Author: mjg
Date: Mon Sep 17 15:51:49 2018
New Revision: 338714
URL: https://svnweb.freebsd.org/changeset/base/338714
Log:
amd64: tidy up kernel memmove, take 2
There is no need to use %rax for temporary values and avoiding doing
so shortens the func.
Handle the explicit 'check for tail' depessimisization for backwards copying.
This reduces the diff against userspace.
Tested with the glibc test suite.
Approved by: re (kib)
Modified:
head/sys/amd64/amd64/support.S
Modified: head/sys/amd64/amd64/support.S
==============================================================================
--- head/sys/amd64/amd64/support.S Mon Sep 17 15:49:35 2018
(r338713)
+++ head/sys/amd64/amd64/support.S Mon Sep 17 15:51:49 2018
(r338714)
@@ -108,40 +108,40 @@ END(sse2_pagezero)
*/
ENTRY(memmove_std)
PUSH_FRAME_POINTER
- movq %rdi,%r9
+ movq %rdi,%rax
movq %rdx,%rcx
- movq %rdi,%rax
- subq %rsi,%rax
- cmpq %rcx,%rax /* overlapping && src < dst? */
- jb 1f
+ movq %rdi,%r8
+ subq %rsi,%r8
+ cmpq %rcx,%r8 /* overlapping && src < dst? */
+ jb 2f
shrq $3,%rcx /* copy by 64-bit words */
rep
movsq
movq %rdx,%rcx
andq $7,%rcx /* any bytes left? */
- jne 2f
- movq %r9,%rax
+ jne 1f
POP_FRAME_POINTER
ret
-2:
+1:
rep
movsb
- movq %r9,%rax
POP_FRAME_POINTER
ret
/* ALIGN_TEXT */
-1:
+2:
addq %rcx,%rdi /* copy backwards */
addq %rcx,%rsi
decq %rdi
decq %rsi
- andq $7,%rcx /* any fractional bytes? */
std
+ andq $7,%rcx /* any fractional bytes? */
+ je 3f
rep
movsb
+3:
movq %rdx,%rcx /* copy remainder by 32-bit
words */
shrq $3,%rcx
subq $7,%rsi
@@ -149,24 +149,22 @@ ENTRY(memmove_std)
rep
movsq
cld
- movq %r9,%rax
POP_FRAME_POINTER
ret
END(memmove_std)
ENTRY(memmove_erms)
PUSH_FRAME_POINTER
- movq %rdi,%r9
+ movq %rdi,%rax
movq %rdx,%rcx
- movq %rdi,%rax
- subq %rsi,%rax
- cmpq %rcx,%rax /* overlapping && src < dst? */
+ movq %rdi,%r8
+ subq %rsi,%r8
+ cmpq %rcx,%r8 /* overlapping && src < dst? */
jb 1f
rep
movsb
- movq %r9,%rax
POP_FRAME_POINTER
ret
@@ -179,7 +177,6 @@ ENTRY(memmove_erms)
rep
movsb
cld
- movq %r9,%rax
POP_FRAME_POINTER
ret
END(memmove_erms)
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