[Bug c++/14042] New: C++ abstraction penalty is high in simple cases

[tjw at omnigroup dot com]

The attached test case shows nearly identical loops, the only difference being that one operates on 
two objects per loop and the other just one.

The iterate_ok() function generates a nice all-register loop like:

L16:
        vaddfp v1,v13,v0
        vmaddfp v13,v1,v13,v0
        vsubfp v0,v1,v0
        bdnz L16

The iterate_bad() function generates tons of load/store operations:

L41:
        lvx v0,r9,r0
        vaddfp v1,v9,v10
        lvx v13,r9,r2
        vaddfp v12,v13,v0
        vmaddfp v9,v1,v9,v10
        stvx v1,0,r11
        vsubfp v10,v1,v10
        vsubfp v11,v12,v0
        stvx v12,0,r9
        vmaddfp v13,v12,v13,v0
        stvx v11,r9,r0
        stvx v13,r9,r2
        bdnz L41


I don't know if this is specific to Altivec, I would assume it isn't, but my real program that is getting 
clobbered by this is Altivec-based.

-- 
           Summary: C++ abstraction penalty is high in simple cases
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tjw at omnigroup dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-apple-darwin7.2.0
  GCC host triplet: powerpc-apple-darwin7.2.0
GCC target triplet: powerpc-apple-darwin7.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14042