// Converts LLVM encoding of comparison predicates to the
// corresponding bitcode versions.
static unsigned GetEncodedCmpPredicate(const CmpInst &Cmp) {
switch (Cmp.getPredicate()) {
default: report_fatal_error(
"Comparison predicate not supported by PNaCl bitcode");
case CmpInst::FCMP_FALSE:
return naclbitc::FCMP_FALSE;
case CmpInst::FCMP_OEQ:
return naclbitc::FCMP_OEQ;
case CmpInst::FCMP_OGT:
return naclbitc::FCMP_OGT;
case CmpInst::FCMP_OGE:
return naclbitc::FCMP_OGE;
case CmpInst::FCMP_OLT:
return naclbitc::FCMP_OLT;
case CmpInst::FCMP_OLE:
return naclbitc::FCMP_OLE;
case CmpInst::FCMP_ONE:
return naclbitc::FCMP_ONE;
case CmpInst::FCMP_ORD:
return naclbitc::FCMP_ORD;
case CmpInst::FCMP_UNO:
return naclbitc::FCMP_UNO;
case CmpInst::FCMP_UEQ:
return naclbitc::FCMP_UEQ;
case CmpInst::FCMP_UGT:
return naclbitc::FCMP_UGT;
case CmpInst::FCMP_UGE:
return naclbitc::FCMP_UGE;
case CmpInst::FCMP_ULT:
return naclbitc::FCMP_ULT;
case CmpInst::FCMP_ULE:
return naclbitc::FCMP_ULE;
case CmpInst::FCMP_UNE:
return naclbitc::FCMP_UNE;
case CmpInst::FCMP_TRUE:
return naclbitc::FCMP_TRUE;
case CmpInst::ICMP_EQ:
return naclbitc::ICMP_EQ;
case CmpInst::ICMP_NE:
return naclbitc::ICMP_NE;
case CmpInst::ICMP_UGT:
return naclbitc::ICMP_UGT;
case CmpInst::ICMP_UGE:
return naclbitc::ICMP_UGE;
case CmpInst::ICMP_ULT:
return naclbitc::ICMP_ULT;
case CmpInst::ICMP_ULE:
return naclbitc::ICMP_ULE;
case CmpInst::ICMP_SGT:
return naclbitc::ICMP_SGT;
case CmpInst::ICMP_SGE:
return naclbitc::ICMP_SGE;
case CmpInst::ICMP_SLT:
return naclbitc::ICMP_SLT;
case CmpInst::ICMP_SLE:
return naclbitc::ICMP_SLE;
}
}
/// Try to simplify cmp instruction.
bool UnrolledInstAnalyzer::visitCmpInst(CmpInst &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// First try to handle simplified comparisons.
if (!isa<Constant>(LHS))
if (Constant *SimpleLHS = SimplifiedValues.lookup(LHS))
LHS = SimpleLHS;
if (!isa<Constant>(RHS))
if (Constant *SimpleRHS = SimplifiedValues.lookup(RHS))
RHS = SimpleRHS;
if (!isa<Constant>(LHS) && !isa<Constant>(RHS)) {
auto SimplifiedLHS = SimplifiedAddresses.find(LHS);
if (SimplifiedLHS != SimplifiedAddresses.end()) {
auto SimplifiedRHS = SimplifiedAddresses.find(RHS);
if (SimplifiedRHS != SimplifiedAddresses.end()) {
SimplifiedAddress &LHSAddr = SimplifiedLHS->second;
SimplifiedAddress &RHSAddr = SimplifiedRHS->second;
if (LHSAddr.Base == RHSAddr.Base) {
LHS = LHSAddr.Offset;
RHS = RHSAddr.Offset;
}
}
}
}
if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
if (Constant *C = ConstantExpr::getCompare(I.getPredicate(), CLHS, CRHS)) {
SimplifiedValues[&I] = C;
return true;
}
}
}
return Base::visitCmpInst(I);
}
void SystemZTDCPass::convertFCmp(CmpInst &I) {
Value *Op0 = I.getOperand(0);
auto *Const = dyn_cast<ConstantFP>(I.getOperand(1));
auto Pred = I.getPredicate();
// Only comparisons with consts are interesting.
if (!Const)
return;
// Compute the smallest normal number (and its negation).
auto &Sem = Op0->getType()->getFltSemantics();
APFloat Smallest = APFloat::getSmallestNormalized(Sem);
APFloat NegSmallest = Smallest;
NegSmallest.changeSign();
// Check if Const is one of our recognized consts.
int WhichConst;
if (Const->isZero()) {
// All comparisons with 0 can be converted.
