[KnownBits] Remove hasConflict() assertions (#94568)

Allow KnownBits to represent "always poison" values via conflict.

close: #94436

Author: c8ef

llvm/include/llvm/Support/KnownBits.h

@@ -48,7 +48,6 @@ struct KnownBits {
 
   /// Returns true if we know the value of all bits.
   bool isConstant() const {
-    assert(!hasConflict() && "KnownBits conflict!");
     return Zero.popcount() + One.popcount() == getBitWidth();
   }
 
@@ -74,16 +73,10 @@ struct KnownBits {
   }
 
   /// Returns true if value is all zero.
-  bool isZero() const {
-    assert(!hasConflict() && "KnownBits conflict!");
-    return Zero.isAllOnes();
-  }
+  bool isZero() const { return Zero.isAllOnes(); }
 
   /// Returns true if value is all one bits.
-  bool isAllOnes() const {
-    assert(!hasConflict() && "KnownBits conflict!");
-    return One.isAllOnes();
-  }
+  bool isAllOnes() const { return One.isAllOnes(); }
 
   /// Make all bits known to be zero and discard any previous information.
   void setAllZero() {

llvm/lib/Analysis/ValueTracking.cpp

@@ -1158,7 +1158,6 @@ static void computeKnownBitsFromOperator(const Operator *I,
           Known.makeNonNegative();
       }
 
-      assert(!Known.hasConflict() && "Bits known to be one AND zero?");
       break;
     }
 
@@ -2055,8 +2054,6 @@ void computeKnownBits(const Value *V, const APInt &DemandedElts,
 
   // Check whether we can determine known bits from context such as assumes.
   computeKnownBitsFromContext(V, Known, Depth, Q);
-
-  assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
 }
 
 /// Try to detect a recurrence that the value of the induction variable is

llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

@@ -607,7 +607,6 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
   }
   }
 
-  assert(!Known.hasConflict() && "Bits known to be one AND zero?");
   LLVM_DEBUG(dumpResult(MI, Known, Depth));
 
   // Update the cache.

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -4212,7 +4212,6 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     break;
   }
 
-  assert(!Known.hasConflict() && "Bits known to be one AND zero?");
   return Known;
 }
 

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -1436,11 +1436,9 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op1, DemandedBits, DemandedElts, Known, TLO,
                              Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     if (SimplifyDemandedBits(Op0, ~Known.Zero & DemandedBits, DemandedElts,
                              Known2, TLO, Depth + 1))
       return true;
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If all of the demanded bits are known one on one side, return the other.
     // These bits cannot contribute to the result of the 'and'.
@@ -1488,7 +1486,7 @@ bool TargetLowering::SimplifyDemandedBits(
       }
       return true;
     }
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
+
     if (SimplifyDemandedBits(Op0, ~Known.One & DemandedBits, DemandedElts,
                              Known2, TLO, Depth + 1)) {
       if (Flags.hasDisjoint()) {
@@ -1497,7 +1495,6 @@ bool TargetLowering::SimplifyDemandedBits(
       }
       return true;
     }
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If all of the demanded bits are known zero on one side, return the other.
     // These bits cannot contribute to the result of the 'or'.
@@ -1563,11 +1560,9 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op1, DemandedBits, DemandedElts, Known, TLO,
                              Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     if (SimplifyDemandedBits(Op0, DemandedBits, DemandedElts, Known2, TLO,
                              Depth + 1))
       return true;
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If all of the demanded bits are known zero on one side, return the other.
     // These bits cannot contribute to the result of the 'xor'.
@@ -1663,8 +1658,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op.getOperand(1), DemandedBits, DemandedElts,
                              Known2, TLO, Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If the operands are constants, see if we can simplify them.
     if (ShrinkDemandedConstant(Op, DemandedBits, DemandedElts, TLO))
@@ -1680,8 +1673,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op.getOperand(1), DemandedBits, DemandedElts,
                              Known2, TLO, Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // Only known if known in both the LHS and RHS.
     Known = Known.intersectWith(Known2);
@@ -1693,8 +1684,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op.getOperand(2), DemandedBits, DemandedElts,
                              Known2, TLO, Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If the operands are constants, see if we can simplify them.
     if (ShrinkDemandedConstant(Op, DemandedBits, DemandedElts, TLO))
@@ -1819,7 +1808,6 @@ bool TargetLowering::SimplifyDemandedBits(
         }
         return true;
       }
-      assert(!Known.hasConflict() && "Bits known to be one AND zero?");
       Known.Zero <<= ShAmt;
       Known.One <<= ShAmt;
       // low bits known zero.
@@ -1993,7 +1981,6 @@ bool TargetLowering::SimplifyDemandedBits(
       if (SimplifyDemandedBits(Op0, InDemandedMask, DemandedElts, Known, TLO,
                                Depth + 1))
         return true;
-      assert(!Known.hasConflict() && "Bits known to be one AND zero?");
       Known.Zero.lshrInPlace(ShAmt);
       Known.One.lshrInPlace(ShAmt);
       // High bits known zero.
@@ -2090,7 +2077,6 @@ bool TargetLowering::SimplifyDemandedBits(
       if (SimplifyDemandedBits(Op0, InDemandedMask, DemandedElts, Known, TLO,
                                Depth + 1))
         return true;
-      assert(!Known.hasConflict() && "Bits known to be one AND zero?");
       Known.Zero.lshrInPlace(ShAmt);
       Known.One.lshrInPlace(ShAmt);
 
