struct LoopProperties {
unsigned CanBeUnswitchedCount;
+ unsigned WasUnswitchedCount;
unsigned SizeEstimation;
UnswitchedValsMap UnswitchedVals;
};
UnswitchedValsMap *CurLoopInstructions;
LoopProperties *CurrentLoopProperties;
- // Max size of code we can produce on remained iterations.
+ // A loop unswitching with an estimated cost above this threshold
+ // is not performed. MaxSize is turned into unswitching quota for
+ // the current loop, and reduced correspondingly, though note that
+ // the quota is returned by releaseMemory() when the loop has been
+ // processed, so that MaxSize will return to its previous
+ // value. So in most cases MaxSize will equal the Threshold flag
+ // when a new loop is processed. An exception to that is that
+ // MaxSize will have a smaller value while processing nested loops
+ // that were introduced due to loop unswitching of an outer loop.
+ //
+ // FIXME: The way that MaxSize works is subtle and depends on the
+ // pass manager processing loops and calling releaseMemory() in a
+ // specific order. It would be good to find a more straightforward
+ // way of doing what MaxSize does.
unsigned MaxSize;
- public:
-
- LUAnalysisCache() :
- CurLoopInstructions(nullptr), CurrentLoopProperties(nullptr),
- MaxSize(Threshold)
- {}
-
- // Analyze loop. Check its size, calculate is it possible to unswitch
- // it. Returns true if we can unswitch this loop.
- bool countLoop(const Loop *L, const TargetTransformInfo &TTI,
- AssumptionCache *AC);
-
- // Clean all data related to given loop.
- void forgetLoop(const Loop *L);
-
- // Mark case value as unswitched.
- // Since SI instruction can be partly unswitched, in order to avoid
- // extra unswitching in cloned loops keep track all unswitched values.
- void setUnswitched(const SwitchInst *SI, const Value *V);
-
- // Check was this case value unswitched before or not.
- bool isUnswitched(const SwitchInst *SI, const Value *V);
-
- // Clone all loop-unswitch related loop properties.
- // Redistribute unswitching quotas.
- // Note, that new loop data is stored inside the VMap.
- void cloneData(const Loop *NewLoop, const Loop *OldLoop,
- const ValueToValueMapTy &VMap);
+ public:
+ LUAnalysisCache()
+ : CurLoopInstructions(nullptr), CurrentLoopProperties(nullptr),
+ MaxSize(Threshold) {}
+
+ // Analyze loop. Check its size, calculate is it possible to unswitch
+ // it. Returns true if we can unswitch this loop.
+ bool countLoop(const Loop *L, const TargetTransformInfo &TTI,
+ AssumptionCache *AC);
+
+ // Clean all data related to given loop.
+ void forgetLoop(const Loop *L);
+
+ // Mark case value as unswitched.
+ // Since SI instruction can be partly unswitched, in order to avoid
+ // extra unswitching in cloned loops keep track all unswitched values.
+ void setUnswitched(const SwitchInst *SI, const Value *V);
+
+ // Check was this case value unswitched before or not.
+ bool isUnswitched(const SwitchInst *SI, const Value *V);
+
+ // Returns true if another unswitching could be done within the cost
+ // threshold.
+ bool CostAllowsUnswitching();
+
+ // Clone all loop-unswitch related loop properties.
+ // Redistribute unswitching quotas.
+ // Note, that new loop data is stored inside the VMap.
+ void cloneData(const Loop *NewLoop, const Loop *OldLoop,
+ const ValueToValueMapTy &VMap);
};
class LoopUnswitch : public LoopPass {
LPPassManager *LPM;
AssumptionCache *AC;
- // LoopProcessWorklist - Used to check if second loop needs processing
- // after RewriteLoopBodyWithConditionConstant rewrites first loop.
+ // Used to check if second loop needs processing after
+ // RewriteLoopBodyWithConditionConstant rewrites first loop.
std::vector<Loop*> LoopProcessWorklist;
LUAnalysisCache BranchesInfo;
/// Split all of the edges from inside the loop to their exit blocks.
/// Update the appropriate Phi nodes as we do so.
- void SplitExitEdges(Loop *L, const SmallVectorImpl<BasicBlock *> &ExitBlocks);
+ void SplitExitEdges(Loop *L,
+ const SmallVectorImpl<BasicBlock *> &ExitBlocks);
+
+ bool TryTrivialLoopUnswitch(bool &Changed);
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val,
TerminatorInst *TI = nullptr);
TerminatorInst *TI);
void SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L);
- bool IsTrivialUnswitchCondition(Value *Cond, Constant **Val = nullptr,
- BasicBlock **LoopExit = nullptr);
-
};
}
// consideration code simplification opportunities and code that can
// be shared by the resultant unswitched loops.
