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glibc/SOURCES/glibc-RHEL-15696-23.patch

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From acfd088a1963ba51cd83c78f95c0ab25ead79e04 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Mon, 3 May 2021 03:01:58 -0400
Subject: [PATCH] x86: Optimize memchr-avx2.S
Content-type: text/plain; charset=UTF-8
No bug. This commit optimizes memchr-avx2.S. The optimizations include
replacing some branches with cmovcc, avoiding some branches entirely
in the less_4x_vec case, making the page cross logic less strict,
asaving a few instructions the in loop return loop. test-memchr,
test-rawmemchr, and test-wmemchr are all passing.
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
---
sysdeps/x86_64/multiarch/memchr-avx2.S | 425 ++++++++++++++-----------
1 file changed, 247 insertions(+), 178 deletions(-)
diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
index cf893e77..b377f22e 100644
--- a/sysdeps/x86_64/multiarch/memchr-avx2.S
+++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
@@ -26,8 +26,22 @@
# ifdef USE_AS_WMEMCHR
# define VPCMPEQ vpcmpeqd
+# define VPBROADCAST vpbroadcastd
+# define CHAR_SIZE 4
# else
# define VPCMPEQ vpcmpeqb
+# define VPBROADCAST vpbroadcastb
+# define CHAR_SIZE 1
+# endif
+
+# ifdef USE_AS_RAWMEMCHR
+# define ERAW_PTR_REG ecx
+# define RRAW_PTR_REG rcx
+# define ALGN_PTR_REG rdi
+# else
+# define ERAW_PTR_REG edi
+# define RRAW_PTR_REG rdi
+# define ALGN_PTR_REG rcx
# endif
# ifndef VZEROUPPER
@@ -39,6 +53,7 @@
# endif
# define VEC_SIZE 32
+# define PAGE_SIZE 4096
.section SECTION(.text),"ax",@progbits
ENTRY (MEMCHR)
@@ -47,295 +62,349 @@ ENTRY (MEMCHR)
test %RDX_LP, %RDX_LP
jz L(null)
# endif
- movl %edi, %ecx
- /* Broadcast CHAR to YMM0. */
- vmovd %esi, %xmm0
# ifdef USE_AS_WMEMCHR
shl $2, %RDX_LP
- vpbroadcastd %xmm0, %ymm0
# else
# ifdef __ILP32__
/* Clear the upper 32 bits. */
movl %edx, %edx
# endif
- vpbroadcastb %xmm0, %ymm0
# endif
+ /* Broadcast CHAR to YMMMATCH. */
+ vmovd %esi, %xmm0
+ VPBROADCAST %xmm0, %ymm0
/* Check if we may cross page boundary with one vector load. */
- andl $(2 * VEC_SIZE - 1), %ecx
- cmpl $VEC_SIZE, %ecx
- ja L(cros_page_boundary)
+ movl %edi, %eax
+ andl $(PAGE_SIZE - 1), %eax
+ cmpl $(PAGE_SIZE - VEC_SIZE), %eax
+ ja L(cross_page_boundary)
/* Check the first VEC_SIZE bytes. */
- VPCMPEQ (%rdi), %ymm0, %ymm1
+ VPCMPEQ (%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
- testl %eax, %eax
-
# ifndef USE_AS_RAWMEMCHR
- jnz L(first_vec_x0_check)
- /* Adjust length and check the end of data. */
- subq $VEC_SIZE, %rdx
- jbe L(zero)
-# else
- jnz L(first_vec_x0)
+ /* If length < CHAR_PER_VEC handle special. */
+ cmpq $VEC_SIZE, %rdx
+ jbe L(first_vec_x0)
# endif
-
- /* Align data for aligned loads in the loop. */
- addq $VEC_SIZE, %rdi
- andl $(VEC_SIZE - 1), %ecx
- andq $-VEC_SIZE, %rdi
+ testl %eax, %eax
+ jz L(aligned_more)
+ tzcntl %eax, %eax
