https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82524
Bug ID: 82524
Summary: expensive-optimizations produces wrong results
Product: gcc
Version: 7.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: Vasilis.Vlachoudis at cern dot ch
Target Milestone: ---
Created attachment 42342
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42342&action=edit
Bug example
System: Fresh installation of Fedora Core 26
Compiler: g++ --version
g++ (GCC) 7.2.1 20170915 (Red Hat 7.2.1-2)
The attached file when compiled with/out the -fexpensive-optimization or
fno-expensive-optimization flag produces different results
$ g++ -O2 -fno-expensive-optimizations bug.cc; a.out
A=00FFFFFF B=FFFFFFFF alphaBlend(A,B)=00FFFFFF
$ g++ -O2 bug.cc; a.out
A=00FFFFFF B=FFFFFFFF alphaBlend(A,B)=0000FFFF
