[ValueTracking] computeKnownBitsFromShiftOperator - merge zero/one callbacks to single KnownBits callback. NFCI.

Another cleanup for D90479 - handle the Known Ones/Zeros in a single callback, which will make it much easier to jump over to the KnownBits shift handling.

Author: RKSimon

llvm/lib/Analysis/ValueTracking.cpp

@@ -979,25 +979,22 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
 /// Compute known bits from a shift operator, including those with a
 /// non-constant shift amount. Known is the output of this function. Known2 is a
 /// pre-allocated temporary with the same bit width as Known and on return
-/// contains the known bit of the shift value source. KZF and KOF are
-/// operator-specific functions that, given the known-zero or known-one bits
-/// respectively, and a shift amount, compute the implied known-zero or
-/// known-one bits of the shift operator's result respectively for that shift
-/// amount. The results from calling KZF and KOF are conservatively combined for
-/// all permitted shift amounts.
+/// contains the known bit of the shift value source. KF is an
+/// operator-specific function that, given the known-bits and a shift amount,
+/// compute the implied known-bits of the shift operator's result respectively
+/// for that shift amount. The results from calling KF are conservatively
+/// combined for all permitted shift amounts.
 static void computeKnownBitsFromShiftOperator(
     const Operator *I, const APInt &DemandedElts, KnownBits &Known,
     KnownBits &Known2, unsigned Depth, const Query &Q,
-    function_ref<APInt(const APInt &, unsigned)> KZF,
-    function_ref<APInt(const APInt &, unsigned)> KOF) {
+    function_ref<KnownBits(const KnownBits &, unsigned)> KF) {
   unsigned BitWidth = Known.getBitWidth();
   computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
   computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
 
   if (Known.isConstant()) {
     unsigned ShiftAmt = Known.getConstant().getLimitedValue(BitWidth - 1);
-    Known.Zero = KZF(Known2.Zero, ShiftAmt);
-    Known.One = KOF(Known2.One, ShiftAmt);
+    Known = KF(Known2, ShiftAmt);
 
     // If the known bits conflict, this must be an overflowing left shift, so
     // the shift result is poison. We can return anything we want. Choose 0 for
@@ -1061,8 +1058,7 @@ static void computeKnownBitsFromShiftOperator(
         continue;
     }
 
-    Known.Zero &= KZF(Known2.Zero, ShiftAmt);
-    Known.One  &= KOF(Known2.One, ShiftAmt);
+    Known = KnownBits::commonBits(Known, KF(Known2, ShiftAmt));
   }
 
   // If the known bits conflict, the result is poison. Return a 0 and hope the
@@ -1227,56 +1223,50 @@ static void computeKnownBitsFromOperator(const Operator *I,
   case Instruction::Shl: {
     // (shl X, C1) & C2 == 0   iff   (X & C2 >>u C1) == 0
     bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
-    auto KZF = [NSW](const APInt &KnownZero, unsigned ShiftAmt) {
-      APInt KZResult = KnownZero << ShiftAmt;
-      KZResult.setLowBits(ShiftAmt); // Low bits known 0.
+    auto KF = [NSW](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
+      KnownBits Result;
+      Result.Zero = KnownShiftVal.Zero << ShiftAmt;
+      Result.One = KnownShiftVal.One << ShiftAmt;
+      // Low bits known zero.
+      Result.Zero.setLowBits(ShiftAmt);
       // If this shift has "nsw" keyword, then the result is either a poison
       // value or has the same sign bit as the first operand.
-      if (NSW && KnownZero.isSignBitSet())
-        KZResult.setSignBit();
-      return KZResult;
-    };
-
-    auto KOF = [NSW](const APInt &KnownOne, unsigned ShiftAmt) {
-      APInt KOResult = KnownOne << ShiftAmt;
-      if (NSW && KnownOne.isSignBitSet())
-        KOResult.setSignBit();
-      return KOResult;
+      if (NSW) {
+        if (KnownShiftVal.Zero.isSignBitSet())
+          Result.Zero.setSignBit();
+        if (KnownShiftVal.One.isSignBitSet())
+          Result.One.setSignBit();
+      }
+      return Result;
     };
-
     computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
-                                      KZF, KOF);
+                                      KF);
     break;
   }
   case Instruction::LShr: {
     // (lshr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
-    auto KZF = [](const APInt &KnownZero, unsigned ShiftAmt) {
-      APInt KZResult = KnownZero.lshr(ShiftAmt);
+    auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
+      KnownBits Result;
+      Result.Zero = KnownShiftVal.Zero.lshr(ShiftAmt);
+      Result.One = KnownShiftVal.One.lshr(ShiftAmt);
       // High bits known zero.
-      KZResult.setHighBits(ShiftAmt);
-      return KZResult;
-    };
-
-    auto KOF = [](const APInt &KnownOne, unsigned ShiftAmt) {
-      return KnownOne.lshr(ShiftAmt);
+      Result.Zero.setHighBits(ShiftAmt);
+      return Result;
     };
-
     computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
-                                      KZF, KOF);
+                                      KF);
     break;
   }
   case Instruction::AShr: {
     // (ashr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
-    auto KZF = [](const APInt &KnownZero, unsigned ShiftAmt) {
-      return KnownZero.ashr(ShiftAmt);
+    auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
+      KnownBits Result;
+      Result.Zero = KnownShiftVal.Zero.ashr(ShiftAmt);
+      Result.One = KnownShiftVal.One.ashr(ShiftAmt);
+      return Result;
     };
-
-    auto KOF = [](const APInt &KnownOne, unsigned ShiftAmt) {
-      return KnownOne.ashr(ShiftAmt);
-    };
-
     computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
-                                      KZF, KOF);
+                                      KF);
     break;
   }
   case Instruction::Sub: {