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
# ifndef USE_AS_RAWMEMCHR
- /* Adjust length. */
- addq %rcx, %rdx
+ .p2align 5
+L(first_vec_x0):
+ /* Check if first match was before length. */
+ tzcntl %eax, %eax
+ xorl %ecx, %ecx
+ cmpl %eax, %edx
+ leaq (%rdi, %rax), %rax
+ cmovle %rcx, %rax
+ VZEROUPPER_RETURN
- subq $(VEC_SIZE * 4), %rdx
- jbe L(last_4x_vec_or_less)
+L(null):
+ xorl %eax, %eax
+ ret
# endif
- jmp L(more_4x_vec)
-
.p2align 4
-L(cros_page_boundary):
- andl $(VEC_SIZE - 1), %ecx
- andq $-VEC_SIZE, %rdi
- VPCMPEQ (%rdi), %ymm0, %ymm1
+L(cross_page_boundary):
+ /* Save pointer before aligning as its original value is necessary
+ for computer return address if byte is found or adjusting length
+ if it is not and this is memchr. */
+ movq %rdi, %rcx
+ /* Align data to VEC_SIZE - 1. ALGN_PTR_REG is rcx for memchr and
+ rdi for rawmemchr. */
+ orq $(VEC_SIZE - 1), %ALGN_PTR_REG
+ VPCMPEQ -(VEC_SIZE - 1)(%ALGN_PTR_REG), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
+# ifndef USE_AS_RAWMEMCHR
+ /* Calculate length until end of page (length checked for a
+ match). */
+ leaq 1(%ALGN_PTR_REG), %rsi
+ subq %RRAW_PTR_REG, %rsi
+# endif
/* Remove the leading bytes. */
- sarl %cl, %eax
- testl %eax, %eax
- jz L(aligned_more)
- tzcntl %eax, %eax
+ sarxl %ERAW_PTR_REG, %eax, %eax
# ifndef USE_AS_RAWMEMCHR
/* Check the end of data. */
- cmpq %rax, %rdx
- jbe L(zero)
+ cmpq %rsi, %rdx
+ jbe L(first_vec_x0)
# endif
- addq %rdi, %rax
- addq %rcx, %rax
+ testl %eax, %eax
+ jz L(cross_page_continue)
+ tzcntl %eax, %eax
+ addq %RRAW_PTR_REG, %rax
L(return_vzeroupper):
ZERO_UPPER_VEC_REGISTERS_RETURN
.p2align 4
-L(aligned_more):
-# ifndef USE_AS_RAWMEMCHR
- /* Calculate "rdx + rcx - VEC_SIZE" with "rdx - (VEC_SIZE - rcx)"
- instead of "(rdx + rcx) - VEC_SIZE" to void possible addition
- overflow. */
- negq %rcx
- addq $VEC_SIZE, %rcx
+L(first_vec_x1):
+ tzcntl %eax, %eax
+ incq %rdi
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
- /* Check the end of data. */
- subq %rcx, %rdx
- jbe L(zero)
-# endif
+ .p2align 4
+L(first_vec_x2):
+ tzcntl %eax, %eax
+ addq $(VEC_SIZE + 1), %rdi
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
+
+ .p2align 4
+L(first_vec_x3):
+ tzcntl %eax, %eax
+ addq $(VEC_SIZE * 2 + 1), %rdi
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
- addq $VEC_SIZE, %rdi
-# ifndef USE_AS_RAWMEMCHR
- subq $(VEC_SIZE * 4), %rdx
- jbe L(last_4x_vec_or_less)
-# endif
+ .p2align 4
+L(first_vec_x4):
+ tzcntl %eax, %eax
+ addq $(VEC_SIZE * 3 + 1), %rdi
+ addq %rdi, %rax
+ VZEROUPPER_RETURN
-L(more_4x_vec):
+ .p2align 4
+L(aligned_more):
/* Check the first 4 * VEC_SIZE. Only one VEC_SIZE at a time
since data is only aligned to VEC_SIZE. */
- VPCMPEQ (%rdi), %ymm0, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x0)
- VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
+# ifndef USE_AS_RAWMEMCHR
+L(cross_page_continue):
+ /* Align data to VEC_SIZE - 1. */
