Reinstate r273711

r273711 was reverted by r273743.  The inliner needs to know about any
call sites in the inlined function.  These were obscured if we replaced
a call to undef with an undef but kept the call around.

This fixes PR28298.

llvm-svn: 273753

1 files changed, 12 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
index 0e93b0a37b0..9d0ef42e039 100644
--- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -582,11 +582,18 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
     // its simpler value.
     if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
       DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << "  to: " << *V << '\n');
-      Inst->replaceAllUsesWith(V);
-      Inst->eraseFromParent();
-      Changed = true;
-      ++NumSimplify;
-      continue;
+      if (!Inst->use_empty()) {
+        Inst->replaceAllUsesWith(V);
+        Changed = true;
+      }
+      if (isInstructionTriviallyDead(Inst, &TLI)) {
+        Inst->eraseFromParent();
+        Changed = true;
+      }
+      if (Changed) {
+        ++NumSimplify;
+        continue;
+      }
     }
 
     // If this is a simple instruction that we can value number, process it.