Adding upstream version 110.0.1.upstream/110.0.1upstream

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

1 files changed, 838 insertions, 0 deletions

diff --git a/js/src/jit/arm64/Trampoline-arm64.cpp b/js/src/jit/arm64/Trampoline-arm64.cpp
new file mode 100644
index 0000000000..99cecdcc1b
--- /dev/null
+++ b/js/src/jit/arm64/Trampoline-arm64.cpp
@@ -0,0 +1,838 @@
+/* -*- 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/arm64/SharedICHelpers-arm64.h"
+#include "jit/Bailouts.h"
+#include "jit/BaselineFrame.h"
+#include "jit/CalleeToken.h"
+#include "jit/JitFrames.h"
+#include "jit/JitRuntime.h"
+#include "jit/PerfSpewer.h"
+#include "jit/VMFunctions.h"
+#include "vm/JitActivation.h"  // js::jit::JitActivation
+#include "vm/JSContext.h"
+
+#include "jit/MacroAssembler-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+/* This method generates a trampoline on ARM64 for a c++ function with
+ * the following signature:
+ *   bool blah(void* code, int argc, Value* argv,
+ *             JSObject* scopeChain, Value* vp)
+ *   ...using standard AArch64 calling convention
+ */
+void JitRuntime::generateEnterJIT(JSContext* cx, MacroAssembler& masm) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateEnterJIT");
+
+  enterJITOffset_ = startTrampolineCode(masm);
+
+  const Register reg_code = IntArgReg0;      // EnterJitData::jitcode.
+  const Register reg_argc = IntArgReg1;      // EnterJitData::maxArgc.
+  const Register reg_argv = IntArgReg2;      // EnterJitData::maxArgv.
+  const Register reg_osrFrame = IntArgReg3;  // EnterJitData::osrFrame.
+  const Register reg_callee = IntArgReg4;    // EnterJitData::calleeToken.
+  const Register reg_scope = IntArgReg5;     // EnterJitData::scopeChain.
+  const Register reg_osrNStack =
+      IntArgReg6;                      // EnterJitData::osrNumStackValues.
+  const Register reg_vp = IntArgReg7;  // Address of EnterJitData::result.
+
+  static_assert(OsrFrameReg == IntArgReg3);
+
+  // During the pushes below, use the normal stack pointer.
+  masm.SetStackPointer64(sp);
+
+  // Save return address and old frame pointer; set new frame pointer.
+  masm.push(r30, r29);
+  masm.moveStackPtrTo(r29);
+
+  // Save callee-save integer registers.
+  // Also save x7 (reg_vp) and x30 (lr), for use later.
+  masm.push(r19, r20, r21, r22);
+  masm.push(r23, r24, r25, r26);
+  masm.push(r27, r28, r7, r30);
+
+  // Save callee-save floating-point registers.
+  // AArch64 ABI specifies that only the lower 64 bits must be saved.
+  masm.push(d8, d9, d10, d11);
+  masm.push(d12, d13, d14, d15);
+
+#ifdef DEBUG
+  // Emit stack canaries.
+  masm.movePtr(ImmWord(0xdeadd00d), r23);
+  masm.movePtr(ImmWord(0xdeadd11d), r24);
+  masm.push(r23, r24);
+#endif
+
+  // Common code below attempts to push single registers at a time,
+  // which breaks the stack pointer's 16-byte alignment requirement.
+  // Note that movePtr() is invalid because StackPointer is treated as xzr.
+  //
+  // FIXME: After testing, this entire function should be rewritten to not
+  // use the PseudoStackPointer: since the amount of data pushed is
+  // precalculated, we can just allocate the whole frame header at once and
+  // index off sp. This will save a significant number of instructions where
+  // Push() updates sp.
+  masm.Mov(PseudoStackPointer64, sp);
+  masm.SetStackPointer64(PseudoStackPointer64);
+
+  // Remember stack depth without padding and arguments.
