[llvm] r222416 - SimplifyCFG: Refactor GatherConstantCompares() result in a struct
Mehdi Amini
mehdi.amini at apple.com
Thu Nov 20 15:31:21 PST 2014
I tried a new version, let me know if you see any other issue.
Thanks,
Mehdi
> On Nov 20, 2014, at 12:44 PM, Timur Iskhodzhanov <timurrrr at google.com> wrote:
>
> The bots were green, but in some of my configurations I got a compiler warning:
> llvm/lib/Transforms/Utils/SimplifyCFG.cpp:392:24: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
>
> I've looked at the code and (based on the comment) thought there had to be == rather than =. Doing that broke some things and you were not available for advice, so I've decided to revert this altogether and let you reland with fixes when it's convenient for you.
>
> Sorry if I was a bit too concise in my communications...
>
> Thanks,
> Tim
>
> On Thu Nov 20 2014 at 7:33:58 PM Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>> wrote:
> Oh for some reason my mail client did not find this thread I used the search function, I apologize.
>
> So the “typo” was indeed not a typo (but I agree it is not well written and I’ll fix it).
>
> The bot is green in r222422 before your change, isn’t it?
>
> Thanks!
>
> Mehdi
>
>
>
>
>> On Nov 20, 2014, at 4:08 AM, Timur Iskhodzhanov <timurrrr at google.com <mailto:timurrrr at google.com>> wrote:
>>
>> Fixing this typo has resulted in buildbot errors, so I'm going to revert both mine and your changes [assuming you're not immediately available for a fix].
>> http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/20839 <http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/20839>
>>
>> On Thu Nov 20 2014 at 2:51:06 PM Timur Iskhodzhanov <timurrrr at google.com <mailto:timurrrr at google.com>> wrote:
>> On Thu Nov 20 2014 at 9:53:42 AM Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>> wrote:
>> Author: mehdi_amini
>> Date: Thu Nov 20 00:51:02 2014
>> New Revision: 222416
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=222416&view=rev <http://llvm.org/viewvc/llvm-project?rev=222416&view=rev>
>> Log:
>> SimplifyCFG: Refactor GatherConstantCompares() result in a struct
>>
>> Code seems cleaner and easier to understand this way
>>
>>
>>
>> Modified:
>> llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=222416&r1=222415&r2=222416&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=222416&r1=222415&r2=222416&view=diff>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Nov 20 00:51:02 2014
>> @@ -357,160 +357,170 @@ static ConstantInt *GetConstantInt(Value
>> 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 = nullptr; /// Value found for the switch comparison
>> + Value *Extra = nullptr; /// Extra clause to be checked before the switch
>> + SmallVector<ConstantInt*, 8> Vals; /// Set of integers to match in switch
>> + unsigned UsedICmps = 0; /// 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) {
>> + gather(Cond, DL);
>> + }
>> +
>> + /// Prevent copy
>> + ConstantComparesGatherer(const ConstantComparesGatherer&) = delete;
>> + ConstantComparesGatherer &operator=(const ConstantComparesGatherer&) = delete;
>> +
>> +private:
>> +
>> + /// 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;
>>
>> This looks like a typo.
>>
>> + }
>> +
>>
>> + /// 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;
>> + }
>>
>> + Value *RHSVal;
>> + ConstantInt *RHSC;
>>
>> -// 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;
>> - }
>> -
>> - 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;
>> + // 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;
>> + }
>> }
>> - }
>>
>> - // If we already have a value for the switch, it has to match!
>> - if(CurrValue && CurrValue != ICI->getOperand(0))
>> - return nullptr;
>> + // If we already have a value for the switch, it has to match!
>> + if(!setValueOnce(ICI->getOperand(0)))
>> + return false;
>>
>> - UsedICmps++;
>> - Vals.push_back(C);
>> - return ICI->getOperand(0);
>> - }
>> + UsedICmps++;
>> + Vals.push_back(C);
>> + return ICI->getOperand(0);
>> + }
>> +
>> + // 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());
>> +
>> + // 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 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 false;
>> + }
>>
>> - // 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(CandidateVal))
>> + return false;
>>
>> - // If we already have a value for the switch, it has to match!
>> - if(CurrValue && CurrValue != CandidateVal)
>> - 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));
>>
>> - // 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 true;
>>
>> - // 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;
>> }
>>
>> - // 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));
>> -
>> - UsedICmps++;
>> - return CandidateVal;
>> -
>> -}
>> -
>> -/// 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;
>> -
>> - 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);
>> -
>> - // 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)) {
>> + /// 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;
>> + }
>>
>> - // 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;
>> + // Try to match the current instruction
>> + if (matchInstruction(I, DL, isEQ))
>> + // Match succeed, continue the loop
>> + continue;
>> }
>>
>> - // Try to match the current instruction
>> - if (Value *Matched = GatherConstantComparesMatch(I,
>> - CurrValue,
>> - Vals,
>> - DL,
>> - UsedICmps,
>> - isEQ)) {
>> - // Match succeed, continue the loop
>> - CurrValue = Matched;
>> + // 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;
>> 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;
>> @@ -2810,18 +2820,17 @@ static bool SimplifyBranchOnICmpChain(Br
>> 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
>> - CompVal = GatherConstantCompares(Cond, Values, ExtraCase, DL, UsedICmps);
>> + ConstantComparesGatherer ConstantCompare{Cond, DL};
>> + // Unpack the result
>> + SmallVectorImpl<ConstantInt*> &Values = ConstantCompare.Vals;
>> + Value *CompVal = ConstantCompare.CompValue;
>> + unsigned UsedICmps = ConstantCompare.UsedICmps;
>> + Value *ExtraCase = ConstantCompare.Extra;
>>
>> // If we didn't have a multiply compared value, fail.
>> if (!CompVal) return false;
>> @@ -2830,6 +2839,8 @@ static bool SimplifyBranchOnICmpChain(Br
>> 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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