@@ -2385,7 +2371,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op0, InputDemandedBits, DemandedElts, Known, TLO,
                              Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
 
     // If the sign bit of the input is known set or clear, then we know the
     // top bits of the result.
@@ -2458,7 +2443,6 @@ bool TargetLowering::SimplifyDemandedBits(
       }
       return true;
     }
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     assert(Known.getBitWidth() == InBits && "Src width has changed?");
     Known = Known.zext(BitWidth);
 
@@ -2508,7 +2492,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Src, InDemandedBits, InDemandedElts, Known, TLO,
                              Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     assert(Known.getBitWidth() == InBits && "Src width has changed?");
 
     // If the sign bit is known one, the top bits match.
@@ -2554,7 +2537,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Src, InDemandedBits, InDemandedElts, Known, TLO,
                              Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     assert(Known.getBitWidth() == InBits && "Src width has changed?");
     Known = Known.anyext(BitWidth);
 
@@ -2620,7 +2602,6 @@ bool TargetLowering::SimplifyDemandedBits(
       break;
     }
 
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     break;
   }
   case ISD::AssertZext: {
@@ -2631,7 +2612,6 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Op.getOperand(0), ~InMask | DemandedBits, Known,
                              TLO, Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
 
     Known.Zero |= ~InMask;
     Known.One &= (~Known.Zero);

llvm/lib/IR/ConstantRange.cpp

@@ -58,8 +58,8 @@ ConstantRange::ConstantRange(APInt L, APInt U)
 
 ConstantRange ConstantRange::fromKnownBits(const KnownBits &Known,
                                            bool IsSigned) {
-  assert(!Known.hasConflict() && "Expected valid KnownBits");
-
+  if (Known.hasConflict())
+    return getEmpty(Known.getBitWidth());
   if (Known.isUnknown())
     return getFull(Known.getBitWidth());
 

llvm/lib/Support/KnownBits.cpp

@@ -18,11 +18,8 @@
 
 using namespace llvm;
 
-static KnownBits computeForAddCarry(
-    const KnownBits &LHS, const KnownBits &RHS,
-    bool CarryZero, bool CarryOne) {
-  assert(!(CarryZero && CarryOne) &&
-         "Carry can't be zero and one at the same time");
+static KnownBits computeForAddCarry(const KnownBits &LHS, const KnownBits &RHS,
+                                    bool CarryZero, bool CarryOne) {
 