+  masm.moveStackPtrTo(r19);
+
+  // If constructing, include newTarget in argument vector.
+  {
+    Label noNewTarget;
+    Imm32 constructingToken(CalleeToken_FunctionConstructing);
+    masm.branchTest32(Assembler::Zero, reg_callee, constructingToken,
+                      &noNewTarget);
+    masm.add32(Imm32(1), reg_argc);
+    masm.bind(&noNewTarget);
+  }
+
+  // JitFrameLayout is as follows (higher is higher in memory):
+  //  N*8  - [ JS argument vector ] (base 16-byte aligned)
+  //  8    - calleeToken
+  //  8    - frameDescriptor (16-byte aligned)
+  //  8    - returnAddress
+  //  8    - frame pointer (16-byte aligned, pushed by callee)
+
+  // Touch frame incrementally (a requirement for Windows).
+  //
+  // Use already saved callee-save registers r20 and r21 as temps.
+  //
+  // This has to be done outside the ScratchRegisterScope, as the temps are
+  // under demand inside the touchFrameValues call.
+
+  // Give sp 16-byte alignment and sync stack pointers.
+  masm.andToStackPtr(Imm32(~0xf));
+  // We needn't worry about the Gecko Profiler mark because touchFrameValues
+  // touches in large increments.
+  masm.touchFrameValues(reg_argc, r20, r21);
+  // Restore stack pointer, preserved above.
+  masm.moveToStackPtr(r19);
+
+  // Push the argument vector onto the stack.
+  // WARNING: destructively modifies reg_argv
+  {
+    vixl::UseScratchRegisterScope temps(&masm.asVIXL());
+
+    const ARMRegister tmp_argc = temps.AcquireX();
+    const ARMRegister tmp_sp = temps.AcquireX();
+
+    Label noArguments;
+    Label loopHead;
+
+    masm.movePtr(reg_argc, tmp_argc.asUnsized());
+
+    // sp -= 8
+    // Since we're using PostIndex Str below, this is necessary to avoid
+    // overwriting the Gecko Profiler mark pushed above.
+    masm.subFromStackPtr(Imm32(8));
+
+    // sp -= 8 * argc
+    masm.Sub(PseudoStackPointer64, PseudoStackPointer64,
+             Operand(tmp_argc, vixl::SXTX, 3));
+
+    // Give sp 16-byte alignment and sync stack pointers.
+    masm.andToStackPtr(Imm32(~0xf));
+    masm.moveStackPtrTo(tmp_sp.asUnsized());
+
+    masm.branchTestPtr(Assembler::Zero, reg_argc, reg_argc, &noArguments);
+
+    // Begin argument-pushing loop.
+    // This could be optimized using Ldp and Stp.
+    {
+      masm.bind(&loopHead);
+
+      // Load an argument from argv, then increment argv by 8.
+      masm.Ldr(x24, MemOperand(ARMRegister(reg_argv, 64), Operand(8),
+                               vixl::PostIndex));
+
+      // Store the argument to tmp_sp, then increment tmp_sp by 8.
+      masm.Str(x24, MemOperand(tmp_sp, Operand(8), vixl::PostIndex));
+
+      // Decrement tmp_argc and set the condition codes for the new value.
+      masm.Subs(tmp_argc, tmp_argc, Operand(1));
+
+      // Branch if arguments remain.
+      masm.B(&loopHead, vixl::Condition::NonZero);
+    }
+
+    masm.bind(&noArguments);
+  }
+  masm.checkStackAlignment();
+
+  // Push the calleeToken and the frame descriptor.
+  // The result address is used to store the actual number of arguments
+  // without adding an argument to EnterJIT.
+  {
+    vixl::UseScratchRegisterScope temps(&masm.asVIXL());
+    MOZ_ASSERT(temps.IsAvailable(ScratchReg64));  // ip0
+    temps.Exclude(ScratchReg64);
+    Register scratch = ScratchReg64.asUnsized();
+    masm.push(reg_callee);
+
+    // Push the descriptor.
