[LLVMbugs] [Bug 21138] New: New vector shuffle lowering produces an insertf128 + blend instead of a single insertf128

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21138

            Bug ID: 21138
           Summary: New vector shuffle lowering produces an insertf128 +
                    blend instead of a single insertf128
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: qcolombet at apple.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 13122
  --> http://llvm.org/bugs/attachment.cgi?id=13122&action=edit
IR to reproduce the problem.

To reproduce:
llc -mattr=+avx -x86-experimental-vector-shuffle-lowering=true
avx_insertf_blendps.ll -o new.s
llc -mattr=+avx -x86-experimental-vector-shuffle-lowering=false
avx_insertf_blendps.ll -o old.s

diff -U 10 old.s new.s
 _foo:                                   ## @foo
     .cfi_startproc
 ## BB#0:                                ## %for.body545
     vextractf128    $1, %ymm1, %xmm2
     vshufps    $-35, %xmm2, %xmm1, %xmm1 ## xmm1 = xmm1[1,3],xmm2[1,3]
+    vinsertf128    $1, %xmm1, %ymm0, %ymm1
     vextractf128    $1, %ymm0, %xmm2
     vshufps    $-35, %xmm2, %xmm0, %xmm0 ## xmm0 = xmm0[1,3],xmm2[1,3]
-    vinsertf128    $1, %xmm1, %ymm0, %ymm0
+    vblendps    $-16, %ymm1, %ymm0, %ymm0 ## ymm0 =
ymm0[0,1,2,3],ymm1[4,5,6,7]
     retq

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