Add Constant Hoisting Pass

Retry commit r200022 with a fix for the build bot errors. Constant expressions
have (unlike instructions) module scope use lists and therefore may have users
in different functions. The fix is to simply ignore these out-of-function uses.

llvm-svn: 200034

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 6c8e2f83a4f..a561c5190ac 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2945,6 +2945,9 @@ void SelectionDAGBuilder::visitBitCast(const User &I) {
   if (DestVT != N.getValueType())
     setValue(&I, DAG.getNode(ISD::BITCAST, getCurSDLoc(),
                              DestVT, N)); // convert types.
+  else if(ConstantSDNode *C = dyn_cast<ConstantSDNode>(N))
+    setValue(&I, DAG.getConstant(C->getAPIntValue(), C->getValueType(0),
+                                 /*isTarget=*/false, /*isOpaque*/true));
   else
     setValue(&I, N);            // noop cast.
 }