[DAG] propagate FMF for all FPMathOperators

This is a simple hack based on what's proposed in D37686, but we can extend it if needed in follow-ups. 
It gets us most of the FMF functionality that we want without adding any state bits to the flags. It 
also intentionally leaves out non-FMF flags (nsw, etc) to minimize the patch.

It should provide a superset of the functionality from D46563 - the extra tests show propagation and 
codegen diffs for fcmp, vecreduce, and FP libcalls.

The PPC log2() test shows the limits of this most basic approach - we only applied 'afn' to the last 
node created for the call. AFAIK, there aren't any libcall optimizations based on the flags currently, 
so that shouldn't make any difference.

Differential Revision: https://reviews.llvm.org/D46854

llvm-svn: 332358

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index bcea94ec5a4..c5c02bff793 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -687,6 +687,13 @@ public:
   SDValue getValue(const Value *V);
   bool findValue(const Value *V) const;
 
+  /// Return the SDNode for the specified IR value if it exists.
+  SDNode *getNodeForIRValue(const Value *V) {
+    if (NodeMap.find(V) == NodeMap.end())
+      return nullptr;
+    return NodeMap[V].getNode();
+  }
+
   SDValue getNonRegisterValue(const Value *V);
   SDValue getValueImpl(const Value *V);