1 files changed, 34 insertions, 14 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index dbefc2d..24cd343 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -440,27 +440,47 @@ void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
                                      const TargetData *TD) {
   assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
   
-  // FromHandle - This keeps a weakvh on the from value so that we can know if
-  // it gets deleted out from under us in a recursive simplification.
+  // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
+  // we can know if it gets deleted out from under us or replaced in a
+  // recursive simplification.
   WeakVH FromHandle(From);
+  WeakVH ToHandle(To);
   
   while (!From->use_empty()) {
     // Update the instruction to use the new value.
-    Use &U = From->use_begin().getUse();
-    Instruction *User = cast<Instruction>(U.getUser());
-    U = To;
+    Use &TheUse = From->use_begin().getUse();
+    Instruction *User = cast<Instruction>(TheUse.getUser());
+    TheUse = To;
+
+    // Check to see if the instruction can be folded due to the operand
+    // replacement.  For example changing (or X, Y) into (or X, -1) can replace
+    // the 'or' with -1.
+    Value *SimplifiedVal;
+    {
+      // Sanity check to make sure 'User' doesn't dangle across
+      // SimplifyInstruction.
+      AssertingVH<> UserHandle(User);
     
-    // See if we can simplify it.
-    if (Value *V = SimplifyInstruction(User, TD)) {
-      // Recursively simplify this.
-      ReplaceAndSimplifyAllUses(User, V, TD);
-      
-      // If the recursive simplification ended up revisiting and deleting 'From'
-      // then we're done.
-      if (FromHandle == 0)
-        return;
+      SimplifiedVal = SimplifyInstruction(User, TD);
+      if (SimplifiedVal == 0) continue;
     }
+    
+    // Recursively simplify this user to the new value.
+    ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD);
+    From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
+    To = ToHandle;
+      
+    assert(ToHandle && "To value deleted by recursive simplification?");
+      
+    // If the recursive simplification ended up revisiting and deleting
+    // 'From' then we're done.
+    if (From == 0)
+      return;
   }
+  
+  // If 'From' has value handles referring to it, do a real RAUW to update them.
+  From->replaceAllUsesWith(To);
+  
   From->eraseFromParent();
 }