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emit_x64: Document ExtractAndDuplicateMostSignificantBitFromPackedWords

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MerryMage 2016-12-20 22:06:14 +00:00
parent 03f168094d
commit 097f6a83da
1 changed files with 8 additions and 0 deletions
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8
src/backend_x64/emit_x64.cpp
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@ -1369,6 +1369,14 @@ static void ExtractMostSignificantBitFromPackedBytes(const Xbyak::util::Cpu& cpu
} }
} }
/**
* Extracts the most significant bits from each of the packed words, duplicates them, and packs them together.
*
* value before: a---------------b---------------
* value after: 0000000000000000000000000000aabb
*
* @param value The register containing the value to operate on. Result will be stored in the same register.
*/
static void ExtractAndDuplicateMostSignificantBitFromPackedWords(BlockOfCode* code, Xbyak::Reg32 value) { static void ExtractAndDuplicateMostSignificantBitFromPackedWords(BlockOfCode* code, Xbyak::Reg32 value) {
code->and_(value, 0x80008000); code->and_(value, 0x80008000);
code->shr(value, 1); code->shr(value, 1);