+
+    Label notOsr;
+    masm.branchTestPtr(Assembler::Zero, OsrFrameReg, OsrFrameReg, &notOsr);
+
+    Register scratch = regs.takeAny();
+
+    Register numStackValues = regs.takeAny();
+    masm.load32(slot_numStackValues, numStackValues);
+
+    // Write return address. On ARM, CodeLabel is only used for tableswitch,
+    // so we can't use it here to get the return address. Instead, we use pc
+    // + a fixed offset to a jump to returnLabel. The pc register holds pc +
+    // 8, so we add the size of 2 instructions to skip the instructions
+    // emitted by storePtr and jump(&skipJump).
+    {
+      AutoForbidPoolsAndNops afp(&masm, 5);
+      Label skipJump;
+      masm.mov(pc, scratch);
+      masm.addPtr(Imm32(2 * sizeof(uint32_t)), scratch);
+      masm.storePtr(scratch, Address(sp, 0));
+      masm.jump(&skipJump);
+      masm.jump(&returnLabel);
+      masm.bind(&skipJump);
+    }
+
+    // Push previous frame pointer.
+    masm.push(r11);
+
+    // Reserve frame.
+    Register framePtr = r11;
+    masm.subPtr(Imm32(BaselineFrame::Size()), sp);
+
+    masm.touchFrameValues(numStackValues, scratch, framePtr);
+    masm.mov(sp, framePtr);
+
+    // Reserve space for locals and stack values.
+    masm.ma_lsl(Imm32(3), numStackValues, scratch);
+    masm.ma_sub(sp, scratch, sp);
+
+    // Enter exit frame.
+    masm.addPtr(
+        Imm32(BaselineFrame::Size() + BaselineFrame::FramePointerOffset),
+        scratch);
+    masm.makeFrameDescriptor(scratch, FrameType::BaselineJS,
+                             ExitFrameLayout::Size());
+    masm.push(scratch);
+    masm.push(Imm32(0));  // Fake return address.
+    // No GC things to mark on the stack, push a bare token.
+    masm.loadJSContext(scratch);
+    masm.enterFakeExitFrame(scratch, scratch, ExitFrameType::Bare);
+
+    masm.push(framePtr);  // BaselineFrame
+    masm.push(r0);        // jitcode
+
+    using Fn = bool (*)(BaselineFrame * frame, InterpreterFrame * interpFrame,
+                        uint32_t numStackValues);
+    masm.setupUnalignedABICall(scratch);
+    masm.passABIArg(r11);          // BaselineFrame
+    masm.passABIArg(OsrFrameReg);  // InterpreterFrame
+    masm.passABIArg(numStackValues);
+    masm.callWithABI<Fn, jit::InitBaselineFrameForOsr>(
+        MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+    Register jitcode = regs.takeAny();
+    masm.pop(jitcode);
+    masm.pop(framePtr);
+
+    MOZ_ASSERT(jitcode != ReturnReg);
+
+    Label error;
+    masm.addPtr(Imm32(ExitFrameLayout::SizeWithFooter()), sp);
+    masm.addPtr(Imm32(BaselineFrame::Size()), framePtr);
+    masm.branchIfFalseBool(ReturnReg, &error);
+
+    // If OSR-ing, then emit instrumentation for setting lastProfilerFrame
+    // if profiler instrumentation is enabled.
+    {
+      Label skipProfilingInstrumentation;
+      Register realFramePtr = numStackValues;
+      AbsoluteAddress addressOfEnabled(
+          cx->runtime()->geckoProfiler().addressOfEnabled());
+      masm.branch32(Assembler::Equal, addressOfEnabled, Imm32(0),
+                    &skipProfilingInstrumentation);
+      masm.as_add(realFramePtr, framePtr, Imm8(sizeof(void*)));
+      masm.profilerEnterFrame(realFramePtr, scratch);
+      masm.bind(&skipProfilingInstrumentation);
+    }
+
+    masm.jump(jitcode);
+
+    // OOM: Load error value, discard return address and previous frame
+    // pointer and return.
+    masm.bind(&error);
+    masm.mov(framePtr, sp);
+    masm.addPtr(Imm32(2 * sizeof(uintptr_t)), sp);
+    masm.moveValue(MagicValue(JS_ION_ERROR), JSReturnOperand);
+    masm.jump(&returnLabel);
+
+    masm.bind(&notOsr);
+    // Load the scope chain in R1.
+    MOZ_ASSERT(R1.scratchReg() != r0);
+    masm.loadPtr(Address(r11, offsetof(EnterJITStack, scopeChain)),
+                 R1.scratchReg());
+  }
+
+  // The Data transfer is pushing 4 words, which already account for the
+  // return address space of the Jit frame.  We have to undo what the data
+  // transfer did before making the call.
+  masm.addPtr(Imm32(sizeof(uintptr_t)), sp);
+
+  // The callee will push the return address on the stack, thus we check that
+  // the stack would be aligned once the call is complete.
+  masm.assertStackAlignment(JitStackAlignment, sizeof(uintptr_t));
+
+  // Call the function.
+  masm.callJitNoProfiler(r0);
+
+  // Interpreter -> Baseline OSR will return here.
+  masm.bind(&returnLabel);
+
+  // The top of the stack now points to the address of the field following the
+  // return address because the return address is popped for the return, so we
+  // need to remove the size of the return address field.
+  aasm->as_sub(sp, sp, Imm8(4));
+
+  // Load off of the stack the size of our local stack.