+    masm.unboxInt32(Address(reg_vp, 0x0), scratch);
+    masm.PushFrameDescriptorForJitCall(FrameType::CppToJSJit, scratch, scratch);
+  }
+  masm.checkStackAlignment();
+
+  Label osrReturnPoint;
+  {
+    // Check for Interpreter -> Baseline OSR.
+
+    AllocatableGeneralRegisterSet regs(GeneralRegisterSet::All());
+    MOZ_ASSERT(!regs.has(FramePointer));
+    regs.take(OsrFrameReg);
+    regs.take(reg_code);
+    regs.take(reg_osrNStack);
+    MOZ_ASSERT(!regs.has(ReturnReg), "ReturnReg matches reg_code");
+
+    Label notOsr;
+    masm.branchTestPtr(Assembler::Zero, OsrFrameReg, OsrFrameReg, &notOsr);
+
+    Register scratch = regs.takeAny();
+
+    // Frame prologue.
+    masm.Adr(ARMRegister(scratch, 64), &osrReturnPoint);
+    masm.push(scratch, FramePointer);
+    masm.moveStackPtrTo(FramePointer);
+
+    // Reserve frame.
+    masm.subFromStackPtr(Imm32(BaselineFrame::Size()));
+
+    Register framePtrScratch = regs.takeAny();
+    masm.touchFrameValues(reg_osrNStack, scratch, framePtrScratch);
+    masm.moveStackPtrTo(framePtrScratch);
+
+    // Reserve space for locals and stack values.
+    // scratch = num_stack_values * sizeof(Value).
+    masm.Lsl(ARMRegister(scratch, 32), ARMRegister(reg_osrNStack, 32), 3);
+    masm.subFromStackPtr(scratch);
+
+    // Enter exit frame.
+    masm.pushFrameDescriptor(FrameType::BaselineJS);
+    masm.push(xzr);  // Push xzr for a fake return address.
+    masm.push(FramePointer);
+    // No GC things to mark: push a bare token.
+    masm.loadJSContext(scratch);
+    masm.enterFakeExitFrame(scratch, scratch, ExitFrameType::Bare);
+
+    masm.push(reg_code);
+
+    // Initialize the frame, including filling in the slots.
+    using Fn = bool (*)(BaselineFrame * frame, InterpreterFrame * interpFrame,
+                        uint32_t numStackValues);
+    masm.setupUnalignedABICall(r19);
+    masm.passABIArg(framePtrScratch);  // BaselineFrame.
+    masm.passABIArg(reg_osrFrame);     // InterpreterFrame.
+    masm.passABIArg(reg_osrNStack);
+    masm.callWithABI<Fn, jit::InitBaselineFrameForOsr>(
+        MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+    masm.pop(scratch);
+    MOZ_ASSERT(scratch != ReturnReg);
+
+    masm.addToStackPtr(Imm32(ExitFrameLayout::SizeWithFooter()));
+
+    Label error;
+    masm.branchIfFalseBool(ReturnReg, &error);
+
+    // If OSR-ing, then emit instrumentation for setting lastProfilerFrame
+    // if profiler instrumentation is enabled.
+    {
+      Label skipProfilingInstrumentation;
+      AbsoluteAddress addressOfEnabled(
+          cx->runtime()->geckoProfiler().addressOfEnabled());
+      masm.branch32(Assembler::Equal, addressOfEnabled, Imm32(0),
+                    &skipProfilingInstrumentation);
+      masm.profilerEnterFrame(FramePointer, regs.getAny());
+      masm.bind(&skipProfilingInstrumentation);
+    }
+
+    masm.jump(scratch);
+
+    // OOM: frame epilogue, load error value, discard return address and return.
+    masm.bind(&error);
+    masm.moveToStackPtr(FramePointer);
+    masm.pop(FramePointer);
+    masm.addToStackPtr(Imm32(sizeof(uintptr_t)));  // Return address.