+ xorl %ecx, %ecx
+ subl %edi, %ecx
+ orq $(VEC_SIZE - 1), %rdi
+ /* esi is for adjusting length to see if near the end. */
+ leal (VEC_SIZE * 4 + 1)(%rdi, %rcx), %esi
+# else
+ orq $(VEC_SIZE - 1), %rdi
+L(cross_page_continue):
+# endif
+ /* Load first VEC regardless. */
+ VPCMPEQ 1(%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
+# ifndef USE_AS_RAWMEMCHR
+ /* Adjust length. If near end handle specially. */
+ subq %rsi, %rdx
+ jbe L(last_4x_vec_or_less)
+# endif
testl %eax, %eax
jnz L(first_vec_x1)
- VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
+ VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
testl %eax, %eax
jnz L(first_vec_x2)
- VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
+ VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
testl %eax, %eax
jnz L(first_vec_x3)
- addq $(VEC_SIZE * 4), %rdi
+ VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(first_vec_x4)
# ifndef USE_AS_RAWMEMCHR
+ /* Check if at last VEC_SIZE * 4 length. */
subq $(VEC_SIZE * 4), %rdx
- jbe L(last_4x_vec_or_less)
-# endif
-
- /* Align data to 4 * VEC_SIZE. */
- movq %rdi, %rcx
- andl $(4 * VEC_SIZE - 1), %ecx
- andq $-(4 * VEC_SIZE), %rdi
-
-# ifndef USE_AS_RAWMEMCHR
- /* Adjust length. */
+ jbe L(last_4x_vec_or_less_cmpeq)
+ /* Align data to VEC_SIZE * 4 - 1 for the loop and readjust
+ length. */
+ incq %rdi
+ movl %edi, %ecx
+ orq $(VEC_SIZE * 4 - 1), %rdi
+ andl $(VEC_SIZE * 4 - 1), %ecx
addq %rcx, %rdx
+# else
+ /* Align data to VEC_SIZE * 4 - 1 for loop. */
+ incq %rdi
+ orq $(VEC_SIZE * 4 - 1), %rdi
# endif
+ /* Compare 4 * VEC at a time forward. */
.p2align 4
L(loop_4x_vec):
- /* Compare 4 * VEC at a time forward. */
- VPCMPEQ (%rdi), %ymm0, %ymm1
- VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm2
- VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm3
- VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm4
-
+ VPCMPEQ 1(%rdi), %ymm0, %ymm1
+ VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm2
+ VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm3
+ VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm4
vpor %ymm1, %ymm2, %ymm5
vpor %ymm3, %ymm4, %ymm6
vpor %ymm5, %ymm6, %ymm5
- vpmovmskb %ymm5, %eax
- testl %eax, %eax
- jnz L(4x_vec_end)
-
- addq $(VEC_SIZE * 4), %rdi
-
+ vpmovmskb %ymm5, %ecx
# ifdef USE_AS_RAWMEMCHR
- jmp L(loop_4x_vec)
+ subq $-(VEC_SIZE * 4), %rdi
+ testl %ecx, %ecx
+ jz L(loop_4x_vec)
# else
- subq $(VEC_SIZE * 4), %rdx
- ja L(loop_4x_vec)
+ testl %ecx, %ecx
+ jnz L(loop_4x_vec_end)
-L(last_4x_vec_or_less):
- /* Less than 4 * VEC and aligned to VEC_SIZE. */
- addl $(VEC_SIZE * 2), %edx
- jle L(last_2x_vec)
+ subq $-(VEC_SIZE * 4), %rdi
- VPCMPEQ (%rdi), %ymm0, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x0)
+ subq $(VEC_SIZE * 4), %rdx
+ ja L(loop_4x_vec)
- VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
+ /* Fall through into less than 4 remaining vectors of length case.