   APInt PossibleSumZero = LHS.getMaxValue() + RHS.getMaxValue() + !CarryZero;
   APInt PossibleSumOne = LHS.getMinValue() + RHS.getMinValue() + CarryOne;
@@ -37,9 +34,6 @@ static KnownBits computeForAddCarry(
   APInt CarryKnownUnion = std::move(CarryKnownZero) | CarryKnownOne;
   APInt Known = std::move(LHSKnownUnion) & RHSKnownUnion & CarryKnownUnion;
 
-  assert((PossibleSumZero & Known) == (PossibleSumOne & Known) &&
-         "known bits of sum differ");
-
   // Compute known bits of the result.
   KnownBits KnownOut;
   KnownOut.Zero = ~std::move(PossibleSumZero) & Known;
@@ -608,14 +602,12 @@ KnownBits KnownBits::abs(bool IntMinIsPoison) const {
     }
   }
 
-  assert(!KnownAbs.hasConflict() && "Bad Output");
   return KnownAbs;
 }
 
 static KnownBits computeForSatAddSub(bool Add, bool Signed,
                                      const KnownBits &LHS,
                                      const KnownBits &RHS) {
-  assert(!LHS.hasConflict() && !RHS.hasConflict() && "Bad inputs");
   // We don't see NSW even for sadd/ssub as we want to check if the result has
   // signed overflow.
   KnownBits Res =
@@ -715,7 +707,6 @@ static KnownBits computeForSatAddSub(bool Add, bool Signed,
     // We know whether or not we overflowed.
     if (!(*Overflow)) {
       // No overflow.
-      assert(!Res.hasConflict() && "Bad Output");
       return Res;
     }
 
@@ -737,7 +728,6 @@ static KnownBits computeForSatAddSub(bool Add, bool Signed,
 
     Res.One = C;
     Res.Zero = ~C;
-    assert(!Res.hasConflict() && "Bad Output");
     return Res;
   }
 
@@ -757,7 +747,6 @@ static KnownBits computeForSatAddSub(bool Add, bool Signed,
     Res.One.clearAllBits();
   }
 
-  assert(!Res.hasConflict() && "Bad Output");
   return Res;
 }
 
@@ -808,8 +797,7 @@ KnownBits KnownBits::avgCeilU(const KnownBits &LHS, const KnownBits &RHS) {
 KnownBits KnownBits::mul(const KnownBits &LHS, const KnownBits &RHS,
                          bool NoUndefSelfMultiply) {
   unsigned BitWidth = LHS.getBitWidth();
-  assert(BitWidth == RHS.getBitWidth() && !LHS.hasConflict() &&
-         !RHS.hasConflict() && "Operand mismatch");
+  assert(BitWidth == RHS.getBitWidth() && "Operand mismatch");
   assert((!NoUndefSelfMultiply || LHS == RHS) &&
          "Self multiplication knownbits mismatch");
 
@@ -905,17 +893,15 @@ KnownBits KnownBits::mul(const KnownBits &LHS, const KnownBits &RHS,
 
 KnownBits KnownBits::mulhs(const KnownBits &LHS, const KnownBits &RHS) {
   unsigned BitWidth = LHS.getBitWidth();
-  assert(BitWidth == RHS.getBitWidth() && !LHS.hasConflict() &&
-         !RHS.hasConflict() && "Operand mismatch");
+  assert(BitWidth == RHS.getBitWidth() && "Operand mismatch");
   KnownBits WideLHS = LHS.sext(2 * BitWidth);
   KnownBits WideRHS = RHS.sext(2 * BitWidth);
   return mul(WideLHS, WideRHS).extractBits(BitWidth, BitWidth);
 }
 
 KnownBits KnownBits::mulhu(const KnownBits &LHS, const KnownBits &RHS) {
   unsigned BitWidth = LHS.getBitWidth();
-  assert(BitWidth == RHS.getBitWidth() && !LHS.hasConflict() &&
-         !RHS.hasConflict() && "Operand mismatch");
+  assert(BitWidth == RHS.getBitWidth() && "Operand mismatch");
   KnownBits WideLHS = LHS.zext(2 * BitWidth);
   KnownBits WideRHS = RHS.zext(2 * BitWidth);
   return mul(WideLHS, WideRHS).extractBits(BitWidth, BitWidth);
@@ -964,7 +950,6 @@ KnownBits KnownBits::sdiv(const KnownBits &LHS, const KnownBits &RHS,
     return udiv(LHS, RHS, Exact);
 
   unsigned BitWidth = LHS.getBitWidth();
-  assert(!LHS.hasConflict() && !RHS.hasConflict() && "Bad inputs");
   KnownBits Known(BitWidth);
 
   if (LHS.isZero() || RHS.isZero()) {
@@ -1011,15 +996,12 @@ KnownBits KnownBits::sdiv(const KnownBits &LHS, const KnownBits &RHS,
   }
 
   Known = divComputeLowBit(Known, LHS, RHS, Exact);
-
-  assert(!Known.hasConflict() && "Bad Output");
   return Known;
 }
 
 KnownBits KnownBits::udiv(const KnownBits &LHS, const KnownBits &RHS,
                           bool Exact) {
   unsigned BitWidth = LHS.getBitWidth();
-  assert(!LHS.hasConflict() && !RHS.hasConflict());
   KnownBits Known(BitWidth);
 
   if (LHS.isZero() || RHS.isZero()) {
@@ -1041,7 +1023,6 @@ KnownBits KnownBits::udiv(const KnownBits &LHS, const KnownBits &RHS,
   Known.Zero.setHighBits(LeadZ);
   Known = divComputeLowBit(Known, LHS, RHS, Exact);
 
-  assert(!Known.hasConflict() && "Bad Output");
   return Known;
 }
 
@@ -1059,8 +1040,6 @@ KnownBits KnownBits::remGetLowBits(const KnownBits &LHS, const KnownBits &RHS) {
 }
 
 KnownBits KnownBits::urem(const KnownBits &LHS, const KnownBits &RHS) {
-  assert(!LHS.hasConflict() && !RHS.hasConflict());
-
   KnownBits Known = remGetLowBits(LHS, RHS);
   if (RHS.isConstant() && RHS.getConstant().isPowerOf2()) {
     // NB: Low bits set in `remGetLowBits`.
@@ -1078,8 +1057,6 @@ KnownBits KnownBits::urem(const KnownBits &LHS, const KnownBits &RHS) {
 }
 
 KnownBits KnownBits::srem(const KnownBits &LHS, const KnownBits &RHS) {
-  assert(!LHS.hasConflict() && !RHS.hasConflict());
-
   KnownBits Known = remGetLowBits(LHS, RHS);
   if (RHS.isConstant() && RHS.getConstant().isPowerOf2()) {
     // NB: Low bits are set in `remGetLowBits`.

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -42452,12 +42452,10 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
     if (SimplifyDemandedBits(Op1, OriginalDemandedBits, OriginalDemandedElts,
                              Known, TLO, Depth + 1))
       return true;
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
 
     if (SimplifyDemandedBits(Op0, ~Known.Zero & OriginalDemandedBits,
                              OriginalDemandedElts, Known2, TLO, Depth + 1))
       return true;
-    assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If the RHS is a constant, see if we can simplify it.
     if (ShrinkDemandedConstant(Op, ~Known2.One & OriginalDemandedBits,
@@ -42508,7 +42506,6 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
                              TLO, Depth + 1))
       return true;
 
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     Known.Zero <<= ShAmt;
     Known.One <<= ShAmt;
 
@@ -42527,7 +42524,6 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
                              OriginalDemandedElts, Known, TLO, Depth + 1))
       return true;
 
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     Known.Zero.lshrInPlace(ShAmt);
     Known.One.lshrInPlace(ShAmt);
 
@@ -42568,7 +42564,6 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
                              TLO, Depth + 1))
       return true;
 
-    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     Known.Zero.lshrInPlace(ShAmt);
     Known.One.lshrInPlace(ShAmt);