[PATCH] Handle cast instructions in complete loop unroll heuristic.

[Michael Zolotukhin]

- Fallback to Base visitor if failed to constant fold (and only then call simplifyInstWithSCEV).
- Add TODO to visitCast.


http://reviews.llvm.org/D10207

Files:
  lib/Transforms/Scalar/LoopUnrollPass.cpp

Index: lib/Transforms/Scalar/LoopUnrollPass.cpp
===================================================================
--- lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -440,6 +440,23 @@
     return true;
   }
 
+  bool visitCastInst(CastInst &I) {
+    // Propagate constants through ptrtoint.
+    Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+    if (!COp)
+      COp = SimplifiedValues.lookup(I.getOperand(0));
+    // TODO: If we do ptrtoint of an expression, which is present in
+    // SimplifiedOffsets, we can propagate this information.
+    if (COp)
+      if (Constant *C =
+              ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) {
+        SimplifiedValues[&I] = C;
+        return true;
+      }
+
+    return Base::visitCastInst(I);
+  }
+
   bool visitCmpInst(CmpInst &I) {
     Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);

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