return nullptr;
}
-/// Given a chain of or (||) or and (&&) comparison of a value against a
-/// constant, this will try to recover the information required for a switch
-/// structure.
-/// It will depth-first traverse the chain of comparison, seeking for patterns
-/// like %a == 12 or %a < 4 and combine them to produce a set of integer
-/// representing the different cases for the switch.
-/// Note that if the chain is composed of '||' it will build the set of elements
-/// that matches the comparisons (i.e. any of this value validate the chain)
-/// while for a chain of '&&' it will build the set elements that make the test
-/// fail.
-struct ConstantComparesGatherer {
-
- Value *CompValue; /// Value found for the switch comparison
- Value *Extra; /// Extra clause to be checked before the switch
- SmallVector<ConstantInt *, 8> Vals; /// Set of integers to match in switch
- unsigned UsedICmps; /// Number of comparisons matched in the and/or chain
-
- /// Construct and compute the result for the comparison instruction Cond
- ConstantComparesGatherer(Instruction *Cond, const DataLayout *DL)
- : CompValue(nullptr), Extra(nullptr), UsedICmps(0) {
- gather(Cond, DL);
+
+
+// Try to match Instruction I as a comparison against a constant and populates
+// Vals with the set of value that match (or does not depending on isEQ).
+// Return nullptr on failure, or return the Value the comparison matched against
+// on success
+// CurrValue, if supplied, is the value we want to match against. The function
+// is expected to fail if a match is found but the value compared to is not the
+// one expected. If CurrValue is supplied, the return value has to be either
+// nullptr or CurrValue
+static Value* GatherConstantComparesMatch(Instruction *I,
+ Value *CurrValue,
+ SmallVectorImpl<ConstantInt*> &Vals,
+ const DataLayout *DL,
+ unsigned &UsedICmps,
+ bool isEQ) {
+
+ // If this is an icmp against a constant, handle this as one of the cases.
+ ICmpInst *ICI;
+ ConstantInt *C;
+ if (!((ICI = dyn_cast<ICmpInst>(I)) &&
+ (C = GetConstantInt(I->getOperand(1), DL)))) {
+ return nullptr;
}
- /// Prevent copy
- ConstantComparesGatherer(const ConstantComparesGatherer &)
- LLVM_DELETED_FUNCTION;
- ConstantComparesGatherer &
- operator=(const ConstantComparesGatherer &) LLVM_DELETED_FUNCTION;
+ Value *RHSVal;
+ ConstantInt *RHSC;
+
+ // Pattern match a special case
+ // (x & ~2^x) == y --> x == y || x == y|2^x
+ // This undoes a transformation done by instcombine to fuse 2 compares.
+ if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) {
+ if (match(ICI->getOperand(0),
+ m_And(m_Value(RHSVal), m_ConstantInt(RHSC)))) {
+ APInt Not = ~RHSC->getValue();
+ if (Not.isPowerOf2()) {
+ // If we already have a value for the switch, it has to match!
+ if(CurrValue && CurrValue != RHSVal)
+ return nullptr;
+
+ Vals.push_back(C);
+ Vals.push_back(ConstantInt::get(C->getContext(),
+ C->getValue() | Not));
+ UsedICmps++;
+ return RHSVal;
+ }
+ }
-private:
+ // If we already have a value for the switch, it has to match!
+ if(CurrValue && CurrValue != ICI->getOperand(0))
+ return nullptr;
- /// Try to set the current value used for the comparison, it succeeds only if
- /// it wasn't set before or if the new value is the same as the old one
- bool setValueOnce(Value *NewVal) {
- if(CompValue && CompValue != NewVal) return false;
- return CompValue == NewVal;
+ UsedICmps++;
+ Vals.push_back(C);
+ return ICI->getOperand(0);
}
- /// Try to match Instruction "I" as a comparison against a constant and
- /// populates the array Vals with the set of values that match (or do not
- /// match depending on isEQ).
- /// Return false on failure. On success, the Value the comparison matched
- /// against is placed in CompValue.
- /// If CompValue is already set, the function is expected to fail if a match
- /// is found but the value compared to is different.
