From 93b1c47bd092f8e1444a10b5d6ec20e44d66459a Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Fri, 23 Apr 2021 15:56:24 -0400
Subject: [PATCH] x86: Optimize strchr-avx2.S
No bug. This commit optimizes strchr-avx2.S. The optimizations are all
small things such as save an ALU in the alignment process, saving a
few instructions in the loop return, saving some bytes in the main
loop, and increasing the ILP in the return cases. test-strchr,
test-strchrnul, test-wcschr, and test-wcschrnul are all passing.
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
(cherry picked from commit ccabe7971f508709d034b63b8672f6f751a3d356)
---
sysdeps/x86_64/multiarch/strchr-avx2.S | 290 +++++++++++++++----------
1 file changed, 170 insertions(+), 120 deletions(-)
diff --git a/sysdeps/x86_64/multiarch/strchr-avx2.S b/sysdeps/x86_64/multiarch/strchr-avx2.S
index 919d256c..5884726b 100644
--- a/sysdeps/x86_64/multiarch/strchr-avx2.S
+++ b/sysdeps/x86_64/multiarch/strchr-avx2.S
@@ -49,133 +49,144 @@
.section SECTION(.text),"ax",@progbits
ENTRY (STRCHR)
- movl %edi, %ecx
-# ifndef USE_AS_STRCHRNUL
- xorl %edx, %edx
-# endif
-
/* Broadcast CHAR to YMM0. */
vmovd %esi, %xmm0
+ movl %edi, %eax
+ andl $(PAGE_SIZE - 1), %eax
+ VPBROADCAST %xmm0, %ymm0
vpxor %xmm9, %xmm9, %xmm9
- VPBROADCAST %xmm0, %ymm0
/* Check if we cross page boundary with one vector load. */
- andl $(PAGE_SIZE - 1), %ecx
- cmpl $(PAGE_SIZE - VEC_SIZE), %ecx
- ja L(cross_page_boundary)
+ cmpl $(PAGE_SIZE - VEC_SIZE), %eax
+ ja L(cross_page_boundary)
/* Check the first VEC_SIZE bytes. Search for both CHAR and the
null byte. */
vmovdqu (%rdi), %ymm8
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
vpor %ymm1, %ymm2, %ymm1
vpmovmskb %ymm1, %eax
testl %eax, %eax
- jz L(more_vecs)
+ jz L(aligned_more)
tzcntl %eax, %eax
+# ifndef USE_AS_STRCHRNUL
/* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero)
+# endif
addq %rdi, %rax
+ VZEROUPPER_RETURN
+
+ /* .p2align 5 helps keep performance more consistent if ENTRY()
+ alignment % 32 was either 16 or 0. As well this makes the
+ alignment % 32 of the loop_4x_vec fixed which makes tuning it
+ easier. */
+ .p2align 5
+L(first_vec_x4):
+ tzcntl %eax, %eax
+ addq $(VEC_SIZE * 3 + 1), %rdi
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero)
# endif
-L(return_vzeroupper):
- ZERO_UPPER_VEC_REGISTERS_RETURN
-
- .p2align 4
-L(more_vecs):
- /* Align data for aligned loads in the loop. */
- andq $-VEC_SIZE, %rdi
-L(aligned_more):
-
- /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time
- since data is only aligned to VEC_SIZE. */
- vmovdqa VEC_SIZE(%rdi), %ymm8
- addq $VEC_SIZE, %rdi
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
- vpor %ymm1, %ymm2, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x0)
-
- vmovdqa VEC_SIZE(%rdi), %ymm8
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
- vpor %ymm1, %ymm2, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x1)
-
- vmovdqa (VEC_SIZE * 2)(%rdi), %ymm8
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