+    masm.syncStackPtr();
+    masm.moveValue(MagicValue(JS_ION_ERROR), JSReturnOperand);
+    masm.B(&osrReturnPoint);
+
+    masm.bind(&notOsr);
+    masm.movePtr(reg_scope, R1_);
+  }
+
+  // The callee will push the return address and frame pointer on the stack,
+  // thus we check that the stack would be aligned once the call is complete.
+  masm.assertStackAlignment(JitStackAlignment, 2 * sizeof(uintptr_t));
+
+  // Call function.
+  // Since AArch64 doesn't have the pc register available, the callee must push
+  // lr.
+  masm.callJitNoProfiler(reg_code);
+
+  // Interpreter -> Baseline OSR will return here.
+  masm.bind(&osrReturnPoint);
+
+  // Discard arguments and padding. Set sp to the address of the saved
+  // registers. In debug builds we have to include the two stack canaries
+  // checked below.
+#ifdef DEBUG
+  static constexpr size_t SavedRegSize = 22 * sizeof(void*);
+#else
+  static constexpr size_t SavedRegSize = 20 * sizeof(void*);
+#endif
+  masm.computeEffectiveAddress(Address(FramePointer, -int32_t(SavedRegSize)),
+                               masm.getStackPointer());
+
+  masm.syncStackPtr();
+  masm.SetStackPointer64(sp);
+
+#ifdef DEBUG
+  // Check that canaries placed on function entry are still present.
+  masm.pop(r24, r23);
+  Label x23OK, x24OK;
+
+  masm.branchPtr(Assembler::Equal, r23, ImmWord(0xdeadd00d), &x23OK);
+  masm.breakpoint();
+  masm.bind(&x23OK);
+
+  masm.branchPtr(Assembler::Equal, r24, ImmWord(0xdeadd11d), &x24OK);
+  masm.breakpoint();
+  masm.bind(&x24OK);
+#endif
+
+  // Restore callee-save floating-point registers.
+  masm.pop(d15, d14, d13, d12);
+  masm.pop(d11, d10, d9, d8);
+
+  // Restore callee-save integer registers.
+  // Also restore x7 (reg_vp) and x30 (lr).
+  masm.pop(r30, r7, r28, r27);
+  masm.pop(r26, r25, r24, r23);
+  masm.pop(r22, r21, r20, r19);
+
+  // Store return value (in JSReturnReg = x2 to just-popped reg_vp).
+  masm.storeValue(JSReturnOperand, Address(reg_vp, 0));
+
+  // Restore old frame pointer.
+  masm.pop(r29, r30);
+
+  // Return using the value popped into x30.
+  masm.abiret();
+
+  // Reset stack pointer.
+  masm.SetStackPointer64(PseudoStackPointer64);
+}
+
+// static
+mozilla::Maybe<::JS::ProfilingFrameIterator::RegisterState>
+JitRuntime::getCppEntryRegisters(JitFrameLayout* frameStackAddress) {
+  // Not supported, or not implemented yet.
+  // TODO: Implement along with the corresponding stack-walker changes, in
+  // coordination with the Gecko Profiler, see bug 1635987 and follow-ups.
+  return mozilla::Nothing{};
+}
+
+static void PushRegisterDump(MacroAssembler& masm) {
+  const LiveRegisterSet First28GeneralRegisters = LiveRegisterSet(
+      GeneralRegisterSet(Registers::AllMask &
+                         ~(1 << 31 | 1 << 30 | 1 << 29 | 1 << 28)),
+      FloatRegisterSet(FloatRegisters::NoneMask));
+
+  const LiveRegisterSet AllFloatRegisters =
+      LiveRegisterSet(GeneralRegisterSet(Registers::NoneMask),
+                      FloatRegisterSet(FloatRegisters::AllMask));
+
+  // Push all general-purpose registers.
+  //
+  // The ARM64 ABI does not treat SP as a normal register that can
+  // be pushed. So pushing happens in two phases.
+  //
+  // Registers are pushed in reverse order of code.
