[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807 --- Comment #6 from liuhongt at gcc dot gnu.org --- Author: liuhongt Date: Tue Dec 17 01:29:09 2019 New Revision: 279451 URL: https://gcc.gnu.org/viewcvs?rev=279451=gcc=rev Log: Use add for a = a + b and a = b + a when possible. Since except for Bonnell, 01 fb add%edi,%ebx is faster and shorter than 8d 1c 1flea(%rdi,%rbx,1),%ebx we should use add for a = a + b and a = b + a when possible if not optimizing for Bonnell. Tested on x86-64. 2019-12-17 H.J. Lu gcc/ PR target/92807 * config/i386/i386.c (ix86_lea_outperforms): Check !TARGET_BONNELL. (ix86_avoid_lea_for_addr): When not optimizing for Bonnell, use add for a = a + b and a = b + a. gcc/testsuite/ PR target/92807 * gcc.target/i386/pr92807-1.c: New test. Added: trunk/gcc/testsuite/gcc.target/i386/pr92807-1.c Modified: trunk/gcc/ChangeLog trunk/gcc/config/i386/i386.c trunk/gcc/testsuite/ChangeLog
[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807 --- Comment #5 from Sunil Pandey --- Patch link: https://gcc.gnu.org/ml/gcc-patches/2019-12/msg00450.html
[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807 --- Comment #4 from H.J. Lu --- Created attachment 47424 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47424=edit A patch
[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek --- Well, lea has to be used in case the flags are live across it. Not the case of this PR though of course.
[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807 H.J. Lu changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2019-12-04 Ever confirmed|0 |1 --- Comment #2 from H.J. Lu --- Shouldn't leal(%rdi,%rax), %eax be changed to addl %edi, %eax unconditionally?
[Bug target/92807] gcc generate extra move for the snippet code along with lea instruction.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92807
Sunil Pandey changed:
What|Removed |Added
CC||hjl.tools at gmail dot com,
||skpgkp2 at gmail dot com
Summary|gcc generate extra move for |gcc generate extra move for
|the snippet code|the snippet code along with
||lea instruction.
--- Comment #1 from Sunil Pandey ---
$ cat t1.c
#include
uint32_t abs2( uint32_t a )
{
uint32_t s = ((a>>15)&0x10001)*0x;
return (a+s)^s;
}
$ gcc --version
gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1)
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -Ofast -S t1.c -o t1.s.gcc.9
$ cat t1.s.gcc.9
.file "t1.c"
.text
.p2align 4
.globl abs2
.type abs2, @function
abs2:
.LFB0:
.cfi_startproc
movl%edi, %edx
shrl$15, %edx
andl$65537, %edx
movl%edx, %eax
sall$16, %eax
subl%edx, %eax
movl%eax, %edx
leal(%rdi,%rax), %eax
xorl%edx, %eax
ret
.cfi_endproc
.LFE0:
.size abs2, .-abs2
.ident "GCC: (GNU) 9.2.1 20190827 (Red Hat 9.2.1-1)"
.section.note.GNU-stack,"",@progbits
Intel compiler generate add instead of lea as well as 1 less mov instruction
for same code.
$ icc -Ofast -S t1.c -o t1.s.icc
$ cat t1.s.icc
.L_2__routine_start_abs2_0:
# -- Begin abs2
.text
# mark_begin;
.align16,0x90
.globl abs2
# --- abs2(uint32_t)
abs2:
# parameter 1: %edi
..B1.1: # Preds ..B1.0
# Execution count [1.00e+00]
.cfi_startproc
..___tag_value_abs2.1:
..L2:
#3.1
movl %edi, %edx#4.23
shrl $15, %edx #4.23
andl $65537, %edx #4.27
movl %edx, %eax#4.36
shll $16, %eax #4.36
subl %edx, %eax#4.36
addl %eax, %edi#5.19
xorl %edi, %eax#5.22
ret #5.22
.align16,0x90
# LOE
.cfi_endproc
# mark_end;
.type abs2,@function
.size abs2,.-abs2
..LNabs2.0:
.data
# -- End abs2
.data
.section .note.GNU-stack, ""
# End
