From: H.J. Lu Date: Fri, 26 Feb 2021 13:36:59 +0000 (-0800) Subject: x86: Set Prefer_No_VZEROUPPER and add Prefer_AVX2_STRCMP X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3bb13e91495c763c1ce7759e3b0d2cb32d4095b6;p=thirdparty%2Fglibc.git x86: Set Prefer_No_VZEROUPPER and add Prefer_AVX2_STRCMP 1. Set Prefer_No_VZEROUPPER if RTM is usable to avoid RTM abort triggered by VZEROUPPER inside a transactionally executing RTM region. 2. Since to compare 2 32-byte strings, 256-bit EVEX strcmp requires 2 loads, 3 VPCMPs and 2 KORDs while AVX2 strcmp requires 1 load, 2 VPCMPEQs, 1 VPMINU and 1 VPMOVMSKB, AVX2 strcmp is faster than EVEX strcmp. Add Prefer_AVX2_STRCMP to prefer AVX2 strcmp family functions. (cherry picked from commit 1da50d4bda07f04135dca39f40e79fc9eabed1f8) --- diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c index 4c24ba7c314..eb554b6d141 100644 --- a/sysdeps/x86/cpu-features.c +++ b/sysdeps/x86/cpu-features.c @@ -546,8 +546,24 @@ init_cpu_features (struct cpu_features *cpu_features) cpu_features->preferred[index_arch_Prefer_No_VZEROUPPER] |= bit_arch_Prefer_No_VZEROUPPER; else - cpu_features->preferred[index_arch_Prefer_No_AVX512] - |= bit_arch_Prefer_No_AVX512; + { + cpu_features->preferred[index_arch_Prefer_No_AVX512] + |= bit_arch_Prefer_No_AVX512; + + /* Avoid RTM abort triggered by VZEROUPPER inside a + transactionally executing RTM region. */ + if (CPU_FEATURE_USABLE_P (cpu_features, RTM)) + cpu_features->preferred[index_arch_Prefer_No_VZEROUPPER] + |= bit_arch_Prefer_No_VZEROUPPER; + + /* Since to compare 2 32-byte strings, 256-bit EVEX strcmp + requires 2 loads, 3 VPCMPs and 2 KORDs while AVX2 strcmp + requires 1 load, 2 VPCMPEQs, 1 VPMINU and 1 VPMOVMSKB, + AVX2 strcmp is faster than EVEX strcmp. */ + if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)) + cpu_features->preferred[index_arch_Prefer_AVX2_STRCMP] + |= bit_arch_Prefer_AVX2_STRCMP; + } } /* This spells out "AuthenticAMD" or "HygonGenuine". */ else if ((ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65) diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h index a0b9b9177c8..72ea74d083e 100644 --- a/sysdeps/x86/cpu-features.h +++ b/sysdeps/x86/cpu-features.h @@ -804,6 +804,7 @@ extern const struct cpu_features *__get_cpu_features (void) #define bit_arch_Prefer_FSRM (1u << 13) #define bit_arch_Prefer_No_AVX512 (1u << 14) #define bit_arch_MathVec_Prefer_No_AVX512 (1u << 15) +#define bit_arch_Prefer_AVX2_STRCMP (1u << 16) #define index_arch_Fast_Rep_String PREFERRED_FEATURE_INDEX_1 #define index_arch_Fast_Copy_Backward PREFERRED_FEATURE_INDEX_1 @@ -821,6 +822,7 @@ extern const struct cpu_features *__get_cpu_features (void) #define index_arch_Prefer_No_AVX512 PREFERRED_FEATURE_INDEX_1 #define index_arch_MathVec_Prefer_No_AVX512 PREFERRED_FEATURE_INDEX_1 #define index_arch_Prefer_FSRM PREFERRED_FEATURE_INDEX_1 +#define index_arch_Prefer_AVX2_STRCMP PREFERRED_FEATURE_INDEX_1 /* XCR0 Feature flags. */ #define bit_XMM_state (1u << 1) diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c index 588bbf9448b..b251a91af3f 100644 --- a/sysdeps/x86/cpu-tunables.c +++ b/sysdeps/x86/cpu-tunables.c @@ -238,6 +238,8 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp) CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Fast_Copy_Backward, disable, 18); + CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH + (n, cpu_features, Prefer_AVX2_STRCMP, AVX2, disable, 18); } break; case 19: