From: Eric Biggers Date: Mon, 10 Feb 2025 21:07:41 +0000 (-0800) Subject: x86/crc32: improve crc32c_arch() code generation with clang X-Git-Tag: v6.15-rc1~184^2~15 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cf1ea3a7c1f63cba7d1dd313ee3accde0c0c8988;p=thirdparty%2Fkernel%2Fstable.git x86/crc32: improve crc32c_arch() code generation with clang crc32c_arch() is affected by https://github.com/llvm/llvm-project/issues/20571 where clang unnecessarily spills the inputs to "rm"-constrained operands to the stack. Replace "rm" with ASM_INPUT_RM which partially works around this by expanding to "r" when the compiler is clang. This results in better code generation with clang, though still not optimal. Link: https://lore.kernel.org/r/20250210210741.471725-1-ebiggers@kernel.org Signed-off-by: Eric Biggers --- diff --git a/arch/x86/lib/crc32-glue.c b/arch/x86/lib/crc32-glue.c index 9c3f9c1b7bb9d..4b4721176799a 100644 --- a/arch/x86/lib/crc32-glue.c +++ b/arch/x86/lib/crc32-glue.c @@ -55,10 +55,10 @@ u32 crc32c_arch(u32 crc, const u8 *p, size_t len) for (num_longs = len / sizeof(unsigned long); num_longs != 0; num_longs--, p += sizeof(unsigned long)) - asm(CRC32_INST : "+r" (crc) : "rm" (*(unsigned long *)p)); + asm(CRC32_INST : "+r" (crc) : ASM_INPUT_RM (*(unsigned long *)p)); for (len %= sizeof(unsigned long); len; len--, p++) - asm("crc32b %1, %0" : "+r" (crc) : "rm" (*p)); + asm("crc32b %1, %0" : "+r" (crc) : ASM_INPUT_RM (*p)); return crc; }