Sanjay Patel 24269f9eb6 [VectorCombine] try to form a better extractelement ... Extracting to the same index that we are going to insert back into allows forming select ("blend") shuffles and enables further transforms. Admittedly, this is a quick-fix for a more general problem that I'm hoping to solve by adding transforms for patterns that start with an insertelement. But this might resolve some regressions known to be caused by the extract-extract transform (although I have not gotten more details on those yet). In the motivating case from PR34724: https://bugs.llvm.org/show_bug.cgi?id=34724 The combination of subsequent instcombine and codegen transforms gets us this improvement: vmovshdup %xmm0, %xmm2 ## xmm2 = xmm0[1,1,3,3] vhaddps %xmm1, %xmm1, %xmm4 vmovshdup %xmm1, %xmm3 ## xmm3 = xmm1[1,1,3,3] vaddps %xmm0, %xmm2, %xmm0 vaddps %xmm1, %xmm3, %xmm1 vshufps $200, %xmm4, %xmm0, %xmm0 ## xmm0 = xmm0[0,2],xmm4[0,3] vinsertps $177, %xmm1, %xmm0, %xmm0 ## xmm0 = zero,xmm0[1,2],xmm1[2] --> vmovshdup %xmm0, %xmm2 ## xmm2 = xmm0[1,1,3,3] vhaddps %xmm1, %xmm1, %xmm1 vaddps %xmm0, %xmm2, %xmm0 vshufps $200, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm0[0,2],xmm1[0,3] Differential Revision: https://reviews.llvm.org/D76623		2020-04-03 13:55:13 -04:00
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extract-binop.ll	[VectorCombine] try to form a better extractelement	2020-04-03 13:55:13 -04:00
extract-cmp.ll	[VectorCombine] try to form a better extractelement	2020-04-03 13:55:13 -04:00
lit.local.cfg
shuffle.ll	[VectorCombine] transform bitcasted shuffle to narrower elements	2020-04-02 13:30:22 -04:00