+  masm.loadPtr(Address(sp, JitFrameLayout::offsetOfDescriptor()), r5);
+  aasm->as_add(sp, sp, lsr(r5, FRAMESIZE_SHIFT));
+
+  // Store the returned value into the slot_vp
+  masm.loadPtr(slot_vp, r5);
+  masm.storeValue(JSReturnOperand, Address(r5, 0));
+
+  // :TODO: Optimize storeValue with:
+  // We're using a load-double here. In order for that to work, the data needs
+  // to be stored in two consecutive registers, make sure this is the case
+  //   MOZ_ASSERT(JSReturnReg_Type.code() == JSReturnReg_Data.code()+1);
+  //   aasm->as_extdtr(IsStore, 64, true, Offset,
+  //                   JSReturnReg_Data, EDtrAddr(r5, EDtrOffImm(0)));
+
+  // Restore non-volatile registers and return.
+  GenerateReturn(masm, true);
+}
+
+void JitRuntime::generateInvalidator(MacroAssembler& masm, Label* bailoutTail) {
+  // See large comment in x86's JitRuntime::generateInvalidator.
+
+  invalidatorOffset_ = startTrampolineCode(masm);
+
+  // At this point, one of two things has happened:
+  // 1) Execution has just returned from C code, which left the stack aligned
+  // 2) Execution has just returned from Ion code, which left the stack
+  // unaligned. The old return address should not matter, but we still want the
+  // stack to be aligned, and there is no good reason to automatically align it
+  // with a call to setupUnalignedABICall.
+  masm.as_bic(sp, sp, Imm8(7));
+  masm.startDataTransferM(IsStore, sp, DB, WriteBack);
+  // We don't have to push everything, but this is likely easier.
+  // Setting regs_.
+  for (uint32_t i = 0; i < Registers::Total; i++) {
+    masm.transferReg(Register::FromCode(i));
+  }
+  masm.finishDataTransfer();
+
+  // Since our datastructures for stack inspection are compile-time fixed,
+  // if there are only 16 double registers, then we need to reserve
+  // space on the stack for the missing 16.
+  if (FloatRegisters::ActualTotalPhys() != FloatRegisters::TotalPhys) {
+    ScratchRegisterScope scratch(masm);
+    int missingRegs =
+        FloatRegisters::TotalPhys - FloatRegisters::ActualTotalPhys();
+    masm.ma_sub(Imm32(missingRegs * sizeof(double)), sp, scratch);
+  }
+
+  masm.startFloatTransferM(IsStore, sp, DB, WriteBack);
+  for (uint32_t i = 0; i < FloatRegisters::ActualTotalPhys(); i++) {
+    masm.transferFloatReg(FloatRegister(i, FloatRegister::Double));
+  }
+  masm.finishFloatTransfer();
+
+  masm.ma_mov(sp, r0);
+  const int sizeOfRetval = sizeof(size_t) * 2;
+  masm.reserveStack(sizeOfRetval);
+  masm.mov(sp, r1);
+  const int sizeOfBailoutInfo = sizeof(void*) * 2;
+  masm.reserveStack(sizeOfBailoutInfo);
+  masm.mov(sp, r2);
+  using Fn = bool (*)(InvalidationBailoutStack * sp, size_t * frameSizeOut,
+                      BaselineBailoutInfo * *info);
+  masm.setupAlignedABICall();
+  masm.passABIArg(r0);
+  masm.passABIArg(r1);
+  masm.passABIArg(r2);
+  masm.callWithABI<Fn, InvalidationBailout>(
+      MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckOther);
+
+  masm.ma_ldr(DTRAddr(sp, DtrOffImm(0)), r2);
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_ldr(Address(sp, sizeOfBailoutInfo), r1, scratch);
+  }
+  // Remove the return address, the IonScript, the register state
+  // (InvaliationBailoutStack) and the space that was allocated for the return
+  // value.
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_add(sp,
+                Imm32(sizeof(InvalidationBailoutStack) + sizeOfRetval +
+                      sizeOfBailoutInfo),
+                sp, scratch);
+  }
+  // Remove the space that this frame was using before the bailout (computed
+  // by InvalidationBailout)
+  masm.ma_add(sp, r1, sp);
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in r2.
+  masm.jump(bailoutTail);
+}
+
+void JitRuntime::generateArgumentsRectifier(MacroAssembler& masm,
+                                            ArgumentsRectifierKind kind) {
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      argumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      trialInliningArgumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+  }
+  masm.pushReturnAddress();
+
+  // Copy number of actual arguments into r0 and r8.
+  masm.ma_ldr(
+      DTRAddr(sp, DtrOffImm(RectifierFrameLayout::offsetOfNumActualArgs())),
+      r0);
+  masm.mov(r0, r8);
+
+  // Load the number of |undefined|s to push into r6.
+  masm.ma_ldr(
+      DTRAddr(sp, DtrOffImm(RectifierFrameLayout::offsetOfCalleeToken())), r1);
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_and(Imm32(CalleeTokenMask), r1, r6, scratch);
+  }
+  masm.ma_ldrh(EDtrAddr(r6, EDtrOffImm(JSFunction::offsetOfNargs())), r6);
+
+  masm.ma_sub(r6, r8, r2);
+
+  // Get the topmost argument.
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_alu(sp, lsl(r8, 3), r3, OpAdd);  // r3 <- r3 + nargs * 8
+    masm.ma_add(r3, Imm32(sizeof(RectifierFrameLayout)), r3, scratch);
+  }
+
+  {
+    Label notConstructing;
+
+    masm.branchTest32(Assembler::Zero, r1,
+                      Imm32(CalleeToken_FunctionConstructing),
+                      &notConstructing);
+
+    // Add sizeof(Value) to overcome |this|
+    masm.as_extdtr(IsLoad, 64, true, Offset, r4, EDtrAddr(r3, EDtrOffImm(8)));
+    masm.as_extdtr(IsStore, 64, true, PreIndex, r4,
+                   EDtrAddr(sp, EDtrOffImm(-8)));
+
+    // Include the newly pushed newTarget value in the frame size
+    // calculated below.
