https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123103
Bug ID: 123103
Summary: missed optimization for redundant conditional
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: 652023330028 at smail dot nju.edu.cn
Target Milestone: ---
Hello, when compiling the following reduced code with -O3, GCC generates
redundant instructions that could be optimized away.
Reduced code (from ABC project
https://github.com/berkeley-abc/abc/blob/362661f00d0ee8b8f15feb6dd2d14c10c4c03640/src/aig/gia/giaPf.c#L777):
https://godbolt.org/z/6rh39hrPd
typedef struct a b;
struct a {
unsigned aa;
int c[]
};
int t1, t2, t3;
int ab(b *d) {
int e=t1, f=t2;
if (d->c[e])
return 0;
if (f)
return 1;
}
int g(b **h) {
int i=t3;
for (;;)
if (h && ab(h[i]))
h[i]->aa = 1;
}
Assembly generated by GCC -O3 includes the following block:
.L8:
movl t2(%rip), %eax
testl %eax, %eax
jne .L10
movl $1, %eax
testl %eax, %eax
je .L14
.L10:
movl $1, (%rcx)
movl t1(%rip), %edx
.L14:
This block is functionally equivalent to a much simpler sequence:
.L8:
movl $1, (%rcx)
movl t1(%rip), %edx
.L14:
