refactor of visitFADD for AllowNewConst cases

Summary: Refactoring for all constant cases which require AllowNewConst and some staging for future fmf usage.

Reviewers: spatel, hfinkel, wristow

Reviewed By: spatel

Subscribers: nhaehnle

Differential Revision: https://reviews.llvm.org/D48289

llvm-svn: 334984

1 files changed, 20 insertions, 17 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d6f815da242..b66b2f8730a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10335,12 +10335,24 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
         return N0;
   }
 
-  // If 'unsafe math' is enabled, fold lots of things.
-  if (Options.UnsafeFPMath) {
-    // No FP constant should be created after legalization as Instruction
-    // Selection pass has a hard time dealing with FP constants.
-    bool AllowNewConst = (Level < AfterLegalizeDAG);
+  // No FP constant should be created after legalization as Instruction
+  // Selection pass has a hard time dealing with FP constants.
+  bool AllowNewConst = (Level < AfterLegalizeDAG);
+
+  // TODO: fmf test for NaNs could be done here too
+  if (Options.UnsafeFPMath && AllowNewConst) {
+    // If allowed, fold (fadd (fneg x), x) -> 0.0
+    if (N0.getOpcode() == ISD::FNEG && N0.getOperand(0) == N1)
+      return DAG.getConstantFP(0.0, DL, VT);
+
+    // If allowed, fold (fadd x, (fneg x)) -> 0.0
+    if (N1.getOpcode() == ISD::FNEG && N1.getOperand(0) == N0)
+      return DAG.getConstantFP(0.0, DL, VT);
+  }
 
+  // If 'unsafe math' is enabled, fold lots of things.
+  // TODO: fmf testing for reassoc/nsz could be done here too
+  if (Options.UnsafeFPMath && AllowNewConst) {
     // fadd (fadd x, c1), c2 -> fadd x, c1 + c2
     if (N1CFP && N0.getOpcode() == ISD::FADD &&
         isConstantFPBuildVectorOrConstantFP(N0.getOperand(1))) {
@@ -10348,14 +10360,6 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
       return DAG.getNode(ISD::FADD, DL, VT, N0.getOperand(0), NewC, Flags);
     }
 
-    // If allowed, fold (fadd (fneg x), x) -> 0.0
-    if (AllowNewConst && N0.getOpcode() == ISD::FNEG && N0.getOperand(0) == N1)
-      return DAG.getConstantFP(0.0, DL, VT);
-
-    // If allowed, fold (fadd x, (fneg x)) -> 0.0
-    if (AllowNewConst && N1.getOpcode() == ISD::FNEG && N1.getOperand(0) == N0)
-      return DAG.getConstantFP(0.0, DL, VT);
-
     // We can fold chains of FADD's of the same value into multiplications.
     // This transform is not safe in general because we are reducing the number
     // of rounding steps.
@@ -10402,7 +10406,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
         }
       }
 
-      if (N0.getOpcode() == ISD::FADD && AllowNewConst) {
+      if (N0.getOpcode() == ISD::FADD) {
         bool CFP00 = isConstantFPBuildVectorOrConstantFP(N0.getOperand(0));
         // (fadd (fadd x, x), x) -> (fmul x, 3.0)
         if (!CFP00 && N0.getOperand(0) == N0.getOperand(1) &&
@@ -10412,7 +10416,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
         }
       }
 
-      if (N1.getOpcode() == ISD::FADD && AllowNewConst) {
+      if (N1.getOpcode() == ISD::FADD) {
         bool CFP10 = isConstantFPBuildVectorOrConstantFP(N1.getOperand(0));
         // (fadd x, (fadd x, x)) -> (fmul x, 3.0)
         if (!CFP10 && N1.getOperand(0) == N1.getOperand(1) &&
@@ -10423,8 +10427,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
       }
 
       // (fadd (fadd x, x), (fadd x, x)) -> (fmul x, 4.0)
-      if (AllowNewConst &&
-          N0.getOpcode() == ISD::FADD && N1.getOpcode() == ISD::FADD &&
+      if (N0.getOpcode() == ISD::FADD && N1.getOpcode() == ISD::FADD &&
           N0.getOperand(0) == N0.getOperand(1) &&
           N1.getOperand(0) == N1.getOperand(1) &&
           N0.getOperand(0) == N1.getOperand(0)) {