+    masm.add32(Imm32(1), r6);
+
+    masm.bind(&notConstructing);
+  }
+
+  // Push undefined.
+  masm.moveValue(UndefinedValue(), ValueOperand(r5, r4));
+  {
+    Label undefLoopTop;
+    masm.bind(&undefLoopTop);
+    masm.as_extdtr(IsStore, 64, true, PreIndex, r4,
+                   EDtrAddr(sp, EDtrOffImm(-8)));
+    masm.as_sub(r2, r2, Imm8(1), SetCC);
+
+    masm.ma_b(&undefLoopTop, Assembler::NonZero);
+  }
+
+  // Push arguments, |nargs| + 1 times (to include |this|).
+  {
+    Label copyLoopTop;
+    masm.bind(&copyLoopTop);
+    masm.as_extdtr(IsLoad, 64, true, PostIndex, r4,
+                   EDtrAddr(r3, EDtrOffImm(-8)));
+    masm.as_extdtr(IsStore, 64, true, PreIndex, r4,
+                   EDtrAddr(sp, EDtrOffImm(-8)));
+
+    masm.as_sub(r8, r8, Imm8(1), SetCC);
+    masm.ma_b(&copyLoopTop, Assembler::NotSigned);
+  }
+
+  // translate the framesize from values into bytes
+  masm.as_add(r6, r6, Imm8(1));
+  masm.ma_lsl(Imm32(3), r6, r6);
+
+  // Construct sizeDescriptor.
+  masm.makeFrameDescriptor(r6, FrameType::Rectifier, JitFrameLayout::Size());
+
+  // Construct JitFrameLayout.
+  masm.ma_push(r0);  // actual arguments.
+  masm.ma_push(r1);  // callee token
+  masm.ma_push(r6);  // frame descriptor.
+
+  // Call the target function.
+  masm.andPtr(Imm32(CalleeTokenMask), r1);
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      masm.loadJitCodeRaw(r1, r3);
+      argumentsRectifierReturnOffset_ = masm.callJitNoProfiler(r3);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      Label noBaselineScript, done;
+      masm.loadBaselineJitCodeRaw(r1, r3, &noBaselineScript);
+      masm.callJitNoProfiler(r3);
+      masm.jump(&done);
+
+      // See BaselineCacheIRCompiler::emitCallInlinedFunction.
+      masm.bind(&noBaselineScript);
+      masm.loadJitCodeRaw(r1, r3);
+      masm.callJitNoProfiler(r3);
+      masm.bind(&done);
+      break;
+  }
+
+  // arg1
+  //  ...
+  // argN
+  // num actual args
+  // callee token
+  // sizeDescriptor     <- sp now
+  // return address
+
+  // Remove the rectifier frame.
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_dtr(IsLoad, sp, Imm32(12), r4, scratch, PostIndex);
+  }
+
+  // arg1
+  //  ...
+  // argN               <- sp now; r4 <- frame descriptor
+  // num actual args
+  // callee token
+  // sizeDescriptor
+  // return address
+
+  // Discard pushed arguments.
+  masm.ma_alu(sp, lsr(r4, FRAMESIZE_SHIFT), sp, OpAdd);
+
+  masm.ret();
+}
+
+static void PushBailoutFrame(MacroAssembler& masm, uint32_t frameClass,
+                             Register spArg) {
+#ifdef ENABLE_WASM_SIMD
+#  error "Needs more careful logic if SIMD is enabled"
+#endif
+
+  // the stack should look like:
+  // [IonFrame]
+  // bailoutFrame.registersnapshot
+  // bailoutFrame.fpsnapshot
+  // bailoutFrame.snapshotOffset
+  // bailoutFrame.frameSize
+
+  // STEP 1a: Save our register sets to the stack so Bailout() can read
+  // everything.
+  // sp % 8 == 0
+
+  masm.startDataTransferM(IsStore, sp, DB, WriteBack);
+  // We don't have to push everything, but this is likely easier.
+  // Setting regs_.
+  for (uint32_t i = 0; i < Registers::Total; i++) {
+    masm.transferReg(Register::FromCode(i));
+  }
+  masm.finishDataTransfer();
+
+  ScratchRegisterScope scratch(masm);
+
+  // Since our datastructures for stack inspection are compile-time fixed,
+  // if there are only 16 double registers, then we need to reserve
+  // space on the stack for the missing 16.
+  if (FloatRegisters::ActualTotalPhys() != FloatRegisters::TotalPhys) {
+    int missingRegs =
+        FloatRegisters::TotalPhys - FloatRegisters::ActualTotalPhys();
+    masm.ma_sub(Imm32(missingRegs * sizeof(double)), sp, scratch);
+  }
+  masm.startFloatTransferM(IsStore, sp, DB, WriteBack);
+  for (uint32_t i = 0; i < FloatRegisters::ActualTotalPhys(); i++) {
+    masm.transferFloatReg(FloatRegister(i, FloatRegister::Double));
+  }
+  masm.finishFloatTransfer();
+
+  // STEP 1b: Push both the "return address" of the function call (the address
+  //          of the instruction after the call that we used to get here) as
+  //          well as the callee token onto the stack. The return address is
+  //          currently in r14. We will proceed by loading the callee token
+  //          into a sacrificial register <= r14, then pushing both onto the
+  //          stack.
+
+  // Now place the frameClass onto the stack, via a register.