- vpor %ymm1, %ymm2, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x2)
-
- vmovdqa (VEC_SIZE * 3)(%rdi), %ymm8
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
- vpor %ymm1, %ymm2, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jz L(prep_loop_4x)
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
- tzcntl %eax, %eax
- leaq (VEC_SIZE * 3)(%rdi, %rax), %rax
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+L(zero):
+ xorl %eax, %eax
+ VZEROUPPER_RETURN
# endif
- VZEROUPPER
- ret
+
.p2align 4
-L(first_vec_x0):
+L(first_vec_x1):
tzcntl %eax, %eax
- /* Found CHAR or the null byte. */
- addq %rdi, %rax
+ incq %rdi
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero)
# endif
+ addq %rdi, %rax
VZEROUPPER_RETURN
.p2align 4
-L(first_vec_x1):
+L(first_vec_x2):
tzcntl %eax, %eax
- leaq VEC_SIZE(%rdi, %rax), %rax
+ addq $(VEC_SIZE + 1), %rdi
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero)
# endif
+ addq %rdi, %rax
VZEROUPPER_RETURN
.p2align 4
-L(first_vec_x2):
+L(first_vec_x3):
tzcntl %eax, %eax
- /* Found CHAR or the null byte. */
- leaq (VEC_SIZE * 2)(%rdi, %rax), %rax
+ addq $(VEC_SIZE * 2 + 1), %rdi
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero)
# endif
+ addq %rdi, %rax
VZEROUPPER_RETURN
-L(prep_loop_4x):
- /* Align data to 4 * VEC_SIZE. */
- andq $-(VEC_SIZE * 4), %rdi
+ .p2align 4
+L(aligned_more):
+ /* Align data to VEC_SIZE - 1. This is the same number of
+ instructions as using andq -VEC_SIZE but saves 4 bytes of code
+ on x4 check. */
+ orq $(VEC_SIZE - 1), %rdi
+L(cross_page_continue):
+ /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time
+ since data is only aligned to VEC_SIZE. */
+ vmovdqa 1(%rdi), %ymm8
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
+ vpor %ymm1, %ymm2, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(first_vec_x1)
+
+ vmovdqa (VEC_SIZE + 1)(%rdi), %ymm8
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
+ vpor %ymm1, %ymm2, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(first_vec_x2)
+
+ vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm8
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
+ vpor %ymm1, %ymm2, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(first_vec_x3)
+ vmovdqa (VEC_SIZE * 3 + 1)(%rdi), %ymm8
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
+ vpor %ymm1, %ymm2, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(first_vec_x4)
+ /* Align data to VEC_SIZE * 4 - 1. */
+ addq $(VEC_SIZE * 4 + 1), %rdi
+ andq $-(VEC_SIZE * 4), %rdi
.p2align 4
L(loop_4x_vec):
/* Compare 4 * VEC at a time forward. */
- vmovdqa (VEC_SIZE * 4)(%rdi), %ymm5
- vmovdqa (VEC_SIZE * 5)(%rdi), %ymm6
- vmovdqa (VEC_SIZE * 6)(%rdi), %ymm7
- vmovdqa (VEC_SIZE * 7)(%rdi), %ymm8
+ vmovdqa (%rdi), %ymm5
+ vmovdqa (VEC_SIZE)(%rdi), %ymm6
+ vmovdqa (VEC_SIZE * 2)(%rdi), %ymm7
+ vmovdqa (VEC_SIZE * 3)(%rdi), %ymm8
/* Leaves only CHARS matching esi as 0. */
vpxor %ymm5, %ymm0, %ymm1
@@ -191,63 +202,102 @@ L(loop_4x_vec):
VPMINU %ymm1, %ymm2, %ymm5
