Add m-esr52 at 52.6.0

1 files changed, 1418 insertions, 0 deletions

diff --git a/js/src/jit/mips32/Trampoline-mips32.cpp b/js/src/jit/mips32/Trampoline-mips32.cpp
new file mode 100644
index 000000000..d422ed757
--- /dev/null
+++ b/js/src/jit/mips32/Trampoline-mips32.cpp
@@ -0,0 +1,1418 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * 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 "mozilla/DebugOnly.h"
+
+#include "jscompartment.h"
+
+#include "jit/Bailouts.h"
+#include "jit/JitCompartment.h"
+#include "jit/JitFrames.h"
+#include "jit/JitSpewer.h"
+#include "jit/Linker.h"
+#include "jit/mips-shared/SharedICHelpers-mips-shared.h"
+#include "jit/mips32/Bailouts-mips32.h"
+#ifdef JS_ION_PERF
+# include "jit/PerfSpewer.h"
+#endif
+#include "jit/VMFunctions.h"
+
+#include "jit/MacroAssembler-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+static_assert(sizeof(uintptr_t) == sizeof(uint32_t), "Not 64-bit clean.");
+
+struct EnterJITRegs
+{
+    double f30;
+    double f28;
+    double f26;
+    double f24;
+    double f22;
+    double f20;
+
+    // empty slot for alignment
+    uintptr_t align;
+
+    // non-volatile registers.
+    uintptr_t ra;
+    uintptr_t s7;
+    uintptr_t s6;
+    uintptr_t s5;
+    uintptr_t s4;
+    uintptr_t s3;
+    uintptr_t s2;
+    uintptr_t s1;
+    uintptr_t s0;
+};
+
+struct EnterJITArgs
+{
+    // First 4 argumet placeholders
+    void* jitcode; // <- sp points here when function is entered.
+    int maxArgc;
+    Value* maxArgv;
+    InterpreterFrame* fp;
+
+    // Arguments on stack
+    CalleeToken calleeToken;
+    JSObject* scopeChain;
+    size_t numStackValues;
+    Value* vp;
+};
+
+static void
+GenerateReturn(MacroAssembler& masm, int returnCode)
+{
+    MOZ_ASSERT(masm.framePushed() == sizeof(EnterJITRegs));
+
+    // Restore non-volatile registers
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s0)), s0);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s1)), s1);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s2)), s2);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s3)), s3);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s4)), s4);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s5)), s5);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s6)), s6);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, s7)), s7);
+    masm.loadPtr(Address(StackPointer, offsetof(EnterJITRegs, ra)), ra);
+
+    // Restore non-volatile floating point registers
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f20)), f20);
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f22)), f22);
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f24)), f24);
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f26)), f26);
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f28)), f28);
+    masm.loadDouble(Address(StackPointer, offsetof(EnterJITRegs, f30)), f30);
+
+    masm.freeStack(sizeof(EnterJITRegs));
+
+    masm.branch(ra);
+}
+
+static void
+GeneratePrologue(MacroAssembler& 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.reserveStack(sizeof(EnterJITRegs));
+    masm.storePtr(s0, Address(StackPointer, offsetof(EnterJITRegs, s0)));
+    masm.storePtr(s1, Address(StackPointer, offsetof(EnterJITRegs, s1)));
+    masm.storePtr(s2, Address(StackPointer, offsetof(EnterJITRegs, s2)));
+    masm.storePtr(s3, Address(StackPointer, offsetof(EnterJITRegs, s3)));
+    masm.storePtr(s4, Address(StackPointer, offsetof(EnterJITRegs, s4)));
+    masm.storePtr(s5, Address(StackPointer, offsetof(EnterJITRegs, s5)));
+    masm.storePtr(s6, Address(StackPointer, offsetof(EnterJITRegs, s6)));
+    masm.storePtr(s7, Address(StackPointer, offsetof(EnterJITRegs, s7)));
+    masm.storePtr(ra, Address(StackPointer, offsetof(EnterJITRegs, ra)));
+
+    masm.as_sd(f20, StackPointer, offsetof(EnterJITRegs, f20));
+    masm.as_sd(f22, StackPointer, offsetof(EnterJITRegs, f22));
+    masm.as_sd(f24, StackPointer, offsetof(EnterJITRegs, f24));
+    masm.as_sd(f26, StackPointer, offsetof(EnterJITRegs, f26));
+    masm.as_sd(f28, StackPointer, offsetof(EnterJITRegs, f28));
+    masm.as_sd(f30, StackPointer, offsetof(EnterJITRegs, f30));
+}
+
+
+/*
+ * 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
+ */
+JitCode*
+JitRuntime::generateEnterJIT(JSContext* cx, EnterJitType type)
+{
+    const Register reg_code = a0;
+    const Register reg_argc = a1;
+    const Register reg_argv = a2;
+    const mozilla::DebugOnly<Register> reg_frame = a3;
+
+    MOZ_ASSERT(OsrFrameReg == reg_frame);
+
+    MacroAssembler masm(cx);
+    GeneratePrologue(masm);
+
+    const Address slotToken(sp, sizeof(EnterJITRegs) + offsetof(EnterJITArgs, calleeToken));
+    const Address slotVp(sp, sizeof(EnterJITRegs) + offsetof(EnterJITArgs, vp));
+
+    // Save stack pointer into s4
+    masm.movePtr(StackPointer, s4);
+
+    // Load calleeToken into s2.
+    masm.loadPtr(slotToken, s2);
+
+    // Save stack pointer as baseline frame.
+    if (type == EnterJitBaseline)
+        masm.movePtr(StackPointer, BaselineFrameReg);
+
+    // Load the number of actual arguments into s3.
+    masm.loadPtr(slotVp, s3);
+    masm.unboxInt32(Address(s3, 0), s3);
+
+    /***************************************************************
+    Loop over argv vector, push arguments onto stack in reverse order
+    ***************************************************************/
+
+    // if we are constructing, that also needs to include newTarget
+    {
+        Label noNewTarget;
+        masm.branchTest32(Assembler::Zero, s2, Imm32(CalleeToken_FunctionConstructing),
+                          &noNewTarget);
+
+        masm.add32(Imm32(1), reg_argc);
+
+        masm.bind(&noNewTarget);
+    }
+
+    masm.as_sll(s0, reg_argc, 3); // s0 = argc * 8
+    masm.addPtr(reg_argv, s0); // s0 = argv + argc * 8
+
+    // 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
+    masm.ma_b(s0, reg_argv, &footer, Assembler::BelowOrEqual, ShortJump);
+    {
+        masm.bind(&header);
+
+        masm.subPtr(Imm32(2 * sizeof(uintptr_t)), s0);
+        masm.subPtr(Imm32(2 * sizeof(uintptr_t)), StackPointer);
+
+        ValueOperand value = ValueOperand(s6, s7);
+        masm.loadValue(Address(s0, 0), value);
+        masm.storeValue(value, Address(StackPointer, 0));
+
+        masm.ma_b(s0, reg_argv, &header, Assembler::Above, ShortJump);
+    }
+    masm.bind(&footer);
+
+    masm.subPtr(Imm32(2 * sizeof(uintptr_t)), StackPointer);
+    masm.storePtr(s3, Address(StackPointer, sizeof(uintptr_t))); // actual arguments
+    masm.storePtr(s2, Address(StackPointer, 0)); // callee token
+
+    masm.subPtr(StackPointer, s4);
+    masm.makeFrameDescriptor(s4, JitFrame_Entry, JitFrameLayout::Size());
+    masm.push(s4); // descriptor
+
+    CodeLabel returnLabel;
+    CodeLabel oomReturnLabel;
+    if (type == EnterJitBaseline) {
+        // Handle OSR.
+        AllocatableGeneralRegisterSet regs(GeneralRegisterSet::All());
+        regs.take(OsrFrameReg);
+        regs.take(BaselineFrameReg);
+        regs.take(reg_code);
+        regs.take(ReturnReg);
+
+        const Address slotNumStackValues(BaselineFrameReg, sizeof(EnterJITRegs) +
+                                         offsetof(EnterJITArgs, numStackValues));
+        const Address slotScopeChain(BaselineFrameReg, sizeof(EnterJITRegs) +
+                                     offsetof(EnterJITArgs, scopeChain));
+
+        Label notOsr;
+        masm.ma_b(OsrFrameReg, OsrFrameReg, &notOsr, Assembler::Zero, ShortJump);
+
+        Register scratch = regs.takeAny();
+
+        Register numStackValues = regs.takeAny();
+        masm.load32(slotNumStackValues, numStackValues);
+
+        // Push return address.
+        masm.subPtr(Imm32(sizeof(uintptr_t)), StackPointer);
+        masm.ma_li(scratch, returnLabel.patchAt());
+        masm.storePtr(scratch, Address(StackPointer, 0));
+
+        // Push previous frame pointer.
+        masm.subPtr(Imm32(sizeof(uintptr_t)), StackPointer);
+        masm.storePtr(BaselineFrameReg, Address(StackPointer, 0));
+
+        // Reserve frame.
+        Register framePtr = BaselineFrameReg;
+        masm.subPtr(Imm32(BaselineFrame::Size()), StackPointer);
+        masm.movePtr(StackPointer, framePtr);
+
+        // Reserve space for locals and stack values.
+        masm.ma_sll(scratch, numStackValues, Imm32(3));
+        masm.subPtr(scratch, StackPointer);
+
+        // Enter exit frame.
+        masm.addPtr(Imm32(BaselineFrame::Size() + BaselineFrame::FramePointerOffset), scratch);
+        masm.makeFrameDescriptor(scratch, JitFrame_BaselineJS, ExitFrameLayout::Size());
+
+        // Push frame descriptor and fake return address.
+        masm.reserveStack(2 * sizeof(uintptr_t));
+        masm.storePtr(scratch, Address(StackPointer, sizeof(uintptr_t))); // Frame descriptor
+        masm.storePtr(zero, Address(StackPointer, 0)); // fake return address
+
+        // No GC things to mark, push a bare token.
+        masm.enterFakeExitFrame(ExitFrameLayoutBareToken);
+
+        masm.reserveStack(2 * sizeof(uintptr_t));
+        masm.storePtr(framePtr, Address(StackPointer, sizeof(uintptr_t))); // BaselineFrame
+        masm.storePtr(reg_code, Address(StackPointer, 0)); // jitcode
+
+        masm.setupUnalignedABICall(scratch);
+        masm.passABIArg(BaselineFrameReg); // BaselineFrame
+        masm.passABIArg(OsrFrameReg); // InterpreterFrame
+        masm.passABIArg(numStackValues);
+        masm.callWithABI(JS_FUNC_TO_DATA_PTR(void*, jit::InitBaselineFrameForOsr));
+
+        regs.add(OsrFrameReg);
+        regs.take(JSReturnOperand);
+        Register jitcode = regs.takeAny();
+        masm.loadPtr(Address(StackPointer, 0), jitcode);
+        masm.loadPtr(Address(StackPointer, sizeof(uintptr_t)), framePtr);
+        masm.freeStack(2 * sizeof(uintptr_t));
+
+        Label error;
+        masm.freeStack(ExitFrameLayout::SizeWithFooter());
+        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()->spsProfiler.addressOfEnabled());
+            masm.branch32(Assembler::Equal, addressOfEnabled, Imm32(0),
+                          &skipProfilingInstrumentation);
+            masm.ma_addu(realFramePtr, framePtr, Imm32(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.movePtr(framePtr, StackPointer);
+        masm.addPtr(Imm32(2 * sizeof(uintptr_t)), StackPointer);
+        masm.moveValue(MagicValue(JS_ION_ERROR), JSReturnOperand);
+        masm.ma_li(scratch, oomReturnLabel.patchAt());
+        masm.jump(scratch);
+
+        masm.bind(&notOsr);
+        // Load the scope chain in R1.
