From 4cc5373f2e749a6c96e8b9fa971931a4dd852860 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 19 Dec 2025 11:20:06 +0000 Subject: [PATCH] clang: work around asm output constraint problems Work around clang problems with "=rm" asm constraint. clang seems to always chose the memory output, while it is almost always the worst choice. Add ASM_OUTPUT_RM so that we can replace "=rm" constraint where it matters for clang, while not penalizing gcc. Signed-off-by: Eric Dumazet Suggested-by: Uros Bizjak Signed-off-by: Linus Torvalds --- include/linux/compiler-clang.h | 1 + include/linux/compiler_types.h | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index 107ce05bd16eb..7edf1a07b5350 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -145,6 +145,7 @@ */ #define ASM_INPUT_G "ir" #define ASM_INPUT_RM "r" +#define ASM_OUTPUT_RM "=r" /* * Declare compiler support for __typeof_unqual__() operator. diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 1280693766b9d..d3318a3c25777 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -548,11 +548,12 @@ struct ftrace_likely_data { /* * Clang has trouble with constraints with multiple - * alternative behaviors (mainly "g" and "rm"). + * alternative behaviors ("g" , "rm" and "=rm"). */ #ifndef ASM_INPUT_G #define ASM_INPUT_G "g" #define ASM_INPUT_RM "rm" + #define ASM_OUTPUT_RM "=rm" #endif #ifdef CONFIG_CC_HAS_ASM_INLINE -- 2.47.3