http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55616
Bug #: 55616
Summary: bogus warning about undefined overflow after overflow
check
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: fwei...@redhat.com
CC: n...@redhat.com
Created attachment 28893
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28893
overflow-check.c
Code which performs proper overflow checking results in a compiler warning (at
-O2, without -fwrapv):
overflow-check.c:9:6: warning: assuming signed overflow does not occur when
assuming that (X + c) < X is always false [-Wstrict-overflow]
if (a > b)
^
I'm surprised that the call to something from f is not optimized away with
-fwrapv. Shouldn't VRP catch this? Addressing this missed optimization
opportunity might also fix the warning.
The g function in the test case intends to make the if statement in r actually
relevant.
This is not a regression, it happens with 4.7.2 as well.
