[v2,4/6] x86-64: Require LZCNT for AVX2 memrchr implementation
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Commit Message
The AVX2 memrchr implementation uses the 'lzcnt' instruction, which
belongs to the LZCNT CPU feature.
Fixes: af5306a735eb ("x86: Optimize memrchr-avx2.S")
Partially resolves: BZ #29611
---
sysdeps/x86/isa-level.h | 1 +
sysdeps/x86_64/multiarch/ifunc-avx2.h | 1 +
sysdeps/x86_64/multiarch/ifunc-impl-list.c | 7 +++++--
3 files changed, 7 insertions(+), 2 deletions(-)
Comments
On Sun, Oct 2, 2022 at 8:34 AM Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> The AVX2 memrchr implementation uses the 'lzcnt' instruction, which
> belongs to the LZCNT CPU feature.
>
> Fixes: af5306a735eb ("x86: Optimize memrchr-avx2.S")
> Partially resolves: BZ #29611
> ---
> sysdeps/x86/isa-level.h | 1 +
> sysdeps/x86_64/multiarch/ifunc-avx2.h | 1 +
> sysdeps/x86_64/multiarch/ifunc-impl-list.c | 7 +++++--
> 3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
> index 3c4480aba7..bbb90f5c5e 100644
> --- a/sysdeps/x86/isa-level.h
> +++ b/sysdeps/x86/isa-level.h
> @@ -80,6 +80,7 @@
> #define AVX_X86_ISA_LEVEL 3
> #define AVX2_X86_ISA_LEVEL 3
> #define BMI2_X86_ISA_LEVEL 3
> +#define LZCNT_X86_ISA_LEVEL 3
> #define MOVBE_X86_ISA_LEVEL 3
>
> /* ISA level >= 2 guaranteed includes. */
> diff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h
> index a57a9952f3..f1741083fd 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-avx2.h
> +++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h
> @@ -37,6 +37,7 @@ IFUNC_SELECTOR (void)
>
> if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> + && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
> && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> AVX_Fast_Unaligned_Load, ))
> {
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 7c84963d92..4ee28c99bd 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -209,13 +209,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> IFUNC_IMPL (i, name, memrchr,
> X86_IFUNC_IMPL_ADD_V4 (array, i, memrchr,
> (CPU_FEATURE_USABLE (AVX512VL)
> - && CPU_FEATURE_USABLE (AVX512BW)),
> + && CPU_FEATURE_USABLE (AVX512BW)
> + && CPU_FEATURE_USABLE (LZCNT)),
> __memrchr_evex)
> X86_IFUNC_IMPL_ADD_V3 (array, i, memrchr,
> - CPU_FEATURE_USABLE (AVX2),
> + (CPU_FEATURE_USABLE (AVX2)
> + && CPU_FEATURE_USABLE (LZCNT)),
> __memrchr_avx2)
> X86_IFUNC_IMPL_ADD_V3 (array, i, memrchr,
> (CPU_FEATURE_USABLE (AVX2)
> + && CPU_FEATURE_USABLE (LZCNT)
> && CPU_FEATURE_USABLE (RTM)),
> __memrchr_avx2_rtm)
> /* ISA V2 wrapper for SSE2 implementation because the SSE2
> --
> 2.35.1
>
LGTM.
@@ -80,6 +80,7 @@
#define AVX_X86_ISA_LEVEL 3
#define AVX2_X86_ISA_LEVEL 3
#define BMI2_X86_ISA_LEVEL 3
+#define LZCNT_X86_ISA_LEVEL 3
#define MOVBE_X86_ISA_LEVEL 3
/* ISA level >= 2 guaranteed includes. */
@@ -37,6 +37,7 @@ IFUNC_SELECTOR (void)
if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
&& X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
+ && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
&& X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
AVX_Fast_Unaligned_Load, ))
{
@@ -209,13 +209,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
IFUNC_IMPL (i, name, memrchr,
X86_IFUNC_IMPL_ADD_V4 (array, i, memrchr,
(CPU_FEATURE_USABLE (AVX512VL)
- && CPU_FEATURE_USABLE (AVX512BW)),
+ && CPU_FEATURE_USABLE (AVX512BW)
+ && CPU_FEATURE_USABLE (LZCNT)),
__memrchr_evex)
X86_IFUNC_IMPL_ADD_V3 (array, i, memrchr,
- CPU_FEATURE_USABLE (AVX2),
+ (CPU_FEATURE_USABLE (AVX2)
+ && CPU_FEATURE_USABLE (LZCNT)),
__memrchr_avx2)
X86_IFUNC_IMPL_ADD_V3 (array, i, memrchr,
(CPU_FEATURE_USABLE (AVX2)
+ && CPU_FEATURE_USABLE (LZCNT)
&& CPU_FEATURE_USABLE (RTM)),
__memrchr_avx2_rtm)
/* ISA V2 wrapper for SSE2 implementation because the SSE2