VPMINU %ymm3, %ymm4, %ymm6
- VPMINU %ymm5, %ymm6, %ymm5
+ VPMINU %ymm5, %ymm6, %ymm6
- VPCMPEQ %ymm5, %ymm9, %ymm5
- vpmovmskb %ymm5, %eax
+ VPCMPEQ %ymm6, %ymm9, %ymm6
+ vpmovmskb %ymm6, %ecx
+ subq $-(VEC_SIZE * 4), %rdi
+ testl %ecx, %ecx
+ jz L(loop_4x_vec)
- addq $(VEC_SIZE * 4), %rdi
- testl %eax, %eax
- jz L(loop_4x_vec)
- VPCMPEQ %ymm1, %ymm9, %ymm1
+ VPCMPEQ %ymm1, %ymm9, %ymm1
vpmovmskb %ymm1, %eax
testl %eax, %eax
- jnz L(first_vec_x0)
+ jnz L(last_vec_x0)
+
- VPCMPEQ %ymm2, %ymm9, %ymm2
+ VPCMPEQ %ymm5, %ymm9, %ymm2
vpmovmskb %ymm2, %eax
testl %eax, %eax
- jnz L(first_vec_x1)
+ jnz L(last_vec_x1)
+
+ VPCMPEQ %ymm3, %ymm9, %ymm3
+ vpmovmskb %ymm3, %eax
+ /* rcx has combined result from all 4 VEC. It will only be used
+ if the first 3 other VEC all did not contain a match. */
+ salq $32, %rcx
+ orq %rcx, %rax
+ tzcntq %rax, %rax
+ subq $(VEC_SIZE * 2), %rdi
+# ifndef USE_AS_STRCHRNUL
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero_end)
+# endif
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
+
+
+ .p2align 4
+L(last_vec_x0):
+ tzcntl %eax, %eax
+ addq $-(VEC_SIZE * 4), %rdi
+# ifndef USE_AS_STRCHRNUL
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero_end)
+# endif
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
- VPCMPEQ %ymm3, %ymm9, %ymm3
- VPCMPEQ %ymm4, %ymm9, %ymm4
- vpmovmskb %ymm3, %ecx
- vpmovmskb %ymm4, %eax
- salq $32, %rax
- orq %rcx, %rax
- tzcntq %rax, %rax
- leaq (VEC_SIZE * 2)(%rdi, %rax), %rax
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+L(zero_end):
+ xorl %eax, %eax
+ VZEROUPPER_RETURN
# endif
- VZEROUPPER
- ret
+
+ .p2align 4
+L(last_vec_x1):
+ tzcntl %eax, %eax
+ subq $(VEC_SIZE * 3), %rdi
+# ifndef USE_AS_STRCHRNUL
+ /* Found CHAR or the null byte. */
+ cmp (%rdi, %rax), %CHAR_REG
+ jne L(zero_end)
+# endif
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
+
/* Cold case for crossing page with first load. */
.p2align 4
L(cross_page_boundary):
- andq $-VEC_SIZE, %rdi
- andl $(VEC_SIZE - 1), %ecx
-
- vmovdqa (%rdi), %ymm8
- VPCMPEQ %ymm8, %ymm0, %ymm1
- VPCMPEQ %ymm8, %ymm9, %ymm2
+ movq %rdi, %rdx
+ /* Align rdi to VEC_SIZE - 1. */
+ orq $(VEC_SIZE - 1), %rdi
+ vmovdqa -(VEC_SIZE - 1)(%rdi), %ymm8
+ VPCMPEQ %ymm8, %ymm0, %ymm1
+ VPCMPEQ %ymm8, %ymm9, %ymm2
vpor %ymm1, %ymm2, %ymm1
vpmovmskb %ymm1, %eax
- /* Remove the leading bits. */
- sarxl %ecx, %eax, %eax
+ /* Remove the leading bytes. sarxl only uses bits [5:0] of COUNT
+ so no need to manually mod edx. */
+ sarxl %edx, %eax, %eax
testl %eax, %eax
- jz L(aligned_more)
+ jz L(cross_page_continue)
tzcntl %eax, %eax
- addq %rcx, %rdi
- addq %rdi, %rax
# ifndef USE_AS_STRCHRNUL
- cmp (%rax), %CHAR_REG
- cmovne %rdx, %rax
+ xorl %ecx, %ecx
+ /* Found CHAR or the null byte. */
+ cmp (%rdx, %rax), %CHAR_REG
+ leaq (%rdx, %rax), %rax
+ cmovne %rcx, %rax
+# else
+ addq %rdx, %rax
# endif
- VZEROUPPER_RETURN
+L(return_vzeroupper):
+ ZERO_UPPER_VEC_REGISTERS_RETURN
END (STRCHR)
# endif
--
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