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| author | Noah Goldstein <goldstein.w.n@gmail.com> | 2022-06-06 21:11:28 -0700 |
|---|---|---|
| committer | Noah Goldstein <goldstein.w.n@gmail.com> | 2022-06-07 13:08:28 -0700 |
| commit | dd5c483b2598f411428df4d8864c15c4b8a3cd68 (patch) | |
| tree | c859b1416e2e839f5d9903efe6358373b9f68b97 /sysdeps/x86_64/multiarch | |
| parent | 8a780a6b910023e71f3173f37f0793834c047554 (diff) | |
| download | glibc-dd5c483b2598f411428df4d8864c15c4b8a3cd68.tar.gz glibc-dd5c483b2598f411428df4d8864c15c4b8a3cd68.tar.xz glibc-dd5c483b2598f411428df4d8864c15c4b8a3cd68.zip | |
x86: Add COND_VZEROUPPER that can replace vzeroupper if no `ret`
The RTM vzeroupper mitigation has no way of replacing inline vzeroupper not before a return. This can be useful when hoisting a vzeroupper to save code size for example: ``` L(foo): cmpl %eax, %edx jz L(bar) tzcntl %eax, %eax addq %rdi, %rax VZEROUPPER_RETURN L(bar): xorl %eax, %eax VZEROUPPER_RETURN ``` Can become: ``` L(foo): COND_VZEROUPPER cmpl %eax, %edx jz L(bar) tzcntl %eax, %eax addq %rdi, %rax ret L(bar): xorl %eax, %eax ret ``` This code does not change any existing functionality. There is no difference in the objdump of libc.so before and after this patch. Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Diffstat (limited to 'sysdeps/x86_64/multiarch')
| -rw-r--r-- | sysdeps/x86_64/multiarch/avx-rtm-vecs.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sysdeps/x86_64/multiarch/avx-rtm-vecs.h b/sysdeps/x86_64/multiarch/avx-rtm-vecs.h index 3f531dd47f..6ca9f5e6ba 100644 --- a/sysdeps/x86_64/multiarch/avx-rtm-vecs.h +++ b/sysdeps/x86_64/multiarch/avx-rtm-vecs.h @@ -20,6 +20,7 @@ #ifndef _AVX_RTM_VECS_H #define _AVX_RTM_VECS_H 1 +#define COND_VZEROUPPER COND_VZEROUPPER_XTEST #define ZERO_UPPER_VEC_REGISTERS_RETURN \ ZERO_UPPER_VEC_REGISTERS_RETURN_XTEST |