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From: Noah Goldstein <nwg@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] x86: Fix backwards Prefer_No_VZEROUPPER check in ifunc-evex.h Date: Mon, 27 Jun 2022 16:34:15 +0000 (GMT) [thread overview] Message-ID: <20220627163415.4C89C38312A3@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4fc321dc58b29217e322526b49549930d0807179 commit 4fc321dc58b29217e322526b49549930d0807179 Author: Noah Goldstein <goldstein.w.n@gmail.com> Date: Fri Jun 24 16:15:42 2022 -0700 x86: Fix backwards Prefer_No_VZEROUPPER check in ifunc-evex.h Add third argument to X86_ISA_CPU_FEATURES_ARCH_P macro so the runtime CPU_FEATURES_ARCH_P check can be inverted if the MINIMUM_X86_ISA_LEVEL is not high enough to constantly evaluate the check. Use this new macro to correct the backwards check in ifunc-evex.h Diff: --- sysdeps/x86/isa-ifunc-macros.h | 28 ++++++++++++++++++++++------ sysdeps/x86/isa-level.h | 28 ++++++++++------------------ sysdeps/x86_64/multiarch/ifunc-evex.h | 4 ++-- 3 files changed, 34 insertions(+), 26 deletions(-) diff --git a/sysdeps/x86/isa-ifunc-macros.h b/sysdeps/x86/isa-ifunc-macros.h index ba6826d518..d69905689b 100644 --- a/sysdeps/x86/isa-ifunc-macros.h +++ b/sysdeps/x86/isa-ifunc-macros.h @@ -56,15 +56,31 @@ # define X86_IFUNC_IMPL_ADD_V1(...) #endif -#define X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED(name) \ - ((name##_X86_ISA_LEVEL) <= MINIMUM_X86_ISA_LEVEL) +/* Both X86_ISA_CPU_FEATURE_USABLE_P and X86_ISA_CPU_FEATURES_ARCH_P + macros are wrappers for the the respective + CPU_FEATURE{S}_{USABLE|ARCH}_P runtime checks. They differ in two + ways. + + 1. The USABLE_P version is evaluated to true when the feature + is enabled. + + 2. The ARCH_P version has a third argument `not`. The `not` + argument can either be '!' or empty. If the feature is + enabled above an ISA level, the third argument should be empty + and the expression is evaluated to true when the feature is + enabled. If the feature is disabled above an ISA level, the + third argument should be `!` and the expression is evaluated + to true when the feature is disabled. + */ #define X86_ISA_CPU_FEATURE_USABLE_P(ptr, name) \ - (X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name) \ + (((name##_X86_ISA_LEVEL) <= MINIMUM_X86_ISA_LEVEL) \ || CPU_FEATURE_USABLE_P (ptr, name)) -#define X86_ISA_CPU_FEATURES_ARCH_P(ptr, name) \ - (X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name) \ - || CPU_FEATURES_ARCH_P (ptr, name)) + +#define X86_ISA_CPU_FEATURES_ARCH_P(ptr, name, not) \ + (((name##_X86_ISA_LEVEL) <= MINIMUM_X86_ISA_LEVEL) \ + || not CPU_FEATURES_ARCH_P (ptr, name)) + #endif diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h index 7cae11c228..075e7c6ee1 100644 --- a/sysdeps/x86/isa-level.h +++ b/sysdeps/x86/isa-level.h @@ -64,14 +64,8 @@ #define MINIMUM_X86_ISA_LEVEL \ (__X86_ISA_V1 + __X86_ISA_V2 + __X86_ISA_V3 + __X86_ISA_V4) - -/* - * CPU Features that are hard coded as enabled depending on ISA build - * level. - * - Values > 0 features are always ENABLED if: - * Value >= MINIMUM_X86_ISA_LEVEL - */ - +/* Depending on the minimum ISA level, a feature check result can be a + compile-time constant.. */ /* ISA level >= 4 guaranteed includes. */ #define AVX512VL_X86_ISA_LEVEL 4 @@ -81,18 +75,16 @@ #define AVX2_X86_ISA_LEVEL 3 #define BMI2_X86_ISA_LEVEL 3 -/* - * NB: This may not be fully assumable for ISA level >= 3. From - * looking over the architectures supported in cpu-features.h the - * following CPUs may have an issue with this being default set: - * - AMD Excavator - */ +/* NB: This feature is enabled when ISA level >= 3, which was disabled + for the following CPUs: + - AMD Excavator + when ISA level < 3. */ #define AVX_Fast_Unaligned_Load_X86_ISA_LEVEL 3 -/* - * KNL (the only cpu that sets this supported in cpu-features.h) - * builds with ISA V1 so this shouldn't harm any architectures. - */ +/* NB: This feature is disabled when ISA level >= 3, which was enabled + for the following CPUs: + - Intel KNL + when ISA level < 3. */ #define Prefer_No_VZEROUPPER_X86_ISA_LEVEL 3 #define ISA_SHOULD_BUILD(isa_build_level) \ diff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h index 856c6261f8..310cfd269f 100644 --- a/sysdeps/x86_64/multiarch/ifunc-evex.h +++ b/sysdeps/x86_64/multiarch/ifunc-evex.h @@ -37,7 +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_FEATURES_ARCH_P (cpu_features, - AVX_Fast_Unaligned_Load)) + AVX_Fast_Unaligned_Load, )) { if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)) @@ -52,7 +52,7 @@ IFUNC_SELECTOR (void) return OPTIMIZE (avx2_rtm); if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, - Prefer_No_VZEROUPPER)) + Prefer_No_VZEROUPPER, !)) return OPTIMIZE (avx2); }
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