1 files changed, 11 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
index 345b030ddc1..33eb80734d1 100644
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1930,10 +1930,7 @@ bool llvm::runIPSCCP(Module &M, const DataLayout &DL,
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
       if (!Solver.isBlockExecutable(&*BB)) {
         LLVM_DEBUG(dbgs() << "  BasicBlock Dead:" << *BB);
-
         ++NumDeadBlocks;
-        NumInstRemoved +=
-            changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false);
 
         MadeChanges = true;
 
@@ -1956,6 +1953,17 @@ bool llvm::runIPSCCP(Module &M, const DataLayout &DL,
       }
     }
 
+    // Change dead blocks to unreachable. We do it after replacing constants in
+    // all executable blocks, because changeToUnreachable may remove PHI nodes
+    // in executable blocks we found values for. The function's entry block is
+    // not part of BlocksToErase, so we have to handle it separately.
+    for (BasicBlock *BB : BlocksToErase)
+      NumInstRemoved +=
+          changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false);
+    if (!Solver.isBlockExecutable(&F.front()))
+      NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
+                                            /*UseLLVMTrap=*/false);
+
     // Now that all instructions in the function are constant folded, erase dead
     // blocks, because we can now use ConstantFoldTerminator to get rid of
     // in-edges.