+        MOZ_ASSERT(R1.scratchReg() != reg_code);
+        masm.loadPtr(slotScopeChain, R1.scratchReg());
+    }
+
+    // The call 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 with pushing return address to stack.
+    masm.callJitNoProfiler(reg_code);
+
+    if (type == EnterJitBaseline) {
+        // Baseline OSR will return here.
+        masm.bind(returnLabel.target());
+        masm.addCodeLabel(returnLabel);
+        masm.bind(oomReturnLabel.target());
+        masm.addCodeLabel(oomReturnLabel);
+    }
+
+    // Pop arguments off the stack.
+    // s0 <- 8*argc (size of all arguments we pushed on the stack)
+    masm.pop(s0);
+    masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), s0);
+    masm.addPtr(s0, StackPointer);
+
+    // Store the returned value into the slotVp
+    masm.loadPtr(slotVp, s1);
+    masm.storeValue(JSReturnOperand, Address(s1, 0));
+
+    // Restore non-volatile registers and return.
+    GenerateReturn(masm, ShortJump);
+
+    Linker linker(masm);
+    AutoFlushICache afc("GenerateEnterJIT");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "EnterJIT");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateInvalidator(JSContext* cx)
+{
+    MacroAssembler masm(cx);
+
+    // NOTE: Members ionScript_ and osiPointReturnAddress_ of
+    // InvalidationBailoutStack are already on the stack.
+    static const uint32_t STACK_DATA_SIZE = sizeof(InvalidationBailoutStack) -
+                                            2 * sizeof(uintptr_t);
+
+    // Stack has to be alligned here. If not, we will have to fix it.
+    masm.checkStackAlignment();
+
+    // Make room for data on stack.
+    masm.subPtr(Imm32(STACK_DATA_SIZE), StackPointer);
+
+    // Save general purpose registers
+    for (uint32_t i = 0; i < Registers::Total; i++) {
+        Address address = Address(StackPointer, InvalidationBailoutStack::offsetOfRegs() +
+                                                i * sizeof(uintptr_t));
+        masm.storePtr(Register::FromCode(i), address);
+    }
+
+    // Save floating point registers
+    // We can use as_sd because stack is alligned.
+    for (uint32_t i = 0; i < FloatRegisters::TotalDouble; i ++)
+        masm.as_sd(FloatRegister::FromIndex(i, FloatRegister::Double), StackPointer,
+                   InvalidationBailoutStack::offsetOfFpRegs() + i * sizeof(double));
+
+    // Pass pointer to InvalidationBailoutStack structure.
+    masm.movePtr(StackPointer, a0);
+
+    // Reserve place for return value and BailoutInfo pointer
+    masm.subPtr(Imm32(2 * sizeof(uintptr_t)), StackPointer);
+    // Pass pointer to return value.
+    masm.ma_addu(a1, StackPointer, Imm32(sizeof(uintptr_t)));
+    // Pass pointer to BailoutInfo
+    masm.movePtr(StackPointer, a2);
+
+    masm.setupAlignedABICall();
+    masm.passABIArg(a0);
+    masm.passABIArg(a1);
+    masm.passABIArg(a2);
+    masm.callWithABI(JS_FUNC_TO_DATA_PTR(void*, InvalidationBailout));
+
+    masm.loadPtr(Address(StackPointer, 0), a2);
+    masm.loadPtr(Address(StackPointer, sizeof(uintptr_t)), a1);
+    // Remove the return address, the IonScript, the register state
+    // (InvaliationBailoutStack) and the space that was allocated for the
+    // return value.
+    masm.addPtr(Imm32(sizeof(InvalidationBailoutStack) + 2 * sizeof(uintptr_t)), StackPointer);
+    // remove the space that this frame was using before the bailout
+    // (computed by InvalidationBailout)
+    masm.addPtr(a1, StackPointer);
+
+    // Jump to shared bailout tail. The BailoutInfo pointer has to be in r2.
+    JitCode* bailoutTail = cx->runtime()->jitRuntime()->getBailoutTail();
+    masm.branch(bailoutTail);
+
+    Linker linker(masm);
+    AutoFlushICache afc("Invalidator");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+    JitSpew(JitSpew_IonInvalidate, "   invalidation thunk created at %p", (void*) code->raw());
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "Invalidator");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateArgumentsRectifier(JSContext* cx, void** returnAddrOut)
+{
+    MacroAssembler masm(cx);
+    masm.pushReturnAddress();
+
+    // ArgumentsRectifierReg contains the |nargs| pushed onto the current
+    // frame. Including |this|, there are (|nargs| + 1) arguments to copy.
+    MOZ_ASSERT(ArgumentsRectifierReg == s3);
+
+    Register numActArgsReg = t6;
+    Register calleeTokenReg = t7;
+    Register numArgsReg = t5;
+
+    // Copy number of actual arguments into numActArgsReg
+    masm.loadPtr(Address(StackPointer, RectifierFrameLayout::offsetOfNumActualArgs()),
+                 numActArgsReg);
+
+    // Load the number of |undefined|s to push into t1.
+    masm.loadPtr(Address(StackPointer, RectifierFrameLayout::offsetOfCalleeToken()),
+                 calleeTokenReg);
+    masm.mov(calleeTokenReg, numArgsReg);
+    masm.andPtr(Imm32(CalleeTokenMask), numArgsReg);
+    masm.load16ZeroExtend(Address(numArgsReg, JSFunction::offsetOfNargs()), numArgsReg);
+
+    masm.as_subu(t1, numArgsReg, s3);
+
+    // Get the topmost argument.
