[Bug tree-optimization/54295] New: [4.7 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

             Bug #: 54295
           Summary: [4.7 regression] Widening multiply-accumulate
                    operation uses wrong value extension
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: rearn...@gcc.gnu.org
            Target: arm aarch64


A widening multiply-accumulate operation can generate an incorrect result if
there are casts in expression.

Compile the attached test-case on ARM at -O2, the result is:

$./a.out 
<aborted>

Correct result, as seen at -O1 is

$./a.out
$