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author | Matthias Kretz <m.kretz@gsi.de> | 2024-06-14 15:11:25 +0200 |
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committer | Matthias Kretz <m.kretz@gsi.de> | 2024-06-20 12:56:45 +0200 |
commit | 1340ddea0158de3f49aeb75b4013e5fc313ff6f4 (patch) | |
tree | fa2c12e6042c294193ac98ee5798abd7c7593e61 | |
parent | 301927d93356871f606ff3db2549bb5d44e74516 (diff) | |
download | gcc-1340ddea0158de3f49aeb75b4013e5fc313ff6f4.zip gcc-1340ddea0158de3f49aeb75b4013e5fc313ff6f4.tar.gz gcc-1340ddea0158de3f49aeb75b4013e5fc313ff6f4.tar.bz2 |
libstdc++: Fix find_last_set(simd_mask) to ignore padding bits
With the change to the AVX512 find_last_set implementation, the change
to AVX512 operator!= is unnecessary. However, the latter was not
producing optimal code and unnecessarily set the padding bits. In
theory, the compiler could determine that with the new !=
implementation, the bit operation for clearing the padding bits is a
no-op and can be elided.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
PR libstdc++/115454
* include/experimental/bits/simd_x86.h (_S_not_equal_to): Use
neq comparison instead of bitwise negation after eq.
(_S_find_last_set): Clear unused high bits before computing
bit_width.
* testsuite/experimental/simd/pr115454_find_last_set.cc: New
test.
-rw-r--r-- | libstdc++-v3/include/experimental/bits/simd_x86.h | 26 | ||||
-rw-r--r-- | libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc | 49 |
2 files changed, 62 insertions, 13 deletions
diff --git a/libstdc++-v3/include/experimental/bits/simd_x86.h b/libstdc++-v3/include/experimental/bits/simd_x86.h index 4ab933b..e498b1e 100644 --- a/libstdc++-v3/include/experimental/bits/simd_x86.h +++ b/libstdc++-v3/include/experimental/bits/simd_x86.h @@ -2339,29 +2339,29 @@ template <typename _Abi, typename> __assert_unreachable<_Tp>(); } else if constexpr (sizeof(__xi) == 64 && sizeof(_Tp) == 8) - return ~_mm512_mask_cmpeq_epi64_mask(__k1, __xi, __yi); + return _mm512_mask_cmpneq_epi64_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 64 && sizeof(_Tp) == 4) - return ~_mm512_mask_cmpeq_epi32_mask(__k1, __xi, __yi); + return _mm512_mask_cmpneq_epi32_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 64 && sizeof(_Tp) == 2) - return ~_mm512_mask_cmpeq_epi16_mask(__k1, __xi, __yi); + return _mm512_mask_cmpneq_epi16_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 64 && sizeof(_Tp) == 1) - return ~_mm512_mask_cmpeq_epi8_mask(__k1, __xi, __yi); + return _mm512_mask_cmpneq_epi8_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 32 && sizeof(_Tp) == 8) - return ~_mm256_mask_cmpeq_epi64_mask(__k1, __xi, __yi); + return _mm256_mask_cmpneq_epi64_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 32 && sizeof(_Tp) == 4) - return ~_mm256_mask_cmpeq_epi32_mask(__k1, __xi, __yi); + return _mm256_mask_cmpneq_epi32_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 32 && sizeof(_Tp) == 2) - return ~_mm256_mask_cmpeq_epi16_mask(__k1, __xi, __yi); + return _mm256_mask_cmpneq_epi16_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 32 && sizeof(_Tp) == 1) - return ~_mm256_mask_cmpeq_epi8_mask(__k1, __xi, __yi); + return _mm256_mask_cmpneq_epi8_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 16 && sizeof(_Tp) == 8) - return ~_mm_mask_cmpeq_epi64_mask(__k1, __xi, __yi); + return _mm_mask_cmpneq_epi64_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 16 && sizeof(_Tp) == 4) - return ~_mm_mask_cmpeq_epi32_mask(__k1, __xi, __yi); + return _mm_mask_cmpneq_epi32_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 16 && sizeof(_Tp) == 2) - return ~_mm_mask_cmpeq_epi16_mask(__k1, __xi, __yi); + return _mm_mask_cmpneq_epi16_mask(__k1, __xi, __yi); else if constexpr (sizeof(__xi) == 16 && sizeof(_Tp) == 1) - return ~_mm_mask_cmpeq_epi8_mask(__k1, __xi, __yi); + return _mm_mask_cmpneq_epi8_mask(__k1, __xi, __yi); else __assert_unreachable<_Tp>(); } // }}} @@ -5292,7 +5292,7 @@ template <typename _Abi, typename> _S_find_last_set(simd_mask<_Tp, _Abi> __k) { if constexpr (__is_avx512_abi<_Abi>()) - return std::__bit_width(__k._M_data._M_data) - 1; + return std::__bit_width(_Abi::_S_masked(__k._M_data)._M_data) - 1; else return _Base::_S_find_last_set(__k); } diff --git a/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc b/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc new file mode 100644 index 0000000..b47f19d --- /dev/null +++ b/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc @@ -0,0 +1,49 @@ +// { dg-options "-std=gnu++17" } +// { dg-do run { target *-*-* } } +// { dg-require-effective-target c++17 } +// { dg-additional-options "-march=x86-64-v4" { target avx512f } } +// { dg-require-cmath "" } + +#include <experimental/simd> + +namespace stdx = std::experimental; + +using T = std::uint64_t; + +template <typename U, int N> +using V = stdx::simd<U, stdx::simd_abi::deduce_t<U, N>>; + +[[gnu::noinline, gnu::noipa]] +int reduce(V<T, 4> x) +{ + static_assert(stdx::find_last_set(V<T, 4>([](unsigned i) { return i; }) != V<T, 4>(0)) == 3); + return stdx::find_last_set(x != -1); +} + +[[gnu::noinline, gnu::noipa]] +int reduce2() +{ + using M8 = typename V<short, 8>::mask_type; + using M4 = typename V<int, 4>::mask_type; + if constexpr (sizeof(M8) == sizeof(M4)) + { + M4 k; + __builtin_memcpy(&__data(k), &__data(M8(true)), sizeof(M4)); + return stdx::find_last_set(k); + } + return 3; +} + + +int main() +{ + const V<T, 4> x {}; + + const int r = reduce(x); + if (r != 3) + __builtin_abort(); + + const int r2 = reduce2(); + if (r2 != 3) + __builtin_abort(); +} |