WhichConst = 0;
} else if (Const->isInfinity()) {
// Likewise for infinities.
WhichConst = Const->isNegative() ? 2 : 1;
} else if (Const->isExactlyValue(Smallest)) {
// For Smallest, we cannot do EQ separately from GT.
if ((Pred & CmpInst::FCMP_OGE) != CmpInst::FCMP_OGE &&
(Pred & CmpInst::FCMP_OGE) != 0)
return;
WhichConst = 3;
} else if (Const->isExactlyValue(NegSmallest)) {
// Likewise for NegSmallest, we cannot do EQ separately from LT.
if ((Pred & CmpInst::FCMP_OLE) != CmpInst::FCMP_OLE &&
(Pred & CmpInst::FCMP_OLE) != 0)
return;
WhichConst = 4;
} else {
// Not one of our special constants.
return;
}
// Partial masks to use for EQ, GT, LT, UN comparisons, respectively.
static const int Masks[][4] = {
{ // 0
SystemZ::TDCMASK_ZERO, // eq
SystemZ::TDCMASK_POSITIVE, // gt
SystemZ::TDCMASK_NEGATIVE, // lt
SystemZ::TDCMASK_NAN, // un
},
{ // inf
SystemZ::TDCMASK_INFINITY_PLUS, // eq
0, // gt
(SystemZ::TDCMASK_ZERO |
SystemZ::TDCMASK_NEGATIVE |
SystemZ::TDCMASK_NORMAL_PLUS |
SystemZ::TDCMASK_SUBNORMAL_PLUS), // lt
SystemZ::TDCMASK_NAN, // un
},
{ // -inf
SystemZ::TDCMASK_INFINITY_MINUS, // eq
(SystemZ::TDCMASK_ZERO |
SystemZ::TDCMASK_POSITIVE |
SystemZ::TDCMASK_NORMAL_MINUS |
SystemZ::TDCMASK_SUBNORMAL_MINUS), // gt
0, // lt
SystemZ::TDCMASK_NAN, // un
},
{ // minnorm
0, // eq (unsupported)
(SystemZ::TDCMASK_NORMAL_PLUS |
SystemZ::TDCMASK_INFINITY_PLUS), // gt (actually ge)
(SystemZ::TDCMASK_ZERO |
SystemZ::TDCMASK_NEGATIVE |
SystemZ::TDCMASK_SUBNORMAL_PLUS), // lt
SystemZ::TDCMASK_NAN, // un
},
{ // -minnorm
0, // eq (unsupported)
(SystemZ::TDCMASK_ZERO |
SystemZ::TDCMASK_POSITIVE |
SystemZ::TDCMASK_SUBNORMAL_MINUS), // gt
(SystemZ::TDCMASK_NORMAL_MINUS |
SystemZ::TDCMASK_INFINITY_MINUS), // lt (actually le)
SystemZ::TDCMASK_NAN, // un
}
};
// Construct the mask as a combination of the partial masks.
int Mask = 0;
if (Pred & CmpInst::FCMP_OEQ)
Mask |= Masks[WhichConst][0];
if (Pred & CmpInst::FCMP_OGT)
Mask |= Masks[WhichConst][1];
if (Pred & CmpInst::FCMP_OLT)
Mask |= Masks[WhichConst][2];
if (Pred & CmpInst::FCMP_UNO)
Mask |= Masks[WhichConst][3];
// A lone fcmp is unworthy of tdc conversion on its own, but may become
// worthy if combined with fabs.
bool Worthy = false;
if (CallInst *CI = dyn_cast<CallInst>(Op0)) {
Function *F = CI->getCalledFunction();
if (F && F->getIntrinsicID() == Intrinsic::fabs) {
// Fold with fabs - adjust the mask appropriately.
