[LLVMbugs] [Bug 22391] New: New vector shuffle legality: turns pshufd+palignr into shufps x2.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22391

            Bug ID: 22391
           Summary: New vector shuffle legality: turns pshufd+palignr into
                    shufps x2.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: ahmed.bougacha at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 13765
  --> http://llvm.org/bugs/attachment.cgi?id=13765&action=edit
IR testcase

For the attached IR, we used to generate (targeting core-avx2):

    vpshufd    $164, %xmm0, %xmm0      ## xmm0 = xmm0[0,1,2,2]
    vpalignr    $12, %xmm0, %xmm1, %xmm0 ## xmm0 =
xmm0[12,13,14,15],xmm1[0,1,2,3,4,5,6,7,8,9,10,11]

With the new all-shuffles-are-legal lowering, we now generate:

    vshufps    $2, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm0[2,0],xmm1[0,0]
    vshufps    $152, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm0[0,2],xmm1[1,2]

Changing from the integer to the FP domain.

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