// processSwitchInst - Replace the specified switch instruction with a sequence
// of chained if-then instructions.
//
void LowerSwitchPass::processSwitchInst(SwitchInst *SI) {
BasicBlock *origBlock = SI->getParent();
BasicBlock *defaultBlock = SI->getDefaultDest();
Function *F = origBlock->getParent();
Value *switchValue = SI->getCondition();
// Create a new, empty default block so that the new hierarchy of
// if-then statements go to this and the PHI nodes are happy.
BasicBlock* newDefault = BasicBlock::Create(getGlobalContext(), "newDefault");
F->getBasicBlockList().insert(defaultBlock, newDefault);
BranchInst::Create(defaultBlock, newDefault);
// If there is an entry in any PHI nodes for the default edge, make sure
// to update them as well.
for (BasicBlock::iterator I = defaultBlock->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
int BlockIdx = PN->getBasicBlockIndex(origBlock);
assert(BlockIdx != -1 && "Switch didn't go to this successor??");
PN->setIncomingBlock((unsigned)BlockIdx, newDefault);
}
CaseVector cases;
for (SwitchInst::CaseIt it = SI->case_begin(), ie = SI->case_end(); it != ie;
++it)
cases.push_back(SwitchCase(it.getCaseValue(), it.getCaseSuccessor()));
// reverse cases, as switchConvert constructs a chain of
// basic blocks by appending to the front. if we reverse,
// the if comparisons will happen in the same order
// as the cases appear in the switch
std::reverse(cases.begin(), cases.end());
switchConvert(cases.begin(), cases.end(), switchValue, origBlock, newDefault);
// We are now done with the switch instruction, so delete it
origBlock->getInstList().erase(SI);
}
bool LowerExpectIntrinsic::HandleSwitchExpect(SwitchInst *SI) {
CallInst *CI = dyn_cast<CallInst>(SI->getCondition());
if (!CI)
return false;
Function *Fn = CI->getCalledFunction();
if (!Fn || Fn->getIntrinsicID() != Intrinsic::expect)
return false;
Value *ArgValue = CI->getArgOperand(0);
ConstantInt *ExpectedValue = dyn_cast<ConstantInt>(CI->getArgOperand(1));
if (!ExpectedValue)
return false;
LLVMContext &Context = CI->getContext();
Type *Int32Ty = Type::getInt32Ty(Context);
SwitchInst::CaseIt Case = SI->findCaseValue(ExpectedValue);
std::vector<Value *> Vec;
unsigned n = SI->getNumCases();
Vec.resize(n + 1 + 1); // +1 for MDString and +1 for default case
Vec[0] = MDString::get(Context, "branch_weights");
Vec[1] = ConstantInt::get(Int32Ty, Case == SI->case_default() ?
LikelyBranchWeight : UnlikelyBranchWeight);
for (unsigned i = 0; i < n; ++i) {
Vec[i + 1 + 1] = ConstantInt::get(Int32Ty, i == Case.getCaseIndex() ?
LikelyBranchWeight : UnlikelyBranchWeight);
}
MDNode *WeightsNode = llvm::MDNode::get(Context, Vec);
SI->setMetadata(LLVMContext::MD_prof, WeightsNode);
SI->setCondition(ArgValue);
return true;
}
/// processSwitch - Simplify a switch instruction by removing cases which can
/// never fire. If the uselessness of a case could be determined locally then
/// constant propagation would already have figured it out. Instead, walk the
/// predecessors and statically evaluate cases based on information available
/// on that edge. Cases that cannot fire no matter what the incoming edge can
/// safely be removed. If a case fires on every incoming edge then the entire
/// switch can be removed and replaced with a branch to the case destination.
bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
Value *Cond = SI->getCondition();
BasicBlock *BB = SI->getParent();
// If the condition was defined in same block as the switch then LazyValueInfo
// currently won't say anything useful about it, though in theory it could.
if (isa<Instruction>(Cond) && cast<Instruction>(Cond)->getParent() == BB)
return false;
// If the switch is unreachable then trying to improve it is a waste of time.
pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
if (PB == PE) return false;
// Analyse each switch case in turn. This is done in reverse order so that
// removing a case doesn't cause trouble for the iteration.
bool Changed = false;
for (SwitchInst::CaseIt CI = SI->case_end(), CE = SI->case_begin(); CI-- != CE;
) {
ConstantInt *Case = CI.getCaseValue();
// Check to see if the switch condition is equal to/not equal to the case
// value on every incoming edge, equal/not equal being the same each time.
LazyValueInfo::Tristate State = LazyValueInfo::Unknown;
for (pred_iterator PI = PB; PI != PE; ++PI) {
// Is the switch condition equal to the case value?