Mask &= SystemZ::TDCMASK_PLUS;
Mask |= Mask >> 1;
Op0 = CI->getArgOperand(0);
// A combination of fcmp with fabs is a win, unless the constant
// involved is 0 (which is handled by later passes).
Worthy = WhichConst != 0;
PossibleJunk.insert(CI);
}
bool CallAnalyzer::visitCmpInst(CmpInst &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// First try to handle simplified comparisons.
if (!isa<Constant>(LHS))
if (Constant *SimpleLHS = SimplifiedValues.lookup(LHS))
LHS = SimpleLHS;
if (!isa<Constant>(RHS))
if (Constant *SimpleRHS = SimplifiedValues.lookup(RHS))
RHS = SimpleRHS;
if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
if (Constant *CRHS = dyn_cast<Constant>(RHS))
if (Constant *C = ConstantExpr::getCompare(I.getPredicate(), CLHS, CRHS)) {
SimplifiedValues[&I] = C;
return true;
}
}
if (I.getOpcode() == Instruction::FCmp)
return false;
// Otherwise look for a comparison between constant offset pointers with
// a common base.
Value *LHSBase, *RHSBase;
APInt LHSOffset, RHSOffset;
std::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS);
if (LHSBase) {
std::tie(RHSBase, RHSOffset) = ConstantOffsetPtrs.lookup(RHS);
if (RHSBase && LHSBase == RHSBase) {
// We have common bases, fold the icmp to a constant based on the
// offsets.
Constant *CLHS = ConstantInt::get(LHS->getContext(), LHSOffset);
Constant *CRHS = ConstantInt::get(RHS->getContext(), RHSOffset);
if (Constant *C = ConstantExpr::getICmp(I.getPredicate(), CLHS, CRHS)) {
SimplifiedValues[&I] = C;
++NumConstantPtrCmps;
return true;
}
}
}
// If the comparison is an equality comparison with null, we can simplify it
// for any alloca-derived argument.
if (I.isEquality() && isa<ConstantPointerNull>(I.getOperand(1)))
if (isAllocaDerivedArg(I.getOperand(0))) {
// We can actually predict the result of comparisons between an
// alloca-derived value and null. Note that this fires regardless of
// SROA firing.
bool IsNotEqual = I.getPredicate() == CmpInst::ICMP_NE;
SimplifiedValues[&I] = IsNotEqual ? ConstantInt::getTrue(I.getType())
: ConstantInt::getFalse(I.getType());
return true;
}
// Finally check for SROA candidates in comparisons.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) {
if (isa<ConstantPointerNull>(I.getOperand(1))) {
accumulateSROACost(CostIt, InlineConstants::InstrCost);
return true;
}
disableSROA(CostIt);
}
return false;
}
/// If \param [in] BB has more than one predecessor that is a conditional
/// branch, attempt to use parallel and/or for the branch condition. \returns
/// true on success.
///
/// Before:
/// ......
/// %cmp10 = fcmp une float %tmp1, %tmp2
/// br i1 %cmp1, label %if.then, label %lor.rhs
///
/// lor.rhs:
/// ......
/// %cmp11 = fcmp une float %tmp3, %tmp4
/// br i1 %cmp11, label %if.then, label %ifend
///
/// if.end: // the merge block
/// ......
///
/// if.then: // has two predecessors, both of them contains conditional branch.
/// ......
/// br label %if.end;
///
/// After:
/// ......
/// %cmp10 = fcmp une float %tmp1, %tmp2
/// ......
/// %cmp11 = fcmp une float %tmp3, %tmp4
/// %cmp12 = or i1 %cmp10, %cmp11 // parallel-or mode.
/// br i1 %cmp12, label %if.then, label %ifend
///
/// if.end:
/// ......
///
/// if.then:
/// ......