+    masm.ma_sll(t0, s3, Imm32(3)); // t0 <- nargs * 8
+    masm.as_addu(t2, sp, t0); // t2 <- sp + nargs * 8
+    masm.addPtr(Imm32(sizeof(RectifierFrameLayout)), t2);
+
+    {
+        Label notConstructing;
+
+        masm.branchTest32(Assembler::Zero, calleeTokenReg, Imm32(CalleeToken_FunctionConstructing),
+                          &notConstructing);
+
+        // Add sizeof(Value) to overcome |this|
+        masm.subPtr(Imm32(sizeof(Value)), StackPointer);
+        masm.load32(Address(t2, NUNBOX32_TYPE_OFFSET + sizeof(Value)), t0);
+        masm.store32(t0, Address(StackPointer, NUNBOX32_TYPE_OFFSET));
+        masm.load32(Address(t2, NUNBOX32_PAYLOAD_OFFSET + sizeof(Value)), t0);
+        masm.store32(t0, Address(StackPointer, NUNBOX32_PAYLOAD_OFFSET));
+
+        // Include the newly pushed newTarget value in the frame size
+        // calculated below.
+        masm.add32(Imm32(1), numArgsReg);
+
+        masm.bind(&notConstructing);
+    }
+
+    // Push undefined.
+    masm.moveValue(UndefinedValue(), ValueOperand(t3, t4));
+    {
+        Label undefLoopTop;
+        masm.bind(&undefLoopTop);
+
+        masm.subPtr(Imm32(sizeof(Value)), StackPointer);
+        masm.storeValue(ValueOperand(t3, t4), Address(StackPointer, 0));
+        masm.sub32(Imm32(1), t1);
+
+        masm.ma_b(t1, t1, &undefLoopTop, Assembler::NonZero, ShortJump);
+    }
+
+    // Push arguments, |nargs| + 1 times (to include |this|).
+    {
+        Label copyLoopTop, initialSkip;
+
+        masm.ma_b(&initialSkip, ShortJump);
+
+        masm.bind(&copyLoopTop);
+        masm.subPtr(Imm32(sizeof(Value)), t2);
+        masm.sub32(Imm32(1), s3);
+
+        masm.bind(&initialSkip);
+
+        MOZ_ASSERT(sizeof(Value) == 2 * sizeof(uint32_t));
+        // Read argument and push to stack.
+        masm.subPtr(Imm32(sizeof(Value)), StackPointer);
+        masm.load32(Address(t2, NUNBOX32_TYPE_OFFSET), t0);
+        masm.store32(t0, Address(StackPointer, NUNBOX32_TYPE_OFFSET));
+        masm.load32(Address(t2, NUNBOX32_PAYLOAD_OFFSET), t0);
+        masm.store32(t0, Address(StackPointer, NUNBOX32_PAYLOAD_OFFSET));
+
+        masm.ma_b(s3, s3, &copyLoopTop, Assembler::NonZero, ShortJump);
+    }
+
+    // translate the framesize from values into bytes
+    masm.ma_addu(t0, numArgsReg, Imm32(1));
+    masm.lshiftPtr(Imm32(3), t0);
+
+    // Construct sizeDescriptor.
+    masm.makeFrameDescriptor(t0, JitFrame_Rectifier, JitFrameLayout::Size());
+
+    // Construct JitFrameLayout.
+    masm.subPtr(Imm32(3 * sizeof(uintptr_t)), StackPointer);
+    // Push actual arguments.
+    masm.storePtr(numActArgsReg, Address(StackPointer, 2 * sizeof(uintptr_t)));
+    // Push callee token.
+    masm.storePtr(calleeTokenReg, Address(StackPointer, sizeof(uintptr_t)));
+    // Push frame descriptor.
+    masm.storePtr(t0, Address(StackPointer, 0));
+
+    // Call the target function.
+    // Note that this code assumes the function is JITted.
+    masm.andPtr(Imm32(CalleeTokenMask), calleeTokenReg);
+    masm.loadPtr(Address(calleeTokenReg, JSFunction::offsetOfNativeOrScript()), t1);
+    masm.loadBaselineOrIonRaw(t1, t1, nullptr);
+    uint32_t returnOffset = masm.callJitNoProfiler(t1);
+
+    // arg1
+    //  ...
+    // argN
+    // num actual args
+    // callee token
+    // sizeDescriptor     <- sp now
+    // return address
+
+    // Remove the rectifier frame.
+    // t0 <- descriptor with FrameType.
+    masm.loadPtr(Address(StackPointer, 0), t0);
+    masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), t0); // t0 <- descriptor.
+
+    // Discard descriptor, calleeToken and number of actual arguments.
+    masm.addPtr(Imm32(3 * sizeof(uintptr_t)), StackPointer);
+
+    // arg1
+    //  ...
+    // argN               <- sp now; t0 <- frame descriptor
+    // num actual args
+    // callee token
+    // sizeDescriptor
+    // return address
+
+    // Discard pushed arguments.
+    masm.addPtr(t0, StackPointer);
+
+    masm.ret();
+    Linker linker(masm);
+    AutoFlushICache afc("ArgumentsRectifier");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+    if (returnAddrOut)
+        *returnAddrOut = (void*) (code->raw() + returnOffset);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "ArgumentsRectifier");
+#endif
+
+    return code;
+}
+
+// NOTE: Members snapshotOffset_ and padding_ of BailoutStack
+// are not stored in PushBailoutFrame().
+static const uint32_t bailoutDataSize = sizeof(BailoutStack) - 2 * sizeof(uintptr_t);
+static const uint32_t bailoutInfoOutParamSize = 2 * sizeof(uintptr_t);
+
+/* There are two different stack layouts when doing bailout. They are
+ * represented via class BailoutStack.