+  masm.ma_mov(Imm32(frameClass), r4);
+  // And onto the stack. Since the stack is full, we need to put this one past
+  // the end of the current stack. Sadly, the ABI says that we need to always
+  // point to the lowest place that has been written. The OS is free to do
+  // whatever it wants below sp.
+  masm.startDataTransferM(IsStore, sp, DB, WriteBack);
+  // Set frameClassId_.
+  masm.transferReg(r4);
+  // Set tableOffset_; higher registers are stored at higher locations on the
+  // stack.
+  masm.transferReg(lr);
+  masm.finishDataTransfer();
+
+  masm.ma_mov(sp, spArg);
+}
+
+static void GenerateBailoutThunk(MacroAssembler& masm, uint32_t frameClass,
+                                 Label* bailoutTail) {
+  PushBailoutFrame(masm, frameClass, r0);
+
+  // SP % 8 == 4
+  // STEP 1c: Call the bailout function, giving a pointer to the
+  //          structure we just blitted onto the stack.
+  const int sizeOfBailoutInfo = sizeof(void*) * 2;
+  masm.reserveStack(sizeOfBailoutInfo);
+  masm.mov(sp, r1);
+  using Fn = bool (*)(BailoutStack * sp, BaselineBailoutInfo * *info);
+  masm.setupAlignedABICall();
+
+  // Decrement sp by another 4, so we keep alignment. Not Anymore! Pushing
+  // both the snapshotoffset as well as the: masm.as_sub(sp, sp, Imm8(4));
+
+  // Set the old (4-byte aligned) value of the sp as the first argument.
+  masm.passABIArg(r0);
+  masm.passABIArg(r1);
+
+  // Sp % 8 == 0
+  masm.callWithABI<Fn, Bailout>(MoveOp::GENERAL,
+                                CheckUnsafeCallWithABI::DontCheckOther);
+  masm.ma_ldr(DTRAddr(sp, DtrOffImm(0)), r2);
+  {
+    ScratchRegisterScope scratch(masm);
+    masm.ma_add(sp, Imm32(sizeOfBailoutInfo), sp, scratch);
+  }
+
+  // Common size of a bailout frame.
+  uint32_t bailoutFrameSize = 0 + sizeof(void*)  // frameClass
+                              + sizeof(RegisterDump);
+
+  if (frameClass == NO_FRAME_SIZE_CLASS_ID) {
+    // Make sure the bailout frame size fits into the offset for a load.
+    masm.as_dtr(IsLoad, 32, Offset, r4, DTRAddr(sp, DtrOffImm(4)));
+    // Used to be: offsetof(BailoutStack, frameSize_)
+    // This structure is no longer available to us :(
+    // We add 12 to the bailoutFrameSize because:
+    // sizeof(uint32_t) for the tableOffset that was pushed onto the stack
+    // sizeof(uintptr_t) for the snapshotOffset;
+    // alignment to round the uintptr_t up to a multiple of 8 bytes.
+    ScratchRegisterScope scratch(masm);
+    masm.ma_add(sp, Imm32(bailoutFrameSize + 12), sp, scratch);
+    masm.as_add(sp, sp, O2Reg(r4));
+  } else {
+    ScratchRegisterScope scratch(masm);
+    uint32_t frameSize = FrameSizeClass::FromClass(frameClass).frameSize();
+    masm.ma_add(Imm32(  // The frame that was added when we entered the most
+                        // recent function.
+                    frameSize
+                    // The size of the "return address" that was dumped on
+                    // the stack.
+                    + sizeof(void*)
+                    // Everything else that was pushed on the stack.
+                    + bailoutFrameSize),
+                sp, scratch);
+  }
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in r2.
+  masm.jump(bailoutTail);
+}
+
+JitRuntime::BailoutTable JitRuntime::generateBailoutTable(MacroAssembler& masm,
+                                                          Label* bailoutTail,
+                                                          uint32_t frameClass) {
+  uint32_t offset = startTrampolineCode(masm);
+
+  {
+    // Emit the table without any pools being inserted.
+    Label bailout;
+    AutoForbidPoolsAndNops afp(&masm, BAILOUT_TABLE_SIZE);
+    for (size_t i = 0; i < BAILOUT_TABLE_SIZE; i++) {
+      masm.ma_bl(&bailout);
+    }
+    masm.bind(&bailout);
+  }
+
+  GenerateBailoutThunk(masm, frameClass, bailoutTail);
+
+  return BailoutTable(offset, masm.currentOffset() - offset);
+}
+
+void JitRuntime::generateBailoutHandler(MacroAssembler& masm,
+                                        Label* bailoutTail) {
+  bailoutHandlerOffset_ = startTrampolineCode(masm);
+
+  GenerateBailoutThunk(masm, NO_FRAME_SIZE_CLASS_ID, bailoutTail);
+}
+
+bool JitRuntime::generateVMWrapper(JSContext* cx, MacroAssembler& masm,
+                                   const VMFunctionData& f, DynFn nativeFun,
+                                   uint32_t* wrapperOffset) {
+  *wrapperOffset = startTrampolineCode(masm);
+
+  AllocatableGeneralRegisterSet regs(Register::Codes::WrapperMask);
+
+  static_assert(
+      (Register::Codes::VolatileMask & ~Register::Codes::WrapperMask) == 0,
+      "Wrapper register set must be a superset of Volatile register set.");
+
+  // The context is the first argument; r0 is the first argument register.
+  Register cxreg = r0;
+  regs.take(cxreg);
+
+  // Stack is:
+  //    ... frame ...
+  //  +8  [args] + argPadding
+  //  +0  ExitFrame
+  //
+  // We're aligned to an exit frame, so link it up.