LazyValueInfo::Tristate Value = LVI->getPredicateOnEdge(CmpInst::ICMP_EQ,
Cond, Case, *PI,
BB, SI);
// Give up on this case if nothing is known.
if (Value == LazyValueInfo::Unknown) {
State = LazyValueInfo::Unknown;
break;
}
// If this was the first edge to be visited, record that all other edges
// need to give the same result.
if (PI == PB) {
State = Value;
continue;
}
// If this case is known to fire for some edges and known not to fire for
// others then there is nothing we can do - give up.
if (Value != State) {
State = LazyValueInfo::Unknown;
break;
}
}
if (State == LazyValueInfo::False) {
// This case never fires - remove it.
CI.getCaseSuccessor()->removePredecessor(BB);
SI->removeCase(CI); // Does not invalidate the iterator.
// The condition can be modified by removePredecessor's PHI simplification
// logic.
Cond = SI->getCondition();
++NumDeadCases;
Changed = true;
} else if (State == LazyValueInfo::True) {
// This case always fires. Arrange for the switch to be turned into an
// unconditional branch by replacing the switch condition with the case
// value.
SI->setCondition(Case);
NumDeadCases += SI->getNumCases();
Changed = true;
break;
}
}
if (Changed)
// If the switch has been simplified to the point where it can be replaced
// by a branch then do so now.
ConstantFoldTerminator(BB);
return Changed;
}
/// getFeasibleSuccessors - Return a vector of booleans to indicate which
/// successors are reachable from a given terminator instruction.
void SparseSolver::getFeasibleSuccessors(TerminatorInst &TI,
SmallVectorImpl<bool> &Succs,
bool AggressiveUndef) {
Succs.resize(TI.getNumSuccessors());
if (TI.getNumSuccessors() == 0) return;
if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
if (BI->isUnconditional()) {
Succs[0] = true;
return;
}
LatticeVal BCValue;
if (AggressiveUndef)
BCValue = getOrInitValueState(BI->getCondition());
else
BCValue = getLatticeState(BI->getCondition());
if (BCValue == LatticeFunc->getOverdefinedVal() ||
BCValue == LatticeFunc->getUntrackedVal()) {
// Overdefined condition variables can branch either way.
Succs[0] = Succs[1] = true;
return;
}
// If undefined, neither is feasible yet.
if (BCValue == LatticeFunc->getUndefVal())
return;
Constant *C = LatticeFunc->GetConstant(BCValue, BI->getCondition(), *this);
if (C == 0 || !isa<ConstantInt>(C)) {
// Non-constant values can go either way.
Succs[0] = Succs[1] = true;
return;
}
// Constant condition variables mean the branch can only go a single way
Succs[C->isNullValue()] = true;
return;
}
if (isa<InvokeInst>(TI)) {
// Invoke instructions successors are always executable.
// TODO: Could ask the lattice function if the value can throw.
Succs[0] = Succs[1] = true;
return;
}
if (isa<IndirectBrInst>(TI)) {
Succs.assign(Succs.size(), true);
return;
}
SwitchInst &SI = cast<SwitchInst>(TI);
LatticeVal SCValue;
if (AggressiveUndef)
SCValue = getOrInitValueState(SI.getCondition());
else
SCValue = getLatticeState(SI.getCondition());
if (SCValue == LatticeFunc->getOverdefinedVal() ||
SCValue == LatticeFunc->getUntrackedVal()) {
// All destinations are executable!
Succs.assign(TI.getNumSuccessors(), true);
return;
}
// If undefined, neither is feasible yet.
if (SCValue == LatticeFunc->getUndefVal())
return;
Constant *C = LatticeFunc->GetConstant(SCValue, SI.getCondition(), *this);
if (C == 0 || !isa<ConstantInt>(C)) {
// All destinations are executable!
Succs.assign(TI.getNumSuccessors(), true);
return;
}
SwitchInst::CaseIt Case = SI.findCaseValue(cast<ConstantInt>(C));
Succs[Case.getSuccessorIndex()] = true;
}
/// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
/// Val is not constrained on the edge.
static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
BasicBlock *BBTo, LVILatticeVal &Result) {
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
// know that v != 0.
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
// If this is a conditional branch and only one successor goes to BBTo, then
// we maybe able to infer something from the condition.
if (BI->isConditional() &&
BI->getSuccessor(0) != BI->getSuccessor(1)) {
bool isTrueDest = BI->getSuccessor(0) == BBTo;
assert(BI->getSuccessor(!isTrueDest) == BBTo &&
"BBTo isn't a successor of BBFrom");
// If V is the condition of the branch itself, then we know exactly what
// it is.
if (BI->getCondition() == Val) {
Result = LVILatticeVal::get(ConstantInt::get(
Type::getInt1Ty(Val->getContext()), isTrueDest));
return true;
}
// If the condition of the branch is an equality comparison, we may be
// able to infer the value.
ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
if (ICI && isa<Constant>(ICI->getOperand(1))) {
if (ICI->isEquality() && ICI->getOperand(0) == Val) {
// We know that V has the RHS constant if this is a true SETEQ or
// false SETNE.
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
else
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
return true;
}
// Recognize the range checking idiom that InstCombine produces.
// (X-C1) u< C2 --> [C1, C1+C2)
ConstantInt *NegOffset = 0;
if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
match(ICI->getOperand(0), m_Add(m_Specific(Val),
m_ConstantInt(NegOffset)));
ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
// Calculate the range of values that would satisfy the comparison.
ConstantRange CmpRange(CI->getValue());
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
if (NegOffset) // Apply the offset from above.
TrueValues = TrueValues.subtract(NegOffset->getValue());
// If we're interested in the false dest, invert the condition.
if (!isTrueDest) TrueValues = TrueValues.inverse();
Result = LVILatticeVal::getRange(TrueValues);
return true;
}
}
}
}
// If the edge was formed by a switch on the value, then we may know exactly
// what it is.
if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
if (SI->getCondition() != Val)
return false;
bool DefaultCase = SI->getDefaultDest() == BBTo;
unsigned BitWidth = Val->getType()->getIntegerBitWidth();
ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
i != e; ++i) {
ConstantRange EdgeVal(i.getCaseValue()->getValue());
if (DefaultCase) {
// It is possible that the default destination is the destination of
// some cases. There is no need to perform difference for those cases.
if (i.getCaseSuccessor() != BBTo)
EdgesVals = EdgesVals.difference(EdgeVal);
} else if (i.getCaseSuccessor() == BBTo)
EdgesVals = EdgesVals.unionWith(EdgeVal);
}
Result = LVILatticeVal::getRange(EdgesVals);
return true;
}
return false;
}
/// IsTrivialUnswitchCondition - Check to see if this unswitch condition is
/// trivial: that is, that the condition controls whether or not the loop does
/// anything at all. If this is a trivial condition, unswitching produces no
/// code duplications (equivalently, it produces a simpler loop and a new empty
/// loop, which gets deleted).
///
/// If this is a trivial condition, return true, otherwise return false. When
/// returning true, this sets Cond and Val to the condition that controls the
/// trivial condition: when Cond dynamically equals Val, the loop is known to
/// exit. Finally, this sets LoopExit to the BB that the loop exits to when
/// Cond == Val.
///
bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val,
BasicBlock **LoopExit) {
BasicBlock *Header = currentLoop->getHeader();
TerminatorInst *HeaderTerm = Header->getTerminator();
LLVMContext &Context = Header->getContext();
BasicBlock *LoopExitBB = 0;
if (BranchInst *BI = dyn_cast<BranchInst>(HeaderTerm)) {
// If the header block doesn't end with a conditional branch on Cond, we
// can't handle it.
if (!BI->isConditional() || BI->getCondition() != Cond)
return false;
// Check to see if a successor of the branch is guaranteed to
// exit through a unique exit block without having any
// side-effects. If so, determine the value of Cond that causes it to do
// this.
if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop,
BI->getSuccessor(0)))) {
if (Val) *Val = ConstantInt::getTrue(Context);
} else if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop,
BI->getSuccessor(1)))) {
if (Val) *Val = ConstantInt::getFalse(Context);
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(HeaderTerm)) {
// If this isn't a switch on Cond, we can't handle it.
if (SI->getCondition() != Cond) return false;
// Check to see if a successor of the switch is guaranteed to go to the
// latch block or exit through a one exit block without having any
// side-effects. If so, determine the value of Cond that causes it to do
// this.
// Note that we can't trivially unswitch on the default case or
// on already unswitched cases.
for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
i != e; ++i) {
BasicBlock* LoopExitCandidate;
if ((LoopExitCandidate = isTrivialLoopExitBlock(currentLoop,
i.getCaseSuccessor()))) {
// Okay, we found a trivial case, remember the value that is trivial.
