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x86: Fix unchecked AVX512-VBMI2 usage in strrchr-evex-base.S

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strrchr-evex-base used `vpcompress{b|d}` in the page cross logic but
was missing the CPU_FEATURE checks for VBMI2 in the
ifunc/ifunc-impl-list.

The fix is either to add those checks or change the logic to not use
`vpcompress{b|d}`. Choosing the latter here so that the strrchr-evex
implementation is usable on SKX.

New implementation is a bit slower, but this is in a cold path so its
probably okay.
This commit is contained in:
Noah Goldstein 2023-11-01 16:42:07 -05:00
parent 0575073dda
commit b7f8b6b64b
1 changed files with 54 additions and 27 deletions
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81
sysdeps/x86_64/multiarch/strrchr-evex-base.S
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@ -35,18 +35,20 @@
# define CHAR_SIZE 4
# define VPCMP vpcmpd
# define VPMIN vpminud
# define VPCOMPRESS vpcompressd
# define VPTESTN vptestnmd
# define VPTEST vptestmd
# define VPBROADCAST vpbroadcastd
# define VPCMPEQ vpcmpeqd
# else
# define SHIFT_REG VRDI
# if VEC_SIZE == 64
# define SHIFT_REG VRCX
# else
# define SHIFT_REG VRDI
# endif
# define CHAR_SIZE 1
# define VPCMP vpcmpb
# define VPMIN vpminub
# define VPCOMPRESS vpcompressb
# define VPTESTN vptestnmb
# define VPTEST vptestmb
# define VPBROADCAST vpbroadcastb
@ -56,6 +58,12 @@
# define KORTEST_M KORTEST
# endif
# if VEC_SIZE == 32 || (defined USE_AS_WCSRCHR)
# define SHIFT_R(cnt, val) shrx cnt, val, val
# else
# define SHIFT_R(cnt, val) shr %cl, val
# endif
# define VMATCH VMM(0)
# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
# define PAGE_SIZE 4096
@ -71,7 +79,7 @@ ENTRY_P2ALIGN(STRRCHR, 6)
andl $(PAGE_SIZE - 1), %eax
cmpl $(PAGE_SIZE - VEC_SIZE), %eax
jg L(cross_page_boundary)
L(page_cross_continue):
VMOVU (%rdi), %VMM(1)
/* k0 has a 1 for each zero CHAR in YMM1. */
VPTESTN %VMM(1), %VMM(1), %k0
@ -79,7 +87,7 @@ ENTRY_P2ALIGN(STRRCHR, 6)
test %VGPR(rsi), %VGPR(rsi)
jz L(aligned_more)
/* fallthrough: zero CHAR in first VEC. */
L(page_cross_return):
/* K1 has a 1 for each search CHAR match in VEC(1). */
VPCMPEQ %VMATCH, %VMM(1), %k1
KMOV %k1, %VGPR(rax)
@ -167,7 +175,6 @@ L(first_vec_x1_return):
.p2align 4,, 12
L(aligned_more):
L(page_cross_continue):
/* Need to keep original pointer incase VEC(1) has last match. */
movq %rdi, %rsi
andq $-VEC_SIZE, %rdi
@ -340,34 +347,54 @@ L(return_new_match_ret):
leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
ret
.p2align 4,, 4
L(cross_page_boundary):
/* eax contains all the page offset bits of src (rdi). `xor rdi,
rax` sets pointer will all page offset bits cleared so
offset of (PAGE_SIZE - VEC_SIZE) will get last aligned VEC
before page cross (guaranteed to be safe to read). Doing this
as opposed to `movq %rdi, %rax; andq $-VEC_SIZE, %rax` saves
a bit of code size. */
xorq %rdi, %rax
mov $-1, %VRDX
VMOVU (PAGE_SIZE - VEC_SIZE)(%rax), %VMM(6)
VPTESTN %VMM(6), %VMM(6), %k0
VMOVU (PAGE_SIZE - VEC_SIZE)(%rax), %VMM(1)
VPTESTN %VMM(1), %VMM(1), %k0
KMOV %k0, %VRSI
# ifdef USE_AS_WCSRCHR
/* Shift out zero CHAR matches that are before the beginning of
src (rdi). */
# if VEC_SIZE == 64 || (defined USE_AS_WCSRCHR)
movl %edi, %ecx
and $(VEC_SIZE - 1), %ecx
# endif
# ifdef USE_AS_WCSRCHR
andl $(VEC_SIZE - 1), %ecx
shrl $2, %ecx
# endif
shlx %SHIFT_REG, %VRDX, %VRDX
# ifdef USE_AS_WCSRCHR
kmovw %edx, %k1
# else
KMOV %VRDX, %k1
# endif
VPCOMPRESS %VMM(6), %VMM(1){%k1}{z}
/* We could technically just jmp back after the vpcompress but
it doesn't save any 16-byte blocks. */
shrx %SHIFT_REG, %VRSI, %VRSI
SHIFT_R (%SHIFT_REG, %VRSI)
# if VEC_SIZE == 32 || (defined USE_AS_WCSRCHR)
/* For strrchr-evex512 we use SHIFT_R as shr which will set zero
flag. */
test %VRSI, %VRSI
jnz L(page_cross_return)
jmp L(page_cross_continue)
/* 1-byte from cache line. */
# endif
jz L(page_cross_continue)
/* Found zero CHAR so need to test for search CHAR. */
VPCMPEQ %VMATCH, %VMM(1), %k1
KMOV %k1, %VRAX
/* Shift out search CHAR matches that are before the beginning of
src (rdi). */
SHIFT_R (%SHIFT_REG, %VRAX)
/* Check if any search CHAR match in range. */
blsmsk %VRSI, %VRSI
and %VRSI, %VRAX
jz L(ret2)
bsr %VRAX, %VRAX
# ifdef USE_AS_WCSRCHR
leaq (%rdi, %rax, CHAR_SIZE), %rax
# else
addq %rdi, %rax
# endif
L(ret2):
ret
/* 3 bytes from cache-line for evex. */
/* 0 bytes from cache-line for evex512. */
END(STRRCHR)
#endif