[llvm] [VPlan] Simplify (X && Y) || (X && !Y) -> X. (PR #89386)

[via llvm-commits]

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@@ -570,16 +564,13 @@ define void @pred_cfg3(i32 %k, i32 %j) {
 ; CHECK-NEXT: Successor(s): then.0.0
 ; CHECK-EMPTY:
 ; CHECK-NEXT: then.0.0:
-; CHECK-NEXT:   EMIT vp<[[NOT:%.+]]> = not ir<%c.0>
-; CHECK-NEXT:   EMIT vp<[[MASK3:%.+]]> = logical-and vp<[[MASK1]]>, vp<[[NOT]]>
-; CHECK-NEXT:   EMIT vp<[[MASK4:%.+]]> = or vp<[[MASK2]]>, vp<[[MASK3]]>
 ; CHECK-NEXT:   BLEND ir<%p> = ir<0> vp<[[PRED]]>/vp<[[MASK2]]>
-; CHECK-NEXT:   EMIT vp<[[MASK5:%.+]]> = logical-and vp<[[MASK4]]>, ir<%c.0>
+; CHECK-NEXT:   EMIT vp<[[MASK3:%.+]]> = logical-and vp<[[MASK1]]>, ir<%c.0>
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ayalz wrote:

Just noting that X is MASK1, Y is ir<%c.0>; all of !Y, X&&Y, (X&&Y) || (X&&!Y) are eliminated, the latter replaced by X, while X&&Y (MASK2) is retained due to another use - by BRANCH-ON-COUNT.

https://github.com/llvm/llvm-project/pull/89386