[llvm-commits] [llvm] r105501 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Fri Jun  4 18:16:05 2010
New Revision: 105501

URL: http://llvm.org/viewvc/llvm-project?rev=105501&view=rev
Log:
Don't track users of undef values; they aren't interesting for
register pressure.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=105501&r1=105500&r2=105501&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Fri Jun  4 18:16:05 2010
@@ -2095,8 +2095,12 @@
     } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
       if (!Inserted.insert(U)) continue;
       const Value *V = U->getValue();
-      if (const Instruction *Inst = dyn_cast<Instruction>(V))
+      if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
+        // Look for instructions defined outside the loop.
         if (L->contains(Inst)) continue;
+      } else if (isa<UndefValue>(V))
+        // Undef doesn't have a live range, so it doesn't matter.
+        continue;
       for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
            UI != UE; ++UI) {
         const Instruction *UserInst = dyn_cast<Instruction>(*UI);