[PATCH] D129297: [LSR] Fix bug - check if loop has preheader before calling isInductionPHI

[Zaara Syeda via Phabricator via llvm-commits]

syzaara created this revision.
syzaara added reviewers: Meinersbur, LoopOptWG.
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Fix bug exposed by https://reviews.llvm.org/D125990, rewriteLoopExitValues calls InductionDescriptor::isInductionPHI which requires the PHI node to have an incoming edge from the loop preheader. This adds checks before calling InductionDescriptor::isInductionPHI to see that the loop has a preheader. Also did some refactoring.


https://reviews.llvm.org/D129297

Files:
  llvm/lib/Transforms/Utils/LoopUtils.cpp


Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1246,6 +1246,19 @@
   return true;
 }
 
+bool checkIsIndPhi(PHINode *Phi, Loop *L, ScalarEvolution *SE,
+                   InductionDescriptor &ID) {
+  if (!Phi)
+    return false;
+  if (!L->getLoopPreheader())
+    return false;
+  if (Phi->getParent() != L->getHeader())
+    return false;
+  if (!InductionDescriptor::isInductionPHI(Phi, L, SE, ID))
+    return false;
+  return true;
+}
+
 int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
                                 ScalarEvolution *SE,
                                 const TargetTransformInfo *TTI,
@@ -1306,10 +1319,7 @@
           InductionDescriptor ID;
           PHINode *IndPhi = dyn_cast<PHINode>(Inst);
           if (IndPhi) {
-            if (IndPhi->getParent() != L->getHeader())
-              continue;
-            // Do not consider non induction phis.
-            if (!InductionDescriptor::isInductionPHI(IndPhi, L, SE, ID))
+            if (!checkIsIndPhi(IndPhi, L, SE, ID))
               continue;
             // This is an induction PHI. Check that the only users are PHI
             // nodes, and induction variable update binary operators.
@@ -1330,12 +1340,8 @@
               continue;
             if (llvm::any_of(Inst->users(), [&](User *U) {
                   PHINode *Phi = dyn_cast<PHINode>(U);
-                  if (!Phi)
+                  if (Phi != PN && !checkIsIndPhi(Phi, L, SE, ID))
                     return true;
-                  if (Phi->getParent() == L->getHeader()) {
-                    if (!InductionDescriptor::isInductionPHI(Phi, L, SE, ID))
-                      return true;
-                  }
                   return false;
                 }))
               continue;


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