[DAGCombiner] Generalize masking of constant rotates.

We don't need a mask of a rotation result to be a constant splat - any constant scalar/vector can be usefully folded.

Followup to D13851.

llvm-svn: 251197

1 files changed, 10 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 53d47c7165e..7cc318ec423 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3796,7 +3796,7 @@ SDValue DAGCombiner::visitOR(SDNode *N) {
 /// Match "(X shl/srl V1) & V2" where V2 may not be present.
 static bool MatchRotateHalf(SDValue Op, SDValue &Shift, SDValue &Mask) {
   if (Op.getOpcode() == ISD::AND) {
-    if (isConstOrConstSplat(Op.getOperand(1))) {
+    if (isConstantIntBuildVectorOrConstantInt(Op.getOperand(1))) {
       Mask = Op.getOperand(1);
       Op = Op.getOperand(0);
     } else {
@@ -3997,18 +3997,23 @@ SDNode *DAGCombiner::MatchRotate(SDValue LHS, SDValue RHS, SDLoc DL) {
 
     // If there is an AND of either shifted operand, apply it to the result.
     if (LHSMask.getNode() || RHSMask.getNode()) {
-      APInt Mask = APInt::getAllOnesValue(EltSizeInBits);
+      APInt AllBits = APInt::getAllOnesValue(EltSizeInBits);
+      SDValue Mask = DAG.getConstant(AllBits, DL, VT);
 
       if (LHSMask.getNode()) {
         APInt RHSBits = APInt::getLowBitsSet(EltSizeInBits, LShVal);
-        Mask &= isConstOrConstSplat(LHSMask)->getAPIntValue() | RHSBits;
+        Mask = DAG.getNode(ISD::AND, DL, VT, Mask,
+                           DAG.getNode(ISD::OR, DL, VT, LHSMask,
+                                       DAG.getConstant(RHSBits, DL, VT)));
       }
       if (RHSMask.getNode()) {
         APInt LHSBits = APInt::getHighBitsSet(EltSizeInBits, RShVal);
-        Mask &= isConstOrConstSplat(RHSMask)->getAPIntValue() | LHSBits;
+        Mask = DAG.getNode(ISD::AND, DL, VT, Mask,
+                           DAG.getNode(ISD::OR, DL, VT, RHSMask,
+                                       DAG.getConstant(LHSBits, DL, VT)));
       }
 
-      Rot = DAG.getNode(ISD::AND, DL, VT, Rot, DAG.getConstant(Mask, DL, VT));
+      Rot = DAG.getNode(ISD::AND, DL, VT, Rot, Mask);
     }
 
     return Rot.getNode();