ConstantInt* CaseVal = i.getCaseValue();
// Check that it was not unswitched before, since already unswitched
// trivial vals are looks trivial too.
if (BranchesInfo.isUnswitched(SI, CaseVal))
continue;
LoopExitBB = LoopExitCandidate;
if (Val) *Val = CaseVal;
break;
}
}
}
// If we didn't find a single unique LoopExit block, or if the loop exit block
// contains phi nodes, this isn't trivial.
if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin()))
return false; // Can't handle this.
if (LoopExit) *LoopExit = LoopExitBB;
// We already know that nothing uses any scalar values defined inside of this
// loop. As such, we just have to check to see if this loop will execute any
// side-effecting instructions (e.g. stores, calls, volatile loads) in the
// part of the loop that the code *would* execute. We already checked the
// tail, check the header now.
for (BasicBlock::iterator I = Header->begin(), E = Header->end(); I != E; ++I)
if (I->mayHaveSideEffects())
return false;
return true;
}
/// processCurrentLoop - Do actual work and unswitch loop if possible
/// and profitable.
bool LoopUnswitch::processCurrentLoop() {
bool Changed = false;
initLoopData();
// If LoopSimplify was unable to form a preheader, don't do any unswitching.
if (!loopPreheader)
return false;
// Loops with indirectbr cannot be cloned.
if (!currentLoop->isSafeToClone())
return false;
// Without dedicated exits, splitting the exit edge may fail.
if (!currentLoop->hasDedicatedExits())
return false;
LLVMContext &Context = loopHeader->getContext();
// Probably we reach the quota of branches for this loop. If so
// stop unswitching.
if (!BranchesInfo.countLoop(currentLoop))
return false;
// Loop over all of the basic blocks in the loop. If we find an interior
// block that is branching on a loop-invariant condition, we can unswitch this
// loop.
for (Loop::block_iterator I = currentLoop->block_begin(),
E = currentLoop->block_end(); I != E; ++I) {
TerminatorInst *TI = (*I)->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
// If this isn't branching on an invariant condition, we can't unswitch
// it.
if (BI->isConditional()) {
// See if this, or some part of it, is loop invariant. If so, we can
// unswitch on it if we desire.
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
currentLoop, Changed);
if (LoopCond && UnswitchIfProfitable(LoopCond,
ConstantInt::getTrue(Context))) {
++NumBranches;
return true;
}
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
currentLoop, Changed);
unsigned NumCases = SI->getNumCases();
if (LoopCond && NumCases) {
// Find a value to unswitch on:
// FIXME: this should chose the most expensive case!
// FIXME: scan for a case with a non-critical edge?
Constant *UnswitchVal = NULL;
// Do not process same value again and again.
// At this point we have some cases already unswitched and
// some not yet unswitched. Let's find the first not yet unswitched one.
for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
i != e; ++i) {
Constant* UnswitchValCandidate = i.getCaseValue();
if (!BranchesInfo.isUnswitched(SI, UnswitchValCandidate)) {
UnswitchVal = UnswitchValCandidate;
break;
}
}
if (!UnswitchVal)
continue;
if (UnswitchIfProfitable(LoopCond, UnswitchVal)) {
++NumSwitches;
return true;
}
}
}
// Scan the instructions to check for unswitchable values.
for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end();
BBI != E; ++BBI)
if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) {
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
currentLoop, Changed);
if (LoopCond && UnswitchIfProfitable(LoopCond,
ConstantInt::getTrue(Context))) {
++NumSelects;
return true;
}
}
}
return Changed;
}
// RewriteLoopBodyWithConditionConstant - We know either that the value LIC has
// the value specified by Val in the specified loop, or we know it does NOT have
// that value. Rewrite any uses of LIC or of properties correlated to it.
void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
Constant *Val,
bool IsEqual) {
assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?");
// FIXME: Support correlated properties, like:
// for (...)
// if (li1 < li2)
// ...
// if (li1 > li2)
// ...
// FOLD boolean conditions (X|LIC), (X&LIC). Fold conditional branches,
// selects, switches.
std::vector<Instruction*> Worklist;
LLVMContext &Context = Val->getContext();
// If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC
// in the loop with the appropriate one directly.
if (IsEqual || (isa<ConstantInt>(Val) &&
Val->getType()->isIntegerTy(1))) {
Value *Replacement;
if (IsEqual)
Replacement = Val;
else
Replacement = ConstantInt::get(Type::getInt1Ty(Val->getContext()),
!cast<ConstantInt>(Val)->getZExtValue());
for (Value::use_iterator UI = LIC->use_begin(), E = LIC->use_end();
UI != E; ++UI) {
Instruction *U = dyn_cast<Instruction>(*UI);
if (!U || !L->contains(U))
continue;
Worklist.push_back(U);
}
for (std::vector<Instruction*>::iterator UI = Worklist.begin();
UI != Worklist.end(); ++UI)
(*UI)->replaceUsesOfWith(LIC, Replacement);
SimplifyCode(Worklist, L);
return;
}
// Otherwise, we don't know the precise value of LIC, but we do know that it
// is certainly NOT "Val". As such, simplify any uses in the loop that we
// can. This case occurs when we unswitch switch statements.
for (Value::use_iterator UI = LIC->use_begin(), E = LIC->use_end();
UI != E; ++UI) {
Instruction *U = dyn_cast<Instruction>(*UI);
if (!U || !L->contains(U))
continue;
Worklist.push_back(U);
// TODO: We could do other simplifications, for example, turning
// 'icmp eq LIC, Val' -> false.