+ *
+ * - First case is when bailout is done trough bailout table. In this case
+ * table offset is stored in $ra (look at JitRuntime::generateBailoutTable())
+ * and thunk code should save it on stack. In this case frameClassId_ cannot
+ * be NO_FRAME_SIZE_CLASS_ID. Members snapshotOffset_ and padding_ are not on
+ * the stack.
+ *
+ * - Other case is when bailout is done via out of line code (lazy bailout).
+ * In this case frame size is stored in $ra (look at
+ * CodeGeneratorMIPS::generateOutOfLineCode()) and thunk code should save it
+ * on stack. Other difference is that members snapshotOffset_ and padding_ are
+ * pushed to the stack by CodeGeneratorMIPS::visitOutOfLineBailout(). Field
+ * frameClassId_ is forced to be NO_FRAME_SIZE_CLASS_ID
+ * (See: JitRuntime::generateBailoutHandler).
+ */
+static void
+PushBailoutFrame(MacroAssembler& masm, uint32_t frameClass, Register spArg)
+{
+    // Make sure that alignment is proper.
+    masm.checkStackAlignment();
+
+    // Make room for data.
+    masm.subPtr(Imm32(bailoutDataSize), StackPointer);
+
+    // Save general purpose registers.
+    for (uint32_t i = 0; i < Registers::Total; i++) {
+        uint32_t off = BailoutStack::offsetOfRegs() + i * sizeof(uintptr_t);
+        masm.storePtr(Register::FromCode(i), Address(StackPointer, off));
+    }
+
+    // Save floating point registers
+    // We can use as_sd because stack is alligned.
+    for (uint32_t i = 0; i < FloatRegisters::TotalDouble; i++)
+        masm.as_sd(FloatRegister::FromIndex(i, FloatRegister::Double), StackPointer,
+                   BailoutStack::offsetOfFpRegs() + i * sizeof(double));
+
+    // Store the frameSize_ or tableOffset_ stored in ra
+    // See: JitRuntime::generateBailoutTable()
+    // See: CodeGeneratorMIPS::generateOutOfLineCode()
+    masm.storePtr(ra, Address(StackPointer, BailoutStack::offsetOfFrameSize()));
+
+    // Put frame class to stack
+    masm.storePtr(ImmWord(frameClass), Address(StackPointer, BailoutStack::offsetOfFrameClass()));
+
+    // Put pointer to BailoutStack as first argument to the Bailout()
+    masm.movePtr(StackPointer, spArg);
+}
+
+static void
+GenerateBailoutThunk(JSContext* cx, MacroAssembler& masm, uint32_t frameClass)
+{
+    PushBailoutFrame(masm, frameClass, a0);
+
+    // Put pointer to BailoutInfo
+    masm.subPtr(Imm32(bailoutInfoOutParamSize), StackPointer);
+    masm.storePtr(ImmPtr(nullptr), Address(StackPointer, 0));
+    masm.movePtr(StackPointer, a1);
+
+    masm.setupAlignedABICall();
+    masm.passABIArg(a0);
+    masm.passABIArg(a1);
+    masm.callWithABI(JS_FUNC_TO_DATA_PTR(void*, Bailout));
+
+    // Get BailoutInfo pointer
+    masm.loadPtr(Address(StackPointer, 0), a2);
+
+    // Remove both the bailout frame and the topmost Ion frame's stack.
+    if (frameClass == NO_FRAME_SIZE_CLASS_ID) {
+        // Load frameSize from stack
+        masm.loadPtr(Address(StackPointer,
+                             bailoutInfoOutParamSize + BailoutStack::offsetOfFrameSize()), a1);
+
+        // Remove complete BailoutStack class and data after it
+        masm.addPtr(Imm32(sizeof(BailoutStack) + bailoutInfoOutParamSize), StackPointer);
+        // Remove frame size srom stack
+        masm.addPtr(a1, StackPointer);
+    } else {
+        uint32_t frameSize = FrameSizeClass::FromClass(frameClass).frameSize();
+        // Remove the data this fuction added and frame size.
+        masm.addPtr(Imm32(bailoutDataSize + bailoutInfoOutParamSize + frameSize), StackPointer);
+    }
+
+    // Jump to shared bailout tail. The BailoutInfo pointer has to be in a2.
+    JitCode* bailoutTail = cx->runtime()->jitRuntime()->getBailoutTail();
+    masm.branch(bailoutTail);
+}
+
+JitCode*
+JitRuntime::generateBailoutTable(JSContext* cx, uint32_t frameClass)
+{
+    MacroAssembler masm(cx);
+
+    Label bailout;
+    for (size_t i = 0; i < BAILOUT_TABLE_SIZE; i++) {
+        // Calculate offset to the end of table
+        int32_t offset = (BAILOUT_TABLE_SIZE - i) * BAILOUT_TABLE_ENTRY_SIZE;
+
+        // We use the 'ra' as table offset later in GenerateBailoutThunk
+        masm.as_bal(BOffImm16(offset));
+        masm.nop();
+    }
+    masm.bind(&bailout);
+
+    GenerateBailoutThunk(cx, masm, frameClass);
+
+    Linker linker(masm);
+    AutoFlushICache afc("BailoutTable");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "BailoutTable");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateBailoutHandler(JSContext* cx)
+{
+    MacroAssembler masm(cx);
+    GenerateBailoutThunk(cx, masm, NO_FRAME_SIZE_CLASS_ID);
+
+    Linker linker(masm);
+    AutoFlushICache afc("BailoutHandler");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "BailoutHandler");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateVMWrapper(JSContext* cx, const VMFunction& f)
+{
+    MOZ_ASSERT(functionWrappers_);
+    MOZ_ASSERT(functionWrappers_->initialized());
+    VMWrapperMap::AddPtr p = functionWrappers_->lookupForAdd(&f);
+    if (p)
+        return p->value();
+
+    MacroAssembler masm(cx);
+
+    AllocatableGeneralRegisterSet regs(Register::Codes::WrapperMask);
+
+    static_assert((Register::Codes::VolatileMask & ~Register::Codes::WrapperMask) == 0,
+                  "Wrapper register set should be a superset of Volatile register set.");
+
+    // The context is the first argument; a0 is the first argument register.