+  //
+  // See block comment in MacroAssembler.h for further required invariants.
+
+  // First, push the last four registers, passing zero for sp.
+  // Zero is pushed for x28 and x31: the pseudo-SP and SP, respectively.
+  masm.asVIXL().Push(xzr, x30, x29, xzr);
+
+  // Second, push the first 28 registers that serve no special purpose.
+  masm.PushRegsInMask(First28GeneralRegisters);
+
+  // Finally, push all floating-point registers, completing the RegisterDump.
+  masm.PushRegsInMask(AllFloatRegisters);
+}
+
+void JitRuntime::generateInvalidator(MacroAssembler& masm, Label* bailoutTail) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateInvalidator");
+
+  invalidatorOffset_ = startTrampolineCode(masm);
+
+  // The InvalidationBailoutStack saved in r0 must be:
+  // - osiPointReturnAddress_
+  // - ionScript_  (pushed by CodeGeneratorARM64::generateInvalidateEpilogue())
+  // - regs_  (pushed here)
+  // - fpregs_  (pushed here) [=r0]
+  PushRegisterDump(masm);
+  masm.moveStackPtrTo(r0);
+
+  // Reserve space for InvalidationBailout's bailoutInfo outparam.
+  masm.Sub(x1, masm.GetStackPointer64(), Operand(sizeof(void*)));
+  masm.moveToStackPtr(r1);
+
+  using Fn =
+      bool (*)(InvalidationBailoutStack * sp, BaselineBailoutInfo * *info);
+  masm.setupUnalignedABICall(r10);
+  masm.passABIArg(r0);
+  masm.passABIArg(r1);
+
+  masm.callWithABI<Fn, InvalidationBailout>(
+      MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckOther);
+
+  masm.pop(r2);  // Get the bailoutInfo outparam.
+
+  // Pop the machine state and the dead frame.
+  masm.moveToStackPtr(FramePointer);
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in r2.
+  masm.jump(bailoutTail);
+}
+
+void JitRuntime::generateArgumentsRectifier(MacroAssembler& masm,
+                                            ArgumentsRectifierKind kind) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateArgumentsRectifier");
+
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      argumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      trialInliningArgumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+  }
+
+  // Save the return address for later.
+  masm.push(lr);
+
+  // Frame prologue.
+  //
+  // NOTE: if this changes, fix the Baseline bailout code too!
+  // See BaselineStackBuilder::calculatePrevFramePtr and
+  // BaselineStackBuilder::buildRectifierFrame (in BaselineBailouts.cpp).
+  masm.push(FramePointer);
+  masm.moveStackPtrTo(FramePointer);
+
+  // Load the information that the rectifier needs from the stack.
+  masm.loadNumActualArgs(FramePointer, r0);
+  masm.loadPtr(
+      Address(FramePointer, RectifierFrameLayout::offsetOfCalleeToken()), r1);
+
+  // Extract a JSFunction pointer from the callee token and keep the
+  // intermediary to avoid later recalculation.
+  masm.And(x5, x1, Operand(CalleeTokenMask));
+
+  // Get the arguments from the function object.
+  masm.loadFunctionArgCount(x5.asUnsized(), x6.asUnsized());
+
+  static_assert(CalleeToken_FunctionConstructing == 0x1,
+                "Constructing must be low-order bit");
+  masm.And(x4, x1, Operand(CalleeToken_FunctionConstructing));
+  masm.Add(x7, x6, x4);
+
+  // Copy the number of actual arguments into r8.
+  masm.mov(r0, r8);
+
+  // Calculate the position that our arguments are at before sp gets modified.
+  masm.Add(x3, masm.GetStackPointer64(), Operand(x8, vixl::LSL, 3));
+  masm.Add(x3, x3, Operand(sizeof(RectifierFrameLayout)));
+
+  // If the number of Values without |this| is even, push 8 padding bytes to
+  // ensure the stack is 16-byte aligned.
