https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114774
Bug ID: 114774
Summary: Missed DSE in simple code
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: hubicka at gcc dot gnu.org
Target Milestone: ---
In the following
#include <stdio.h>
int a;
short *p;
void
test (int b)
{
a=1;
if (b)
{
(*p)++;
a=2;
printf ("1\n");
}
else
{
(*p)++;
a=3;
printf ("2\n");
}
}
We are not able to optimize out "a=1". This is simplified real-world scenario
where SRA does not remove definition of SRAed variables.
Note that clang does conditional move here
test: # @test
.cfi_startproc
# %bb.0:
movq p(%rip), %rax
incw (%rax)
xorl %eax, %eax
testl %edi, %edi
leaq .Lstr(%rip), %rcx
leaq .Lstr.2(%rip), %rdi
cmoveq %rcx, %rdi
sete %al
orl $2, %eax
movl %eax, a(%rip)
jmp puts@PLT # TAILCALL