+    Register cxreg = a0;
+    regs.take(cxreg);
+
+    // If it isn't a tail call, then the return address needs to be saved
+    if (f.expectTailCall == NonTailCall)
+        masm.pushReturnAddress();
+
+    // We're aligned to an exit frame, so link it up.
+    masm.enterExitFrame(&f);
+    masm.loadJSContext(cxreg);
+
+    // Save the base of the argument set stored on the stack.
+    Register argsBase = InvalidReg;
+    if (f.explicitArgs) {
+        argsBase = t1; // Use temporary register.
+        regs.take(argsBase);
+        masm.ma_addu(argsBase, StackPointer, Imm32(ExitFrameLayout::SizeWithFooter()));
+    }
+
+    masm.alignStackPointer();
+
+    // Reserve space for the outparameter. Reserve sizeof(Value) for every
+    // case so that stack stays aligned.
+    uint32_t outParamSize = 0;
+    switch (f.outParam) {
+      case Type_Value:
+        outParamSize = sizeof(Value);
+        masm.reserveStack(outParamSize);
+        break;
+
+      case Type_Handle:
+        {
+            uint32_t pushed = masm.framePushed();
+            masm.PushEmptyRooted(f.outParamRootType);
+            outParamSize = masm.framePushed() - pushed;
+        }
+        break;
+
+      case Type_Bool:
+      case Type_Int32:
+        MOZ_ASSERT(sizeof(uintptr_t) == sizeof(uint32_t));
+      case Type_Pointer:
+        outParamSize = sizeof(uintptr_t);
+        masm.reserveStack(outParamSize);
+        break;
+
+      case Type_Double:
+        outParamSize = sizeof(double);
+        masm.reserveStack(outParamSize);
+        break;
+      default:
+        MOZ_ASSERT(f.outParam == Type_Void);
+        break;
+    }
+
+    uint32_t outParamOffset = 0;
+    if (f.outParam != Type_Void) {
+        // Make sure that stack is double aligned after outParam.
+        MOZ_ASSERT(outParamSize <= sizeof(double));
+        outParamOffset += sizeof(double) - outParamSize;
+    }
+    // Reserve stack for double sized args that are copied to be aligned.
+    outParamOffset += f.doubleByRefArgs() * sizeof(double);
+
+    Register doubleArgs = t0;
+    masm.reserveStack(outParamOffset);
+    masm.movePtr(StackPointer, doubleArgs);
+
+    if (!generateTLEnterVM(cx, masm, f))
+        return nullptr;
+
+    masm.setupAlignedABICall();
+    masm.passABIArg(cxreg);
+
+    size_t argDisp = 0;
+    size_t doubleArgDisp = 0;
+
+    // Copy any arguments.
+    for (uint32_t explicitArg = 0; explicitArg < f.explicitArgs; explicitArg++) {
+        MoveOperand from;
+        switch (f.argProperties(explicitArg)) {
+          case VMFunction::WordByValue:
+            masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::GENERAL);
+            argDisp += sizeof(uint32_t);
+            break;
+          case VMFunction::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 VMFunction::WordByRef:
+            masm.passABIArg(MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+                            MoveOp::GENERAL);
+            argDisp += sizeof(uint32_t);
+            break;
+          case VMFunction::DoubleByRef:
+            // Copy double sized argument to aligned place.
+            masm.ma_ld(ScratchDoubleReg, Address(argsBase, argDisp));
+            masm.as_sd(ScratchDoubleReg, doubleArgs, doubleArgDisp);
+            masm.passABIArg(MoveOperand(doubleArgs, doubleArgDisp, MoveOperand::EFFECTIVE_ADDRESS),
+                            MoveOp::GENERAL);
+            doubleArgDisp += sizeof(double);
+            argDisp += sizeof(double);
+            break;
+        }
+    }
+
+    MOZ_ASSERT_IF(f.outParam != Type_Void,
+                  doubleArgDisp + sizeof(double) == outParamOffset + outParamSize);
+
+    // Copy the implicit outparam, if any.
+    if (f.outParam != Type_Void) {
+        masm.passABIArg(MoveOperand(doubleArgs, outParamOffset, MoveOperand::EFFECTIVE_ADDRESS),
+                            MoveOp::GENERAL);
+    }
+
+    masm.callWithABI(f.wrapped);
+
+    if (!generateTLExitVM(cx, masm, f))
+        return nullptr;
+
+    // Test for failure.
+    switch (f.failType()) {
+      case Type_Object:
+        masm.branchTestPtr(Assembler::Zero, v0, v0, masm.failureLabel());
+        break;
+      case Type_Bool:
+        // Called functions return bools, which are 0/false and non-zero/true
+        masm.branchIfFalseBool(v0, masm.failureLabel());
+        break;
+      default:
+        MOZ_CRASH("unknown failure kind");
+    }
+
+    masm.freeStack(outParamOffset);
+
+    // 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(StackPointer, 0), JSReturnOperand);
+        masm.freeStack(sizeof(Value));
+        break;
+
+      case Type_Int32:
+        MOZ_ASSERT(sizeof(uintptr_t) == sizeof(uint32_t));
+      case Type_Pointer:
+        masm.load32(Address(StackPointer, 0), ReturnReg);
+        masm.freeStack(sizeof(uintptr_t));
+        break;
+
+      case Type_Bool:
+        masm.load8ZeroExtend(Address(StackPointer, 0), ReturnReg);
+        masm.freeStack(sizeof(uintptr_t));
+        break;
+
+      case Type_Double:
+        if (cx->runtime()->jitSupportsFloatingPoint) {
+            masm.as_ld(ReturnDoubleReg, StackPointer, 0);
+        } 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;
+    }
+
+    masm.restoreStackPointer();
+
+    masm.leaveExitFrame();
+    masm.retn(Imm32(sizeof(ExitFrameLayout) +
+                    f.explicitStackSlots() * sizeof(uintptr_t) +
+                    f.extraValuesToPop * sizeof(Value)));
+
+    Linker linker(masm);
+    AutoFlushICache afc("VMWrapper");
+    JitCode* wrapper = linker.newCode<NoGC>(cx, OTHER_CODE);
+    if (!wrapper)
+        return nullptr;
+
+    // linker.newCode may trigger a GC and sweep functionWrappers_ so we have
+    // to use relookupOrAdd instead of add.
