[PATCH] libstdc++: Skip integer division optimization for Clang

[PATCH] libstdc++: Skip integer division optimization for Clang

[Matthias Kretz]

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Tested on x86_64-pc-linux-gnu.

--------- 8< -----------

Clang ICEs on _SimdImplX86::_S_divides. The function is only working
around a missed optimization and not necessary for correctness.
Therefore, don't use it for Clang.

Signed-off-by: Matthias Kretz <m.kretz@gsi.de>

libstdc++-v3/ChangeLog:

	* include/experimental/bits/simd_detail.h: Don't define
	_GLIBCXX_SIMD_WORKAROUND_PR90993 for Clang.
	* include/experimental/bits/simd_x86.h (_S_divides): Remove
	check for __clang__.
---
 libstdc++-v3/include/experimental/bits/simd_detail.h | 2 ++
 libstdc++-v3/include/experimental/bits/simd_x86.h    | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)


--
──────────────────────────────────────────────────────────────────────────
 Dr. Matthias Kretz                           https://mattkretz.github.io
 GSI Helmholtz Centre for Heavy Ion Research               https://gsi.de
 stdₓ::simd
──────────────────────────────────────────────────────────────────────────

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diff --git a/libstdc++-v3/include/experimental/bits/simd_detail.h b/libstdc++-v3/include/experimental/bits/simd_detail.h
index 49b94decf0a..1fb77866bb2 100644
--- a/libstdc++-v3/include/experimental/bits/simd_detail.h
+++ b/libstdc++-v3/include/experimental/bits/simd_detail.h
@@ -320,7 +320,9 @@ namespace experimental
 #endif
 
 // integer division not optimized
+#ifndef __clang__
 #define _GLIBCXX_SIMD_WORKAROUND_PR90993 1
+#endif
 
 // very bad codegen for extraction and concatenation of 128/256 "subregisters"
 // with sizeof(element type) < 8: https://godbolt.org/g/mqUsgM
diff --git a/libstdc++-v3/include/experimental/bits/simd_x86.h b/libstdc++-v3/include/experimental/bits/simd_x86.h
index 7b8f1c664b3..28ba344c2b2 100644
--- a/libstdc++-v3/include/experimental/bits/simd_x86.h
+++ b/libstdc++-v3/include/experimental/bits/simd_x86.h
@@ -1469,7 +1469,7 @@ _CsrGuard()
 		[&__xf, &__yf](auto __i) _GLIBCXX_SIMD_ALWAYS_INLINE_LAMBDA
 		  -> _SimdWrapper<_Float, __n_intermediate>
 		{
-#if !defined __clang__ && __GCC_IEC_559 == 0
+#if __GCC_IEC_559 == 0
 		  // If -freciprocal-math is active, using the `/` operator is
 		  // incorrect because it may be translated to an imprecise
 		  // multiplication with reciprocal. We need to use inline
@@ -1524,7 +1524,7 @@ _CsrGuard()
 	  */
 	return _Base::_S_divides(__x, __y);
       }
-  #endif // _GLIBCXX_SIMD_WORKAROUND_PR90993
+#endif // _GLIBCXX_SIMD_WORKAROUND_PR90993
 
     // }}}
     // _S_modulus {{{

Re: [PATCH] libstdc++: Skip integer division optimization for Clang

[Jonathan Wakely]

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On Tue, 21 Mar 2023 at 17:06, Matthias Kretz via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> Tested on x86_64-pc-linux-gnu.
>
> --------- 8< -----------
>
> Clang ICEs on _SimdImplX86::_S_divides. The function is only working
> around a missed optimization and not necessary for correctness.
> Therefore, don't use it for Clang.
>
> Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
>
> libstdc++-v3/ChangeLog:
>
>         * include/experimental/bits/simd_detail.h: Don't define
>         _GLIBCXX_SIMD_WORKAROUND_PR90993 for Clang.
>         * include/experimental/bits/simd_x86.h (_S_divides): Remove
>         check for __clang__.


OK