[PATCH] D94712: Do not traverse ConstantData use-list in LookInterchange

[Anton Rapetov via Phabricator via llvm-commits]

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Walking the use list of a Constant (particularly, ConstantData)
is not scalable, since a given constant may be used by many
instructinos in many functions in many modules.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94712

Files:
  llvm/lib/Transforms/Scalar/LoopInterchange.cpp


Index: llvm/lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -661,15 +661,12 @@
 
 // Check V's users to see if it is involved in a reduction in L.
 static PHINode *findInnerReductionPhi(Loop *L, Value *V) {
-  for (Value *User : V->users()) {
-    if (PHINode *PHI = dyn_cast<PHINode>(User)) {
-      if (PHI->getNumIncomingValues() == 1)
-        continue;
-      RecurrenceDescriptor RD;
-      if (RecurrenceDescriptor::isReductionPHI(PHI, L, RD))
-        return PHI;
-      return nullptr;
-    }
+  for (PHINode &PHI : L->getHeader()->phis()) {
+    if (PHI.getNumIncomingValues() == 1 ||
+        !llvm::is_contained(PHI.incoming_values(), V))
+      continue;
+    RecurrenceDescriptor RD;
+    return RecurrenceDescriptor::isReductionPHI(&PHI, L, RD) ? &PHI : nullptr;
   }
 
   return nullptr;


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