https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103535
Bug ID: 103535
Summary: [missed optimization] remainder-of-2 with subtract-1
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jengelh at inai dot de
Target Milestone: ---
gcc version 11.2.1 20210816 [revision 056e324ce46a7924b5cf10f61010cf9dd2ca10e9]
(SUSE Linux) x86_64
== input ==
unsigned int fff(unsigned int p)
{
// equivalent to return p & ~1;
if (p % 2 != 0)
--p;
return p;
}
== Observed output ==
ยป gcc -O2 -c x.cpp; objdump -Mintel -d x.o
0: 89 fa mov edx,edi
2: 89 f8 mov eax,edi
4: 83 e2 01 and edx,0x1
7: 83 fa 01 cmp edx,0x1
a: 83 d0 ff adc eax,0xffffffff
d: c3 ret
== Expected output ==
0: 89 f8 mov eax,edi
2: 83 e0 fe and eax,0xfffffffe
5: c3 ret
