An sinkable instruction may exist with uses, if those uses are in dead blocks.

Handle this.  This fixes PR908 and Transforms/LICM/2006-09-12-DeadUserOfSunkInstr.ll

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30275 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index a24b366e8d9361a72bc5055c3b35a1e257dfabb6..7ca9be01359e869e93e00bd8b8bfc3815a7ab881 100644 (file)
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -447,6 +447,8 @@ void LICM::sink(Instruction &I) {
     if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) {
       // Instruction is not used, just delete it.
       CurAST->deleteValue(&I);
+      if (!I.use_empty())  // If I has users in unreachable blocks, eliminate.
+        I.replaceAllUsesWith(UndefValue::get(I.getType()));
       I.eraseFromParent();
     } else {
       // Move the instruction to the start of the exit block, after any PHI
@@ -460,6 +462,8 @@ void LICM::sink(Instruction &I) {
   } else if (ExitBlocks.size() == 0) {
     // The instruction is actually dead if there ARE NO exit blocks.
     CurAST->deleteValue(&I);
+    if (!I.use_empty())  // If I has users in unreachable blocks, eliminate.
+      I.replaceAllUsesWith(UndefValue::get(I.getType()));
     I.eraseFromParent();
   } else {
     // Otherwise, if we have multiple exits, use the PromoteMem2Reg function to