https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70038
Bug ID: 70038
Summary: [5.3.0 and 4.9.1]Wrong optimization with -O2
Product: gcc
Version: 5.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: 366899789 at qq dot com
Target Milestone: ---
Compile the following code with -O2 -fdump-tree-optimized:
-------------------------
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
void create_link(char *pfilename,
const char *linkname, mode_t linktype,
const char *prevlinkname)
{
struct stat stat_buf;
if (stat(prevlinkname, &stat_buf) == 0)
{
unlink(prevlinkname);
}
printf("%p %s\n",prevlinkname,(prevlinkname ? "TRUE":"NULL"));
if (stat(linkname, &stat_buf) == 0)
{
if (prevlinkname) {
rename(linkname, prevlinkname);
printf("%p %s\n",prevlinkname,(prevlinkname ?
"TRUE":"NULL"));
}
else {
unlink(linkname);
}
}
if (linktype == S_IFLNK)
{
symlink(pfilename, linkname);
}
else
{
link(pfilename, linkname);
}
}
int main(int argc,char *argv[])
{
if(argc > 1) {
create_link(argv[1], "link", S_IFLNK, NULL);
}
return 0;
}
-------------------------
~~~~~
Start binary with "./a.out test.sh"
test.sh is a exist file.
It will print:
(nil) TRUE
(nil) TRUE,
but expected output is:
(nil) NULL.
the assembly code is:
--------------------------
.file "test.c"
.section .rodata.str1.1,"aMS",@progbits,1
.LC0:
.string "TRUE"
.LC1:
.string "%p %s\n"
.section .text.unlikely,"ax",@progbits
.LCOLDB2:
.text
.LHOTB2:
.p2align 4,,15
.globl create_link
.type create_link, @function
create_link:
.LFB20:
.cfi_startproc
pushq %r13
.cfi_def_cfa_offset 16
.cfi_offset 13, -16
pushq %r12
.cfi_def_cfa_offset 24
.cfi_offset 12, -24
movq %rdi, %r13
pushq %rbp
.cfi_def_cfa_offset 32
.cfi_offset 6, -32
pushq %rbx
.cfi_def_cfa_offset 40
.cfi_offset 3, -40
movq %rsi, %rbp
movl %edx, %r12d
movq %rcx, %rsi
movl $1, %edi
subq $152, %rsp
.cfi_def_cfa_offset 192
movq %rcx, %rbx
movq %rsp, %rdx
call __xstat
testl %eax, %eax
je .L8
.L2:
movl $.LC0, %edx
movq %rbx, %rsi
movl $.LC1, %edi
xorl %eax, %eax
call printf
movq %rsp, %rdx
movq %rbp, %rsi
movl $1, %edi
call __xstat
testl %eax, %eax
jne .L3
movq %rbx, %rsi
movq %rbp, %rdi
call rename
movl $.LC0, %edx
movq %rbx, %rsi
movl $.LC1, %edi
xorl %eax, %eax
call printf
.L3:
cmpl $40960, %r12d
movq %rbp, %rsi
movq %r13, %rdi
je .L9
call link
addq $152, %rsp
.cfi_remember_state
.cfi_def_cfa_offset 40
popq %rbx
.cfi_def_cfa_offset 32
popq %rbp
.cfi_def_cfa_offset 24
popq %r12
.cfi_def_cfa_offset 16
popq %r13
.cfi_def_cfa_offset 8
ret
.p2align 4,,10
.p2align 3
.L8:
.cfi_restore_state
movq %rbx, %rdi
call unlink
jmp .L2
.p2align 4,,10
.p2align 3
.L9:
call symlink
addq $152, %rsp
.cfi_def_cfa_offset 40
popq %rbx
.cfi_def_cfa_offset 32
popq %rbp
.cfi_def_cfa_offset 24
popq %r12
.cfi_def_cfa_offset 16
popq %r13
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE20:
.size create_link, .-create_link
.section .text.unlikely
.LCOLDE2:
.text
.LHOTE2:
.section .rodata.str1.1
.LC3:
.string "link"
.section .text.unlikely
.LCOLDB4:
.section .text.startup,"ax",@progbits
.LHOTB4:
.p2align 4,,15
.globl main
.type main, @function
main:
.LFB21:
.cfi_startproc
cmpl $1, %edi
jle .L13
pushq %rax
.cfi_def_cfa_offset 16
movq 8(%rsi), %rdi
movl $40960, %edx
xorl %ecx, %ecx
movl $.LC3, %esi
call create_link
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
.L13:
xorl %eax, %eax
ret
.cfi_endproc
.LFE21:
.size main, .-main
.section .text.unlikely
.LCOLDE4:
.section .text.startup
.LHOTE4:
.ident "GCC: (GNU) 5.3.0"
.section .note.GNU-stack,"",@progbits
--------------------
and the optimized code is:
---------------------
;; Function create_link (create_link, funcdef_no=20, decl_uid=3254,
cgraph_uid=20, symbol_order=20)
Removing basic block 10
Removing basic block 11
create_link (char * pfilename, const char * linkname, mode_t linktype, const
char * prevlinkname)
{
struct stat stat_buf;
int _21;
int _25;
<bb 2>:
_21 = __xstat (1, prevlinkname_7(D), &stat_buf);
if (_21 == 0)
goto <bb 3>;
else
goto <bb 4>;
<bb 3>:
unlink (prevlinkname_7(D));
<bb 4>:
printf ("%p %s\n", prevlinkname_7(D), "TRUE");
_25 = __xstat (1, linkname_11(D), &stat_buf);
if (_25 == 0)
goto <bb 5>;
else
goto <bb 6>;
<bb 5>:
rename (linkname_11(D), prevlinkname_7(D));
printf ("%p %s\n", prevlinkname_7(D), "TRUE");
<bb 6>:
if (linktype_16(D) == 40960)
goto <bb 7>;
else
goto <bb 8>;
<bb 7>:
symlink (pfilename_17(D), linkname_11(D));
goto <bb 9>;
<bb 8>:
link (pfilename_17(D), linkname_11(D));
<bb 9>:
stat_buf ={v} {CLOBBER};
return;
}
;; Function main (main, funcdef_no=21, decl_uid=3259, cgraph_uid=21,
symbol_order=21) (executed once)
Removing basic block 5
main (int argc, char * * argv)
{
char * _5;
<bb 2>:
if (argc_2(D) > 1)
goto <bb 3>;
else
goto <bb 4>;
<bb 3>:
_5 = MEM[(char * *)argv_4(D) + 8B];
create_link (_5, "link", 40960, 0B);
<bb 4>:
return 0;
}
-----------------------
I tried it with "gcc 4.4.7" and it is correct.
