[Bug target/29401] New: [regression] missed-optimization (in unneeded code elimination)

["Petr dot Salinger at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

Hi.

There is a regression on i386 platforms.


int f(int a, int b)
{return (((long long) a) * b) >> 15;}

The gcc 4.0/4.1 generates with "-O3 -fomit-frame-pointer"

        movl    8(%esp), %eax
        imull   4(%esp)
        shrdl   $15, %edx, %eax
        sarl    $15, %edx
        ret

While gcc-3.3/3.4 generates equal and faster

        movl    8(%esp), %eax
        imull   4(%esp)
        shrdl   $15, %edx, %eax
        ret


-- 
           Summary: [regression] missed-optimization (in unneeded code
                    elimination)
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Petr dot Salinger at seznam dot cz
  GCC host triplet: i486


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29401