+  // If it isn't a tail call, then the return address needs to be saved
+  if (f.expectTailCall == NonTailCall) {
+    masm.pushReturnAddress();
+  }
+
+  masm.loadJSContext(cxreg);
+  masm.enterExitFrame(cxreg, regs.getAny(), &f);
+
+  // Save the base of the argument set stored on the stack.
+  Register argsBase = InvalidReg;
+  if (f.explicitArgs) {
+    argsBase = r5;
+    regs.take(argsBase);
+    ScratchRegisterScope scratch(masm);
+    masm.ma_add(sp, Imm32(ExitFrameLayout::SizeWithFooter()), argsBase,
+                scratch);
+  }
+
+  // Reserve space for the outparameter.
+  Register outReg = InvalidReg;
+  switch (f.outParam) {
+    case Type_Value:
+      outReg = r4;
+      regs.take(outReg);
+      masm.reserveStack(sizeof(Value));
+      masm.ma_mov(sp, outReg);
+      break;
+
+    case Type_Handle:
+      outReg = r4;
+      regs.take(outReg);
+      masm.PushEmptyRooted(f.outParamRootType);
+      masm.ma_mov(sp, outReg);
+      break;
+
+    case Type_Int32:
+    case Type_Pointer:
+    case Type_Bool:
+      outReg = r4;
+      regs.take(outReg);
+      masm.reserveStack(sizeof(int32_t));
+      masm.ma_mov(sp, outReg);
+      break;
+
+    case Type_Double:
+      outReg = r4;
+      regs.take(outReg);
+      masm.reserveStack(sizeof(double));
+      masm.ma_mov(sp, outReg);
+      break;
+
+    default:
+      MOZ_ASSERT(f.outParam == Type_Void);
+      break;
+  }
+
+  if (!generateTLEnterVM(masm, f)) {
+    return false;
+  }
+
+  masm.setupUnalignedABICall(regs.getAny());
+  masm.passABIArg(cxreg);
+
+  size_t argDisp = 0;
+
+  // Copy any arguments.
+  for (uint32_t explicitArg = 0; explicitArg < f.explicitArgs; explicitArg++) {
+    switch (f.argProperties(explicitArg)) {
+      case VMFunctionData::WordByValue:
+        masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+      case VMFunctionData::DoubleByValue:
+        // Values should be passed by reference, not by value, so we assert
+        // that the argument is a double-precision float.
+        MOZ_ASSERT(f.argPassedInFloatReg(explicitArg));
+        masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::DOUBLE);
+        argDisp += sizeof(double);
+        break;
+      case VMFunctionData::WordByRef:
+        masm.passABIArg(
+            MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+            MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+      case VMFunctionData::DoubleByRef:
+        masm.passABIArg(
+            MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+            MoveOp::GENERAL);
+        argDisp += 2 * sizeof(void*);
+        break;
+    }
+  }
+
+  // Copy the implicit outparam, if any.
+  if (outReg != InvalidReg) {
+    masm.passABIArg(outReg);
+  }
+
+  masm.callWithABI(nativeFun, MoveOp::GENERAL,
+                   CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+  if (!generateTLExitVM(masm, f)) {
+    return false;
+  }
+
+  // Test for failure.
+  switch (f.failType()) {
+    case Type_Object:
+      masm.branchTestPtr(Assembler::Zero, r0, r0, masm.failureLabel());
+      break;
+    case Type_Bool:
+      masm.branchIfFalseBool(r0, masm.failureLabel());
+      break;
+    case Type_Void:
+      break;
+    default:
+      MOZ_CRASH("unknown failure kind");
+  }
+
+  // Load the outparam and free any allocated stack.
+  switch (f.outParam) {
+    case Type_Handle:
+      masm.popRooted(f.outParamRootType, ReturnReg, JSReturnOperand);
+      break;
+
+    case Type_Value:
+      masm.loadValue(Address(sp, 0), JSReturnOperand);
+      masm.freeStack(sizeof(Value));
+      break;
+
+    case Type_Int32:
+    case Type_Pointer:
+      masm.load32(Address(sp, 0), ReturnReg);
+      masm.freeStack(sizeof(int32_t));
+      break;
+
+    case Type_Bool:
+      masm.load8ZeroExtend(Address(sp, 0), ReturnReg);
+      masm.freeStack(sizeof(int32_t));
+      break;
+
+    case Type_Double:
+      if (JitOptions.supportsFloatingPoint) {
+        masm.loadDouble(Address(sp, 0), ReturnDoubleReg);
+      } else {
+        masm.assumeUnreachable(
+            "Unable to load into float reg, with no FP support.");
+      }
+      masm.freeStack(sizeof(double));
+      break;
+
+    default:
+      MOZ_ASSERT(f.outParam == Type_Void);
+      break;
+  }
+
+  // Until C++ code is instrumented against Spectre, prevent speculative
+  // execution from returning any private data.
+  if (f.returnsData() && JitOptions.spectreJitToCxxCalls) {
+    masm.speculationBarrier();
+  }
+
+  masm.leaveExitFrame();
+  masm.retn(Imm32(sizeof(ExitFrameLayout) +
+                  f.explicitStackSlots() * sizeof(void*) +
+                  f.extraValuesToPop * sizeof(Value)));
+
+  return true;
+}
+
+uint32_t JitRuntime::generatePreBarrier(JSContext* cx, MacroAssembler& masm,
+                                        MIRType type) {
+  uint32_t offset = startTrampolineCode(masm);
+
+  masm.pushReturnAddress();
+
+  static_assert(PreBarrierReg == r1);
+  Register temp1 = r2;
+  Register temp2 = r3;
+  Register temp3 = r4;
+  masm.push(temp1);
+  masm.push(temp2);
+  masm.push(temp3);
+
+  Label noBarrier;
+  masm.emitPreBarrierFastPath(cx->runtime(), type, temp1, temp2, temp3,
+                              &noBarrier);
+
+  // Call into C++ to mark this GC thing.
