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Use relative displacement in mov [abs], ax if base-address is known and the displacement encodable (#275)

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kobalicek
2020-02-23 00:05:36 +01:00
parent 8e1eb4f5dc
commit 967dde0fc4
2 changed files with 57 additions and 8 deletions
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10
CMakeLists.txt
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@@ -179,9 +179,15 @@ if (NOT ASMJIT_NO_CUSTOM_FLAGS)
-Oi) # [+] Generate intrinsic functions.
elseif ("${CMAKE_CXX_COMPILER_ID}" MATCHES "^(GNU|Clang|AppleClang)$")
list(APPEND ASMJIT_PRIVATE_CFLAGS -Wall -Wextra)
list(APPEND ASMJIT_PRIVATE_CFLAGS -fno-math-errno -fno-threadsafe-statics)
list(APPEND ASMJIT_PRIVATE_CFLAGS -fno-math-errno)
list(APPEND ASMJIT_PRIVATE_CFLAGS_REL -O2)
asmjit_detect_cflags(ASMJIT_PRIVATE_CFLAGS_REL -fmerge-all-constants)
asmjit_detect_cflags(ASMJIT_PRIVATE_CFLAGS
-fno-threadsafe-statics
-fno-semantic-interposition)
asmjit_detect_cflags(ASMJIT_PRIVATE_CFLAGS_REL
-fmerge-all-constants)
endif()
endif()

55
src/asmjit/x86/x86assembler.cpp
View File

@@ -473,6 +473,49 @@ public:
#define ENC_OPS3(OP0, OP1, OP2) ((Operand::kOp##OP0) + ((Operand::kOp##OP1) << 3) + ((Operand::kOp##OP2) << 6))
#define ENC_OPS4(OP0, OP1, OP2, OP3) ((Operand::kOp##OP0) + ((Operand::kOp##OP1) << 3) + ((Operand::kOp##OP2) << 6) + ((Operand::kOp##OP3) << 9))
// ============================================================================
// [asmjit::x86::Assembler - Movabs Heuristics]
// ============================================================================
static ASMJIT_INLINE bool x86GetMovAbsInstSize64Bit(uint32_t regSize, uint32_t options, const Mem& rmRel) noexcept {
uint32_t segmentPrefixSize = rmRel.segmentId() != 0;
uint32_t _66hPrefixSize = regSize == 2;
uint32_t rexPrefixSize = (regSize == 8) || ((options & Inst::kOptionRex) != 0);
uint32_t opCodeByteSize = 1;
uint32_t immediateSize = 8;
return segmentPrefixSize + _66hPrefixSize + rexPrefixSize + opCodeByteSize + immediateSize;
}
static ASMJIT_INLINE uint32_t x86GetMovAbsAddrType(Assembler* self, X86BufferWriter& writer, uint32_t regSize, uint32_t options, const Mem& rmRel) noexcept {
uint32_t addrType = rmRel.addrType();
int64_t addrValue = rmRel.offset();
if (addrType == BaseMem::kAddrTypeDefault && !(options & Inst::kOptionModMR)) {
if (self->is64Bit()) {
uint64_t baseAddress = self->codeInfo().baseAddress();
if (baseAddress != Globals::kNoBaseAddress && !rmRel.hasSegment()) {
uint32_t instructionSize = x86GetMovAbsInstSize64Bit(regSize, options, rmRel);
uint64_t virtualOffset = uint64_t(writer.offsetFrom(self->_bufferData));
uint64_t rip64 = baseAddress + self->_section->offset() + virtualOffset + instructionSize;
uint64_t rel64 = uint64_t(addrValue) - rip64;
if (!Support::isInt32(int64_t(rel64)))
addrType = BaseMem::kAddrTypeAbs;
}
else {
if (!Support::isInt32(addrValue))
addrType = BaseMem::kAddrTypeAbs;
}
}
else {
addrType = BaseMem::kAddrTypeAbs;
}
}
return addrType;
}
// ============================================================================
// [asmjit::x86::Assembler - Construction / Destruction]
// ============================================================================
@@ -1536,10 +1579,10 @@ CaseX86M_GPB_MulDiv:
if (o0.size() == 1)
FIXUP_GPB(o0, opReg);
// Handle a special form `mov al|ax|eax|rax, [ptr64]` that doesn't use MOD.
if (o0.id() == Gp::kIdAx && !rmRel->as<Mem>().hasBaseOrIndex() && !rmRel->as<Mem>().isRel()) {
// Handle a special form of `mov al|ax|eax|rax, [ptr64]` that doesn't use MOD.
if (opReg == Gp::kIdAx && !rmRel->as<Mem>().hasBaseOrIndex()) {
immValue = rmRel->as<Mem>().offset();
if (!is64Bit() || (is64Bit() && ((options & Inst::kOptionLongForm) || !Support::isInt32(immValue)))) {
if (x86GetMovAbsAddrType(this, writer, o0.size(), options, rmRel->as<Mem>()) == BaseMem::kAddrTypeAbs) {
opcode += 0xA0;
goto EmitX86OpMovAbs;
}
@@ -1569,10 +1612,10 @@ CaseX86M_GPB_MulDiv:
if (o1.size() == 1)
FIXUP_GPB(o1, opReg);
// Handle a special form `mov [ptr64], al|ax|eax|rax` that doesn't use MOD.
if (o1.id() == Gp::kIdAx && !rmRel->as<Mem>().hasBaseOrIndex() && !rmRel->as<Mem>().isRel()) {
// Handle a special form of `mov [ptr64], al|ax|eax|rax` that doesn't use MOD.
if (opReg == Gp::kIdAx && !rmRel->as<Mem>().hasBaseOrIndex()) {
immValue = rmRel->as<Mem>().offset();
if (!is64Bit() || (is64Bit() && ((options & Inst::kOptionLongForm) || !Support::isInt32(immValue)))) {
if (x86GetMovAbsAddrType(this, writer, o1.size(), options, rmRel->as<Mem>()) == BaseMem::kAddrTypeAbs) {
opcode += 0xA2;
goto EmitX86OpMovAbs;
}