// If we know that LIC is not Val, use this info to simplify code.
SwitchInst *SI = dyn_cast<SwitchInst>(U);
if (SI == 0 || !isa<ConstantInt>(Val)) continue;
SwitchInst::CaseIt DeadCase = SI->findCaseValue(cast<ConstantInt>(Val));
// Default case is live for multiple values.
if (DeadCase == SI->case_default()) continue;
// Found a dead case value. Don't remove PHI nodes in the
// successor if they become single-entry, those PHI nodes may
// be in the Users list.
BasicBlock *Switch = SI->getParent();
BasicBlock *SISucc = DeadCase.getCaseSuccessor();
BasicBlock *Latch = L->getLoopLatch();
BranchesInfo.setUnswitched(SI, Val);
if (!SI->findCaseDest(SISucc)) continue; // Edge is critical.
// If the DeadCase successor dominates the loop latch, then the
// transformation isn't safe since it will delete the sole predecessor edge
// to the latch.
if (Latch && DT->dominates(SISucc, Latch))
continue;
// FIXME: This is a hack. We need to keep the successor around
// and hooked up so as to preserve the loop structure, because
// trying to update it is complicated. So instead we preserve the
// loop structure and put the block on a dead code path.
SplitEdge(Switch, SISucc, this);
// Compute the successors instead of relying on the return value
// of SplitEdge, since it may have split the switch successor
// after PHI nodes.
BasicBlock *NewSISucc = DeadCase.getCaseSuccessor();
BasicBlock *OldSISucc = *succ_begin(NewSISucc);
// Create an "unreachable" destination.
BasicBlock *Abort = BasicBlock::Create(Context, "us-unreachable",
Switch->getParent(),
OldSISucc);
new UnreachableInst(Context, Abort);
// Force the new case destination to branch to the "unreachable"
// block while maintaining a (dead) CFG edge to the old block.
NewSISucc->getTerminator()->eraseFromParent();
BranchInst::Create(Abort, OldSISucc,
ConstantInt::getTrue(Context), NewSISucc);
// Release the PHI operands for this edge.
for (BasicBlock::iterator II = NewSISucc->begin();
PHINode *PN = dyn_cast<PHINode>(II); ++II)
PN->setIncomingValue(PN->getBasicBlockIndex(Switch),
UndefValue::get(PN->getType()));
// Tell the domtree about the new block. We don't fully update the
// domtree here -- instead we force it to do a full recomputation
// after the pass is complete -- but we do need to inform it of
// new blocks.
if (DT)
DT->addNewBlock(Abort, NewSISucc);
}
SimplifyCode(Worklist, L);
}
// Set outgoing edges alive dependent on the terminator instruction SI.
// If the terminator is an Invoke instruction, the call has already been run.
// Return true if anything changed.
bool IntegrationAttempt::checkBlockOutgoingEdges(ShadowInstruction* SI) {
// TOCHECK: I think this only returns false if the block ends with an Unreachable inst?
switch(SI->invar->I->getOpcode()) {
case Instruction::Br:
case Instruction::Switch:
case Instruction::Invoke:
case Instruction::Resume:
break;
default:
return false;
}
if(inst_is<InvokeInst>(SI)) {
InlineAttempt* IA = getInlineAttempt(SI);
bool changed = false;
// !localStore indicates the invoke instruction doesn't return normally
if(SI->parent->localStore) {
changed |= !SI->parent->succsAlive[0];
SI->parent->succsAlive[0] = true;
}
// I mark the exceptional edge reachable here if the call is disabled, even though
// we might have proved it isn't feasible. This could be improved by converting the
// invoke into a call in the final program.
if((!IA) || (!IA->isEnabled()) || IA->mayUnwind) {
changed |= !SI->parent->succsAlive[1];
SI->parent->succsAlive[1] = true;
}
return changed;
}
else if(inst_is<ResumeInst>(SI)) {
bool changed = !mayUnwind;
mayUnwind = true;
return changed;
}
else if(BranchInst* BI = dyn_cast_inst<BranchInst>(SI)) {
if(BI->isUnconditional()) {
bool changed = !SI->parent->succsAlive[0];
SI->parent->succsAlive[0] = true;
return changed;
}
}
// Both switches and conditional branches use operand 0 for the condition.