/// br label %if.end;
///
/// Current implementation handles two cases.
/// Case 1: \param BB is on the else-path.
///
/// BB1
/// / |
/// BB2 |
/// / \ |
/// BB3 \ | where, BB1, BB2 contain conditional branches.
/// \ | / BB3 contains unconditional branch.
/// \ | / BB4 corresponds to \param BB which is also the merge.
/// BB => BB4
///
///
/// Corresponding source code:
///
/// if (a == b && c == d)
/// statement; // BB3
///
/// Case 2: \param BB BB is on the then-path.
///
/// BB1
/// / |
/// | BB2
/// \ / | where BB1, BB2 contain conditional branches.
/// BB => BB3 | BB3 contains unconditiona branch and corresponds
/// \ / to \param BB. BB4 is the merge.
/// BB4
///
/// Corresponding source code:
///
/// if (a == b || c == d)
/// statement; // BB3
///
/// In both cases, \param BB is the common successor of conditional branches.
/// In Case 1, \param BB (BB4) has an unconditional branch (BB3) as
/// its predecessor. In Case 2, \param BB (BB3) only has conditional branches
/// as its predecessors.
///
bool FlattenCFGOpt::FlattenParallelAndOr(BasicBlock *BB, IRBuilder<> &Builder,
Pass *P) {
PHINode *PHI = dyn_cast<PHINode>(BB->begin());
if (PHI)
return false; // For simplicity, avoid cases containing PHI nodes.
BasicBlock *LastCondBlock = NULL;
BasicBlock *FirstCondBlock = NULL;
BasicBlock *UnCondBlock = NULL;
int Idx = -1;
// Check predecessors of \param BB.
SmallPtrSet<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));
for (SmallPtrSetIterator<BasicBlock *> PI = Preds.begin(), PE = Preds.end();
PI != PE; ++PI) {
BasicBlock *Pred = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(Pred->getTerminator());
// All predecessors should terminate with a branch.
if (!PBI)
return false;
BasicBlock *PP = Pred->getSinglePredecessor();
if (PBI->isUnconditional()) {
// Case 1: Pred (BB3) is an unconditional block, it should
// have a single predecessor (BB2) that is also a predecessor
// of \param BB (BB4) and should not have address-taken.
// There should exist only one such unconditional
// branch among the predecessors.
if (UnCondBlock || !PP || (Preds.count(PP) == 0) ||
Pred->hasAddressTaken())
return false;
UnCondBlock = Pred;
continue;
}
// Only conditional branches are allowed beyond this point.
assert(PBI->isConditional());
// Condition's unique use should be the branch instruction.
Value *PC = PBI->getCondition();
if (!PC || !PC->hasOneUse())
return false;
if (PP && Preds.count(PP)) {
// These are internal condition blocks to be merged from, e.g.,
// BB2 in both cases.
// Should not be address-taken.
if (Pred->hasAddressTaken())
return false;
// Instructions in the internal condition blocks should be safe
// to hoist up.
for (BasicBlock::iterator BI = Pred->begin(), BE = PBI; BI != BE;) {
Instruction *CI = BI++;
if (isa<PHINode>(CI) || !isSafeToSpeculativelyExecute(CI))
return false;
}
} else {
// This is the condition block to be merged into, e.g. BB1 in
// both cases.
if (FirstCondBlock)
return false;
FirstCondBlock = Pred;
}
// Find whether BB is uniformly on the true (or false) path
// for all of its predecessors.
BasicBlock *PS1 = PBI->getSuccessor(0);
BasicBlock *PS2 = PBI->getSuccessor(1);
BasicBlock *PS = (PS1 == BB) ? PS2 : PS1;
int CIdx = (PS1 == BB) ? 0 : 1;
if (Idx == -1)
Idx = CIdx;
else if (CIdx != Idx)
return false;
// PS is the successor which is not BB. Check successors to identify
// the last conditional branch.
if (Preds.count(PS) == 0) {
// Case 2.
