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x86: Small improvements for wcslen

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Just a few QOL changes.
    1. Prefer `add` > `lea` as it has high execution units it can run
       on.
    2. Don't break macro-fusion between `test` and `jcc`
    3. Reduce code size by removing gratuitous padding bytes (-90
       bytes).

geometric_mean(N=20) of all benchmarks New / Original: 0.959

All string/memory tests pass.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Noah Goldstein 2022-03-25 17:13:33 -05:00
parent f5bff979d0
commit 244b415d38
1 changed files with 41 additions and 45 deletions
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86
sysdeps/x86_64/wcslen.S
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@ -40,82 +40,82 @@ ENTRY (__wcslen)
pxor %xmm0, %xmm0
lea 32(%rdi), %rax
lea 16(%rdi), %rcx
addq $16, %rdi
and $-16, %rax
pcmpeqd (%rax), %xmm0
pmovmskb %xmm0, %edx
pxor %xmm1, %xmm1
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm1
pmovmskb %xmm1, %edx
pxor %xmm2, %xmm2
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm2
pmovmskb %xmm2, %edx
pxor %xmm3, %xmm3
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm3
pmovmskb %xmm3, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm0
pmovmskb %xmm0, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm1
pmovmskb %xmm1, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm2
pmovmskb %xmm2, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm3
pmovmskb %xmm3, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm0
pmovmskb %xmm0, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm1
pmovmskb %xmm1, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm2
pmovmskb %xmm2, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
pcmpeqd (%rax), %xmm3
pmovmskb %xmm3, %edx
addq $16, %rax
test %edx, %edx
lea 16(%rax), %rax
jnz L(exit)
and $-0x40, %rax
@ -132,104 +132,100 @@ L(aligned_64_loop):
pminub %xmm0, %xmm2
pcmpeqd %xmm3, %xmm2
pmovmskb %xmm2, %edx
addq $64, %rax
test %edx, %edx
lea 64(%rax), %rax
jz L(aligned_64_loop)
pcmpeqd -64(%rax), %xmm3
pmovmskb %xmm3, %edx
addq $48, %rdi
test %edx, %edx
lea 48(%rcx), %rcx
jnz L(exit)
pcmpeqd %xmm1, %xmm3
pmovmskb %xmm3, %edx
addq $-16, %rdi
test %edx, %edx
lea -16(%rcx), %rcx
jnz L(exit)
pcmpeqd -32(%rax), %xmm3
pmovmskb %xmm3, %edx
addq $-16, %rdi
test %edx, %edx
lea -16(%rcx), %rcx
jnz L(exit)
pcmpeqd %xmm6, %xmm3
pmovmskb %xmm3, %edx
addq $-16, %rdi
test %edx, %edx
lea -16(%rcx), %rcx
jnz L(exit)
jmp L(aligned_64_loop)
jz L(aligned_64_loop)
.p2align 4
L(exit):
sub %rcx, %rax
sub %rdi, %rax
shr $2, %rax
test %dl, %dl
jz L(exit_high)
mov %dl, %cl
and $15, %cl
andl $15, %edx
jz L(exit_1)
ret
.p2align 4
/* No align here. Naturally aligned % 16 == 1. */
L(exit_high):
mov %dh, %ch
and $15, %ch
andl $(15 << 8), %edx
jz L(exit_3)
add $2, %rax
ret
.p2align 4
.p2align 3
L(exit_1):
add $1, %rax
ret
.p2align 4
.p2align 3
L(exit_3):
add $3, %rax
ret
.p2align 4
.p2align 3
L(exit_tail0):
xor %rax, %rax
xorl %eax, %eax
ret
.p2align 4
.p2align 3
L(exit_tail1):
mov $1, %rax
movl $1, %eax
ret
.p2align 4
.p2align 3
L(exit_tail2):
mov $2, %rax
movl $2, %eax
ret
.p2align 4
.p2align 3
L(exit_tail3):
mov $3, %rax
movl $3, %eax
ret
.p2align 4
.p2align 3
L(exit_tail4):
mov $4, %rax
movl $4, %eax
ret
.p2align 4
.p2align 3
L(exit_tail5):
mov $5, %rax
movl $5, %eax
ret
.p2align 4
.p2align 3
L(exit_tail6):
mov $6, %rax
movl $6, %eax
ret
.p2align 4
.p2align 3
L(exit_tail7):
mov $7, %rax
movl $7, %eax
ret
END (__wcslen)