+  masm.pop(temp3);
+  masm.pop(temp2);
+  masm.pop(temp1);
+
+  LiveRegisterSet save;
+  if (JitOptions.supportsFloatingPoint) {
+    save.set() =
+        RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                    FloatRegisterSet(FloatRegisters::VolatileDoubleMask));
+  } else {
+    save.set() = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                             FloatRegisterSet());
+  }
+  masm.PushRegsInMask(save);
+
+  masm.movePtr(ImmPtr(cx->runtime()), r0);
+
+  masm.setupUnalignedABICall(r2);
+  masm.passABIArg(r0);
+  masm.passABIArg(r1);
+  masm.callWithABI(JitMarkFunction(type));
+  masm.PopRegsInMask(save);
+  masm.ret();
+
+  masm.bind(&noBarrier);
+  masm.pop(temp3);
+  masm.pop(temp2);
+  masm.pop(temp1);
+  masm.ret();
+
+  return offset;
+}
+
+void JitRuntime::generateExceptionTailStub(MacroAssembler& masm,
+                                           Label* profilerExitTail) {
+  exceptionTailOffset_ = startTrampolineCode(masm);
+
+  masm.bind(masm.failureLabel());
+  masm.handleFailureWithHandlerTail(profilerExitTail);
+}
+
+void JitRuntime::generateBailoutTailStub(MacroAssembler& masm,
+                                         Label* bailoutTail) {
+  bailoutTailOffset_ = startTrampolineCode(masm);
+  masm.bind(bailoutTail);
+
+  masm.generateBailoutTail(r1, r2);
+}
+
+void JitRuntime::generateProfilerExitFrameTailStub(MacroAssembler& masm,
+                                                   Label* profilerExitTail) {
+  profilerExitFrameTailOffset_ = startTrampolineCode(masm);
+  masm.bind(profilerExitTail);
+
+  Register scratch1 = r5;
+  Register scratch2 = r6;
+  Register scratch3 = r7;
+  Register scratch4 = r8;
+
+  //
+  // The code generated below expects that the current stack pointer points
+  // to an Ion or Baseline frame, at the state it would be immediately
+  // before a ret().  Thus, after this stub's business is done, it executes
+  // a ret() and returns directly to the caller script, on behalf of the
+  // callee script that jumped to this code.
+  //
+  // Thus the expected stack is:
+  //
+  //                                   StackPointer ----+
+  //                                                    v
+  // ..., ActualArgc, CalleeToken, Descriptor, ReturnAddr
+  // MEM-HI                                       MEM-LOW
+  //
+  //
+  // The generated jitcode is responsible for overwriting the
+  // jitActivation->lastProfilingFrame field with a pointer to the previous
+  // Ion or Baseline jit-frame that was pushed before this one. It is also
+  // responsible for overwriting jitActivation->lastProfilingCallSite with
+  // the return address into that frame.  The frame could either be an
+  // immediate "caller" frame, or it could be a frame in a previous
+  // JitActivation (if the current frame was entered from C++, and the C++
+  // was entered by some caller jit-frame further down the stack).
+  //
+  // So this jitcode is responsible for "walking up" the jit stack, finding
+  // the previous Ion or Baseline JS frame, and storing its address and the
+  // return address into the appropriate fields on the current jitActivation.
+  //
+  // There are a fixed number of different path types that can lead to the
+  // current frame, which is either a baseline or ion frame:
+  //
+  // <Baseline-Or-Ion>
+  // ^
+  // |
+  // ^--- Ion
+  // |
+  // ^--- Baseline Stub <---- Baseline
+  // |
+  // ^--- Argument Rectifier
+  // |    ^
+  // |    |
+  // |    ^--- Ion
+  // |    |
+  // |    ^--- Baseline Stub <---- Baseline
+  // |
+  // ^--- Entry Frame (From C++)
+  //
+  Register actReg = scratch4;
+  masm.loadJSContext(actReg);
+  masm.loadPtr(Address(actReg, offsetof(JSContext, profilingActivation_)),
+               actReg);
+
+  Address lastProfilingFrame(actReg,
+                             JitActivation::offsetOfLastProfilingFrame());
+  Address lastProfilingCallSite(actReg,
+                                JitActivation::offsetOfLastProfilingCallSite());
+
+#ifdef DEBUG
+  // Ensure that frame we are exiting is current lastProfilingFrame
+  {
+    masm.loadPtr(lastProfilingFrame, scratch1);
+    Label checkOk;
+    masm.branchPtr(Assembler::Equal, scratch1, ImmWord(0), &checkOk);
+    masm.branchPtr(Assembler::Equal, StackPointer, scratch1, &checkOk);
+    masm.assumeUnreachable(
+        "Mismatch between stored lastProfilingFrame and current stack "
+        "pointer.");
+    masm.bind(&checkOk);
+  }
+#endif
+
+  // Load the frame descriptor into |scratch1|, figure out what to do depending
+  // on its type.
