[LLVMbugs] [Bug 1286] insertelement of undef generates horrible code

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=1286

sabre at nondot.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
          Component|Backend: X86                |Scalar Optimizations
           Keywords|                            |code-quality
         Resolution|                            |FIXED
            Summary|This SSE Code is Horrid!    |insertelement of undef
                   |                            |generates horrible code
   Target Milestone|---                         |2.0



------- Additional Comments From sabre at nondot.org  2007-04-08 20:12 -------
Fixed, patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070402/047039.html

Testcase here: Transforms/InstCombine/vec_insertelt.ll

We now compile this to:

_foo:
        movl 4(%esp), %eax
        movdqa (%eax), %xmm0
        movl 8(%esp), %ecx
        psllw (%ecx), %xmm0
        movdqa %xmm0, (%eax)
        ret

GCC manages:

_foo:
        subl    $12, %esp
        movl    16(%esp), %edx
        movl    20(%esp), %eax
        movdqa  (%eax), %xmm0
        movdqa  (%edx), %xmm1
        psllw   %xmm0, %xmm1
        movdqa  %xmm1, (%edx)
        addl    $12, %esp
        ret

-Chris



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