LastCondBlock = Pred;
} else {
// Case 1
BranchInst *BPS = dyn_cast<BranchInst>(PS->getTerminator());
if (BPS && BPS->isUnconditional()) {
// Case 1: PS(BB3) should be an unconditional branch.
LastCondBlock = Pred;
}
}
}
if (!FirstCondBlock || !LastCondBlock || (FirstCondBlock == LastCondBlock))
return false;
TerminatorInst *TBB = LastCondBlock->getTerminator();
BasicBlock *PS1 = TBB->getSuccessor(0);
BasicBlock *PS2 = TBB->getSuccessor(1);
BranchInst *PBI1 = dyn_cast<BranchInst>(PS1->getTerminator());
BranchInst *PBI2 = dyn_cast<BranchInst>(PS2->getTerminator());
// If PS1 does not jump into PS2, but PS2 jumps into PS1,
// attempt branch inversion.
if (!PBI1 || !PBI1->isUnconditional() ||
(PS1->getTerminator()->getSuccessor(0) != PS2)) {
// Check whether PS2 jumps into PS1.
if (!PBI2 || !PBI2->isUnconditional() ||
(PS2->getTerminator()->getSuccessor(0) != PS1))
return false;
// Do branch inversion.
BasicBlock *CurrBlock = LastCondBlock;
bool EverChanged = false;
while (1) {
BranchInst *BI = dyn_cast<BranchInst>(CurrBlock->getTerminator());
CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
CmpInst::Predicate Predicate = CI->getPredicate();
// Cannonicalize icmp_ne -> icmp_eq, fcmp_one -> fcmp_oeq
if ((Predicate == CmpInst::ICMP_NE) || (Predicate == CmpInst::FCMP_ONE)) {
CI->setPredicate(ICmpInst::getInversePredicate(Predicate));
BI->swapSuccessors();
EverChanged = true;
}
if (CurrBlock == FirstCondBlock)
break;
CurrBlock = CurrBlock->getSinglePredecessor();
}
return EverChanged;
}
// PS1 must have a conditional branch.
if (!PBI1 || !PBI1->isUnconditional())
return false;
// PS2 should not contain PHI node.
PHI = dyn_cast<PHINode>(PS2->begin());
if (PHI)
return false;
// Do the transformation.
BasicBlock *CB;
BranchInst *PBI = dyn_cast<BranchInst>(FirstCondBlock->getTerminator());
bool Iteration = true;
BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
Value *PC = PBI->getCondition();
do {
CB = PBI->getSuccessor(1 - Idx);
// Delete the conditional branch.
FirstCondBlock->getInstList().pop_back();
FirstCondBlock->getInstList()
.splice(FirstCondBlock->end(), CB->getInstList());
PBI = cast<BranchInst>(FirstCondBlock->getTerminator());
Value *CC = PBI->getCondition();
// Merge conditions.
Builder.SetInsertPoint(PBI);
Value *NC;
if (Idx == 0)
// Case 2, use parallel or.
NC = Builder.CreateOr(PC, CC);
else
// Case 1, use parallel and.
NC = Builder.CreateAnd(PC, CC);
PBI->replaceUsesOfWith(CC, NC);
PC = NC;
if (CB == LastCondBlock)
Iteration = false;
// Remove internal conditional branches.
CB->dropAllReferences();
// make CB unreachable and let downstream to delete the block.