+  Label noPadding;
+  masm.Tbnz(x7, 0, &noPadding);
+  masm.asVIXL().Push(xzr);
+  masm.bind(&noPadding);
+
+  {
+    Label notConstructing;
+    masm.Cbz(x4, &notConstructing);
+
+    // new.target lives at the end of the pushed args
+    // NB: The arg vector holder starts at the beginning of the last arg,
+    //     add a value to get to argv[argc]
+    masm.loadPtr(Address(r3, sizeof(Value)), r4);
+    masm.Push(r4);
+
+    masm.bind(&notConstructing);
+  }
+
+  // Calculate the number of undefineds that need to be pushed.
+  masm.Sub(w2, w6, w8);
+
+  // Put an undefined in a register so it can be pushed.
+  masm.moveValue(UndefinedValue(), ValueOperand(r4));
+
+  // Push undefined N times.
+  {
+    Label undefLoopTop;
+    masm.bind(&undefLoopTop);
+    masm.Push(r4);
+    masm.Subs(w2, w2, Operand(1));
+    masm.B(&undefLoopTop, Assembler::NonZero);
+  }
+
+  // Arguments copy loop. Copy for x8 >= 0 to include |this|.
+  {
+    Label copyLoopTop;
+    masm.bind(&copyLoopTop);
+    masm.Ldr(x4, MemOperand(x3, -sizeof(Value), vixl::PostIndex));
+    masm.Push(r4);
+    masm.Subs(x8, x8, Operand(1));
+    masm.B(&copyLoopTop, Assembler::NotSigned);
+  }
+
+  masm.push(r1);  // Callee token.
+  masm.pushFrameDescriptorForJitCall(FrameType::Rectifier, r0, r0);
+
+  // Call the target function.
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      masm.loadJitCodeRaw(r5, r3);
+      argumentsRectifierReturnOffset_ = masm.callJitNoProfiler(r3);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      Label noBaselineScript, done;
+      masm.loadBaselineJitCodeRaw(r5, r3, &noBaselineScript);
+      masm.callJitNoProfiler(r3);
+      masm.jump(&done);
+
+      // See BaselineCacheIRCompiler::emitCallInlinedFunction.
+      masm.bind(&noBaselineScript);
+      masm.loadJitCodeRaw(r5, r3);
+      masm.callJitNoProfiler(r3);
+      masm.bind(&done);
+      break;
+  }
+
+  masm.moveToStackPtr(FramePointer);
+  masm.pop(FramePointer);
+  masm.ret();
+}
+
+static void PushBailoutFrame(MacroAssembler& masm, Register spArg) {
+  // This assumes no SIMD registers, as JS does not support SIMD.
+
+  // The stack saved in spArg must be (higher entries have higher memory
+  // addresses):
+  // - snapshotOffset_
+  // - frameSize_
+  // - regs_
+  // - fpregs_ (spArg + 0)
+  PushRegisterDump(masm);
+  masm.moveStackPtrTo(spArg);
+}
+
+static void GenerateBailoutThunk(MacroAssembler& masm, Label* bailoutTail) {
+  PushBailoutFrame(masm, r0);
+
+  // SP % 8 == 4
+  // STEP 1c: Call the bailout function, giving a pointer to the
+  //          structure we just blitted onto the stack.
+  // Make space for the BaselineBailoutInfo* outparam.
+  masm.reserveStack(sizeof(void*));
+  masm.moveStackPtrTo(r1);
+
+  using Fn = bool (*)(BailoutStack * sp, BaselineBailoutInfo * *info);
+  masm.setupUnalignedABICall(r2);
+  masm.passABIArg(r0);
+  masm.passABIArg(r1);
+  masm.callWithABI<Fn, Bailout>(MoveOp::GENERAL,
+                                CheckUnsafeCallWithABI::DontCheckOther);
+
+  // Get the bailoutInfo outparam.
+  masm.pop(r2);
+
+  // Remove both the bailout frame and the topmost Ion frame's stack.
+  masm.moveToStackPtr(FramePointer);
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in r2.
