Add a minor optimization: if we haven't changed the operands of an

add, there is no need to scan the world to find the same add again.
This invalidates the previous testcase, which wasn't wonderful anyway,
because it needed a run of instcombine to permute the use-lists in 
just the right way to before GVN was run (so it was really fragile).
Not a big loss.

llvm-svn: 90973

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/PHITransAddr.cpp b/llvm/lib/Analysis/PHITransAddr.cpp
index a1b2afbaf7f..07e291971a8 100644
--- a/llvm/lib/Analysis/PHITransAddr.cpp
+++ b/llvm/lib/Analysis/PHITransAddr.cpp
@@ -275,6 +275,10 @@ Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
       RemoveInstInputs(LHS, InstInputs);
       return AddAsInput(Res);
     }
+
+    // If we didn't modify the add, just return it.
+    if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1))
+      return Inst;
     
     // Otherwise, see if we have this add available somewhere.
     for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end();