ShadowValue Condition = SI->getOperand(0);
bool changed = false;
ConstantInt* ConstCondition = dyn_cast_or_null<ConstantInt>(getConstReplacement(Condition));
if(!ConstCondition) {
if(Condition.t == SHADOWVAL_INST || Condition.t == SHADOWVAL_ARG) {
// Switch statements can operate on a ptrtoint operand, of which only ptrtoint(null) is useful:
if(ImprovedValSetSingle* IVS = dyn_cast_or_null<ImprovedValSetSingle>(getIVSRef(Condition))) {
if(IVS->onlyContainsNulls()) {
ConstCondition = cast<ConstantInt>(Constant::getNullValue(SI->invar->I->getOperand(0)->getType()));
}
}
}
}
if(!ConstCondition) {
std::pair<ValSetType, ImprovedVal> PathVal;
if(tryGetPathValue(Condition, SI->parent, PathVal))
ConstCondition = dyn_cast_val<ConstantInt>(PathVal.second.V);
}
TerminatorInst* TI = cast_inst<TerminatorInst>(SI);
const unsigned NumSucc = TI->getNumSuccessors();
if(ConstCondition) {
BasicBlock* takenTarget = 0;
if(BranchInst* BI = dyn_cast_inst<BranchInst>(SI)) {
// This ought to be a boolean.
if(ConstCondition->isZero())
takenTarget = BI->getSuccessor(1);
else
takenTarget = BI->getSuccessor(0);
}
else {
SwitchInst* SwI = cast_inst<SwitchInst>(SI);
SwitchInst::CaseIt targetidx = SwI->findCaseValue(ConstCondition);
takenTarget = targetidx.getCaseSuccessor();
}
if(takenTarget) {
// We know where the instruction is going -- remove this block as a predecessor for its other targets.
LPDEBUG("Branch or switch instruction given known target: " << takenTarget->getName() << "\n");
return setEdgeAlive(TI, SI->parent, takenTarget);
}
// Else fall through to set all alive.
}
SwitchInst* Switch;
ImprovedValSetSingle* IVS;
if((Switch = dyn_cast_inst<SwitchInst>(SI)) &&
(IVS = dyn_cast<ImprovedValSetSingle>(getIVSRef(Condition))) &&
IVS->SetType == ValSetTypeScalar &&
!IVS->Values.empty()) {
// A set of values feeding a switch. Set each corresponding edge alive.
bool changed = false;
for (unsigned i = 0, ilim = IVS->Values.size(); i != ilim; ++i) {
SwitchInst::CaseIt targetit = Switch->findCaseValue(cast<ConstantInt>(getConstReplacement(IVS->Values[i].V)));
BasicBlock* target = targetit.getCaseSuccessor();
changed |= setEdgeAlive(TI, SI->parent, target);
}
return changed;
}
// Condition unknown -- set all successors alive.
for (unsigned I = 0; I != NumSucc; ++I) {
// Mark outgoing edge alive
if(!SI->parent->succsAlive[I])
changed = true;
SI->parent->succsAlive[I] = true;
}
return changed;
}
static void convertInstruction(Instruction *Inst, ConversionState &State) {
if (SExtInst *Sext = dyn_cast<SExtInst>(Inst)) {
Value *Op = Sext->getOperand(0);
Value *NewInst = NULL;
// If the operand to be extended is illegal, we first need to fill its
// upper bits (which are zero) with its sign bit.
if (shouldConvert(Op)) {
NewInst = getSignExtend(State.getConverted(Op), Op, Sext);
}
// If the converted type of the operand is the same as the converted
// type of the result, we won't actually be changing the type of the
// variable, just its value.
if (getPromotedType(Op->getType()) !=
getPromotedType(Sext->getType())) {
NewInst = new SExtInst(
NewInst ? NewInst : State.getConverted(Op),
getPromotedType(cast<IntegerType>(Sext->getType())),
Sext->getName() + ".sext", Sext);
}
// Now all the bits of the result are correct, but we need to restore
// the bits above its type to zero.
if (shouldConvert(Sext)) {
NewInst = getClearUpper(NewInst, Sext->getType(), Sext);
}
assert(NewInst && "Failed to convert sign extension");
State.recordConverted(Sext, NewInst);
} else if (ZExtInst *Zext = dyn_cast<ZExtInst>(Inst)) {
Value *Op = Zext->getOperand(0);
Value *NewInst = NULL;
// TODO(dschuff): Some of these zexts could be no-ops.
