Revert "[ValueTracking] Understand more select patterns in ComputeKnownBits"
This reverts commit r257769. Backing this out because of stage2 failures.
llvm-svn: 257773
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 50dd03f..a83e207 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1140,52 +1140,14 @@
KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ);
break;
}
- case Instruction::Select: {
+ case Instruction::Select:
computeKnownBits(I->getOperand(2), KnownZero, KnownOne, DL, Depth + 1, Q);
computeKnownBits(I->getOperand(1), KnownZero2, KnownOne2, DL, Depth + 1, Q);
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
-
- // There are several cmp+select patterns that ensure their result will be no
- // greater than a constant. Detect a number of these.
- Value *X, *Y;
- ConstantInt *C1, *C2;
- ICmpInst::Predicate Pred;
-
- auto IsLessThanOrEqualTo = [](Value *X, Value *Y) {
- if (X == Y)
- return true;
- Value *M1, *M2;
- ConstantInt *C1, *C2;
- if (!match(X, m_NSWAdd(m_Value(M1), m_ConstantInt(C1))))
- C1 = nullptr;
- if (!match(Y, m_NSWAdd(m_Value(M2), m_ConstantInt(C2))))
- C2 = nullptr;
- if (C1 && M1 == Y && C1->isNegative())
- return true;
- if (C2 && M2 == X && !C2->isNegative())
- return true;
- if (C1 && C2 && M1 == M2 && !C1->isNegative() && !C2->isNegative() &&
- C1->getValue().ule(C2->getValue()))
- return true;
- return false;
- };
-
- // (select (icmp ugt X, C1), C2, Y)
- // if Y <= X and C2 <= C1
- // then maximum value = C1.
- if (match(I, m_Select(m_ICmp(Pred, m_Value(X), m_ConstantInt(C1)),
- m_ConstantInt(C2), m_Value(Y)))) {
- if (Pred == ICmpInst::ICMP_UGT && IsLessThanOrEqualTo(Y, X) &&
- C2->getValue().ule(C1->getValue())) {
- auto V = cast<ConstantInt>(C1)->getValue() - 1;
- KnownZero = ~APInt::getLowBitsSet(V.getBitWidth(), V.getActiveBits());
- }
- }
break;
- }
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::FPToUI: