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/* -*- 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/x64/Assembler-x64.h"
#include "gc/Tracer.h"
#include "util/Memory.h"
using namespace js;
using namespace js::jit;
ABIArgGenerator::ABIArgGenerator()
:
#if defined(XP_WIN)
regIndex_(0),
stackOffset_(ShadowStackSpace),
#else
intRegIndex_(0),
floatRegIndex_(0),
stackOffset_(0),
#endif
current_() {
}
ABIArg ABIArgGenerator::next(MIRType type) {
#if defined(XP_WIN)
static_assert(NumIntArgRegs == NumFloatArgRegs);
if (regIndex_ == NumIntArgRegs) {
if (type == MIRType::Simd128) {
// On Win64, >64 bit args need to be passed by reference. However, wasm
// doesn't allow passing SIMD values to JS, so the only way to reach this
// is wasm to wasm calls. Ergo we can break the native ABI here and use
// the Wasm ABI instead.
stackOffset_ = AlignBytes(stackOffset_, SimdMemoryAlignment);
current_ = ABIArg(stackOffset_);
stackOffset_ += Simd128DataSize;
} else {
current_ = ABIArg(stackOffset_);
stackOffset_ += sizeof(uint64_t);
}
return current_;
}
switch (type) {
case MIRType::Int32:
case MIRType::Int64:
case MIRType::Pointer:
case MIRType::RefOrNull:
case MIRType::StackResults:
current_ = ABIArg(IntArgRegs[regIndex_++]);
break;
case MIRType::Float32:
current_ = ABIArg(FloatArgRegs[regIndex_++].asSingle());
break;
case MIRType::Double:
current_ = ABIArg(FloatArgRegs[regIndex_++]);
break;
case MIRType::Simd128:
// On Win64, >64 bit args need to be passed by reference, but wasm
// doesn't allow passing SIMD values to FFIs. The only way to reach
// here is asm to asm calls, so we can break the ABI here.
current_ = ABIArg(FloatArgRegs[regIndex_++].asSimd128());
break;
default:
MOZ_CRASH("Unexpected argument type");
}
return current_;
#else
switch (type) {
case MIRType::Int32:
case MIRType::Int64:
case MIRType::Pointer:
case MIRType::RefOrNull:
case MIRType::StackResults:
if (intRegIndex_ == NumIntArgRegs) {
current_ = ABIArg(stackOffset_);
stackOffset_ += sizeof(uint64_t);
break;
}
current_ = ABIArg(IntArgRegs[intRegIndex_++]);
break;
case MIRType::Double:
case MIRType::Float32:
if (floatRegIndex_ == NumFloatArgRegs) {
current_ = ABIArg(stackOffset_);
stackOffset_ += sizeof(uint64_t);
break;
}
if (type == MIRType::Float32) {
current_ = ABIArg(FloatArgRegs[floatRegIndex_++].asSingle());
} else {
current_ = ABIArg(FloatArgRegs[floatRegIndex_++]);
}
break;
case MIRType::Simd128:
if (floatRegIndex_ == NumFloatArgRegs) {
stackOffset_ = AlignBytes(stackOffset_, SimdMemoryAlignment);
current_ = ABIArg(stackOffset_);
stackOffset_ += Simd128DataSize;
break;
}
current_ = ABIArg(FloatArgRegs[floatRegIndex_++].asSimd128());
break;
default:
MOZ_CRASH("Unexpected argument type");
}
return current_;
#endif
}
void Assembler::addPendingJump(JmpSrc src, ImmPtr target,
RelocationKind reloc) {
MOZ_ASSERT(target.value != nullptr);
// Emit reloc before modifying the jump table, since it computes a 0-based
// index. This jump is not patchable at runtime.
if (reloc == RelocationKind::JITCODE) {
jumpRelocations_.writeUnsigned(src.offset());
}
static_assert(MaxCodeBytesPerProcess <= uint64_t(2) * 1024 * 1024 * 1024,
"Code depends on using int32_t for cross-JitCode jump offsets");
MOZ_ASSERT_IF(reloc == RelocationKind::JITCODE,
AddressIsInExecutableMemory(target.value));
RelativePatch patch(src.offset(), target.value, reloc);
if (reloc == RelocationKind::JITCODE ||
AddressIsInExecutableMemory(target.value)) {
enoughMemory_ &= codeJumps_.append(patch);
} else {
enoughMemory_ &= extendedJumps_.append(patch);
}
}
void Assembler::finish() {
if (oom()) {
return;
}
AutoCreatedBy acb(*this, "Assembler::finish");
if (!extendedJumps_.length()) {
// Since we may be folowed by non-executable data, eagerly insert an
// undefined instruction byte to prevent processors from decoding
// gibberish into their pipelines. See Intel performance guides.
masm.ud2();
return;
}
// Emit the jump table.
masm.haltingAlign(SizeOfJumpTableEntry);
extendedJumpTable_ = masm.size();
// Zero the extended jumps table.
for (size_t i = 0; i < extendedJumps_.length(); i++) {
#ifdef DEBUG
size_t oldSize = masm.size();
#endif
MOZ_ASSERT(hasCreator());
masm.jmp_rip(2);
MOZ_ASSERT_IF(!masm.oom(), masm.size() - oldSize == 6);
// Following an indirect branch with ud2 hints to the hardware that
// there's no fall-through. This also aligns the 64-bit immediate.
masm.ud2();
MOZ_ASSERT_IF(!masm.oom(), masm.size() - oldSize == 8);
masm.immediate64(0);
MOZ_ASSERT_IF(!masm.oom(), masm.size() - oldSize == SizeOfExtendedJump);
MOZ_ASSERT_IF(!masm.oom(), masm.size() - oldSize == SizeOfJumpTableEntry);
}
}
void Assembler::executableCopy(uint8_t* buffer) {
AssemblerX86Shared::executableCopy(buffer);
for (RelativePatch& rp : codeJumps_) {
uint8_t* src = buffer + rp.offset;
MOZ_ASSERT(rp.target);
MOZ_RELEASE_ASSERT(X86Encoding::CanRelinkJump(src, rp.target));
X86Encoding::SetRel32(src, rp.target);
}
for (size_t i = 0; i < extendedJumps_.length(); i++) {
RelativePatch& rp = extendedJumps_[i];
uint8_t* src = buffer + rp.offset;
MOZ_ASSERT(rp.target);
if (X86Encoding::CanRelinkJump(src, rp.target)) {
X86Encoding::SetRel32(src, rp.target);
} else {
// An extended jump table must exist, and its offset must be in
// range.
MOZ_ASSERT(extendedJumpTable_);
MOZ_ASSERT((extendedJumpTable_ + i * SizeOfJumpTableEntry) <=
size() - SizeOfJumpTableEntry);
// Patch the jump to go to the extended jump entry.
uint8_t* entry = buffer + extendedJumpTable_ + i * SizeOfJumpTableEntry;
X86Encoding::SetRel32(src, entry);
// Now patch the pointer, note that we need to align it to
// *after* the extended jump, i.e. after the 64-bit immedate.
X86Encoding::SetPointer(entry + SizeOfExtendedJump, rp.target);
}
}
}
class RelocationIterator {
CompactBufferReader reader_;
uint32_t offset_ = 0;
public:
explicit RelocationIterator(CompactBufferReader& reader) : reader_(reader) {}
bool read() {
if (!reader_.more()) {
return false;
}
offset_ = reader_.readUnsigned();
return true;
}
uint32_t offset() const { return offset_; }
};
JitCode* Assembler::CodeFromJump(JitCode* code, uint8_t* jump) {
uint8_t* target = (uint8_t*)X86Encoding::GetRel32Target(jump);
MOZ_ASSERT(!code->containsNativePC(target),
"Extended jump table not used for cross-JitCode jumps");
return JitCode::FromExecutable(target);
}
void Assembler::TraceJumpRelocations(JSTracer* trc, JitCode* code,
CompactBufferReader& reader) {
RelocationIterator iter(reader);
while (iter.read()) {
JitCode* child = CodeFromJump(code, code->raw() + iter.offset());
TraceManuallyBarrieredEdge(trc, &child, "rel32");
MOZ_ASSERT(child == CodeFromJump(code, code->raw() + iter.offset()));
}
}
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