[APInt] Use lshrInPlace to replace lshr where possible

This patch uses lshrInPlace to replace code where the object that lshr is called on is being overwritten with the result.

This adds an lshrInPlace(const APInt &) version as well.

Differential Revision: https://reviews.llvm.org/D32155

llvm-svn: 300566

1 files changed, 7 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 2756e276c6a..ce892eb3ec1 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -929,8 +929,8 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
                                KnownZero, KnownOne, TLO, Depth+1))
         return true;
       assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
-      KnownZero = KnownZero.lshr(ShAmt);
-      KnownOne  = KnownOne.lshr(ShAmt);
+      KnownZero.lshrInPlace(ShAmt);
+      KnownOne.lshrInPlace(ShAmt);
 
       KnownZero.setHighBits(ShAmt);  // High bits known zero.
     }
@@ -970,8 +970,8 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
                                KnownZero, KnownOne, TLO, Depth+1))
         return true;
       assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
-      KnownZero = KnownZero.lshr(ShAmt);
-      KnownOne  = KnownOne.lshr(ShAmt);
+      KnownZero.lshrInPlace(ShAmt);
+      KnownOne.lshrInPlace(ShAmt);
 
       // Handle the sign bit, adjusted to where it is now in the mask.
       APInt SignBit = APInt::getSignBit(BitWidth).lshr(ShAmt);
@@ -1207,7 +1207,8 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
 
         APInt HighBits = APInt::getHighBitsSet(OperandBitWidth,
                                                OperandBitWidth - BitWidth);
-        HighBits = HighBits.lshr(ShAmt->getZExtValue()).trunc(BitWidth);
+        HighBits.lshrInPlace(ShAmt->getZExtValue());
+        HighBits = HighBits.trunc(BitWidth);
 
         if (ShAmt->getZExtValue() < BitWidth && !(HighBits & NewMask)) {
           // None of the shifted in bits are needed.  Add a truncate of the
@@ -2055,7 +2056,7 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
         } else {
           ShiftBits = C1.countTrailingZeros();
         }
-        NewC = NewC.lshr(ShiftBits);
+        NewC.lshrInPlace(ShiftBits);
         if (ShiftBits && NewC.getMinSignedBits() <= 64 &&
           isLegalICmpImmediate(NewC.getSExtValue())) {
           auto &DL = DAG.getDataLayout();