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[NFC][InstSimplify] Refactoring ThreadCmpOverSelect function

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Removed code duplication in ThreadCmpOverSelect and broke it
into several smaller functions for reusing them.

Differential Revision: https://reviews.llvm.org/D71158
This commit is contained in:
Denis Bakhvalov 2019-12-12 22:45:52 +01:00
parent 05003a5b3c
commit 6605830fb0
1 changed files with 79 additions and 44 deletions
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123
lib/Analysis/InstructionSimplify.cpp
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@ -137,6 +137,71 @@ static bool isSameCompare(Value *V, CmpInst::Predicate Pred, Value *LHS,
CRHS == LHS;
}
/// Simplify comparison with true or false branch of select:
/// %sel = select i1 %cond, i32 %tv, i32 %fv
/// %cmp = icmp sle i32 %sel, %rhs
/// Compose new comparison by substituting %sel with either %tv or %fv
/// and see if it simplifies.
static Value *simplifyCmpSelCase(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, Value *Cond,
const SimplifyQuery &Q, unsigned MaxRecurse,
Constant *TrueOrFalse) {
Value *SimplifiedCmp = SimplifyCmpInst(Pred, LHS, RHS, Q, MaxRecurse);
if (SimplifiedCmp == Cond) {
// %cmp simplified to the select condition (%cond).
return TrueOrFalse;
} else if (!SimplifiedCmp && isSameCompare(Cond, Pred, LHS, RHS)) {
// It didn't simplify. However, if composed comparison is equivalent
// to the select condition (%cond) then we can replace it.
return TrueOrFalse;
}
return SimplifiedCmp;
}
/// Simplify comparison with true branch of select
static Value *simplifyCmpSelTrueCase(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, Value *Cond,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
return simplifyCmpSelCase(Pred, LHS, RHS, Cond, Q, MaxRecurse,
getTrue(Cond->getType()));
}
/// Simplify comparison with false branch of select
static Value *simplifyCmpSelFalseCase(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, Value *Cond,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
return simplifyCmpSelCase(Pred, LHS, RHS, Cond, Q, MaxRecurse,
getFalse(Cond->getType()));
}
/// We know comparison with both branches of select can be simplified, but they
/// are not equal. This routine handles some logical simplifications.
static Value *handleOtherCmpSelSimplifications(Value *TCmp, Value *FCmp,
Value *Cond,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
// If the false value simplified to false, then the result of the compare
// is equal to "Cond && TCmp". This also catches the case when the false
// value simplified to false and the true value to true, returning "Cond".
if (match(FCmp, m_Zero()))
if (Value *V = SimplifyAndInst(Cond, TCmp, Q, MaxRecurse))
return V;
// If the true value simplified to true, then the result of the compare
// is equal to "Cond || FCmp".
if (match(TCmp, m_One()))
if (Value *V = SimplifyOrInst(Cond, FCmp, Q, MaxRecurse))
return V;
// Finally, if the false value simplified to true and the true value to
// false, then the result of the compare is equal to "!Cond".
if (match(FCmp, m_One()) && match(TCmp, m_Zero()))
if (Value *V = SimplifyXorInst(
Cond, Constant::getAllOnesValue(Cond->getType()), Q, MaxRecurse))
return V;
return nullptr;
}
/// Does the given value dominate the specified phi node?
static bool valueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
Instruction *I = dyn_cast<Instruction>(V);
@ -398,6 +463,12 @@ static Value *ThreadBinOpOverSelect(Instruction::BinaryOps Opcode, Value *LHS,
/// In the case of a comparison with a select instruction, try to simplify the
/// comparison by seeing whether both branches of the select result in the same
/// value. Returns the common value if so, otherwise returns null.
/// For example, if we have:
/// %tmp = select i1 %cmp, i32 1, i32 2
/// %cmp1 = icmp sle i32 %tmp, 3
/// We can simplify %cmp1 to true, because both branches of select are
/// less than 3. We compose new comparison by substituting %tmp with both
/// branches of select and see if it can be simplified.
static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, const SimplifyQuery &Q,
unsigned MaxRecurse) {
@ -418,32 +489,14 @@ static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
// Now that we have "cmp select(Cond, TV, FV), RHS", analyse it.
// Does "cmp TV, RHS" simplify?
Value *TCmp = SimplifyCmpInst(Pred, TV, RHS, Q, MaxRecurse);
if (TCmp == Cond) {
// It not only simplified, it simplified to the select condition. Replace
// it with 'true'.
TCmp = getTrue(Cond->getType());
} else if (!TCmp) {
// It didn't simplify. However if "cmp TV, RHS" is equal to the select
// condition then we can replace it with 'true'. Otherwise give up.
if (!isSameCompare(Cond, Pred, TV, RHS))
return nullptr;
TCmp = getTrue(Cond->getType());
}
Value *TCmp = simplifyCmpSelTrueCase(Pred, TV, RHS, Cond, Q, MaxRecurse);
if (!TCmp)
return nullptr;
// Does "cmp FV, RHS" simplify?
Value *FCmp = SimplifyCmpInst(Pred, FV, RHS, Q, MaxRecurse);
if (FCmp == Cond) {
// It not only simplified, it simplified to the select condition. Replace
// it with 'false'.
FCmp = getFalse(Cond->getType());
} else if (!FCmp) {
// It didn't simplify. However if "cmp FV, RHS" is equal to the select
// condition then we can replace it with 'false'. Otherwise give up.
if (!isSameCompare(Cond, Pred, FV, RHS))
return nullptr;
FCmp = getFalse(Cond->getType());
}
Value *FCmp = simplifyCmpSelFalseCase(Pred, FV, RHS, Cond, Q, MaxRecurse);
if (!FCmp)
return nullptr;
// If both sides simplified to the same value, then use it as the result of
// the original comparison.
@ -452,26 +505,8 @@ static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
// The remaining cases only make sense if the select condition has the same
// type as the result of the comparison, so bail out if this is not so.
if (Cond->getType()->isVectorTy() != RHS->getType()->isVectorTy())
return nullptr;
// If the false value simplified to false, then the result of the compare
// is equal to "Cond && TCmp". This also catches the case when the false
// value simplified to false and the true value to true, returning "Cond".
if (match(FCmp, m_Zero()))
if (Value *V = SimplifyAndInst(Cond, TCmp, Q, MaxRecurse))
return V;
// If the true value simplified to true, then the result of the compare
// is equal to "Cond || FCmp".
if (match(TCmp, m_One()))
if (Value *V = SimplifyOrInst(Cond, FCmp, Q, MaxRecurse))
return V;
// Finally, if the false value simplified to true and the true value to
// false, then the result of the compare is equal to "!Cond".
if (match(FCmp, m_One()) && match(TCmp, m_Zero()))
if (Value *V =
SimplifyXorInst(Cond, Constant::getAllOnesValue(Cond->getType()),
Q, MaxRecurse))
return V;
if (Cond->getType()->isVectorTy() == RHS->getType()->isVectorTy())
return handleOtherCmpSelSimplifications(TCmp, FCmp, Cond, Q, MaxRecurse);
return nullptr;
}