+  masm.loadPtr(Address(StackPointer, JitFrameLayout::offsetOfDescriptor()),
+               scratch1);
+
+  // Going into the conditionals, we will have:
+  //      FrameDescriptor.size in scratch1
+  //      FrameDescriptor.type in scratch2
+  {
+    ScratchRegisterScope asmScratch(masm);
+    masm.ma_and(Imm32((1 << FRAMETYPE_BITS) - 1), scratch1, scratch2,
+                asmScratch);
+  }
+  masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch1);
+
+  // Handling of each case is dependent on FrameDescriptor.type
+  Label handle_IonJS;
+  Label handle_BaselineStub;
+  Label handle_Rectifier;
+  Label handle_IonICCall;
+  Label handle_Entry;
+  Label end;
+
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::IonJS),
+                &handle_IonJS);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::BaselineJS),
+                &handle_IonJS);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::BaselineStub),
+                &handle_BaselineStub);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::Rectifier),
+                &handle_Rectifier);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::IonICCall),
+                &handle_IonICCall);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::CppToJSJit),
+                &handle_Entry);
+
+  // The WasmToJSJit is just another kind of entry.
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::WasmToJSJit),
+                &handle_Entry);
+
+  masm.assumeUnreachable(
+      "Invalid caller frame type when exiting from Ion frame.");
+
+  //
+  // FrameType::IonJS
+  //
+  // Stack layout:
+  //                  ...
+  //                  Ion-Descriptor
+  //     Prev-FP ---> Ion-ReturnAddr
+  //                  ... previous frame data ... |- Descriptor.Size
+  //                  ... arguments ...           |
+  //                  ActualArgc          |
+  //                  CalleeToken         |- JitFrameLayout::Size()
+  //                  Descriptor          |
+  //        FP -----> ReturnAddr          |
+  //
+  masm.bind(&handle_IonJS);
+  {
+    // |scratch1| contains Descriptor.size
+
+    // returning directly to an IonJS frame.  Store return addr to frame
+    // in lastProfilingCallSite.
+    masm.loadPtr(Address(StackPointer, JitFrameLayout::offsetOfReturnAddress()),
+                 scratch2);
+    masm.storePtr(scratch2, lastProfilingCallSite);
+
+    // Store return frame in lastProfilingFrame.
+    // scratch2 := StackPointer + Descriptor.size*1 + JitFrameLayout::Size();
+    masm.ma_add(StackPointer, scratch1, scratch2);
+    masm.as_add(scratch2, scratch2, Imm8(JitFrameLayout::Size()));
+    masm.storePtr(scratch2, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::BaselineStub
+  //
+  // Look past the stub and store the frame pointer to
+  // the baselineJS frame prior to it.
+  //
+  // Stack layout:
+  //              ...
+  //              BL-Descriptor
+  // Prev-FP ---> BL-ReturnAddr
+  //      +-----> BL-PrevFramePointer
+  //      |       ... BL-FrameData ...
+  //      |       BLStub-Descriptor
+  //      |       BLStub-ReturnAddr
+  //      |       BLStub-StubPointer          |
+  //      +------ BLStub-SavedFramePointer    |- Descriptor.Size
+  //              ... arguments ...           |
+  //              ActualArgc          |
+  //              CalleeToken         |- JitFrameLayout::Size()
+  //              Descriptor          |
+  //    FP -----> ReturnAddr          |
+  //
+  // We take advantage of the fact that the stub frame saves the frame
+  // pointer pointing to the baseline frame, so a bunch of calculation can
+  // be avoided.
+  //
+  masm.bind(&handle_BaselineStub);
+  {
+    masm.ma_add(StackPointer, scratch1, scratch3);
+    Address stubFrameReturnAddr(
+        scratch3, JitFrameLayout::Size() +
+                      BaselineStubFrameLayout::offsetOfReturnAddress());
+    masm.loadPtr(stubFrameReturnAddr, scratch2);
+    masm.storePtr(scratch2, lastProfilingCallSite);
+
+    Address stubFrameSavedFramePtr(
+        scratch3, JitFrameLayout::Size() - (2 * sizeof(void*)));
+    masm.loadPtr(stubFrameSavedFramePtr, scratch2);
+    masm.addPtr(Imm32(sizeof(void*)), scratch2);  // Skip past BL-PrevFramePtr
+    masm.storePtr(scratch2, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::Rectifier
+  //
+  // The rectifier frame can be preceded by either an IonJS, a BaselineStub,
+  // or a CppToJSJit/WasmToJSJit frame.
+  //
+  // Stack layout if caller of rectifier was Ion or CppToJSJit/WasmToJSJit:
+  //
+  //              Ion-Descriptor
+  //              Ion-ReturnAddr
+  //              ... ion frame data ... |- Rect-Descriptor.Size
+  //              < COMMON LAYOUT >
+  //
+  // Stack layout if caller of rectifier was Baseline:
+  //
+  //              BL-Descriptor
+  // Prev-FP ---> BL-ReturnAddr
+  //      +-----> BL-SavedFramePointer
+  //      |       ... baseline frame data ...
+  //      |       BLStub-Descriptor
+  //      |       BLStub-ReturnAddr
+  //      |       BLStub-StubPointer          |
+  //      +------ BLStub-SavedFramePointer    |- Rect-Descriptor.Size
+  //              ... args to rectifier ...   |
+  //              < COMMON LAYOUT >
+  //
+  // Common stack layout:
+  //
+  //              ActualArgc          |
+  //              CalleeToken         |- IonRectitiferFrameLayout::Size()
+  //              Rect-Descriptor     |
+  //              Rect-ReturnAddr     |
+  //              ... rectifier data & args ... |- Descriptor.Size
+  //              ActualArgc      |
+  //              CalleeToken     |- JitFrameLayout::Size()
+  //              Descriptor      |
+  //    FP -----> ReturnAddr      |
+  //
+  masm.bind(&handle_Rectifier);
+  {
+    // scratch2 := StackPointer + Descriptor.size*1 + JitFrameLayout::Size();
+    masm.ma_add(StackPointer, scratch1, scratch2);
+    masm.add32(Imm32(JitFrameLayout::Size()), scratch2);
+    masm.loadPtr(Address(scratch2, RectifierFrameLayout::offsetOfDescriptor()),
+                 scratch3);
+    masm.ma_lsr(Imm32(FRAMESIZE_SHIFT), scratch3, scratch1);
+    masm.and32(Imm32((1 << FRAMETYPE_BITS) - 1), scratch3);
+
+    // Now |scratch1| contains Rect-Descriptor.Size
+    // and |scratch2| points to Rectifier frame
+    // and |scratch3| contains Rect-Descriptor.Type
+
+    masm.assertRectifierFrameParentType(scratch3);
+
+    // Check for either Ion or BaselineStub frame.
