https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96317
Bug ID: 96317
Summary: [8/9/10/11] Int compare optimizations make some errors
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: 570070308 at qq dot com
Target Milestone: ---
for the code:
signed int a=2147483647;
if( (signed int)( (signed int)a + (signed int)1 ) < (signed int)2147483647
)
{
printf("111\n");
}
if( (signed int)( (signed int)a + (signed int)1 ) < (signed int)2147483646
)
{
printf("222\n");
}
signed int b=2147483646;
if( (signed int)( (signed int)a + (signed int)1 ) < (signed int)b )
{
printf("333\n");
}
The result is:
111
333
I have checked the assembly files. It seems that the compiler optimize the
a+1<2147483646 to a<=2147483644. There are some other similar situations in
compartion of <=,>,>=. I think it is better to change the ways or give out a
warning.
