[Bug c/65307] New: Incorrect optimization breaks basic arithmetic

[madars+gccbug at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65307

            Bug ID: 65307
           Summary: Incorrect optimization breaks basic arithmetic
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: madars+gccbug at gmail dot com

The following code sample exhibits a bug in a gcc -O2 optimization pass.
Namely, having defined two() and six() with the obvious return values, the
value of two() * 2 + six() * 5 gets an assembly of 1 shl 5 (i.e. 32, instead of
the correct 34).

Code: http://web.mit.edu/madars/Public/gcc-basic-arithmetic-bug.c

gcc 4.9.1 and 4.9.2 with -O2 are both buggy, -O1 makes the bug go away; the bug
does not seem to be present in gcc 4.8 and earlier.