[DAG] clean up foldSelectOfConstants(); NFCI

Rename variables, simplify logic. 
Not clear yet why we don't handle a target with ZeroOrNegativeOneBooleanContent too.

llvm-svn: 283613

1 files changed, 14 insertions, 19 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3f62f0af9e1..1f298427499 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5108,13 +5108,14 @@ static SDValue combineMinNumMaxNum(const SDLoc &DL, EVT VT, SDValue LHS,
 
 // TODO: We should handle other cases of selecting between {-1,0,1} here.
 SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
-  SDValue N0 = N->getOperand(0);
+  SDValue Cond = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   SDValue N2 = N->getOperand(2);
   EVT VT = N->getValueType(0);
-  EVT VT0 = N0.getValueType();
+  EVT CondVT = Cond.getValueType();
+  SDLoc DL(N);
 
-  // fold (select C, 0, 1) -> (xor C, 1)
+  // fold (select Cond, 0, 1) -> (xor Cond, 1)
   // We can't do this reliably if integer based booleans have different contents
   // to floating point based booleans. This is because we can't tell whether we
   // have an integer-based boolean or a floating-point-based boolean unless we
@@ -5124,23 +5125,17 @@ SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
   // in another basic block or it could require searching a complicated
   // expression.
   if (VT.isInteger() &&
-      (VT0 == MVT::i1 || (VT0.isInteger() &&
-                          TLI.getBooleanContents(false, false) ==
-                              TLI.getBooleanContents(false, true) &&
-                          TLI.getBooleanContents(false, false) ==
-                              TargetLowering::ZeroOrOneBooleanContent)) &&
+      (CondVT == MVT::i1 || (CondVT.isInteger() &&
+                             TLI.getBooleanContents(false, true) ==
+                                 TargetLowering::ZeroOrOneBooleanContent &&
+                             TLI.getBooleanContents(false, false) ==
+                                 TargetLowering::ZeroOrOneBooleanContent)) &&
       isNullConstant(N1) && isOneConstant(N2)) {
-    SDValue XORNode;
-    if (VT == VT0) {
-      SDLoc DL(N);
-      return DAG.getNode(ISD::XOR, DL, VT0, N0, DAG.getConstant(1, DL, VT0));
-    }
-    SDLoc DL0(N0);
-    XORNode = DAG.getNode(ISD::XOR, DL0, VT0, N0, DAG.getConstant(1, DL0, VT0));
-    AddToWorklist(XORNode.getNode());
-    if (VT.bitsGT(VT0))
-      return DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N), VT, XORNode);
-    return DAG.getNode(ISD::TRUNCATE, SDLoc(N), VT, XORNode);
+    SDValue NotCond = DAG.getNode(ISD::XOR, DL, CondVT, Cond,
+                                  DAG.getConstant(1, DL, CondVT));
+    if (VT.bitsEq(CondVT))
+      return NotCond;
+    return DAG.getZExtOrTrunc(NotCond, DL, VT);
   }
 
   return SDValue();