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

[Andrei Elovikov via llvm-branch-commits]

================
@@ -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
----------------
eas wrote:

Thanks, your https://github.com/llvm/llvm-project/pull/220801 improved this a bit, before the rebase this PR had

```llvm
; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT1]], <4 x i1> poison, <4 x i32> zeroinitializer
; 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
; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
```

And from what I can see, AArch64/drop-poison-generating-flags.ll improvement in the current version of this PR was unlocked by your change.

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