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([192.55.60.37]) by smtp.gmail.com with ESMTPSA id bf27-20020a056a000d9b00b0051bd9981ccbsm2076347pfb.39.2022.06.24.13.10.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jun 2022 13:10:41 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v2] x86: Fix backwards Prefer_No_VZEROUPPER check in ifunc-evex.h Date: Fri, 24 Jun 2022 13:10:36 -0700 Message-Id: <20220624201036.3740866-1-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220624063653.2126416-3-goldstein.w.n@gmail.com> References: <20220624063653.2126416-3-goldstein.w.n@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Noah Goldstein via Libc-alpha From: Noah Goldstein Reply-To: Noah Goldstein Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" 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 --- sysdeps/x86/isa-ifunc-macros.h | 29 +++++++++++++++++++++------ sysdeps/x86/isa-level.h | 26 +++++++++--------------- sysdeps/x86_64/multiarch/ifunc-evex.h | 4 ++-- 3 files changed, 35 insertions(+), 24 deletions(-) diff --git a/sysdeps/x86/isa-ifunc-macros.h b/sysdeps/x86/isa-ifunc-macros.h index ba6826d518..a3c98c841c 100644 --- a/sysdeps/x86/isa-ifunc-macros.h +++ b/sysdeps/x86/isa-ifunc-macros.h @@ -56,15 +56,32 @@ # 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 + should only be used to check if a condition is true. I.e: + + if (X86_ISA_CPU_FEATURE{S}_{USABLE|ARCH}_P (...)) // Good + if (!X86_ISA_CPU_FEATURE{S}_{USABLE|ARCH}_P (...)) // Bad + + There should be no need for inverting USABLE_P checks, but there is + often need for inverting ARCH_P checks. If you want to get the not + of an ARCH_P feature do: + + if (X86_ISA_CPU_FEATURES_ARCH_P (..., !)) // Good + */ + #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)) + +/* When using X86_ISA_CPU_FEATURES_ARCH_P a third argument must be + provided to optionally invert the runtime CPU_FEATURES_ARCH_P + check. This is so we can consistently constant-evaluate conditions + using Feature_X86_ISA_LEVEL <= MINIMUM_X86_ISA_LEVEL. */ +#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..bad9aba099 100644 --- a/sysdeps/x86/isa-level.h +++ b/sysdeps/x86/isa-level.h @@ -65,12 +65,8 @@ (__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 - */ +/* CPU Features that are default set depending on ISA build level. + Feature is assumed set if: Value <= MINIMUM_X86_ISA_LEVEL. */ /* ISA level >= 4 guaranteed includes. */ @@ -81,18 +77,16 @@ #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); }