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Merge pull request #1163 from oguzhanozfe/fix/decoder-rexw-immediate-size 

fix(relinker): let REX.W override 0x66 when sizing decoder immediates
This commit is contained in:
Adrià 2026-10-08 10:23:35 +02:00 committed by GitHub
parent e705d430d6 d64c0605ea
commit 61896dea23
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GPG Key ID: B5690EEEBB952194
2 changed files with 10 additions and 4 deletions
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10
core/relinker/codegen/src/x86/X64InstructionDecoder.cpp
View File

@ -39,6 +39,9 @@ std::size_t X64InstructionDecoder::Decode(const std::uint8_t* data, std::size_t
pos += 1;
}
const bool rexW = rexPresent && (rex & RexWBit) != 0;
const std::size_t operandImmediateSize = operandSizeOverride && !rexW ? ImmSize16 : ImmSize32;
if (pos >= available) {
throw CodegenException("Instruction truncated after prefixes");
}
@ -172,10 +175,9 @@ std::size_t X64InstructionDecoder::Decode(const std::uint8_t* data, std::size_t
opcode == OneByteTestEaxImm32 ||
(opcode >= OneByteMovImm32RegMin && opcode <= OneByteMovImm32RegMax)) {
if (opcode >= OneByteMovImm32RegMin && opcode <= OneByteMovImm32RegMax) {
immediateSize = (rexPresent && (rex & RexWBit) != 0) ? ImmSize64 :
(operandSizeOverride ? ImmSize16 : ImmSize32);
immediateSize = rexW ? ImmSize64 : operandImmediateSize;
} else {
immediateSize = operandSizeOverride ? ImmSize16 : ImmSize32;
immediateSize = operandImmediateSize;
}
} else if (opcode == OneByteImm8Grp1 || opcode == OneByteImulRm32Imm8) {
immediateSize = ImmSize8;
@ -279,7 +281,7 @@ std::size_t X64InstructionDecoder::Decode(const std::uint8_t* data, std::size_t
reg <= Grp3RegTestMax) {
immediateSize = (opcode == OneByteTestGrp3Rm8)
? ImmSize8
: (operandSizeOverride ? ImmSize16 : ImmSize32);
: operandImmediateSize;
}
if (mod != ModRmModRegister && rm == ModRmRmSibPresent) {

4
core/relinker/codegen/tests/Amd64OnlyConverterTests.cpp
View File

@ -127,6 +127,10 @@ void decoderLengths() {
{0x0F, 0x38, 0xCB, 0xCA}, {0x45, 0x0F, 0x38, 0xCC, 0xE1}, {0x0F, 0x38, 0xCD, 0x08}, {0x0F, 0x38, 0xCB, 0x0D, 0x10, 0x00, 0x00, 0x00},
{0x0F, 0x3A, 0xCC, 0xD5, 0x03}, {0x45, 0x0F, 0x3A, 0xCC, 0xE1, 0x00}, {0x0F, 0x3A, 0xCC, 0x08, 0x01}, {0x0F, 0x38, 0xC8, 0xCA}, {0x0F, 0x38, 0xC9, 0xCA}, {0x0F, 0x38, 0xCA, 0x08},
{0x48, 0x66, 0xB8, 0x34, 0x12}, {0x66, 0x48, 0xB8, 1, 2, 3, 4, 5, 6, 7, 8}, {0x41, 0x48, 0xB8, 1, 2, 3, 4, 5, 6, 7, 8},
{0x66, 0x48, 0x81, 0xC0, 1, 2, 3, 4}, {0x66, 0x48, 0x05, 1, 2, 3, 4}, {0x66, 0x48, 0xC7, 0xC0, 1, 2, 3, 4},
{0x66, 0x48, 0x69, 0xC0, 1, 2, 3, 4}, {0x66, 0x48, 0x68, 1, 2, 3, 4}, {0x66, 0x48, 0xA9, 1, 2, 3, 4},
{0x66, 0x48, 0xF7, 0xC0, 1, 2, 3, 4}, {0x66, 0x81, 0xC0, 0x34, 0x12}, {0x48, 0x66, 0x81, 0xC0, 0x34, 0x12},
{0x66, 0x41, 0x81, 0xC0, 0x34, 0x12}, {0x66, 0xF7, 0xC0, 0x34, 0x12},
{0x48, 0x64, 0x8B, 0x00}, {0x48, 0xF3, 0x0F, 0x2B, 0x00}, {0x48, 0x67, 0x0F, 0x01, 0xFC}, {0x48, 0x48, 0x0F, 0x01, 0xFC}};
Bytes padded;
for (const auto& instruction : instructions) {