[LoopUnrolling] Handle cast instructions.

During estimation of unrolling effect we should be able to propagate
constants through casts.

Differential Revision: http://reviews.llvm.org/D10207

llvm-svn: 242257

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index d78db6c369b..ff1acc1f579 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -436,6 +436,21 @@ private:
 
     return true;
   }
+
+  bool visitCastInst(CastInst &I) {
+    // Propagate constants through casts.
+    Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+    if (!COp)
+      COp = SimplifiedValues.lookup(I.getOperand(0));
+    if (COp)
+      if (Constant *C =
+              ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) {
+        SimplifiedValues[&I] = C;
+        return true;
+      }
+
+    return Base::visitCastInst(I);
+  }
 };
 } // namespace