[llvm-branch-commits] [llvm] [VPlan] Make blend operands non-reorderable to optimize their masks in predicator (PR #219060)

[Luke Lau via llvm-branch-commits]

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@@ -182,8 +182,11 @@ define void @blend_masks_triangle_phi(ptr noalias %p, i1 %c0, i1 %c1) {
 ; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT]], <4 x i1> poison, <4 x i32> zeroinitializer
 ; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <4 x i1> poison, i1 [[C0]], i64 0
 ; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT1]], <4 x i1> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP0:%.*]] = select <4 x i1> [[BROADCAST_SPLAT2]], <4 x i1> [[BROADCAST_SPLAT]], <4 x i1> zeroinitializer
-; CHECK-NEXT:    [[PREDPHI:%.*]] = select <4 x i1> [[TMP0]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 1)
+; CHECK-NEXT:    [[TMP0:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT]], splat (i1 true)
+; CHECK-NEXT:    [[TMP4:%.*]] = select <4 x i1> [[BROADCAST_SPLAT2]], <4 x i1> [[TMP0]], <4 x i1> zeroinitializer
+; CHECK-NEXT:    [[TMP5:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT2]], splat (i1 true)
+; CHECK-NEXT:    [[TMP3:%.*]] = or <4 x i1> [[TMP4]], [[TMP5]]
+; CHECK-NEXT:    [[PREDPHI:%.*]] = select <4 x i1> [[TMP3]], <4 x i32> splat (i32 1), <4 x i32> zeroinitializer
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lukel97 wrote:

I think this regressed because we're now using choosing the edge mask `bb2->bb3` where it was `bb1->bb3` previously. I wonder if we need something in simplifyRecipes for `c0 && !c1 || !c0 -> !(c0 && c1)` or similar

https://github.com/llvm/llvm-project/pull/219060