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GET /api/patches/2216294/?format=api
{ "id": 2216294, "url": "http://patchwork.ozlabs.org/api/patches/2216294/?format=api", "web_url": "http://patchwork.ozlabs.org/project/glibc/patch/20260326092130.941264-1-sajan.karumanchi@amd.com/", "project": { "id": 41, "url": "http://patchwork.ozlabs.org/api/projects/41/?format=api", "name": "GNU C Library", "link_name": "glibc", "list_id": "libc-alpha.sourceware.org", "list_email": "libc-alpha@sourceware.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260326092130.941264-1-sajan.karumanchi@amd.com>", "list_archive_url": null, "date": "2026-03-26T09:21:30", "name": "[v3] x86_64: Prefer EVEX512 code-path on AMD Zen5 CPUs", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "184e8f7ac06bea307c3f225fa2d5c8b4857b8b4c", "submitter": { "id": 79912, "url": "http://patchwork.ozlabs.org/api/people/79912/?format=api", "name": "Sajan Karumanchi", "email": "sajan.karumanchi@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/glibc/patch/20260326092130.941264-1-sajan.karumanchi@amd.com/mbox/", "series": [ { "id": 497560, "url": "http://patchwork.ozlabs.org/api/series/497560/?format=api", "web_url": "http://patchwork.ozlabs.org/project/glibc/list/?series=497560", "date": "2026-03-26T09:21:30", "name": "[v3] x86_64: Prefer EVEX512 code-path on AMD Zen5 CPUs", "version": 3, "mbox": "http://patchwork.ozlabs.org/series/497560/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2216294/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2216294/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "libc-alpha@sourceware.org" ], "Delivered-To": [ "patchwork-incoming@legolas.ozlabs.org", "libc-alpha@sourceware.org" ], "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=UjnCeTdn;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; 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This change affects six string/memory functions:\n\n - strchr\n - strlen\n - strnlen\n - strrchr\n - strchrnul\n - memchr\n\nBenchmarks conducted on AMD Zen5 hardware demonstrate significant\nperformance improvements across all affected functions:\n\nFunction Baseline Patched Avg Avg Avg Max\n Variant Variant Baseline Patched Change Improve\n (ns) (ns) % %\n------------+----------+----------+-----------+----------+--------+--------\nSTRCHR evex evex512 16.408 12.293 25.08% 37.69%\nSTRLEN evex evex512 16.862 11.436 32.18% 56.74%\nSTRNLEN evex evex512 18.493 11.762 36.40% 64.40%\nSTRRCHR evex evex512 15.154 10.874 28.24% 44.38%\nSTRCHRNUL evex evex512 16.464 12.605 23.44% 45.56%\nMEMCHR evex evex512 9.984 8.268 17.19% 39.99%\n\nAdditionally, a tunable option (glibc.cpu.x86_cpu_features.preferred)\nis provided to allow runtime control of the Prefer_EVEX512 flag for testing\nand compatibility.\n\nReviewed-by: Ganesh Gopalasubramanian <Ganesh.Gopalasubramanian@amd.com>\n---\nHi H.J.Lu,\n Addressed your review comment.\n---\n sysdeps/x86/cpu-features.c | 6 ++++++\n sysdeps/x86/cpu-tunables.c | 6 ++++++\n .../cpu-features-preferred_feature_index_1.def | 1 +\n sysdeps/x86_64/multiarch/ifunc-avx2.h | 15 ++++++++++++---\n sysdeps/x86_64/multiarch/ifunc-evex.h | 11 ++++++++++-\n sysdeps/x86_64/multiarch/memchr.c | 1 +\n sysdeps/x86_64/multiarch/strchr.c | 8 +++++++-\n sysdeps/x86_64/multiarch/strchrnul.c | 1 +\n sysdeps/x86_64/multiarch/strlen.c | 1 +\n sysdeps/x86_64/multiarch/strnlen.c | 1 +\n sysdeps/x86_64/multiarch/strrchr.c | 1 +\n 11 files changed, 47 insertions(+), 5 deletions(-)", "diff": "diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c\nindex ccfef55652..73ee4f2bb8 100644\n--- a/sysdeps/x86/cpu-features.c\n+++ b/sysdeps/x86/cpu-features.c\n@@ -1009,6 +1009,12 @@ disable_tsx:\n cpu_features->preferred[index_arch_Avoid_Non_Temporal_Memset]\n \t &= ~bit_arch_Avoid_Non_Temporal_Memset;\n \n+ /* Prefer EVEX512 string/memory variants on AMD Zen5 (Family 0x1A)\n+ when AVX-512 is usable. */\n+ if (family == 0x1A && CPU_FEATURE_USABLE_P (cpu_features, AVX512F))\n+ cpu_features->preferred[index_arch_Prefer_EVEX512]\n+ |= bit_arch_Prefer_EVEX512;\n+\n if (CPU_FEATURE_USABLE_P (cpu_features, AVX))\n \t{\n \t /* Since the FMA4 bit is in CPUID_INDEX_80000001 and\ndiff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c\nindex 51769a5493..59dde5f1d7 100644\n--- a/sysdeps/x86/cpu-tunables.c\n+++ b/sysdeps/x86/cpu-tunables.c\n@@ -203,6 +203,12 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)\n \t\t\t\t\t\t 11);\n \t }\n \t break;\n+\tcase 14:\n+\t {\n+\t CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH\n+\t\t(n, cpu_features, Prefer_EVEX512, AVX512F, 14);\n+\t }\n+\t break;\n \tcase 15:\n \t {\n \t CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,\ndiff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def\nindex 8cab2ae248..74acb3fde1 100644\n--- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def\n+++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def\n@@ -35,3 +35,4 @@ BIT (Prefer_FSRM)\n BIT (Avoid_Short_Distance_REP_MOVSB)\n BIT (Avoid_Non_Temporal_Memset)\n BIT (Avoid_STOSB)\n+BIT (Prefer_EVEX512)\ndiff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h\nindex bc7178d97e..474466ba93 100644\n--- a/sysdeps/x86_64/multiarch/ifunc-avx2.h\n+++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h\n@@ -1,4 +1,4 @@\n-/* Common definition for ifunc selections optimized with SSE2 and AVX2.\n+/* Common definition for ifunc selections optimized with SSE2, AVX2 and EVEX512.\n All versions must be listed in ifunc-impl-list.c.\n Copyright (C) 2017-2026 Free Software Foundation, Inc.\n This file is part of the GNU C Library.\n@@ -25,6 +25,10 @@\n \n extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;\n \n+#ifdef USE_EVEX512\n+extern __typeof (REDIRECT_NAME) OPTIMIZE (evex512) attribute_hidden;\n+#endif\n+\n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;\n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;\n \n@@ -44,8 +48,13 @@ IFUNC_SELECTOR (void)\n {\n if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)\n \t && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))\n-\treturn OPTIMIZE (evex);\n-\n+ {\n+#ifdef USE_EVEX512\n+ if (CPU_FEATURES_ARCH_P (cpu_features, Prefer_EVEX512))\n+ return OPTIMIZE (evex512);\n+#endif\n+\t return OPTIMIZE (evex);\n+ }\n if (CPU_FEATURE_USABLE_P (cpu_features, RTM))\n \treturn OPTIMIZE (avx2_rtm);\n \ndiff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h\nindex 973a5b3d15..02ca749a72 100644\n--- a/sysdeps/x86_64/multiarch/ifunc-evex.h\n+++ b/sysdeps/x86_64/multiarch/ifunc-evex.h\n@@ -1,4 +1,4 @@\n-/* Common definition for ifunc selection optimized with EVEX.\n+/* Common definition for ifunc selection optimized with EVEX and EVEX512.\n All versions must be listed in ifunc-impl-list.c.\n Copyright (C) 2017-2026 Free Software Foundation, Inc.\n This file is part of the GNU C Library.