+    if (!functionWrappers_->relookupOrAdd(p, &f, wrapper))
+        return nullptr;
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(wrapper, "VMWrapper");
+#endif
+
+    return wrapper;
+}
+
+JitCode*
+JitRuntime::generatePreBarrier(JSContext* cx, MIRType type)
+{
+    MacroAssembler masm(cx);
+
+    LiveRegisterSet save;
+    if (cx->runtime()->jitSupportsFloatingPoint) {
+        save.set() = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                           FloatRegisterSet(FloatRegisters::VolatileMask));
+    } else {
+        save.set() = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                           FloatRegisterSet());
+    }
+    save.add(ra);
+    masm.PushRegsInMask(save);
+
+    MOZ_ASSERT(PreBarrierReg == a1);
+    masm.movePtr(ImmPtr(cx->runtime()), a0);
+
+    masm.setupUnalignedABICall(a2);
+    masm.passABIArg(a0);
+    masm.passABIArg(a1);
+    masm.callWithABI(IonMarkFunction(type));
+
+    save.take(AnyRegister(ra));
+    masm.PopRegsInMask(save);
+    masm.ret();
+
+    Linker linker(masm);
+    AutoFlushICache afc("PreBarrier");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "PreBarrier");
+#endif
+
+    return code;
+}
+
+typedef bool (*HandleDebugTrapFn)(JSContext*, BaselineFrame*, uint8_t*, bool*);
+static const VMFunction HandleDebugTrapInfo =
+    FunctionInfo<HandleDebugTrapFn>(HandleDebugTrap, "HandleDebugTrap");
+
+JitCode*
+JitRuntime::generateDebugTrapHandler(JSContext* cx)
+{
+    MacroAssembler masm(cx);
+
+    Register scratch1 = t0;
+    Register scratch2 = t1;
+
+    // Load BaselineFrame pointer in scratch1.
+    masm.movePtr(s5, scratch1);
+    masm.subPtr(Imm32(BaselineFrame::Size()), scratch1);
+
+    // Enter a stub frame and call the HandleDebugTrap VM function. Ensure
+    // the stub frame has a nullptr ICStub pointer, since this pointer is
+    // marked during GC.
+    masm.movePtr(ImmPtr(nullptr), ICStubReg);
+    EmitBaselineEnterStubFrame(masm, scratch2);
+
+    JitCode* code = cx->runtime()->jitRuntime()->getVMWrapper(HandleDebugTrapInfo);
+    if (!code)
+        return nullptr;
+
+    masm.subPtr(Imm32(2 * sizeof(uintptr_t)), StackPointer);
+    masm.storePtr(ra, Address(StackPointer, sizeof(uintptr_t)));
+    masm.storePtr(scratch1, Address(StackPointer, 0));
+
+    EmitBaselineCallVM(code, masm);
+
+    EmitBaselineLeaveStubFrame(masm);
+
+    // If the stub returns |true|, we have to perform a forced return
+    // (return from the JS frame). If the stub returns |false|, just return
+    // from the trap stub so that execution continues at the current pc.
+    Label forcedReturn;
+    masm.branchTest32(Assembler::NonZero, ReturnReg, ReturnReg, &forcedReturn);
+
+    // ra was restored by EmitLeaveStubFrame
+    masm.branch(ra);
+
+    masm.bind(&forcedReturn);
+    masm.loadValue(Address(s5, BaselineFrame::reverseOffsetOfReturnValue()),
+                   JSReturnOperand);
+    masm.movePtr(s5, StackPointer);
+    masm.pop(s5);
+
+    // Before returning, if profiling is turned on, make sure that lastProfilingFrame
+    // is set to the correct caller frame.
+    {
+        Label skipProfilingInstrumentation;
+        AbsoluteAddress addressOfEnabled(cx->runtime()->spsProfiler.addressOfEnabled());
+        masm.branch32(Assembler::Equal, addressOfEnabled, Imm32(0), &skipProfilingInstrumentation);
+        masm.profilerExitFrame();
+        masm.bind(&skipProfilingInstrumentation);
+    }
+
+    masm.ret();
+
+    Linker linker(masm);
+    AutoFlushICache afc("DebugTrapHandler");
+    JitCode* codeDbg = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(codeDbg, "DebugTrapHandler");
+#endif
+
+    return codeDbg;
+}
+
+
+JitCode*
+JitRuntime::generateExceptionTailStub(JSContext* cx, void* handler)
+{
+    MacroAssembler masm;
+
+    masm.handleFailureWithHandlerTail(handler);
+
+    Linker linker(masm);
+    AutoFlushICache afc("ExceptionTailStub");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "ExceptionTailStub");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateBailoutTailStub(JSContext* cx)
+{
+    MacroAssembler masm;
+
+    masm.generateBailoutTail(a1, a2);
+
+    Linker linker(masm);
+    AutoFlushICache afc("BailoutTailStub");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "BailoutTailStub");
+#endif
+
+    return code;
+}
+
+JitCode*
+JitRuntime::generateProfilerExitFrameTailStub(JSContext* cx)
+{
+    MacroAssembler masm;
+
+    Register scratch1 = t0;
+    Register scratch2 = t1;
+    Register scratch3 = t2;
+    Register scratch4 = t3;
+
+    //
+    // 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;
+    AbsoluteAddress activationAddr(GetJitContext()->runtime->addressOfProfilingActivation());
+    masm.loadPtr(activationAddr, 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
+    masm.ma_and(scratch2, scratch1, Imm32((1 << FRAMETYPE_BITS) - 1));
+    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_IonAccessorIC;
+    Label handle_Entry;
+    Label end;
+
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_IonJS), &handle_IonJS);
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_BaselineJS), &handle_IonJS);
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_BaselineStub), &handle_BaselineStub);
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_Rectifier), &handle_Rectifier);
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_IonAccessorIC), &handle_IonAccessorIC);
+    masm.branch32(Assembler::Equal, scratch2, Imm32(JitFrame_Entry), &handle_Entry);
+
+    masm.assumeUnreachable("Invalid caller frame type when exiting from Ion frame.");
+
+    //
+    // JitFrame_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.as_addu(scratch2, StackPointer, scratch1);
+        masm.ma_addu(scratch2, scratch2, Imm32(JitFrameLayout::Size()));
+        masm.storePtr(scratch2, lastProfilingFrame);
+        masm.ret();
+    }
+
+    //
+    // JitFrame_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.as_addu(scratch3, StackPointer, scratch1);
+        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();
+    }
+
+
+    //
+    // JitFrame_Rectifier
+    //
+    // The rectifier frame can be preceded by either an IonJS or a
+    // BaselineStub frame.
+    //
+    // Stack layout if caller of rectifier was Ion:
+    //
+    //              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.as_addu(scratch2, StackPointer, scratch1);
+        masm.add32(Imm32(JitFrameLayout::Size()), scratch2);
+        masm.loadPtr(Address(scratch2, RectifierFrameLayout::offsetOfDescriptor()), scratch3);
+        masm.ma_srl(scratch1, scratch3, Imm32(FRAMESIZE_SHIFT));
+        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
+
+        // Check for either Ion or BaselineStub frame.
+        Label handle_Rectifier_BaselineStub;
+        masm.branch32(Assembler::NotEqual, scratch3, Imm32(JitFrame_IonJS),
+                      &handle_Rectifier_BaselineStub);
+
+        // 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.as_addu(scratch3, scratch2, scratch1);
+        masm.add32(Imm32(RectifierFrameLayout::Size()), scratch3);
+        masm.storePtr(scratch3, lastProfilingFrame);
+        masm.ret();
+
+        // Handle Rectifier <- BaselineStub <- BaselineJS
+        masm.bind(&handle_Rectifier_BaselineStub);
+#ifdef DEBUG
+        {
+            Label checkOk;
+            masm.branch32(Assembler::Equal, scratch3, Imm32(JitFrame_BaselineStub), &checkOk);
+            masm.assumeUnreachable("Unrecognized frame preceding baselineStub.");
+            masm.bind(&checkOk);
+        }
+#endif
+        masm.as_addu(scratch3, scratch2, scratch1);
+        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();
+    }
+
+    // JitFrame_IonAccessorIC
+    //
+    // The caller is always an IonJS frame.
+    //
+    //              Ion-Descriptor
+    //              Ion-ReturnAddr
+    //              ... ion frame data ... |- AccFrame-Descriptor.Size
+    //              StubCode             |
+    //              AccFrame-Descriptor  |- IonAccessorICFrameLayout::Size()
+    //              AccFrame-ReturnAddr  |
+    //              ... accessor frame data & args ... |- Descriptor.Size
+    //              ActualArgc      |
+    //              CalleeToken     |- JitFrameLayout::Size()
+    //              Descriptor      |
+    //    FP -----> ReturnAddr      |
+    masm.bind(&handle_IonAccessorIC);
+    {
+        // scratch2 := StackPointer + Descriptor.size + JitFrameLayout::Size()
+        masm.as_addu(scratch2, StackPointer, scratch1);
+        masm.addPtr(Imm32(JitFrameLayout::Size()), scratch2);
+
+        // scratch3 := AccFrame-Descriptor.Size
+        masm.loadPtr(Address(scratch2, IonAccessorICFrameLayout::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(JitFrame_IonJS), &checkOk);
+            masm.assumeUnreachable("IonAccessorIC frame must be preceded by IonJS frame");
+            masm.bind(&checkOk);
+        }
+#endif
+        masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch3);
+
+        // lastProfilingCallSite := AccFrame-ReturnAddr
+        masm.loadPtr(Address(scratch2, IonAccessorICFrameLayout::offsetOfReturnAddress()), scratch1);
+        masm.storePtr(scratch1, lastProfilingCallSite);
+
+        // lastProfilingFrame := AccessorFrame + AccFrame-Descriptor.Size +
+        //                       IonAccessorICFrameLayout::Size()
+        masm.as_addu(scratch1, scratch2, scratch3);
+        masm.addPtr(Imm32(IonAccessorICFrameLayout::Size()), scratch1);
+        masm.storePtr(scratch1, lastProfilingFrame);
+        masm.ret();
+    }
+
+    //
+    // JitFrame_Entry
+    //
+    // If at an entry frame, store null into both fields.
+    //
+    masm.bind(&handle_Entry);
+    {
+        masm.movePtr(ImmPtr(nullptr), scratch1);
+        masm.storePtr(scratch1, lastProfilingCallSite);
+        masm.storePtr(scratch1, lastProfilingFrame);
+        masm.ret();
+    }
+
+    Linker linker(masm);
+    AutoFlushICache afc("ProfilerExitFrameTailStub");
+    JitCode* code = linker.newCode<NoGC>(cx, OTHER_CODE);
+
+#ifdef JS_ION_PERF
+    writePerfSpewerJitCodeProfile(code, "ProfilerExitFrameStub");
+#endif
+
+    return code;
+}