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

[Luke Lau via llvm-commits]

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@@ -1614,6 +1605,31 @@ void VPlanTransforms::simplifyRecipes(VPlan &Plan) {
   }
 }
 
+/// Reassociate (headermask && x) && y -> headermask && (x && y) to allow the
+/// header mask to be simplified further, e.g. in optimizeEVLMasks.
+static void reassociateHeaderMask(VPlan &Plan) {
+  VPValue *HeaderMask = vputils::findHeaderMask(Plan);
+  if (!HeaderMask)
+    return;
+  SmallSetVector<VPUser *, 8> Worklist(HeaderMask->user_begin(),
+                                       HeaderMask->user_end());
+  while (!Worklist.empty()) {
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lukel97 wrote:

I've just removed the call to R.eraseFromParent() to remove the need for SmallSetVector now in 66bc4579b9a07ae0998b618e13593d622fea00cd

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