[SelectionDAG] Rename and clarify visitFMULForFMADCombine (NFC)

Summary: Suggested by @spatel in D26602.

Reviewers: spatel, hfinkel

Subscribers: spatel, llvm-commits

Differential Revision: https://reviews.llvm.org/D27260

llvm-svn: 288336

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a76c7a15b0d..57d866ad730 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -326,7 +326,7 @@ namespace {
 
     SDValue visitFADDForFMACombine(SDNode *N);
     SDValue visitFSUBForFMACombine(SDNode *N);
-    SDValue visitFMULForFMACombine(SDNode *N);
+    SDValue visitFMULForFMADistributiveCombine(SDNode *N);
 
     SDValue XformToShuffleWithZero(SDNode *N);
     SDValue ReassociateOps(unsigned Opc, const SDLoc &DL, SDValue LHS,
@@ -8380,8 +8380,10 @@ SDValue DAGCombiner::visitFSUBForFMACombine(SDNode *N) {
   return SDValue();
 }
 
-/// Try to perform FMA combining on a given FMUL node.
-SDValue DAGCombiner::visitFMULForFMACombine(SDNode *N) {
+/// Try to perform FMA combining on a given FMUL node based on the distributive
+/// law x * (y + 1) = x * y + x and variants thereof (commuted versions,
+/// subtraction instead of addition).
+SDValue DAGCombiner::visitFMULForFMADistributiveCombine(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   EVT VT = N->getValueType(0);
@@ -8776,7 +8778,7 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
   }
 
   // FMUL -> FMA combines:
-  if (SDValue Fused = visitFMULForFMACombine(N)) {
+  if (SDValue Fused = visitFMULForFMADistributiveCombine(N)) {
     AddToWorklist(Fused.getNode());
     return Fused;
   }