new UnreachableInst(CB->getContext(), CB);
} while (Iteration);
Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt);
DEBUG(dbgs() << "Use parallel and/or in:\n" << *FirstCondBlock);
return true;
}
void CGGraph::constructGraph() {
std::vector<CGConstraint*>::iterator it;
std::string nodeName;
CGConstraint* curConstraint;
CGNode* firstNode;
CGNode* secondNode;
std::vector<int>::iterator lengthIt;
int curValue;
ConstantInt* cInt;
for (it = constraints.begin(); it != constraints.end(); ++it) {
curConstraint = *it;
Instruction* PP = curConstraint->programPoint;
switch(curConstraint->type) {
case CGConstraint::C1:
{
firstNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(0), PP));
secondNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(1), PP));
firstNode->connectTo(secondNode, 0);
break;
}
case CGConstraint::C2:
{
if (isa<StoreInst>(PP)) {
/*
operand(0) = constant int or variable of int type
operand(1) = var being stored into
*/
firstNode = getNode(getNameFromValue(PP->getOperand(0), PP));
secondNode = getNode(getNameFromValue(PP->getOperand(1), PP));
firstNode->connectTo(secondNode, 0);
}
else if (isa<LoadInst>(PP)) {
/*
operand(0) = pointer being loaded from
(Value*)PP = var being loaded into
*/
firstNode = getNode(getNameFromValue(PP->getOperand(0), PP));
secondNode = getNode(getNameFromValue(PP, PP));
firstNode->connectTo(secondNode, 0);
}
else if (isa<CastInst>(PP)) {
/*
operand(0) = var being casted
(Value*)PP = var getting the result of the cast
*/
firstNode = getNode(getNameFromValue(PP->getOperand(0), PP));
secondNode = getNode(getNameFromValue(PP, PP));
firstNode->connectTo(secondNode, 0);
}
break;
}
case CGConstraint::C3:
{
secondNode = getNode(getNameFromValue(PP, PP));
if ((cInt = dyn_cast<ConstantInt>(curConstraint->programPoint->getOperand(0)))) {
firstNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(1), PP));
} else if ((cInt = dyn_cast<ConstantInt>(curConstraint->programPoint->getOperand(1)))) {
firstNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(0), PP));
} else {
return;
}
curValue = cInt->getSExtValue();
firstNode->connectTo(secondNode, curValue);
break;
}
case CGConstraint::C4:
{
CmpInst* cmpInst;
BranchInst* branchInst;
if( !(branchInst = dyn_cast<BranchInst>(curConstraint->programPoint)) ) {
errs() << "ERROR: BranchInst cast unsuccessful for C4 in CGGraph::constructGraph() \n";
return;
}
if( !(cmpInst = dyn_cast<CmpInst>(owner->branchToCompare[branchInst])) ) {
errs() << "ERROR: CmpInst not found for C4 in CGGraph::constructGraph() \n";
return;
}
int size1, size2;
size1 = curConstraint->piAssignments.size();
size2 = curConstraint->piAssignments2.size();
/*
There are two possibilities here: (a) size1 = size2 = 2, or (b) size1 = size2 = 1;
If (b), there will be one operand in the compare inst that is a literal value.
That literal value still generates a constraint although it does not generate a pi assignment.
We need to account for that.
*/
if (size1 != size2) {
errs() << "ERROR: piAssignments not of equal length for C4 in CGGraph::constructGraph()\n";
return;
}
if ( (size1 < 1) || (size1 > 2) ) {
errs() << "ERROR: piAssignments.size() != 1 or 2 for C4 in CGGraph::constructGraph()\n";
return;
}
//this takes care of the first two constraints for both cases (size = 1 or size = 2)
//first branch
for (int i = 0; i < size1; ++i) {
firstNode = getNode(curConstraint->piAssignments[i]->getOperandName()); //vi - wr
secondNode = getNode(curConstraint->piAssignments[i]->getAssignedName()); //vj - ws
firstNode->connectTo(secondNode, 0); //vi -> vj 0 - wr -> ws 0
}
//second branch
for (int i = 0; i < size2; ++i) {
firstNode = getNode(curConstraint->piAssignments2[i]->getOperandName()); //vi - wr
secondNode = getNode(curConstraint->piAssignments2[i]->getAssignedName()); //vk - wt
firstNode->connectTo(secondNode, 0); //vi -> vk 0 - wr -> wt 0
}
/*
- first and second op names for the third constraint for branches 1 and 2
- each case is stored in the order of the pi assignments, which is also the
order of the cmp instruction operands
*/
std::string firstOpNameBr1, secondOpNameBr1, firstOpNameBr2, secondOpNameBr2;
if (size1 == 1) {
/*
the 2nd constraint in the table will not exist in this case, but there will be a 3rd constraint
that was missed by the above, e.g.