+ */
+ VPCMPEQ (VEC_SIZE * 0 + 1)(%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
+ .p2align 4
+L(last_4x_vec_or_less):
+ /* Check if first VEC contained match. */
testl %eax, %eax
- jnz L(first_vec_x1)
+ jnz L(first_vec_x1_check)
- VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
+ /* If remaining length > VEC_SIZE * 2. */
+ addl $(VEC_SIZE * 2), %edx
+ jg L(last_4x_vec)
- jnz L(first_vec_x2_check)
- subl $VEC_SIZE, %edx
- jle L(zero)
+L(last_2x_vec):
+ /* If remaining length < VEC_SIZE. */
+ addl $VEC_SIZE, %edx
+ jle L(zero_end)
- VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
+ /* Check VEC2 and compare any match with remaining length. */
+ VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
vpmovmskb %ymm1, %eax
- testl %eax, %eax
-
- jnz L(first_vec_x3_check)
- xorl %eax, %eax
+ tzcntl %eax, %eax
+ cmpl %eax, %edx
+ jbe L(set_zero_end)
+ addq $(VEC_SIZE + 1), %rdi
+ addq %rdi, %rax
+L(zero_end):
VZEROUPPER_RETURN
.p2align 4
-L(last_2x_vec):
- addl $(VEC_SIZE * 2), %edx
- VPCMPEQ (%rdi), %ymm0, %ymm1
+L(loop_4x_vec_end):
+# endif
+ /* rawmemchr will fall through into this if match was found in
+ loop. */
+
vpmovmskb %ymm1, %eax
testl %eax, %eax
+ jnz L(last_vec_x1_return)
- jnz L(first_vec_x0_check)
- subl $VEC_SIZE, %edx
- jle L(zero)
-
- VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
- vpmovmskb %ymm1, %eax
+ vpmovmskb %ymm2, %eax
testl %eax, %eax
- jnz L(first_vec_x1_check)
- xorl %eax, %eax
- VZEROUPPER_RETURN
+ jnz L(last_vec_x2_return)
- .p2align 4
-L(first_vec_x0_check):
- tzcntl %eax, %eax
- /* Check the end of data. */
- cmpq %rax, %rdx
- jbe L(zero)
+ vpmovmskb %ymm3, %eax
+ /* Combine VEC3 matches (eax) with VEC4 matches (ecx). */
+ salq $32, %rcx
+ orq %rcx, %rax
+ tzcntq %rax, %rax
+# ifdef USE_AS_RAWMEMCHR
+ subq $(VEC_SIZE * 2 - 1), %rdi
+# else
+ subq $-(VEC_SIZE * 2 + 1), %rdi
+# endif
addq %rdi, %rax
VZEROUPPER_RETURN
+# ifndef USE_AS_RAWMEMCHR
.p2align 4
L(first_vec_x1_check):
tzcntl %eax, %eax
- /* Check the end of data. */
- cmpq %rax, %rdx
- jbe L(zero)
- addq $VEC_SIZE, %rax
+ /* Adjust length. */
+ subl $-(VEC_SIZE * 4), %edx
+ /* Check if match within remaining length. */
+ cmpl %eax, %edx
+ jbe L(set_zero_end)
+ incq %rdi
addq %rdi, %rax
VZEROUPPER_RETURN
+ .p2align 4
+L(set_zero_end):
+ xorl %eax, %eax
+ VZEROUPPER_RETURN
+# endif
.p2align 4
-L(first_vec_x2_check):
+L(last_vec_x1_return):
tzcntl %eax, %eax
- /* Check the end of data. */
- cmpq %rax, %rdx
- jbe L(zero)
- addq $(VEC_SIZE * 2), %rax
