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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-05-22 23:13:22 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-05-22 23:13:22 +0200 |
| commit | f8a6e48c6c6dc30dbd423a3f4b082df625664730 (patch) | |
| tree | 19b68bfffb5483634ec52f0c39a657f3cb54b929 /include | |
| parent | Merge tag 'char-misc-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/g... (diff) | |
| parent | x86: improve bitop code generation with clang (diff) | |
| download | linux-f8a6e48c6c6dc30dbd423a3f4b082df625664730.tar.xz linux-f8a6e48c6c6dc30dbd423a3f4b082df625664730.zip | |
Merge local branch 'x86-codegen'
Merge trivial x86 code generation annoyances
- Introduce helper macros for clang asm input problems
- use said macros to improve trivially stupid code generation issues in
bitops and array_index_mask_nospec
- also improve codegen with 32-bit array index comparisons
None of these really matter, but I look at code generation and profiles
fairly regularly, and these misfeatures caused the generated code to
look really odd and distract from the real issues.
* branch 'x86-codegen' of local tree:
x86: improve bitop code generation with clang
x86: improve array_index_mask_nospec() code generation
clang: work around asm input constraint problems
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compiler-clang.h | 10 | ||||
| -rw-r--r-- | include/linux/compiler_types.h | 9 |
2 files changed, 19 insertions, 0 deletions
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index 49feac0162a5..4c1a39dcb624 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -118,3 +118,13 @@ #define __diag_ignore_all(option, comment) \ __diag_clang(13, ignore, option) + +/* + * clang has horrible behavior with "g" or "rm" constraints for asm + * inputs, turning them into something worse than "m". Avoid using + * constraints with multiple possible uses (but "ir" seems to be ok): + * + * https://github.com/llvm/llvm-project/issues/20571 + */ +#define ASM_INPUT_G "ir" +#define ASM_INPUT_RM "r" diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index d1a9dbb8e1a7..93600de3800b 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -409,6 +409,15 @@ struct ftrace_likely_data { #define asm_goto_output(x...) asm volatile goto(x) #endif +/* + * Clang has trouble with constraints with multiple + * alternative behaviors (mainly "g" and "rm"). + */ +#ifndef ASM_INPUT_G + #define ASM_INPUT_G "g" + #define ASM_INPUT_RM "rm" +#endif + #ifdef CONFIG_CC_HAS_ASM_INLINE #define asm_inline asm __inline #else |