+    Label notIonFrame;
+    masm.branch32(Assembler::NotEqual, scratch3, Imm32(FrameType::IonJS),
+                  &notIonFrame);
+
+    // Handle Rectifier <- IonJS
+    // scratch3 := RectFrame[ReturnAddr]
+    masm.loadPtr(
+        Address(scratch2, RectifierFrameLayout::offsetOfReturnAddress()),
+        scratch3);
+    masm.storePtr(scratch3, lastProfilingCallSite);
+
+    // scratch3 := RectFrame + Rect-Descriptor.Size +
+    //             RectifierFrameLayout::Size()
+    masm.ma_add(scratch2, scratch1, scratch3);
+    masm.add32(Imm32(RectifierFrameLayout::Size()), scratch3);
+    masm.storePtr(scratch3, lastProfilingFrame);
+    masm.ret();
+
+    masm.bind(&notIonFrame);
+
+    // Check for either BaselineStub or a CppToJSJit/WasmToJSJit entry
+    // frame.
+    masm.branch32(Assembler::NotEqual, scratch3, Imm32(FrameType::BaselineStub),
+                  &handle_Entry);
+
+    // Handle Rectifier <- BaselineStub <- BaselineJS
+    masm.ma_add(scratch2, scratch1, scratch3);
+    Address stubFrameReturnAddr(
+        scratch3, RectifierFrameLayout::Size() +
+                      BaselineStubFrameLayout::offsetOfReturnAddress());
+    masm.loadPtr(stubFrameReturnAddr, scratch2);
+    masm.storePtr(scratch2, lastProfilingCallSite);
+
+    Address stubFrameSavedFramePtr(
+        scratch3, RectifierFrameLayout::Size() - (2 * sizeof(void*)));
+    masm.loadPtr(stubFrameSavedFramePtr, scratch2);
+    masm.addPtr(Imm32(sizeof(void*)), scratch2);
+    masm.storePtr(scratch2, lastProfilingFrame);
+    masm.ret();
+  }
+
+  // FrameType::IonICCall
+  //
+  // The caller is always an IonJS frame.
+  //
+  //              Ion-Descriptor
+  //              Ion-ReturnAddr
+  //              ... ion frame data ... |- CallFrame-Descriptor.Size
+  //              StubCode               |
+  //              ICCallFrame-Descriptor |- IonICCallFrameLayout::Size()
+  //              ICCallFrame-ReturnAddr |
+  //              ... call frame data & args ... |- Descriptor.Size
+  //              ActualArgc      |
+  //              CalleeToken     |- JitFrameLayout::Size()
+  //              Descriptor      |
+  //    FP -----> ReturnAddr      |
+  masm.bind(&handle_IonICCall);
+  {
+    // scratch2 := StackPointer + Descriptor.size + JitFrameLayout::Size()
+    masm.ma_add(StackPointer, scratch1, scratch2);
+    masm.addPtr(Imm32(JitFrameLayout::Size()), scratch2);
+
+    // scratch3 := ICCallFrame-Descriptor.Size
+    masm.loadPtr(Address(scratch2, IonICCallFrameLayout::offsetOfDescriptor()),
+                 scratch3);
+#ifdef DEBUG
+    // Assert previous frame is an IonJS frame.
+    masm.movePtr(scratch3, scratch1);
+    masm.and32(Imm32((1 << FRAMETYPE_BITS) - 1), scratch1);
+    {
+      Label checkOk;
+      masm.branch32(Assembler::Equal, scratch1, Imm32(FrameType::IonJS),
+                    &checkOk);
+      masm.assumeUnreachable("IonICCall frame must be preceded by IonJS frame");
+      masm.bind(&checkOk);
+    }
+#endif
+    masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch3);
+
+    // lastProfilingCallSite := ICCallFrame-ReturnAddr
+    masm.loadPtr(
+        Address(scratch2, IonICCallFrameLayout::offsetOfReturnAddress()),
+        scratch1);
+    masm.storePtr(scratch1, lastProfilingCallSite);
+
+    // lastProfilingFrame := ICCallFrame + ICCallFrame-Descriptor.Size +
+    //                       IonICCallFrameLayout::Size()
+    masm.ma_add(scratch2, scratch3, scratch1);
+    masm.addPtr(Imm32(IonICCallFrameLayout::Size()), scratch1);
+    masm.storePtr(scratch1, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::CppToJSJit / FrameType::WasmToJSJit
+  //
+  // If at an entry frame, store null into both fields.
+  // A fast-path wasm->jit transition frame is an entry frame from the point
+  // of view of the JIT.
+  //
+  masm.bind(&handle_Entry);
+  {
+    masm.movePtr(ImmPtr(nullptr), scratch1);
+    masm.storePtr(scratch1, lastProfilingCallSite);
+    masm.storePtr(scratch1, lastProfilingFrame);
+    masm.ret();
+  }
+}