[Bug target/48701] New: [missed optimization] GCC fails to use aliasing of ymm and xmm registers

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48701

           Summary: [missed optimization] GCC fails to use aliasing of ymm
                    and xmm registers
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: kretz@kde.org


The two functions in the attached test case demonstrate the problem. The
intermediate stores/loads on the stack really should be optimized away.

testStore output now:
vmovdqa %xmm1,-0x30(%rsp)   
vmovdqa %xmm0,-0x20(%rsp)   
vmovdqa -0x30(%rsp),%ymm0   
vmovdqa %ymm0,(<blackhole>)

should be either:
vinsertf128 $1,%xmm0,%ymm1,%ymm0
vmovdqa %ymm0,(<blackhole>)

or:
vmovdqa %xmm1,(<blackhole>)
vmovdqa %xmm0,0x10(<blackhole>)

depending on the target microarchitecture and accompanying code.

likewise the testLoad output now is:
vmovdqa (<blackhole>),%ymm0
vmovdqa %ymm0,-0x30(%rsp)
vmovdqa -0x20(%rsp),%xmm1
vmovdqa -0x30(%rsp),%xmm0

and should be either:
vmovdqa (<blackhole>),%ymm0
vextractf128 $1,%ymm0,%xmm1

or:
vmovdqa (<blackhole>),%xmm0
vmovdqa 0x10(<blackhole>),%xmm1