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fix clang dbg : disable builtin bf16 type #2631

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Merged
copybara-service merged 1 commit into from
Jul 23, 2025
Merged

fix clang dbg : disable builtin bf16 type #2631

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27 changes: 15 additions & 12 deletions hwy/base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1710,9 +1710,12 @@ HWY_F16_CONSTEXPR inline std::partial_ordering operator<=>(
#endif

// x86 compiler supports __bf16, not necessarily with operators.
// Disable in debug builds due to clang miscompiles as of 2025-07-22: casting
// bf16 <-> f32 in convert_test results in 0x2525 for 1.0 instead of 0x3f80.
#ifndef HWY_SSE2_HAVE_SCALAR_BF16_TYPE
#if HWY_ARCH_X86 && defined(__SSE2__) && \
((HWY_COMPILER_CLANG >= 1700 && !HWY_COMPILER_CLANGCL) || \
#if HWY_ARCH_X86 && defined(__SSE2__) && \
((HWY_COMPILER_CLANG >= 1700 && !HWY_COMPILER_CLANGCL && \
!HWY_IS_DEBUG_BUILD) || \
HWY_COMPILER_GCC_ACTUAL >= 1300)
#define HWY_SSE2_HAVE_SCALAR_BF16_TYPE 1
#else
Expand Down Expand Up @@ -1949,21 +1952,21 @@ static HWY_INLINE HWY_MAYBE_UNUSED constexpr uint32_t F32BitsToBF16RoundIncr(
: 0u);
}

// If f32_bits is the bit representation of a NaN F32 value, make sure that
// bit 6 of the BF16 result is set to convert SNaN F32 values to QNaN BF16
// values and to prevent NaN F32 values from being converted to an infinite
// BF16 value
static HWY_INLINE constexpr uint32_t BF16BitsIfSNAN(uint32_t f32_bits) {
return ((f32_bits & 0x7FFFFFFFu) > 0x7F800000u) ? (uint32_t{1} << 6) : 0;
}

// Converts f32_bits (which is the bits of a F32 value) to BF16 bits,
// rounded to the nearest F16 value
static HWY_INLINE HWY_MAYBE_UNUSED constexpr uint16_t F32BitsToBF16Bits(
const uint32_t f32_bits) {
// Round f32_bits to the nearest BF16 by first adding
// F32BitsToBF16RoundIncr(f32_bits) to f32_bits and then right shifting
// f32_bits + F32BitsToBF16RoundIncr(f32_bits) by 16

// If f32_bits is the bit representation of a NaN F32 value, make sure that
// bit 6 of the BF16 result is set to convert SNaN F32 values to QNaN BF16
// values and to prevent NaN F32 values from being converted to an infinite
// BF16 value
return static_cast<uint16_t>(
((f32_bits + F32BitsToBF16RoundIncr(f32_bits)) >> 16) |
(static_cast<uint32_t>((f32_bits & 0x7FFFFFFFu) > 0x7F800000u) << 6));
BF16BitsIfSNAN(f32_bits) |
((f32_bits + F32BitsToBF16RoundIncr(f32_bits)) >> 16));
}

} // namespace detail
Expand Down
6 changes: 3 additions & 3 deletions run_tests.sh
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Expand Up @@ -14,9 +14,9 @@ cmake .. -DHWY_WARNINGS_ARE_ERRORS:BOOL=ON -DCMAKE_BUILD_TYPE=Release
make -j && ctest -j && cd .. && rm -rf build

#######################################
echo DEBUG Clang 15
echo DEBUG Clang 17
rm -rf build_dbg && mkdir build_dbg && cd build_dbg
CXX=clang++-15 CC=clang-15 cmake .. -DHWY_WARNINGS_ARE_ERRORS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug
CXX=clang++-17 CC=clang-17 cmake .. -DHWY_WARNINGS_ARE_ERRORS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug
make -j && ctest -j && cd .. && rm -rf build_dbg

#######################################
Expand Down Expand Up @@ -59,7 +59,7 @@ clear && make -j && ctest -j && cd .. && rm -rf build_ppc_gcc
echo POWER clang
export QEMU_LD_PREFIX=/usr/powerpc64le-linux-gnu
rm -rf build_ppc_clang && mkdir build_ppc_clang && cd build_ppc_clang
CC=clang-15 CXX=clang++-15 cmake .. -DCMAKE_BUILD_TYPE=Release -DHWY_WARNINGS_ARE_ERRORS:BOOL=ON -DCMAKE_CROSSCOMPILING_EMULATOR=/usr/bin/qemu-ppc64le-static -DCMAKE_C_COMPILER_TARGET="powerpc64le-linux-gnu" -DCMAKE_CXX_COMPILER_TARGET="powerpc64le-linux-gnu" -DCMAKE_CROSSCOMPILING=true -DCMAKE_SYSTEM_NAME=Linux
CC=clang-17 CXX=clang++-17 cmake .. -DCMAKE_BUILD_TYPE=Release -DHWY_WARNINGS_ARE_ERRORS:BOOL=ON -DCMAKE_CROSSCOMPILING_EMULATOR=/usr/bin/qemu-ppc64le-static -DCMAKE_C_COMPILER_TARGET="powerpc64le-linux-gnu" -DCMAKE_CXX_COMPILER_TARGET="powerpc64le-linux-gnu" -DCMAKE_CROSSCOMPILING=true -DCMAKE_SYSTEM_NAME=Linux

clear && make -j && ctest -j && cd .. && rm -rf build_ppc_clang

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