[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

2 files changed, 14 insertions, 9 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 0534909a5e4..278b65c68f8 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -1093,7 +1093,7 @@ static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
     APInt Mult(W, i);
     unsigned TwoFactors = Mult.countTrailingZeros();
     T += TwoFactors;
-    Mult = Mult.lshr(TwoFactors);
+    Mult.lshrInPlace(TwoFactors);
     OddFactorial *= Mult;
   }
 
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 2079c1b33ae..974ec02598f 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -661,8 +661,10 @@ static void computeKnownBitsFromAssume(const Value *V, APInt &KnownZero,
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them to known
       // bits in V shifted to the right by C.
-      KnownZero |= RHSKnownZero.lshr(C->getZExtValue());
-      KnownOne  |= RHSKnownOne.lshr(C->getZExtValue());
+      RHSKnownZero.lshrInPlace(C->getZExtValue());
+      KnownZero |= RHSKnownZero;
+      RHSKnownOne.lshrInPlace(C->getZExtValue());
+      KnownOne  |= RHSKnownOne;
     // assume(~(v << c) = a)
     } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
                                    m_Value(A))) &&
@@ -672,8 +674,10 @@ static void computeKnownBitsFromAssume(const Value *V, APInt &KnownZero,
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them inverted
       // to known bits in V shifted to the right by C.
-      KnownZero |= RHSKnownOne.lshr(C->getZExtValue());
-      KnownOne  |= RHSKnownZero.lshr(C->getZExtValue());
+      RHSKnownOne.lshrInPlace(C->getZExtValue());
+      KnownZero |= RHSKnownOne;
+      RHSKnownZero.lshrInPlace(C->getZExtValue());
+      KnownOne  |= RHSKnownZero;
     // assume(v >> c = a)
     } else if (match(Arg,
                      m_c_ICmp(Pred, m_CombineOr(m_LShr(m_V, m_ConstantInt(C)),
@@ -1111,10 +1115,11 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero,
   }
   case Instruction::LShr: {
     // (ushr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
-    auto KZF = [BitWidth](const APInt &KnownZero, unsigned ShiftAmt) {
-      return KnownZero.lshr(ShiftAmt) |
-             // High bits known zero.
-             APInt::getHighBitsSet(BitWidth, ShiftAmt);
+    auto KZF = [](const APInt &KnownZero, unsigned ShiftAmt) {
+      APInt KZResult = KnownZero.lshr(ShiftAmt);
+      // High bits known zero.
+      KZResult.setHighBits(ShiftAmt);
+      return KZResult;
     };
 
     auto KOF = [](const APInt &KnownOne, unsigned ShiftAmt) {