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[Bug tree-optimization/77980] New: Regression in GCC-7.0.0's optimizer.
- From: "ishiura-compiler at ml dot kwansei.ac.jp" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 14 Oct 2016 03:53:13 +0000
- Subject: [Bug tree-optimization/77980] New: Regression in GCC-7.0.0's optimizer.
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77980
Bug ID: 77980
Summary: Regression in GCC-7.0.0's optimizer.
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ishiura-compiler at ml dot kwansei.ac.jp
Target Milestone: ---
We compiled a program (A.c) by GCC-7.0.0 and clang-3.8.0 with -O3 option.
clang-3.8.0 performed better optimization than GCC-7.0.0.
(A.c)
#include <stdio.h>
int x1 = 0;
unsigned int x2 = 1;
int main ()
{
int t1 = x1*(1/(x2+x2));
if (t1 != 0) __builtin_abort();
return 0;
}
/*
+---------------------------------------+--------------------------------------+
|gcc-7.0.s(gcc-7.0.0 A.c -O3 -S) |clang.s(clang-3.8.0 A.c -O3 -S)
|
+---------------------------------------+--------------------------------------+
|main: |\t.type\tmain,@function
|
|.LFB11: |main:
|
| .cfi_startproc | .cfi_startproc
|
|\tmovl\tx2(%rip), %eax |# BB#0:
|
| xorl %edx, %edx |
|
| leal (%rax,%rax), %ecx |
|
| movl $1, %eax |
|
| divl %ecx |
|
| imull x1(%rip), %eax |
|
| testl %eax, %eax |
|
| jne .L7 |
|
| xorl %eax, %eax | xorl %eax, %eax
|
| ret | retq
|
|.L7: |.Lfunc_end0:
|
| subq $8, %rsp | .size main,
.Lfunc_end0-main|
| .cfi_def_cfa_offset 16 |
|
| call abort |
|
| .cfi_endproc | .cfi_endproc
|
|.LFE11:\n |\n
|
| .size main, .-main | .type x1,@object
|
| .globl x2 |
|
| .data |
|
| .align 4 |
|
| .type x2, @object |
|
| .size x2, 4 |
|
|x2: |
|
| .long 1 |
|
| .globl x1 |
|
| .bss | .bss
|
| .align 4 | .globl x1
|
| .type x1, @object | .align 4
|
| .size x1, 4 |
|
|x1: |x1:
|
| .zero 4 | .long 0
|
| .ident "GCC: (GNU) 7.0.0 20...| .size x1, 4
|
|\t.section\t.note.GNU-stack,"",@prog...|\n
|
| | .type x2,@object
|
| | .data
|
| | .globl x2
|
| | .align 4
|
| |x2:
|
| | .long 1
|
| | .size x2, 4
|
| |\n
|
| |\n
|
| | .ident "clang version
3.8....|
| | .section
".note.GNU-...|
+---------------------------------------+--------------------------------------+
/*
using built-in specs.
COLLECT_GCC=gcc-7.0
COLLECT_LTO_WRAPPER=/home/kota/opt/gcc/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
target: x86_64-pc-linux-gnu
configure woth: ../gcc/configure --prefix=/home/kota/opt/gcc
--program-suffix=-7.0 --disable-multilib --enable-languages=c
thred model: posix
gcc version 7.0.0 20161013 (experimental) (GCC)
using built-in specs.
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
*/