+# ifdef USE_AS_RAWMEMCHR
+ subq $(VEC_SIZE * 4 - 1), %rdi
+# else
+ incq %rdi
+# endif
addq %rdi, %rax
VZEROUPPER_RETURN
.p2align 4
-L(first_vec_x3_check):
+L(last_vec_x2_return):
tzcntl %eax, %eax
- /* Check the end of data. */
- cmpq %rax, %rdx
- jbe L(zero)
- addq $(VEC_SIZE * 3), %rax
+# ifdef USE_AS_RAWMEMCHR
+ subq $(VEC_SIZE * 3 - 1), %rdi
+# else
+ subq $-(VEC_SIZE + 1), %rdi
+# endif
addq %rdi, %rax
VZEROUPPER_RETURN
+# ifndef USE_AS_RAWMEMCHR
.p2align 4
-L(zero):
- xorl %eax, %eax
- jmp L(return_vzeroupper)
+L(last_4x_vec_or_less_cmpeq):
+ VPCMPEQ (VEC_SIZE * 4 + 1)(%rdi), %ymm0, %ymm1
+ vpmovmskb %ymm1, %eax
+ subq $-(VEC_SIZE * 4), %rdi
+ /* Check first VEC regardless. */
+ testl %eax, %eax
+ jnz L(first_vec_x1_check)
+ /* If remaining length <= CHAR_PER_VEC * 2. */
+ addl $(VEC_SIZE * 2), %edx
+ jle L(last_2x_vec)
.p2align 4
-L(null):
- xorl %eax, %eax
- ret
-# endif
+L(last_4x_vec):
+ VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
+ vpmovmskb %ymm1, %eax
+ testl %eax, %eax
+ jnz L(last_vec_x2_return)
- .p2align 4
-L(first_vec_x0):
- tzcntl %eax, %eax
- addq %rdi, %rax
- VZEROUPPER_RETURN
+ VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
+ vpmovmskb %ymm1, %eax
- .p2align 4
-L(first_vec_x1):
- tzcntl %eax, %eax
- addq $VEC_SIZE, %rax
- addq %rdi, %rax
- VZEROUPPER_RETURN
+ /* Create mask for possible matches within remaining length. */
+ movq $-1, %rcx
+ bzhiq %rdx, %rcx, %rcx
- .p2align 4
-L(first_vec_x2):
+ /* Test matches in data against length match. */
+ andl %ecx, %eax
+ jnz L(last_vec_x3)
+
+ /* if remaining length <= VEC_SIZE * 3 (Note this is after
+ remaining length was found to be > VEC_SIZE * 2. */
+ subl $VEC_SIZE, %edx
+ jbe L(zero_end2)
+
+ VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
+ vpmovmskb %ymm1, %eax
+ /* Shift remaining length mask for last VEC. */
+ shrq $32, %rcx
+ andl %ecx, %eax
+ jz L(zero_end2)
tzcntl %eax, %eax
- addq $(VEC_SIZE * 2), %rax
+ addq $(VEC_SIZE * 3 + 1), %rdi
addq %rdi, %rax
+L(zero_end2):
VZEROUPPER_RETURN
.p2align 4
-L(4x_vec_end):
- vpmovmskb %ymm1, %eax
- testl %eax, %eax
- jnz L(first_vec_x0)
- vpmovmskb %ymm2, %eax
- testl %eax, %eax
- jnz L(first_vec_x1)
- vpmovmskb %ymm3, %eax
- testl %eax, %eax
- jnz L(first_vec_x2)
- vpmovmskb %ymm4, %eax
- testl %eax, %eax
-L(first_vec_x3):
+L(last_vec_x3):
tzcntl %eax, %eax
- addq $(VEC_SIZE * 3), %rax
+ subq $-(VEC_SIZE * 2 + 1), %rdi
addq %rdi, %rax
VZEROUPPER_RETURN
+# endif
END (MEMCHR)
#endif
--
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