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[InstSimplify] Reduce code duplication in icmp of binop folds (NFC)
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For folds where we check for the binop on both the LHS and RHS,
extract a function that expects it on the LHS and call it with
swapped order.
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@nikic
nikic committed Aug 2, 2020
1 parent 8d1b950 commit a0addbb
Showing 1 changed file with 82 additions and 133 deletions.
215 changes: 82 additions & 133 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2753,14 +2753,87 @@ static Value *simplifyICmpWithConstant(CmpInst::Predicate Pred, Value *LHS,
return nullptr;
}

static Value *simplifyICmpWithBinOpOnLHS(
CmpInst::Predicate Pred, BinaryOperator *LBO, Value *RHS,
const SimplifyQuery &Q, unsigned MaxRecurse) {
Type *ITy = GetCompareTy(RHS); // The return type.

Value *Y = nullptr;
// icmp pred (or X, Y), X
if (match(LBO, m_c_Or(m_Value(Y), m_Specific(RHS)))) {
if (Pred == ICmpInst::ICMP_ULT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_UGE)
return getTrue(ITy);

if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGE) {
KnownBits RHSKnown = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (RHSKnown.isNonNegative() && YKnown.isNegative())
return Pred == ICmpInst::ICMP_SLT ? getTrue(ITy) : getFalse(ITy);
if (RHSKnown.isNegative() || YKnown.isNonNegative())
return Pred == ICmpInst::ICMP_SLT ? getFalse(ITy) : getTrue(ITy);
}
}

// icmp pred (and X, Y), X
if (match(LBO, m_c_And(m_Value(), m_Specific(RHS)))) {
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
}

// icmp pred (urem X, Y), Y
if (match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
switch (Pred) {
default:
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: {
KnownBits Known = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
return getFalse(ITy);
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: {
KnownBits Known = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
return getTrue(ITy);
}
}

// x >> y <=u x
// x udiv y <=u x.
if (match(LBO, m_LShr(m_Specific(RHS), m_Value())) ||
match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) {
// icmp pred (X op Y), X
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
}

return nullptr;
}

/// TODO: A large part of this logic is duplicated in InstCombine's
/// foldICmpBinOp(). We should be able to share that and avoid the code
/// duplication.
static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, const SimplifyQuery &Q,
unsigned MaxRecurse) {
Type *ITy = GetCompareTy(LHS); // The return type.

BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS);
BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS);
if (MaxRecurse && (LBO || RBO)) {
Expand Down Expand Up @@ -2831,56 +2904,14 @@ static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
}
}

{
Value *Y = nullptr;
// icmp pred (or X, Y), X
if (LBO && match(LBO, m_c_Or(m_Value(Y), m_Specific(RHS)))) {
if (Pred == ICmpInst::ICMP_ULT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_UGE)
return getTrue(ITy);

if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGE) {
KnownBits RHSKnown = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (RHSKnown.isNonNegative() && YKnown.isNegative())
return Pred == ICmpInst::ICMP_SLT ? getTrue(ITy) : getFalse(ITy);
if (RHSKnown.isNegative() || YKnown.isNonNegative())
return Pred == ICmpInst::ICMP_SLT ? getFalse(ITy) : getTrue(ITy);
}
}
// icmp pred X, (or X, Y)
if (RBO && match(RBO, m_c_Or(m_Value(Y), m_Specific(LHS)))) {
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);

if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLE) {
KnownBits LHSKnown = computeKnownBits(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (LHSKnown.isNonNegative() && YKnown.isNegative())
return Pred == ICmpInst::ICMP_SGT ? getTrue(ITy) : getFalse(ITy);
if (LHSKnown.isNegative() || YKnown.isNonNegative())
return Pred == ICmpInst::ICMP_SGT ? getFalse(ITy) : getTrue(ITy);
}
}
}
if (LBO)
if (Value *V = simplifyICmpWithBinOpOnLHS(Pred, LBO, RHS, Q, MaxRecurse))
return V;

// icmp pred (and X, Y), X
if (LBO && match(LBO, m_c_And(m_Value(), m_Specific(RHS)))) {
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
}
// icmp pred X, (and X, Y)
if (RBO && match(RBO, m_c_And(m_Value(), m_Specific(LHS)))) {
if (Pred == ICmpInst::ICMP_UGE)
return getTrue(ITy);
if (Pred == ICmpInst::ICMP_ULT)
return getFalse(ITy);
}
if (RBO)
if (Value *V = simplifyICmpWithBinOpOnLHS(
ICmpInst::getSwappedPredicate(Pred), RBO, LHS, Q, MaxRecurse))
return V;

// 0 - (zext X) pred C
if (!CmpInst::isUnsigned(Pred) && match(LHS, m_Neg(m_ZExt(m_Value())))) {
Expand All @@ -2904,88 +2935,6 @@ static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
}
}

// icmp pred (urem X, Y), Y
if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
switch (Pred) {
default:
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: {
KnownBits Known = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
return getFalse(ITy);
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: {
KnownBits Known = computeKnownBits(RHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
return getTrue(ITy);
}
}

// icmp pred X, (urem Y, X)
if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) {
switch (Pred) {
default:
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: {
KnownBits Known = computeKnownBits(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
return getTrue(ITy);
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: {
KnownBits Known = computeKnownBits(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (!Known.isNonNegative())
break;
LLVM_FALLTHROUGH;
}
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
return getFalse(ITy);
}
}

// x >> y <=u x
// x udiv y <=u x.
if (LBO && (match(LBO, m_LShr(m_Specific(RHS), m_Value())) ||
match(LBO, m_UDiv(m_Specific(RHS), m_Value())))) {
// icmp pred (X op Y), X
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
}

// x >=u x >> y
// x >=u x udiv y.
if (RBO && (match(RBO, m_LShr(m_Specific(LHS), m_Value())) ||
match(RBO, m_UDiv(m_Specific(LHS), m_Value())))) {
// icmp pred X, (X op Y)
if (Pred == ICmpInst::ICMP_ULT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_UGE)
return getTrue(ITy);
}

// handle:
// CI2 << X == CI
// CI2 << X != CI
Expand Down

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