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[SimplifyCFG] Avoid redundant calls in gather. (NFC) #154133

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Merged
andjo403 merged 1 commit into from
Aug 18, 2025
Merged

[SimplifyCFG] Avoid redundant calls in gather. (NFC) #154133

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28 changes: 15 additions & 13 deletions llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -565,6 +565,9 @@ struct ConstantComparesGatherer {
/// Number of comparisons matched in the and/or chain
unsigned UsedICmps = 0;

/// If the elements in Vals matches the comparisons
bool IsEq = false;

/// Construct and compute the result for the comparison instruction Cond
ConstantComparesGatherer(Instruction *Cond, const DataLayout &DL) : DL(DL) {
gather(Cond);
Expand Down Expand Up @@ -736,23 +739,23 @@ struct ConstantComparesGatherer {
/// vector.
/// One "Extra" case is allowed to differ from the other.
void gather(Value *V) {
bool isEQ = match(V, m_LogicalOr(m_Value(), m_Value()));

Value *Op0, *Op1;
if (match(V, m_LogicalOr(m_Value(Op0), m_Value(Op1))))
IsEq = true;
else if (match(V, m_LogicalAnd(m_Value(Op0), m_Value(Op1))))
IsEq = false;
else
return;
// Keep a stack (SmallVector for efficiency) for depth-first traversal
SmallVector<Value *, 8> DFT;
SmallPtrSet<Value *, 8> Visited;

// Initialize
Visited.insert(V);
DFT.push_back(V);
SmallVector<Value *, 8> DFT{Op0, Op1};
SmallPtrSet<Value *, 8> Visited{V, Op0, Op1};

while (!DFT.empty()) {
V = DFT.pop_back_val();

if (Instruction *I = dyn_cast<Instruction>(V)) {
// If it is a || (or && depending on isEQ), process the operands.
Value *Op0, *Op1;
if (isEQ ? match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1)))
if (IsEq ? match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1)))
: match(I, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) {
if (Visited.insert(Op1).second)
DFT.push_back(Op1);
Expand All @@ -763,7 +766,7 @@ struct ConstantComparesGatherer {
}

// Try to match the current instruction
if (matchInstruction(I, isEQ))
if (matchInstruction(I, IsEq))
// Match succeed, continue the loop
continue;
}
Expand Down Expand Up @@ -5103,6 +5106,7 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
Value *CompVal = ConstantCompare.CompValue;
unsigned UsedICmps = ConstantCompare.UsedICmps;
Value *ExtraCase = ConstantCompare.Extra;
bool TrueWhenEqual = ConstantCompare.IsEq;

// If we didn't have a multiply compared value, fail.
if (!CompVal)
Expand All @@ -5112,8 +5116,6 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
if (UsedICmps <= 1)
return false;

bool TrueWhenEqual = match(Cond, m_LogicalOr(m_Value(), m_Value()));

// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), constantIntSortPredicate);
Expand Down