https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103647
Bug ID: 103647
Summary: constant array comparison not always folded
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: denis.campredon at gmail dot com
Target Milestone: ---
On trunk and gcc 11, with -O2 the following functions are not optimized to
xor eax, eax
------------
bool f() {
char a[] = {'a', 'c'};
char b[] = {'a', 'b'};
return __builtin_memcmp(a, b, 2);
}
bool g() {
char a[] = {'a', 'b'};
char b[] = {'a', 'b', 'c'};
return __builtin_memcmp(a, b, 2);
}
------------
.LC1:
.string "ab"
.LC0:
.string "ac"
f():
movzx eax, WORD PTR .LC1[rip]
cmp WORD PTR .LC0[rip], ax
setne al
ret
g():
cmp WORD PTR .LC1[rip], 25185
setne al
ret
