https://github.com/Thibault-Monnier updated https://github.com/llvm/llvm-project/pull/171914
>From 4fc9a07698e1a4627a050ba6fa9df3f1f8725451 Mon Sep 17 00:00:00 2001 From: Thibault-Monnier <[email protected]> Date: Thu, 11 Dec 2025 22:02:35 +0100 Subject: [PATCH 1/5] Detect sse4.2 availability at runtime to use it on modern processors --- clang/lib/Lex/Lexer.cpp | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp index b282a600c0e56..3b8fa0b9b7f36 100644 --- a/clang/lib/Lex/Lexer.cpp +++ b/clang/lib/Lex/Lexer.cpp @@ -46,9 +46,7 @@ #include <string> #include <tuple> -#ifdef __SSE4_2__ #include <nmmintrin.h> -#endif using namespace clang; @@ -1921,9 +1919,17 @@ bool Lexer::LexUnicodeIdentifierStart(Token &Result, uint32_t C, } static const char * -fastParseASCIIIdentifier(const char *CurPtr, - [[maybe_unused]] const char *BufferEnd) { -#ifdef __SSE4_2__ +fastParseASCIIIdentifierScalar(const char *CurPtr, + [[maybe_unused]] const char *BufferEnd) { + unsigned char C = *CurPtr; + while (isAsciiIdentifierContinue(C)) + C = *++CurPtr; + return CurPtr; +} + +__attribute__((target("sse4.2"))) static const char * +fastParseASCIIIdentifierSSE42(const char *CurPtr, + [[maybe_unused]] const char *BufferEnd) { alignas(16) static constexpr char AsciiIdentifierRange[16] = { '_', '_', 'A', 'Z', 'a', 'z', '0', '9', }; @@ -1943,12 +1949,23 @@ fastParseASCIIIdentifier(const char *CurPtr, continue; return CurPtr; } + + return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); +} + +static bool supportsSSE42() { + static bool SupportsSSE42 = __builtin_cpu_supports("sse4.2"); + return SupportsSSE42; +} + +static const char *fastParseASCIIIdentifier(const char *CurPtr, + const char *BufferEnd) { +#ifndef __SSE4_2__ + if (LLVM_UNLIKELY(!supportsSSE42())) + return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); #endif - unsigned char C = *CurPtr; - while (isAsciiIdentifierContinue(C)) - C = *++CurPtr; - return CurPtr; + return fastParseASCIIIdentifierSSE42(CurPtr, BufferEnd); } bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) { >From ce3bf515e7a60bd58ff5871352979999f5864b4b Mon Sep 17 00:00:00 2001 From: Thibault-Monnier <[email protected]> Date: Thu, 11 Dec 2025 23:15:40 +0100 Subject: [PATCH 2/5] Only on x86 --- clang/lib/Lex/Lexer.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp index 3b8fa0b9b7f36..c195237dae1f4 100644 --- a/clang/lib/Lex/Lexer.cpp +++ b/clang/lib/Lex/Lexer.cpp @@ -46,7 +46,9 @@ #include <string> #include <tuple> +#if defined(__i386__) || defined(__x86_64__) #include <nmmintrin.h> +#endif using namespace clang; @@ -1927,6 +1929,8 @@ fastParseASCIIIdentifierScalar(const char *CurPtr, return CurPtr; } +#if defined(__i386__) || defined(__x86_64__) + __attribute__((target("sse4.2"))) static const char * fastParseASCIIIdentifierSSE42(const char *CurPtr, [[maybe_unused]] const char *BufferEnd) { @@ -1958,14 +1962,22 @@ static bool supportsSSE42() { return SupportsSSE42; } +#endif + static const char *fastParseASCIIIdentifier(const char *CurPtr, const char *BufferEnd) { +#if !defined(__i386__) && !defined(__x86_64__) + return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); +#else + #ifndef __SSE4_2__ if (LLVM_UNLIKELY(!supportsSSE42())) return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); #endif return fastParseASCIIIdentifierSSE42(CurPtr, BufferEnd); + +#endif } bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) { >From 2109fdd371822ec77f870c5edbbdfccaaa7615be Mon Sep 17 00:00:00 2001 From: Thibault-Monnier <[email protected]> Date: Sun, 14 Dec 2025 11:32:30 +0100 Subject: [PATCH 3/5] Not on windows --- clang/lib/Lex/Lexer.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp index c195237dae1f4..86cfb47ca84d5 100644 --- a/clang/lib/Lex/Lexer.cpp +++ b/clang/lib/Lex/Lexer.cpp @@ -36,6 +36,7 @@ #include "llvm/Support/NativeFormatting.h" #include "llvm/Support/Unicode.h" #include "llvm/Support/UnicodeCharRanges.h" + #include <algorithm> #include <cassert> #include <cstddef> @@ -1929,7 +1930,7 @@ fastParseASCIIIdentifierScalar(const char *CurPtr, return CurPtr; } -#if defined(__i386__) || defined(__x86_64__) +#if defined(__i386__) || defined(__x86_64__) && !defined(_WIN32) __attribute__((target("sse4.2"))) static const char * fastParseASCIIIdentifierSSE42(const char *CurPtr, @@ -1966,7 +1967,7 @@ static bool supportsSSE42() { static const char *fastParseASCIIIdentifier(const char *CurPtr, const char *BufferEnd) { -#if !defined(__i386__) && !defined(__x86_64__) +#if !defined(__i386__) && !defined(__x86_64__) || defined(_WIN32) return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); #else >From d5485438edd460892bf210916827e0d92fc24065 Mon Sep 17 00:00:00 2001 From: Thibault-Monnier <[email protected]> Date: Sun, 14 Dec 2025 14:37:43 +0100 Subject: [PATCH 4/5] Address comments --- clang/lib/Lex/Lexer.cpp | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp index 86cfb47ca84d5..470579df233d1 100644 --- a/clang/lib/Lex/Lexer.cpp +++ b/clang/lib/Lex/Lexer.cpp @@ -1930,7 +1930,12 @@ fastParseASCIIIdentifierScalar(const char *CurPtr, return CurPtr; } -#if defined(__i386__) || defined(__x86_64__) && !defined(_WIN32) +// Fast path for lexing ASCII identifiers using SSE4.2 instructions. +// Only enabled on x86/x86_64 when building with a compiler that supports +// the 'target' attribute, which is used for runtime dispatch. Otherwise, we +// fall back to the scalar implementation. +#if (defined(__i386__) || defined(__x86_64__)) && defined(__has_attribute) && \ + __has_attribute(target) __attribute__((target("sse4.2"))) static const char * fastParseASCIIIdentifierSSE42(const char *CurPtr, @@ -1958,27 +1963,16 @@ fastParseASCIIIdentifierSSE42(const char *CurPtr, return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); } -static bool supportsSSE42() { - static bool SupportsSSE42 = __builtin_cpu_supports("sse4.2"); - return SupportsSSE42; +__attribute__((target("sse4.2"))) static const char * +fastParseASCIIIdentifier(const char *CurPtr, const char *BufferEnd) { + return fastParseASCIIIdentifierSSE42(CurPtr, BufferEnd); } +__attribute__((target("default"))) #endif - static const char *fastParseASCIIIdentifier(const char *CurPtr, const char *BufferEnd) { -#if !defined(__i386__) && !defined(__x86_64__) || defined(_WIN32) return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); -#else - -#ifndef __SSE4_2__ - if (LLVM_UNLIKELY(!supportsSSE42())) - return fastParseASCIIIdentifierScalar(CurPtr, BufferEnd); -#endif - - return fastParseASCIIIdentifierSSE42(CurPtr, BufferEnd); - -#endif } bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) { >From 82cf41e460d2fa1105e9abbf925837fa9e9c7b45 Mon Sep 17 00:00:00 2001 From: Thibault-Monnier <[email protected]> Date: Sun, 14 Dec 2025 19:32:29 +0100 Subject: [PATCH 5/5] Not on MSVC --- clang/lib/Lex/Lexer.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp index 470579df233d1..58cd9348d3027 100644 --- a/clang/lib/Lex/Lexer.cpp +++ b/clang/lib/Lex/Lexer.cpp @@ -1935,7 +1935,7 @@ fastParseASCIIIdentifierScalar(const char *CurPtr, // the 'target' attribute, which is used for runtime dispatch. Otherwise, we // fall back to the scalar implementation. #if (defined(__i386__) || defined(__x86_64__)) && defined(__has_attribute) && \ - __has_attribute(target) + __has_attribute(target) && !defined(_MSC_VER) __attribute__((target("sse4.2"))) static const char * fastParseASCIIIdentifierSSE42(const char *CurPtr, _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