if (shouldConvert(Op)) {
NewInst = getClearUpper(State.getConverted(Op),
Op->getType(),
Zext);
}
// If the converted type of the operand is the same as the converted
// type of the result, we won't actually be changing the type of the
// variable, just its value.
if (getPromotedType(Op->getType()) !=
getPromotedType(Zext->getType())) {
NewInst = CastInst::CreateZExtOrBitCast(
NewInst ? NewInst : State.getConverted(Op),
getPromotedType(cast<IntegerType>(Zext->getType())),
"", Zext);
}
assert(NewInst);
State.recordConverted(Zext, NewInst);
} else if (TruncInst *Trunc = dyn_cast<TruncInst>(Inst)) {
Value *Op = Trunc->getOperand(0);
Value *NewInst = NULL;
// If the converted type of the operand is the same as the converted
// type of the result, we won't actually be changing the type of the
// variable, just its value.
if (getPromotedType(Op->getType()) !=
getPromotedType(Trunc->getType())) {
NewInst = new TruncInst(
State.getConverted(Op),
getPromotedType(cast<IntegerType>(Trunc->getType())),
State.getConverted(Op)->getName() + ".trunc",
Trunc);
}
// Restoring the upper-bits-are-zero invariant effectively truncates the
// value.
if (shouldConvert(Trunc)) {
NewInst = getClearUpper(NewInst ? NewInst : Op,
Trunc->getType(),
Trunc);
}
assert(NewInst);
State.recordConverted(Trunc, NewInst);
} else if (AllocaInst *Alloc = dyn_cast<AllocaInst>(Inst)) {
// Don't handle arrays of illegal types, but we could handle an array
// with size specified as an illegal type, as unlikely as that seems.
if (shouldConvert(Alloc) && Alloc->isArrayAllocation())
report_fatal_error("Can't convert arrays of illegal type");
AllocaInst *NewInst = new AllocaInst(
getPromotedType(Alloc->getAllocatedType()),
State.getConverted(Alloc->getArraySize()),
"", Alloc);
NewInst->setAlignment(Alloc->getAlignment());
State.recordConverted(Alloc, NewInst);
} else if (BitCastInst *BCInst = dyn_cast<BitCastInst>(Inst)) {
// Only handle pointers. Ints can't be casted to/from other ints
Type *DestType = shouldConvert(BCInst) ?
getPromotedType(BCInst->getDestTy()) : BCInst->getDestTy();
BitCastInst *NewInst = new BitCastInst(
State.getConverted(BCInst->getOperand(0)),
DestType,
"", BCInst);
State.recordConverted(BCInst, NewInst);
} else if (LoadInst *Load = dyn_cast<LoadInst>(Inst)) {
if (shouldConvert(Load)) {
splitLoad(Load, State);
}
} else if (StoreInst *Store = dyn_cast<StoreInst>(Inst)) {
if (shouldConvert(Store->getValueOperand())) {
splitStore(Store, State);
}
} else if (isa<CallInst>(Inst)) {
report_fatal_error("can't convert calls with illegal types");
} else if (BinaryOperator *Binop = dyn_cast<BinaryOperator>(Inst)) {
Value *NewInst = NULL;
if (Binop->getOpcode() == Instruction::AShr) {
// The AShr operand needs to be sign-extended to the promoted size
// before shifting. Because the sign-extension is implemented with
// with AShr, it can be combined with the original operation.
Value *Op = Binop->getOperand(0);
Value *ShiftAmount = NULL;
APInt SignShiftAmt = APInt(
getPromotedType(Op->getType())->getIntegerBitWidth(),
getPromotedType(Op->getType())->getIntegerBitWidth() -
Op->getType()->getIntegerBitWidth());
NewInst = BinaryOperator::Create(
Instruction::Shl,
State.getConverted(Op),
ConstantInt::get(getPromotedType(Op->getType()), SignShiftAmt),
State.getConverted(Op)->getName() + ".getsign",
Binop);
if (ConstantInt *C = dyn_cast<ConstantInt>(
State.getConverted(Binop->getOperand(1)))) {
ShiftAmount = ConstantInt::get(getPromotedType(Op->getType()),
SignShiftAmt + C->getValue());
} else {
ShiftAmount = BinaryOperator::Create(
Instruction::Add,
State.getConverted(Binop->getOperand(1)),
ConstantInt::get(
getPromotedType(Binop->getOperand(1)->getType()),
SignShiftAmt),
State.getConverted(Op)->getName() + ".shamt", Binop);
}
NewInst = BinaryOperator::Create(
Instruction::AShr,
NewInst,
ShiftAmount,
Binop->getName() + ".result", Binop);
} else {
// If the original operation is not AShr, just recreate it as usual.
NewInst = BinaryOperator::Create(
Binop->getOpcode(),
State.getConverted(Binop->getOperand(0)),
State.getConverted(Binop->getOperand(1)),
Binop->getName() + ".result", Binop);
if (isa<OverflowingBinaryOperator>(NewInst)) {
cast<BinaryOperator>(NewInst)->setHasNoUnsignedWrap
(Binop->hasNoUnsignedWrap());
cast<BinaryOperator>(NewInst)->setHasNoSignedWrap(
Binop->hasNoSignedWrap());
}
}
// Now restore the invariant if necessary.
// This switch also sanity-checks the operation.
switch (Binop->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::LShr:
// These won't change the upper bits.
break;
// These can change the upper bits, unless we are sure they never
// overflow. So clear them now.
case Instruction::Add:
case Instruction::Sub:
if (!(Binop->hasNoUnsignedWrap() && Binop->hasNoSignedWrap()))
NewInst = getClearUpper(NewInst, Binop->getType(), Binop);
break;
case Instruction::Shl:
if (!Binop->hasNoUnsignedWrap())
NewInst = getClearUpper(NewInst, Binop->getType(), Binop);
break;
// We modified the upper bits ourselves when implementing AShr
case Instruction::AShr:
NewInst = getClearUpper(NewInst, Binop->getType(), Binop);
break;
// We should not see FP operators here.
// We don't handle mul/div.
case Instruction::FAdd:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
case Instruction::BinaryOpsEnd:
errs() << *Inst << "\n";
llvm_unreachable("Cannot handle binary operator");
break;
}
State.recordConverted(Binop, NewInst);
} else if (ICmpInst *Cmp = dyn_cast<ICmpInst>(Inst)) {
Value *Op0, *Op1;
// For signed compares, operands are sign-extended to their
// promoted type. For unsigned or equality compares, the comparison
// is equivalent with the larger type because they are already
// zero-extended.
if (Cmp->isSigned()) {
Op0 = getSignExtend(State.getConverted(Cmp->getOperand(0)),
Cmp->getOperand(0),
Cmp);
Op1 = getSignExtend(State.getConverted(Cmp->getOperand(1)),
Cmp->getOperand(1),
Cmp);
} else {
Op0 = State.getConverted(Cmp->getOperand(0));
Op1 = State.getConverted(Cmp->getOperand(1));
}
ICmpInst *NewInst = new ICmpInst(
Cmp, Cmp->getPredicate(), Op0, Op1, "");
State.recordConverted(Cmp, NewInst);
} else if (SelectInst *Select = dyn_cast<SelectInst>(Inst)) {
SelectInst *NewInst = SelectInst::Create(
Select->getCondition(),
State.getConverted(Select->getTrueValue()),
State.getConverted(Select->getFalseValue()),
"", Select);
State.recordConverted(Select, NewInst);
} else if (PHINode *Phi = dyn_cast<PHINode>(Inst)) {
PHINode *NewPhi = PHINode::Create(
getPromotedType(Phi->getType()),
Phi->getNumIncomingValues(),
"", Phi);
for (unsigned I = 0, E = Phi->getNumIncomingValues(); I < E; ++I) {
NewPhi->addIncoming(State.getConverted(Phi->getIncomingValue(I)),
Phi->getIncomingBlock(I));
}
State.recordConverted(Phi, NewPhi);
} else if (SwitchInst *Switch = dyn_cast<SwitchInst>(Inst)) {
SwitchInst *NewInst = SwitchInst::Create(
State.getConverted(Switch->getCondition()),
Switch->getDefaultDest(),
Switch->getNumCases(),
Switch);
for (SwitchInst::CaseIt I = Switch->case_begin(),
E = Switch->case_end();
I != E; ++I) {
// Build a new case from the ranges that map to the successor BB. Each
// range consists of a high and low value which are typed, so the ranges
// must be rebuilt and a new case constructed from them.
IntegersSubset CaseRanges = I.getCaseValueEx();
IntegersSubsetToBB CaseBuilder;
for (unsigned RI = 0, RE = CaseRanges.getNumItems(); RI < RE; ++RI) {
CaseBuilder.add(
IntItem::fromConstantInt(cast<ConstantInt>(convertConstant(
CaseRanges.getItem(RI).getLow().toConstantInt()))),
IntItem::fromConstantInt(cast<ConstantInt>(convertConstant(
CaseRanges.getItem(RI).getHigh().toConstantInt()))));
}
IntegersSubset Case = CaseBuilder.getCase();
NewInst->addCase(Case, I.getCaseSuccessor());
}
Switch->eraseFromParent();
} else {
errs() << *Inst<<"\n";
llvm_unreachable("unhandled instruction");
}
}