if (x1 <= 10)
1. x2 <= x1
2. nothing
3. x2 <= 10 <---- we need to add this here
*/
//prune the int from the CmpInst
if (cmpInst->getNumOperands() != 2) {
errs() << "ERROR: cmpInst->getNumOperands() != 2 in CGGraph::constructGraph()\n";
return;
}
if ((cInt = dyn_cast<ConstantInt>(cmpInst->getOperand(0)))) {
//int is first op
firstOpNameBr1 = getNameFromValue(cInt, PP);
secondOpNameBr1 = curConstraint->piAssignments[0]->getAssignedName();
firstOpNameBr2 = firstOpNameBr1;
secondOpNameBr2 = curConstraint->piAssignments2[0]->getAssignedName();
} else if ((cInt = dyn_cast<ConstantInt>(cmpInst->getOperand(1)))) {
//int is second op
firstOpNameBr1 = curConstraint->piAssignments[0]->getAssignedName();
secondOpNameBr1 = getNameFromValue(cInt, PP);
firstOpNameBr2 = curConstraint->piAssignments2[0]->getAssignedName();
secondOpNameBr2 = secondOpNameBr1;
} else {
errs() << "ERROR: int not found in cmpInstr in CGGraph::constructGraph()\n";
return;
}
}
else if (size1 == 2) {
//store in order of pi assignments
firstOpNameBr1 = curConstraint->piAssignments[0]->getAssignedName();
secondOpNameBr1 = curConstraint->piAssignments[1]->getAssignedName();
firstOpNameBr2 = curConstraint->piAssignments2[0]->getAssignedName();
secondOpNameBr2 = curConstraint->piAssignments2[1]->getAssignedName();
}
CGNode* firstNodeBr1 = getNode(firstOpNameBr1);
CGNode* secondNodeBr1 = getNode(secondOpNameBr1);
CGNode* firstNodeBr2 = getNode(firstOpNameBr2);
CGNode* secondNodeBr2 = getNode(secondOpNameBr2);
switch(cmpInst->getPredicate()) {
case CmpInst::ICMP_SGT: // >
firstNodeBr1->connectTo(secondNodeBr1, -1); //vj -> ws -1
secondNodeBr2->connectTo(firstNodeBr2, 0); //wt -> vk 0
break;
case CmpInst::ICMP_SLT: // <
secondNodeBr1->connectTo(firstNodeBr1, -1); //ws -> vj -1
firstNodeBr2->connectTo(secondNodeBr2, 0); //vk -> wt 0
break;
case CmpInst::ICMP_SGE: // >=
firstNodeBr1->connectTo(secondNodeBr1, 0); //vj -> ws 0
secondNodeBr2->connectTo(firstNodeBr2, -1); //wt -> vk -1
break;
case CmpInst::ICMP_SLE: // <=
secondNodeBr1->connectTo(firstNodeBr1, 0); //ws -> vj 0
firstNodeBr2->connectTo(secondNodeBr2, -1); //vk -> wt -1
break;
default:
break;
}
break;
}
case CGConstraint::C5:
{
//operand 1 = array length
firstNode = getNode(getNameFromValue(PP->getOperand(1), PP));
secondNode = getNode(curConstraint->piAssignments[0]->getAssignedName());
firstNode->connectTo(secondNode, -1);
break;
}
case CGConstraint::CONTROL_FLOW:
{
//Done and ready to test
firstNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(0), PP));
secondNode = getNode(getNameFromValue(curConstraint->programPoint, PP));
firstNode->connectTo(secondNode, 0);
firstNode = getNode(getNameFromValue(curConstraint->programPoint->getOperand(1), PP));
firstNode->connectTo(secondNode, 0);
break;
}
} //end switch
} //end for
} //end constructGraph()
// Compute the unlikely successors to the block BB in the loop L, specifically
// those that are unlikely because this is a loop, and add them to the
// UnlikelyBlocks set.
static void
computeUnlikelySuccessors(const BasicBlock *BB, Loop *L,
SmallPtrSetImpl<const BasicBlock*> &UnlikelyBlocks) {
// Sometimes in a loop we have a branch whose condition is made false by
// taking it. This is typically something like
// int n = 0;
// while (...) {
// if (++n >= MAX) {
// n = 0;
// }
// }
// In this sort of situation taking the branch means that at the very least it
// won't be taken again in the next iteration of the loop, so we should
// consider it less likely than a typical branch.
