[Bug target/45198] New: Unnecessary spill slot for highpart extraction of xmm reg

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

When building g++.dg/torture/pr36445.C at -O2 you can see

        call    _Z5func2v
        movaps  %xmm0, (%rsp)
        movq    (%rsp), %rdx
        movq    8(%rsp), %rax
        movq    %rdx, 16(%rsp)
        movl    %eax, 24(%rsp)

where the stack-slot spills are caused by

(insn 26 5 27 2 (set (reg:V4SF 72)
        (reg:V4SF 21 xmm0))
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/torture/pr36445.C:20 1054
{*movv4sf_internal}
     (nil))

(insn 27 26 28 2 (set (reg:DI 70 [ D.2130 ])
        (subreg:DI (reg:V4SF 72) 0))
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/torture/pr36445.C:20 61
{*movdi_internal_rex64}
     (nil))

(insn 28 27 24 2 (set (reg:DI 71 [ D.2130+8 ])
        (subreg:DI (reg:V4SF 72) 8))
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/torture/pr36445.C:20 61
{*movdi_internal_rex64}
     (nil))

where we are unable to verify the constraints for insn 28 because there
is no move pattern that would special case hipart extraction (which
could use movhps).


-- 
           Summary: Unnecessary spill slot for highpart extraction of xmm
                    reg
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
GCC target triplet: x86-64-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45198