[llvm] [VPlan] Explicitly reassociate header mask in logical and (PR #180898)

[via llvm-commits]

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@@ -219,7 +217,8 @@ define void @test_exit_branch_cost(ptr %dst, ptr noalias %x.ptr, ptr noalias %y.
 ; COMMON-NEXT:    store i64 0, ptr [[DST_3]], align 8
 ; COMMON-NEXT:    br label %[[PRED_STORE_CONTINUE9]]
 ; COMMON:       [[PRED_STORE_CONTINUE9]]:
-; COMMON-NEXT:    [[TMP13:%.*]] = select <2 x i1> [[TMP7]], <2 x i1> [[TMP2]], <2 x i1> zeroinitializer
+; COMMON-NEXT:    [[TMP22:%.*]] = select <2 x i1> [[TMP7]], <2 x i1> [[BROADCAST_SPLAT]], <2 x i1> zeroinitializer
+; COMMON-NEXT:    [[TMP13:%.*]] = select <2 x i1> [[TMP22]], <2 x i1> [[BROADCAST_SPLAT3]], <2 x i1> zeroinitializer
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ayalz wrote:

Potential source for slight degradation (for non EVL targets)?

https://github.com/llvm/llvm-project/pull/180898