1 files changed, 25 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 29911a4ed28..65ba0bbc9a7 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1164,15 +1164,30 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
 
     // Do PHI translation to get its value in the predecessor if necessary.  The
     // returned pointer (if non-null) is guaranteed to dominate UnavailablePred.
+    // We do the translation for each edge we skipped by going from LI's block
+    // to LoadBB, otherwise we might miss pieces needing translation.
 
     // If all preds have a single successor, then we know it is safe to insert
     // the load on the pred (?!?), so we can insert code to materialize the
     // pointer if it is not available.
-    PHITransAddr Address(LI->getPointerOperand(), DL, AC);
-    Value *LoadPtr = nullptr;
-    LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
-                                                *DT, NewInsts);
+    Value *LoadPtr = LI->getPointerOperand();
+    BasicBlock *Cur = LI->getParent();
+    while (Cur != LoadBB) {
+      PHITransAddr Address(LoadPtr, DL, AC);
+      LoadPtr = Address.PHITranslateWithInsertion(
+          Cur, Cur->getSinglePredecessor(), *DT, NewInsts);
+      if (!LoadPtr) {
+        CanDoPRE = false;
+        break;
+      }
+      Cur = Cur->getSinglePredecessor();
+    }
 
+    if (LoadPtr) {
+      PHITransAddr Address(LoadPtr, DL, AC);
+      LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred, *DT,
+                                                  NewInsts);
+    }
     // If we couldn't find or insert a computation of this phi translated value,
     // we fail PRE.
     if (!LoadPtr) {
@@ -1187,8 +1202,12 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
 
   if (!CanDoPRE) {
     while (!NewInsts.empty()) {
-      Instruction *I = NewInsts.pop_back_val();
-      markInstructionForDeletion(I);
+      // Erase instructions generated by the failed PHI translation before
+      // trying to number them. PHI translation might insert instructions
+      // in basic blocks other than the current one, and we delete them
+      // directly, as markInstructionForDeletion only allows removing from the
+      // current basic block.
+      NewInsts.pop_back_val()->eraseFromParent();
     }
     // HINT: Don't revert the edge-splitting as following transformation may
     // also need to split these critical edges.