[DAG] Expose NoSignedWrap, NoUnsignedWrap and Exact flags to SelectionDAG.

This patch modifies SelectionDAGBuilder to construct SDNodes with associated
NoSignedWrap, NoUnsignedWrap and Exact flags coming from IR BinaryOperator
instructions.

Added a new SDNode type called 'BinaryWithFlagsSDNode' to allow accessing
nsw/nuw/exact flags during codegen.

Patch by Marcello Maggioni.

llvm-svn: 210467
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 3731aea..75bbbe7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2617,7 +2617,8 @@
   if (ShAmt) {
     // TODO: For UDIV use SRL instead of SRA.
     SDValue Amt = DAG.getConstant(ShAmt, getShiftAmountTy(Op1.getValueType()));
-    Op1 = DAG.getNode(ISD::SRA, dl, Op1.getValueType(), Op1, Amt);
+    Op1 = DAG.getNode(ISD::SRA, dl, Op1.getValueType(), Op1, Amt, false, false,
+                      true);
     d = d.ashr(ShAmt);
   }