Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[InstCombine] Simplify select if it combinated and/or/xor #73362

Merged
merged 2 commits into from
Apr 3, 2024
Merged

[InstCombine] Simplify select if it combinated and/or/xor #73362

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
07479dd
[InstCombine] Add test for simplify select if it combinated and/or/xor
ParkHanbum Nov 27, 2023
3ae57ad
[InstCombine] Simplify select if it combinated `and/or/xor` (#71792)
ParkHanbum Nov 23, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
106 changes: 106 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1687,6 +1687,109 @@ static Value *foldSelectInstWithICmpConst(SelectInst &SI, ICmpInst *ICI,
return nullptr;
}

static Instruction *foldSelectICmpEq(SelectInst &SI, ICmpInst *ICI,
InstCombinerImpl &IC) {
ICmpInst::Predicate Pred = ICI->getPredicate();
if (!ICmpInst::isEquality(Pred))
return nullptr;

Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
Value *CmpLHS = ICI->getOperand(0);
Value *CmpRHS = ICI->getOperand(1);

if (Pred == ICmpInst::ICMP_NE)
std::swap(TrueVal, FalseVal);

// Transform (X == C) ? X : Y -> (X == C) ? C : Y
// specific handling for Bitwise operation.
// x&y -> (x|y) ^ (x^y) or (x|y) & ~(x^y)
// x|y -> (x&y) | (x^y) or (x&y) ^ (x^y)
// x^y -> (x|y) ^ (x&y) or (x|y) & ~(x&y)
Value *X, *Y;
if (!match(CmpLHS, m_BitwiseLogic(m_Value(X), m_Value(Y))) ||
!match(TrueVal, m_c_BitwiseLogic(m_Specific(X), m_Specific(Y))))
return nullptr;

const unsigned AndOps = Instruction::And, OrOps = Instruction::Or,
XorOps = Instruction::Xor, NoOps = 0;
enum NotMask { None = 0, NotInner, NotRHS };

auto matchFalseVal = [&](unsigned OuterOpc, unsigned InnerOpc,
unsigned NotMask) {
auto matchInner = m_c_BinOp(InnerOpc, m_Specific(X), m_Specific(Y));
if (OuterOpc == NoOps)
return match(CmpRHS, m_Zero()) && match(FalseVal, matchInner);

if (NotMask == NotInner) {
return match(FalseVal,
m_c_BinOp(OuterOpc, m_Not(matchInner), m_Specific(CmpRHS)));
} else if (NotMask == NotRHS) {
return match(FalseVal,
m_c_BinOp(OuterOpc, matchInner, m_Not(m_Specific(CmpRHS))));
} else {
return match(FalseVal,
m_c_BinOp(OuterOpc, matchInner, m_Specific(CmpRHS)));
}
};

// (X&Y)==C ? X|Y : X^Y -> (X^Y)|C : X^Y or (X^Y)^ C : X^Y
// (X&Y)==C ? X^Y : X|Y -> (X|Y)^C : X|Y or (X|Y)&~C : X|Y
if (match(CmpLHS, m_And(m_Value(X), m_Value(Y)))) {
if (match(TrueVal, m_c_Or(m_Specific(X), m_Specific(Y)))) {
// (X&Y)==C ? X|Y : (X^Y)|C -> (X^Y)|C : (X^Y)|C -> (X^Y)|C
// (X&Y)==C ? X|Y : (X^Y)^C -> (X^Y)^C : (X^Y)^C -> (X^Y)^C
if (matchFalseVal(OrOps, XorOps, None) ||
matchFalseVal(XorOps, XorOps, None))
return IC.replaceInstUsesWith(SI, FalseVal);
} else if (match(TrueVal, m_c_Xor(m_Specific(X), m_Specific(Y)))) {
// (X&Y)==C ? X^Y : (X|Y)^ C -> (X|Y)^ C : (X|Y)^ C -> (X|Y)^ C
// (X&Y)==C ? X^Y : (X|Y)&~C -> (X|Y)&~C : (X|Y)&~C -> (X|Y)&~C
if (matchFalseVal(XorOps, OrOps, None) ||
matchFalseVal(AndOps, OrOps, NotRHS))
return IC.replaceInstUsesWith(SI, FalseVal);
}
}

// (X|Y)==C ? X&Y : X^Y -> (X^Y)^C : X^Y or ~(X^Y)&C : X^Y
// (X|Y)==C ? X^Y : X&Y -> (X&Y)^C : X&Y or ~(X&Y)&C : X&Y
if (match(CmpLHS, m_Or(m_Value(X), m_Value(Y)))) {
if (match(TrueVal, m_c_And(m_Specific(X), m_Specific(Y)))) {
// (X|Y)==C ? X&Y: (X^Y)^C -> (X^Y)^C: (X^Y)^C -> (X^Y)^C
// (X|Y)==C ? X&Y:~(X^Y)&C ->~(X^Y)&C:~(X^Y)&C -> ~(X^Y)&C
if (matchFalseVal(XorOps, XorOps, None) ||
matchFalseVal(AndOps, XorOps, NotInner))
return IC.replaceInstUsesWith(SI, FalseVal);
} else if (match(TrueVal, m_c_Xor(m_Specific(X), m_Specific(Y)))) {
// (X|Y)==C ? X^Y : (X&Y)^C -> (X&Y)^C : (X&Y)^C -> (X&Y)^C
// (X|Y)==C ? X^Y :~(X&Y)&C -> ~(X&Y)&C :~(X&Y)&C -> ~(X&Y)&C
if (matchFalseVal(XorOps, AndOps, None) ||
matchFalseVal(AndOps, AndOps, NotInner))
return IC.replaceInstUsesWith(SI, FalseVal);
}
}

// (X^Y)==C ? X&Y : X|Y -> (X|Y)^C : X|Y or (X|Y)&~C : X|Y
// (X^Y)==C ? X|Y : X&Y -> (X&Y)|C : X&Y or (X&Y)^ C : X&Y
if (match(CmpLHS, m_Xor(m_Value(X), m_Value(Y)))) {
if ((match(TrueVal, m_c_And(m_Specific(X), m_Specific(Y))))) {
// (X^Y)==C ? X&Y : (X|Y)^C -> (X|Y)^C
// (X^Y)==C ? X&Y : (X|Y)&~C -> (X|Y)&~C
if (matchFalseVal(XorOps, OrOps, None) ||
matchFalseVal(AndOps, OrOps, NotRHS))
return IC.replaceInstUsesWith(SI, FalseVal);
} else if (match(TrueVal, m_c_Or(m_Specific(X), m_Specific(Y)))) {
// (X^Y)==C ? (X|Y) : (X&Y)|C -> (X&Y)|C
// (X^Y)==C ? (X|Y) : (X&Y)^C -> (X&Y)^C
if (matchFalseVal(OrOps, AndOps, None) ||
matchFalseVal(XorOps, AndOps, None))
return IC.replaceInstUsesWith(SI, FalseVal);
}
}

return nullptr;
}

/// Visit a SelectInst that has an ICmpInst as its first operand.
Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
ICmpInst *ICI) {
Expand Down Expand Up @@ -1729,6 +1832,9 @@ Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
}
}

if (Instruction *NewSel = foldSelectICmpEq(SI, ICI, *this))
return NewSel;

// Canonicalize a signbit condition to use zero constant by swapping:
// (CmpLHS > -1) ? TV : FV --> (CmpLHS < 0) ? FV : TV
// To avoid conflicts (infinite loops) with other canonicalizations, this is
Expand Down
Loading
Loading