\n@@ -22,6 +22,10 @@\n extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;\n extern __typeof (REDIRECT_NAME) OPTIMIZE (evex_rtm) attribute_hidden;\n \n+#ifdef USE_EVEX512\n+extern __typeof (REDIRECT_NAME) OPTIMIZE (evex512) attribute_hidden;\n+#endif\n+\n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;\n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;\n \n@@ -42,6 +46,11 @@ IFUNC_SELECTOR (void)\n if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)\n \t && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))\n \t{\n+#ifdef USE_EVEX512\n+ if (CPU_FEATURES_ARCH_P (cpu_features, Prefer_EVEX512))\n+ return OPTIMIZE (evex512);\n+#endif\n+\n \t if (CPU_FEATURE_USABLE_P (cpu_features, RTM))\n \t return OPTIMIZE (evex_rtm);\n \ndiff --git a/sysdeps/x86_64/multiarch/memchr.c b/sysdeps/x86_64/multiarch/memchr.c\nindex cea0518787..b2a6c666a9 100644\n--- a/sysdeps/x86_64/multiarch/memchr.c\n+++ b/sysdeps/x86_64/multiarch/memchr.c\n@@ -24,6 +24,7 @@\n # undef memchr\n \n # define SYMBOL_NAME memchr\n+# define USE_EVEX512 1\n # include \"ifunc-evex.h\"\n \n libc_ifunc_redirected (__redirect_memchr, memchr, IFUNC_SELECTOR ());\ndiff --git a/sysdeps/x86_64/multiarch/strchr.c b/sysdeps/x86_64/multiarch/strchr.c\nindex 1064bc8e5b..f6bd36ba73 100644\n--- a/sysdeps/x86_64/multiarch/strchr.c\n+++ b/sysdeps/x86_64/multiarch/strchr.c\n@@ -27,6 +27,7 @@\n # include <init-arch.h>\n \n extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;\n+extern __typeof (REDIRECT_NAME) OPTIMIZE (evex512) attribute_hidden;\n \n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;\n extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;\n@@ -46,7 +47,12 @@ IFUNC_SELECTOR (void)\n {\n if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)\n \t && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))\n-\treturn OPTIMIZE (evex);\n+\t{\n+\t if (CPU_FEATURES_ARCH_P (cpu_features, Prefer_EVEX512))\n+\t return OPTIMIZE (evex512);\n+\n+\t return OPTIMIZE (evex);\n+\t}\n \n if (CPU_FEATURE_USABLE_P (cpu_features, RTM))\n \treturn OPTIMIZE (avx2_rtm);\ndiff --git a/sysdeps/x86_64/multiarch/strchrnul.c b/sysdeps/x86_64/multiarch/strchrnul.c\nindex f4bfc28c7b..3bb93bb812 100644\n--- a/sysdeps/x86_64/multiarch/strchrnul.c\n+++ b/sysdeps/x86_64/multiarch/strchrnul.c\n@@ -26,6 +26,7 @@\n # undef strchrnul\n \n # define SYMBOL_NAME strchrnul\n+# define USE_EVEX512 1\n # include \"ifunc-avx2.h\"\n \n libc_ifunc_redirected (__redirect_strchrnul, __strchrnul,\ndiff --git a/sysdeps/x86_64/multiarch/strlen.c b/sysdeps/x86_64/multiarch/strlen.c\nindex 95aa48e5d3..2f93abf1c8 100644\n--- a/sysdeps/x86_64/multiarch/strlen.c\n+++ b/sysdeps/x86_64/multiarch/strlen.c\n@@ -24,6 +24,7 @@\n # undef strlen\n \n # define SYMBOL_NAME strlen\n+# define USE_EVEX512 1\n # include \"ifunc-avx2.h\"\n \n libc_ifunc_redirected (__redirect_strlen, strlen, IFUNC_SELECTOR ());\ndiff --git a/sysdeps/x86_64/multiarch/strnlen.c b/sysdeps/x86_64/multiarch/strnlen.c\nindex bfe4d7abf0..62e50a27e4 100644\n--- a/sysdeps/x86_64/multiarch/strnlen.c\n+++ b/sysdeps/x86_64/multiarch/strnlen.c\n@@ -26,6 +26,7 @@\n # undef strnlen\n \n # define SYMBOL_NAME strnlen\n+# define USE_EVEX512 1\n # include \"ifunc-avx2.h\"\n \n libc_ifunc_redirected (__redirect_strnlen, __strnlen, IFUNC_SELECTOR ());\ndiff --git a/sysdeps/x86_64/multiarch/strrchr.c b/sysdeps/x86_64/multiarch/strrchr.c\nindex 66d3f5b1d1..0965938561 100644\n--- a/sysdeps/x86_64/multiarch/strrchr.c\n+++ b/sysdeps/x86_64/multiarch/strrchr.c\n@@ -23,6 +23,7 @@\n # undef strrchr\n \n # define SYMBOL_NAME strrchr\n+# define USE_EVEX512 1\n # include \"ifunc-avx2.h\"\n \n libc_ifunc_redirected (__redirect_strrchr, strrchr, IFUNC_SELECTOR ());\n", "prefixes": [ "v3" ] }