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AArch64: Revert previous branch optimization

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Revert a branch optimization that was based on an incorrect
assumption in the AArch64 part of ZSTD_decodeSequence. In extreme
cases the existing implementation could lead to data corruption.

Insert an UNLIKELY hint to guide the compilers toward generating more
efficient machine code.
This commit is contained in:
Arpad Panyik
2025-10-08 18:58:45 +00:00
parent 23dae4bf49
commit 33618c89e5
1 changed files with 3 additions and 6 deletions
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9
lib/decompress/zstd_decompress_block.c
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@@ -1332,14 +1332,11 @@ ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets, c
seq.offset = offset;
}
if (mlBits > 0) {
if (mlBits > 0)
seq.matchLength += BIT_readBitsFast(&seqState->DStream, mlBits/*>0*/);
if (MEM_32bits() && (mlBits+llBits >= STREAM_ACCUMULATOR_MIN_32-LONG_OFFSETS_MAX_EXTRA_BITS_32))
BIT_reloadDStream(&seqState->DStream);
if (MEM_64bits() && (totalBits >= STREAM_ACCUMULATOR_MIN_64-(LLFSELog+MLFSELog+OffFSELog)))
BIT_reloadDStream(&seqState->DStream);
}
if (UNLIKELY(totalBits >= STREAM_ACCUMULATOR_MIN_64-(LLFSELog+MLFSELog+OffFSELog)))
BIT_reloadDStream(&seqState->DStream);
/* Ensure there are enough bits to read the rest of data in 64-bit mode. */
ZSTD_STATIC_ASSERT(16+LLFSELog+MLFSELog+OffFSELog < STREAM_ACCUMULATOR_MIN_64);