https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105835
Bug ID: 105835
Summary: Dead Code Elimination Regression at -O1 (trunk vs.
12.1.0)
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: theodort at inf dot ethz.ch
Target Milestone: ---
cat case.c
void foo();
static int b;
static short a(short c, unsigned short d) { return c - d; }
int main() {
int e = -(0 < b);
if (a(1, e))
b = 0;
else
foo();
}
`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O1` can not eliminate
`foo` but `gcc-releases/gcc-12.1.0 -O1` can.
`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O1 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
cmpl $0, b(%rip)
movl $65535, %eax
movl $0, %edx
cmovle %edx, %eax
cmpw $1, %ax
je .L2
movl $0, b(%rip)
movl $0, %eax
ret
.L2:
subq $8, %rsp
.cfi_def_cfa_offset 16
movl $0, %eax
call foo
movl $0, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.1.0 -O1 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movl $0, b(%rip)
movl $0, %eax
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=8fb94fc6097c0a934aac0d89c9c5e2038da67655
