[ARM] Remove redundant computeKnownBits helper.

Move the BFI logic to computeKnownBitsForTargetNode, and delete
the redundant CMOV logic.

This is intended as a cleanup, but it's probably possible to construct
a case where moving the BFI logic allows more combines.

Differential Revision: https://reviews.llvm.org/D31795

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300752 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 4ea04b191d30eba891880875ff05792d3334ca31..92d1d86a285b501fcfddd06818c388c3591a7b4e 100644 (file)
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -11694,34 +11694,6 @@ static SDValue PerformExtendCombine(SDNode *N, SelectionDAG &DAG,
   return SDValue();
 }
 
-static void computeKnownBits(SelectionDAG &DAG, SDValue Op, APInt &KnownZero,
-                             APInt &KnownOne) {
-  if (Op.getOpcode() == ARMISD::BFI) {
-    // Conservatively, we can recurse down the first operand
-    // and just mask out all affected bits.
-    computeKnownBits(DAG, Op.getOperand(0), KnownZero, KnownOne);
-
-    // The operand to BFI is already a mask suitable for removing the bits it
-    // sets.
-    ConstantSDNode *CI = cast<ConstantSDNode>(Op.getOperand(2));
-    const APInt &Mask = CI->getAPIntValue();
-    KnownZero &= Mask;
-    KnownOne &= Mask;
-    return;
-  }
-  if (Op.getOpcode() == ARMISD::CMOV) {
-    APInt KZ2(KnownZero.getBitWidth(), 0);
-    APInt KO2(KnownOne.getBitWidth(), 0);
-    computeKnownBits(DAG, Op.getOperand(0), KnownZero, KnownOne);
-    computeKnownBits(DAG, Op.getOperand(1), KZ2, KO2);
-
-    KnownZero &= KZ2;
-    KnownOne &= KO2;
-    return;
-  }
-  return DAG.computeKnownBits(Op, KnownZero, KnownOne);
-}
-
 SDValue ARMTargetLowering::PerformCMOVToBFICombine(SDNode *CMOV, SelectionDAG &DAG) const {
   // If we have a CMOV, OR and AND combination such as:
   //   if (x & CN)
@@ -11783,7 +11755,7 @@ SDValue ARMTargetLowering::PerformCMOVToBFICombine(SDNode *CMOV, SelectionDAG &D
   // Lastly, can we determine that the bits defined by OrCI
   // are zero in Y?
   APInt KnownZero, KnownOne;
-  computeKnownBits(DAG, Y, KnownZero, KnownOne);
+  DAG.computeKnownBits(Y, KnownZero, KnownOne);
   if ((OrCI & KnownZero) != OrCI)
     return SDValue();
 
@@ -12663,6 +12635,19 @@ void ARMTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     }
     }
   }
+  case ARMISD::BFI: {
+    // Conservatively, we can recurse down the first operand
+    // and just mask out all affected bits.
+    DAG.computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, Depth + 1);
+
+    // The operand to BFI is already a mask suitable for removing the bits it
+    // sets.
+    ConstantSDNode *CI = cast<ConstantSDNode>(Op.getOperand(2));
+    const APInt &Mask = CI->getAPIntValue();
+    KnownZero &= Mask;
+    KnownOne &= Mask;
+    return;
+  }
   }
 }