[llvm] [VPlan] Make canonical IV part of the region (PR #156262)

[via llvm-commits]

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@@ -448,12 +442,13 @@ SmallVector<VPRegisterUsage, 8> llvm::calculateRegisterUsageForPlan(
         // FIXME: Might need some motivation why these values are ignored. If
         // for example an argument is used inside the loop it will increase the
         // register pressure (so shouldn't we add it to LoopInvariants).
-        if (!DefR && (!U->getLiveInIRValue() ||
-                      !isa<Instruction>(U->getLiveInIRValue())))
+        if (!isa<VPRegionValue>(U) && !DefR &&
+            (!U->getLiveInIRValue() ||
+             !isa<Instruction>(U->getLiveInIRValue())))
           continue;
 
         // If this recipe is outside the loop then record it and continue.
-        if (!DefR) {
+        if (!DefR && !isa<VPRegionValue>(U)) {
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ayalz wrote:

ditto

https://github.com/llvm/llvm-project/pull/156262