- bool matchInstruction(Instruction *I, const DataLayout *DL, bool isEQ) {
- // If this is an icmp against a constant, handle this as one of the cases.
- ICmpInst *ICI;
- ConstantInt *C;
- if (!((ICI = dyn_cast<ICmpInst>(I)) &&
- (C = GetConstantInt(I->getOperand(1), DL)))) {
- return false;
- }
+ // If we have "x ult 3", for example, then we can add 0,1,2 to the set.
+ ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(),
+ C->getValue());
- Value *RHSVal;
- ConstantInt *RHSC;
-
- // Pattern match a special case
- // (x & ~2^x) == y --> x == y || x == y|2^x
- // This undoes a transformation done by instcombine to fuse 2 compares.
- if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) {
- if (match(ICI->getOperand(0),
- m_And(m_Value(RHSVal), m_ConstantInt(RHSC)))) {
- APInt Not = ~RHSC->getValue();
- if (Not.isPowerOf2()) {
- // If we already have a value for the switch, it has to match!
- if(!setValueOnce(RHSVal))
- return false;
-
- Vals.push_back(C);
- Vals.push_back(ConstantInt::get(C->getContext(),
- C->getValue() | Not));
- UsedICmps++;
- return true;
- }
- }
+ // Shift the range if the compare is fed by an add. This is the range
+ // compare idiom as emitted by instcombine.
+ Value *CandidateVal = I->getOperand(0);
+ if(match(I->getOperand(0), m_Add(m_Value(RHSVal), m_ConstantInt(RHSC)))) {
+ Span = Span.subtract(RHSC->getValue());
+ CandidateVal = RHSVal;
+ }
- // If we already have a value for the switch, it has to match!
- if(!setValueOnce(ICI->getOperand(0)))
- return false;
+ // If we already have a value for the switch, it has to match!
+ if(CurrValue && CurrValue != CandidateVal)
+ return nullptr;
- UsedICmps++;
- Vals.push_back(C);
- return ICI->getOperand(0);
- }
+ // If this is an and/!= check, then we are looking to build the set of
+ // value that *don't* pass the and chain. I.e. to turn "x ugt 2" into
+ // x != 0 && x != 1.
+ if (!isEQ)
+ Span = Span.inverse();
- // If we have "x ult 3", for example, then we can add 0,1,2 to the set.
- ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(),
- C->getValue());
+ // If there are a ton of values, we don't want to make a ginormous switch.
+ if (Span.getSetSize().ugt(8) || Span.isEmptySet()) {
+ return nullptr;
+ }
- // Shift the range if the compare is fed by an add. This is the range
- // compare idiom as emitted by instcombine.
- Value *CandidateVal = I->getOperand(0);
- if(match(I->getOperand(0), m_Add(m_Value(RHSVal), m_ConstantInt(RHSC)))) {
- Span = Span.subtract(RHSC->getValue());
- CandidateVal = RHSVal;
- }
+ // Add all values from the range to the set
+ for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
+ Vals.push_back(ConstantInt::get(I->getContext(), Tmp));
- // If this is an and/!= check, then we are looking to build the set of
- // value that *don't* pass the and chain. I.e. to turn "x ugt 2" into
- // x != 0 && x != 1.
- if (!isEQ)
- Span = Span.inverse();
+ UsedICmps++;
+ return CandidateVal;
- // If there are a ton of values, we don't want to make a ginormous switch.
- if (Span.getSetSize().ugt(8) || Span.isEmptySet()) {
- return false;
- }
+}
- // If we already have a value for the switch, it has to match!
- if(!setValueOnce(CandidateVal))
- return false;
+/// GatherConstantCompares - Given a potentially 'or'd or 'and'd together
+/// collection of icmp eq/ne instructions that compare a value against a
+/// constant, return the value being compared, and stick the constant into the
+/// Values vector.
+/// One "Extra" case is allowed to differ from the other.
+static Value *
+GatherConstantCompares(Value *V, SmallVectorImpl<ConstantInt*> &Vals, Value *&Extra,
+ const DataLayout *DL, unsigned &UsedICmps) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I) return nullptr;
- // Add all values from the range to the set
- for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
- Vals.push_back(ConstantInt::get(I->getContext(), Tmp));
+ bool isEQ = (I->getOpcode() == Instruction::Or);
- UsedICmps++;
- return true;
+ // Keep a stack (SmallVector for efficiency) for depth-first traversal
+ SmallVector<Value *, 8> DFT;
- }
+ // Initialize
+ DFT.push_back(V);
- /// gather - Given a potentially 'or'd or 'and'd together collection of icmp
- /// eq/ne/lt/gt instructions that compare a value against a constant, extract
- /// the value being compared, and stick the list constants into the Vals
- /// vector.
- /// One "Extra" case is allowed to differ from the other.
- void gather(Value *V, const DataLayout *DL) {
- Instruction *I = dyn_cast<Instruction>(V);
- bool isEQ = (I->getOpcode() == Instruction::Or);
-
- // Keep a stack (SmallVector for efficiency) for depth-first traversal
- SmallVector<Value *, 8> DFT;
-
- // Initialize
- DFT.push_back(V);
-
- 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.
- if (I->getOpcode() == (isEQ ? Instruction::Or : Instruction::And)) {
- DFT.push_back(I->getOperand(1));
- DFT.push_back(I->getOperand(0));
- continue;
- }
+ // Will hold the value used for the switch comparison
+ Value *CurrValue = nullptr;
+
+ while(!DFT.empty()) {
+ V = DFT.pop_back_val();
+
+ if (Instruction *I = dyn_cast<Instruction>(V)) {
- // Try to match the current instruction
- if (matchInstruction(I, DL, isEQ))
- // Match succeed, continue the loop
- continue;
+ // If it is a || (or && depending on isEQ), process the operands.
+ if (I->getOpcode() == (isEQ ? Instruction::Or : Instruction::And)) {
+ DFT.push_back(I->getOperand(1));
+ DFT.push_back(I->getOperand(0));
+ continue;
}
- // One element of the sequence of || (or &&) could not be match as a
- // comparison against the same value as the others.
- // We allow only one "Extra" case to be checked before the switch
- if (!Extra) {
- Extra = V;
+ // Try to match the current instruction
+ if (Value *Matched = GatherConstantComparesMatch(I,
+ CurrValue,
+ Vals,
+ DL,
+ UsedICmps,
+ isEQ)) {
+ // Match succeed, continue the loop
+ CurrValue = Matched;
continue;
}
- // Failed to parse a proper sequence, abort now
- CompValue = nullptr;
- break;
}
+
+ // One element of the sequence of || (or &&) could not be match as a
+ // comparison against the same value as the others.
+ // We allow only one "Extra" case to be checked before the switch
+ if (Extra == nullptr) {
+ Extra = V;
+ continue;
+ }
+ return nullptr;
+
}
-};
+
+ // Return the value to be used for the switch comparison (if any)
+ return CurrValue;
+}
static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) {
Instruction *Cond = nullptr;
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (!Cond) return false;
+
// Change br (X == 0 | X == 1), T, F into a switch instruction.
// If this is a bunch of seteq's or'd together, or if it's a bunch of
// 'setne's and'ed together, collect them.
+ Value *CompVal = nullptr;
+ SmallVector<ConstantInt*, 8> Values;
+ bool TrueWhenEqual = (Cond->getOpcode() == Instruction::Or);
+ Value *ExtraCase = nullptr;
+ unsigned UsedICmps = 0;
// Try to gather values from a chain of and/or to be turned into a switch
- ConstantComparesGatherer ConstantCompare(Cond, DL);
- // Unpack the result
- SmallVectorImpl<ConstantInt*> &Values = ConstantCompare.Vals;
- Value *CompVal = ConstantCompare.CompValue;
- unsigned UsedICmps = ConstantCompare.UsedICmps;
- Value *ExtraCase = ConstantCompare.Extra;
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, DL, UsedICmps);
// If we didn't have a multiply compared value, fail.
if (!CompVal) return false;
if (UsedICmps <= 1)
return false;
- bool TrueWhenEqual = (Cond->getOpcode() == Instruction::Or);
-
// 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);
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