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LibWasm: Use 0x40 flag for SIMD memory memidx like scalar ops

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SIMD loads/stores checked bit 0x20 of the align immediate to detect a
following memory index, unlike scalar mem ops which use 0x40 per the
multi-memory encoding. This caused the memidx byte to be misparsed as
the next immediate (e.g. offset).

Update both SIMD sites (v128 load/store and lane variants) to check and
clear 0x40, then read LEB128<u32> memidx.

Repro:
  (module (memory $m0 1) (memory $m1 1)
    (func (export "go")
      i32.const 0
      v128.load (memory 1)
      drop))
Before: printed memidx 0 with offset 1.
After:  prints memidx 1 with offset 0.
This commit is contained in:
Pavel Shliak 2025-09-06 07:02:27 +04:00 • committed by Ali Mohammad Pur
commit c53d9d7122
Notes: github-actions[bot] 2025-09-06 04:20:37 +00:00
1 changed files with 4 additions and 4 deletions
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8
Libraries/LibWasm/Parser/Parser.cpp
View file

@ -588,8 +588,8 @@ ParseResult<Instruction> Instruction::parse(ConstrainedStream& stream)
// Proposal "multi-memory", if bit 6 of alignment is set, then a memory index follows the alignment.
auto memory_index = 0;
if ((align & 0x20) != 0) {
align &= ~0x20;
if ((align & 0x40) != 0) {
align &= ~0x40;
memory_index = TRY_READ(stream, LEB128<u32>, ParseError::InvalidInput);
}
@ -610,8 +610,8 @@ ParseResult<Instruction> Instruction::parse(ConstrainedStream& stream)
// Proposal "multi-memory", if bit 6 of alignment is set, then a memory index follows the alignment.
auto memory_index = 0;
if ((align & 0x20) != 0) {
align &= ~0x20;
if ((align & 0x40) != 0) {
align &= ~0x40;
memory_index = TRY_READ(stream, LEB128<u32>, ParseError::InvalidInput);
}