+  masm.jump(bailoutTail);
+}
+
+void JitRuntime::generateBailoutHandler(MacroAssembler& masm,
+                                        Label* bailoutTail) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateBailoutHandler");
+
+  bailoutHandlerOffset_ = startTrampolineCode(masm);
+
+  GenerateBailoutThunk(masm, bailoutTail);
+}
+
+bool JitRuntime::generateVMWrapper(JSContext* cx, MacroAssembler& masm,
+                                   const VMFunctionData& f, DynFn nativeFun,
+                                   uint32_t* wrapperOffset) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateVMWrapper");
+
+  *wrapperOffset = startTrampolineCode(masm);
+
+  // Avoid conflicts with argument registers while discarding the result after
+  // the function call.
+  AllocatableGeneralRegisterSet regs(Register::Codes::WrapperMask);
+
+  static_assert(
+      (Register::Codes::VolatileMask & ~Register::Codes::WrapperMask) == 0,
+      "Wrapper register set must be a superset of the Volatile register set.");
+
+  // Unlike on other platforms, it is the responsibility of the VM *callee* to
+  // push the return address, while the caller must ensure that the address
+  // is stored in lr on entry. This allows the VM wrapper to work with both
+  // direct calls and tail calls.
+  masm.push(lr);
+
+  // First argument is the JSContext.
+  Register reg_cx = IntArgReg0;
+  regs.take(reg_cx);
+
+  // Stack is:
+  //    ... frame ...
+  //  +12 [args]
+  //  +8  descriptor
+  //  +0  returnAddress (pushed by this function, caller sets as lr)
+  //
+  // Push the frame pointer to finish the exit frame, then link it up.
+  masm.Push(FramePointer);
+  masm.loadJSContext(reg_cx);
+  masm.enterExitFrame(reg_cx, regs.getAny(), &f);
+
+  // Save the current stack pointer as the base for copying arguments.
+  Register argsBase = InvalidReg;
+  if (f.explicitArgs) {
+    // argsBase can't be an argument register. Bad things would happen if
+    // the MoveResolver didn't throw an assertion failure first.
+    argsBase = r8;
+    regs.take(argsBase);
+    masm.Add(ARMRegister(argsBase, 64), masm.GetStackPointer64(),
+             Operand(ExitFrameLayout::SizeWithFooter()));
+  }
+
+  // Reserve space for any outparameter.
+  Register outReg = InvalidReg;
+  switch (f.outParam) {
+    case Type_Value:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(Value));
+      masm.moveStackPtrTo(outReg);
+      break;
+
+    case Type_Handle:
+      outReg = regs.takeAny();
+      masm.PushEmptyRooted(f.outParamRootType);
+      masm.moveStackPtrTo(outReg);
+      break;
+
+    case Type_Int32:
+    case Type_Bool:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(int64_t));
+      masm.moveStackPtrTo(outReg);
+      break;
+
+    case Type_Double:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(double));
+      masm.moveStackPtrTo(outReg);
+      break;
+
+    case Type_Pointer:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(uintptr_t));
+      masm.moveStackPtrTo(outReg);
+      break;
+
+    default:
+      MOZ_ASSERT(f.outParam == Type_Void);
+      break;
+  }
+
+  masm.setupUnalignedABICall(regs.getAny());
+  masm.passABIArg(reg_cx);
+
+  size_t argDisp = 0;
+
+  // Copy arguments.
+  for (uint32_t explicitArg = 0; explicitArg < f.explicitArgs; explicitArg++) {
+    switch (f.argProperties(explicitArg)) {
+      case VMFunctionData::WordByValue:
+        masm.passABIArg(MoveOperand(argsBase, argDisp),
+                        (f.argPassedInFloatReg(explicitArg) ? MoveOp::DOUBLE
+                                                            : MoveOp::GENERAL));
+        argDisp += sizeof(void*);
+        break;
+
+      case VMFunctionData::WordByRef:
+        masm.passABIArg(
+            MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+            MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+
+      case VMFunctionData::DoubleByValue:
+      case VMFunctionData::DoubleByRef:
+        MOZ_CRASH("NYI: AArch64 callVM should not be used with 128bit values.");
+    }
+  }
+
+  // Copy the semi-implicit outparam, if any.
+  // It is not a C++-abi outparam, which would get passed in the
+  // outparam register, but a real parameter to the function, which
+  // was stack-allocated above.
+  if (outReg != InvalidReg) {
+    masm.passABIArg(outReg);
+  }
+
+  masm.callWithABI(nativeFun, MoveOp::GENERAL,
+                   CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+  // SP is used to transfer stack across call boundaries.
+  masm.initPseudoStackPtr();
+
+  // Test for failure.
+  switch (f.failType()) {
+    case Type_Cell:
+      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_Value:
+      masm.Ldr(ARMRegister(JSReturnReg, 64),
+               MemOperand(masm.GetStackPointer64()));
+      masm.freeStack(sizeof(Value));
+      break;
+
+    case Type_Handle:
+      masm.popRooted(f.outParamRootType, ReturnReg, JSReturnOperand);
+      break;
+
+    case Type_Int32:
+      masm.Ldr(ARMRegister(ReturnReg, 32),
+               MemOperand(masm.GetStackPointer64()));
+      masm.freeStack(sizeof(int64_t));
+      break;
+
+    case Type_Bool:
+      masm.Ldrb(ARMRegister(ReturnReg, 32),
+                MemOperand(masm.GetStackPointer64()));
+      masm.freeStack(sizeof(int64_t));
+      break;
+
+    case Type_Double:
+      masm.Ldr(ARMFPRegister(ReturnDoubleReg, 64),
+               MemOperand(masm.GetStackPointer64()));
+      masm.freeStack(sizeof(double));
+      break;
+
+    case Type_Pointer:
+      masm.Ldr(ARMRegister(ReturnReg, 64),
+               MemOperand(masm.GetStackPointer64()));
+      masm.freeStack(sizeof(uintptr_t));
+      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();
+  }
+
+  // Pop ExitFooterFrame and the frame pointer.
+  masm.leaveExitFrame(sizeof(void*));
+
+  // Return. Subtract sizeof(void*) for the frame pointer.
+  masm.retn(Imm32(sizeof(ExitFrameLayout) - sizeof(void*) +
+                  f.explicitStackSlots() * sizeof(void*) +
+                  f.extraValuesToPop * sizeof(Value)));
+
+  return true;
+}
+
+uint32_t JitRuntime::generatePreBarrier(JSContext* cx, MacroAssembler& masm,
+                                        MIRType type) {
+  AutoCreatedBy acb(masm, "JitRuntime::generatePreBarrier");
+
+  uint32_t offset = startTrampolineCode(masm);
+
+  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 regs =
+      LiveRegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                      FloatRegisterSet(FloatRegisters::VolatileMask));
+
+  // Also preserve the return address.
+  regs.add(lr);
+
+  masm.PushRegsInMask(regs);
+
+  masm.movePtr(ImmPtr(cx->runtime()), r3);
+
+  masm.setupUnalignedABICall(r0);
+  masm.passABIArg(r3);
+  masm.passABIArg(PreBarrierReg);
+  masm.callWithABI(JitPreWriteBarrier(type));
+
+  // Pop the volatile regs and restore LR.
+  masm.PopRegsInMask(regs);
+  masm.abiret();
+
+  masm.bind(&noBarrier);
+  masm.pop(temp3);
+  masm.pop(temp2);
+  masm.pop(temp1);
+  masm.abiret();
+
+  return offset;
+}
+
+void JitRuntime::generateBailoutTailStub(MacroAssembler& masm,
+                                         Label* bailoutTail) {
+  AutoCreatedBy acb(masm, "JitRuntime::generateBailoutTailStub");
+
+  masm.bind(bailoutTail);
+  masm.generateBailoutTail(r1, r2);
+}