http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61064
Bug ID: 61064
Summary: ARM G++ compiler mis-optimizes safe Abs function
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: quanxunzhen at gmail dot com
Created attachment 32737
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32737&action=edit
testcase
The attachment is the code shows this problem. It is some code extracted from
mozilla. Sorry for such large code, but I could not reproduce this problem when
it was simplified.
If you compile mytest.cpp with ARM G++ (I tested 4.6 and 4.8), and then input
-2147483648, it will shows that the absolute value of this number is smaller
than 2147483647.
In this code, a safe Abs implementation is used. However, it seems that ARM G++
mis-optimizes it when -O2 is applied. This problem is not present in clang++ or
x86 G++.
