[KnownBits] Move AND, OR and XOR logic into KnownBits

Summary:
There are at least three clients for KnownBits calculations:
ValueTracking, SelectionDAG and GlobalISel. To reduce duplication the
common logic should be moved out of these clients and into KnownBits
itself.

This patch does this for AND, OR and XOR calculations by implementing
and using appropriate operator overloads KnownBits::operator& etc.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74060

1 files changed, 4 insertions, 15 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 713e09e..6b61983 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1134,10 +1134,7 @@ static void computeKnownBitsFromOperator(const Operator *I,
     computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
     computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
 
-    // Output known-1 bits are only known if set in both the LHS & RHS.
-    Known.One &= Known2.One;
-    // Output known-0 are known to be clear if zero in either the LHS | RHS.
-    Known.Zero |= Known2.Zero;
+    Known &= Known2;
 
     // and(x, add (x, -1)) is a common idiom that always clears the low bit;
     // here we handle the more general case of adding any odd number by
@@ -1158,22 +1155,14 @@ static void computeKnownBitsFromOperator(const Operator *I,
     computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
     computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
 
-    // Output known-0 bits are only known if clear in both the LHS & RHS.
-    Known.Zero &= Known2.Zero;
-    // Output known-1 are known to be set if set in either the LHS | RHS.
-    Known.One |= Known2.One;
+    Known |= Known2;
     break;
-  case Instruction::Xor: {
+  case Instruction::Xor:
     computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
     computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
 
-    // Output known-0 bits are known if clear or set in both the LHS & RHS.
-    APInt KnownZeroOut = (Known.Zero & Known2.Zero) | (Known.One & Known2.One);
-    // Output known-1 are known to be set if set in only one of the LHS, RHS.
-    Known.One = (Known.Zero & Known2.One) | (Known.One & Known2.Zero);
-    Known.Zero = std::move(KnownZeroOut);
+    Known ^= Known2;
     break;
-  }
   case Instruction::Mul: {
     bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
     computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, DemandedElts,