Open QwertyJack opened 2 years ago
Pull request invited.
Hi
Recently we added support of aarch64 to iresearch project and to ArangoDB. And we found out some bugs while using combination of simdcomp and sse2neon.
In function _SIMD_fastunpack132 following instruction is used: mm_srliepi32 Everything works fine on x86 architecture but on aarch64 we got some strange bug with double increment of shift variable. After deep investigation we found that sse2neon implementation of this intrinsic use macros which substitute second parameter twice. And there are a lot of other places where such situation is possible.
The solution is quite simple: Move increment from function call to single line.
static void __SIMD_fastunpack1_32(const __m128i* in, uint32_t * _out) {
__m128i* out = (__m128i*)(_out);
__m128i InReg1 = _mm_loadu_si128(in);
__m128i InReg2 = InReg1;
__m128i OutReg1, OutReg2, OutReg3, OutReg4;
const __m128i mask = _mm_set1_epi32(1);
uint32_t i, shift = 0;
for (i = 0; i < 8; ++i) {
OutReg1 = _mm_and_si128( _mm_srli_epi32(InReg1, shift) , mask);
++shift;
OutReg2 = _mm_and_si128( _mm_srli_epi32(InReg2, shift) , mask);
++shift;
OutReg3 = _mm_and_si128( _mm_srli_epi32(InReg1, shift) , mask);
++shift;
OutReg4 = _mm_and_si128( _mm_srli_epi32(InReg2, shift) , mask);
++shift;
_mm_storeu_si128(out++, OutReg1);
_mm_storeu_si128(out++, OutReg2);
_mm_storeu_si128(out++, OutReg3);
_mm_storeu_si128(out++, OutReg4);
}
}
Please be careful
In function _SIMD_fastunpack132 following instruction is used: mm_srliepi32 Everything works fine on x86 architecture but on aarch64 we got some strange bug with double increment of shift variable. After deep investigation we found that sse2neon implementation of this intrinsic use macros which substitute second parameter twice. And there are a lot of other places where such situation is possible.
Recent SSE2NEON improves _mm_srai_epi32
to handle complex arguments.
commit 7ef68928 Author: Developer-Ecosystem-Engineering AuthorDate: Fri Jul 8 10:52:46 2022 -0700
Would you add arm support? Say arm64 or aarch64. I find DLTcollab/sse2neon might be helpful.