//
// We detect this by looking back through the graph of PHI nodes that sets the
// value that the condition depends on, and seeing if we can reach a successor
// block which can be determined to make the condition false.
//
// FIXME: We currently consider unlikely blocks to be half as likely as other
// blocks, but if we consider the example above the likelyhood is actually
// 1/MAX. We could therefore be more precise in how unlikely we consider
// blocks to be, but it would require more careful examination of the form
// of the comparison expression.
const BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return;
// Check if the branch is based on an instruction compared with a constant
CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
if (!CI || !isa<Instruction>(CI->getOperand(0)) ||
!isa<Constant>(CI->getOperand(1)))
return;
// Either the instruction must be a PHI, or a chain of operations involving
// constants that ends in a PHI which we can then collapse into a single value
// if the PHI value is known.
Instruction *CmpLHS = dyn_cast<Instruction>(CI->getOperand(0));
PHINode *CmpPHI = dyn_cast<PHINode>(CmpLHS);
Constant *CmpConst = dyn_cast<Constant>(CI->getOperand(1));
// Collect the instructions until we hit a PHI
SmallVector<BinaryOperator *, 1> InstChain;
while (!CmpPHI && CmpLHS && isa<BinaryOperator>(CmpLHS) &&
isa<Constant>(CmpLHS->getOperand(1))) {
// Stop if the chain extends outside of the loop
if (!L->contains(CmpLHS))
return;
InstChain.push_back(cast<BinaryOperator>(CmpLHS));
CmpLHS = dyn_cast<Instruction>(CmpLHS->getOperand(0));
if (CmpLHS)
CmpPHI = dyn_cast<PHINode>(CmpLHS);
}
if (!CmpPHI || !L->contains(CmpPHI))
return;
// Trace the phi node to find all values that come from successors of BB
SmallPtrSet<PHINode*, 8> VisitedInsts;
SmallVector<PHINode*, 8> WorkList;
WorkList.push_back(CmpPHI);
VisitedInsts.insert(CmpPHI);
while (!WorkList.empty()) {
PHINode *P = WorkList.back();
WorkList.pop_back();
for (BasicBlock *B : P->blocks()) {
// Skip blocks that aren't part of the loop
if (!L->contains(B))
continue;
Value *V = P->getIncomingValueForBlock(B);
// If the source is a PHI add it to the work list if we haven't
// already visited it.
if (PHINode *PN = dyn_cast<PHINode>(V)) {
if (VisitedInsts.insert(PN).second)
WorkList.push_back(PN);
continue;
}
// If this incoming value is a constant and B is a successor of BB, then
// we can constant-evaluate the compare to see if it makes the branch be
// taken or not.
Constant *CmpLHSConst = dyn_cast<Constant>(V);
if (!CmpLHSConst ||
std::find(succ_begin(BB), succ_end(BB), B) == succ_end(BB))
continue;
// First collapse InstChain
for (Instruction *I : llvm::reverse(InstChain)) {
CmpLHSConst = ConstantExpr::get(I->getOpcode(), CmpLHSConst,
cast<Constant>(I->getOperand(1)), true);
if (!CmpLHSConst)
break;
}
if (!CmpLHSConst)
continue;
// Now constant-evaluate the compare
Constant *Result = ConstantExpr::getCompare(CI->getPredicate(),
CmpLHSConst, CmpConst, true);
// If the result means we don't branch to the block then that block is
// unlikely.
if (Result &&
((Result->isZeroValue() && B == BI->getSuccessor(0)) ||
(Result->isOneValue() && B == BI->getSuccessor(1))))
UnlikelyBlocks.insert(B);
}
}
}