CodeMetrics Metrics;
- for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
- I != E; ++I)
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); I != E;
+ ++I)
Metrics.analyzeBasicBlock(*I, TTI, EphValues);
- Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
+ Props.SizeEstimation = Metrics.NumInsts;
Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
+ Props.WasUnswitchedCount = 0;
MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
if (Metrics.notDuplicatable) {
}
}
- if (!Props.CanBeUnswitchedCount) {
- DEBUG(dbgs() << "NOT unswitching loop %"
- << L->getHeader()->getName() << ", cost too high: "
- << L->getBlocks().size() << "\n");
- return false;
- }
-
// Be careful. This links are good only before new loop addition.
CurrentLoopProperties = &Props;
CurLoopInstructions = &Props.UnswitchedVals;
if (LIt != LoopsProperties.end()) {
LoopProperties &Props = LIt->second;
- MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
+ MaxSize += (Props.CanBeUnswitchedCount + Props.WasUnswitchedCount) *
+ Props.SizeEstimation;
LoopsProperties.erase(LIt);
}
return (*CurLoopInstructions)[SI].count(V);
}
+bool LUAnalysisCache::CostAllowsUnswitching() {
+ return CurrentLoopProperties->CanBeUnswitchedCount > 0;
+}
+
// Clone all loop-unswitch related loop properties.
// Redistribute unswitching quotas.
// Note, that new loop data is stored inside the VMap.
// Reallocate "can-be-unswitched quota"
--OldLoopProps.CanBeUnswitchedCount;
+ ++OldLoopProps.WasUnswitchedCount;
+ NewLoopProps.WasUnswitchedCount = 0;
unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
NewLoopProps.CanBeUnswitchedCount = Quota / 2;
OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
return new LoopUnswitch(Os);
}
-/// FindLIVLoopCondition - Cond is a condition that occurs in L. If it is
-/// invariant in the loop, or has an invariant piece, return the invariant.
-/// Otherwise, return null.
+/// Cond is a condition that occurs in L. If it is invariant in the loop, or has
+/// an invariant piece, return the invariant. Otherwise, return null.
static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) {
// We started analyze new instruction, increment scanned instructions counter.
return Changed;
}
-/// processCurrentLoop - Do actual work and unswitch loop if possible
-/// and profitable.
+/// Do actual work and unswitch loop if possible and profitable.
bool LoopUnswitch::processCurrentLoop() {
bool Changed = false;
AC))
return false;
+ // Try trivial unswitch first before loop over other basic blocks in the loop.
+ if (TryTrivialLoopUnswitch(Changed)) {
+ return true;
+ }
+
// 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.
return Changed;
}
-/// isTrivialLoopExitBlock - Check to see if all paths from BB exit the
-/// loop with no side effects (including infinite loops).
+/// Check to see if all paths from BB exit the loop with no side effects
+/// (including infinite loops).
///
/// If true, we return true and set ExitBB to the block we
/// exit through.
return true;
}
-/// isTrivialLoopExitBlock - Return true if the specified block unconditionally
-/// leads to an exit from the specified loop, and has no side-effects in the
-/// process. If so, return the block that is exited to, otherwise return null.
+/// Return true if the specified block unconditionally leads to an exit from
+/// the specified loop, and has no side-effects in the process. If so, return
+/// the block that is exited to, otherwise return null.
static BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) {
std::set<BasicBlock*> Visited;
Visited.insert(L->getHeader()); // Branches to header make infinite loops.
return nullptr;
}
-/// 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 = nullptr;
- 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;
-}
-
-/// UnswitchIfProfitable - We have found that we can unswitch currentLoop when
-/// LoopCond == Val to simplify the loop. If we decide that this is profitable,
+/// We have found that we can unswitch currentLoop when LoopCond == Val to
+/// simplify the loop. If we decide that this is profitable,
/// unswitch the loop, reprocess the pieces, then return true.
bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val,
TerminatorInst *TI) {
Function *F = loopHeader->getParent();
- Constant *CondVal = nullptr;
- BasicBlock *ExitBlock = nullptr;
-
- if (IsTrivialUnswitchCondition(LoopCond, &CondVal, &ExitBlock)) {
- // If the condition is trivial, always unswitch. There is no code growth
- // for this case.
- UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock, TI);
- return true;
- }
// Check to see if it would be profitable to unswitch current loop.
+ if (!BranchesInfo.CostAllowsUnswitching()) {
+ DEBUG(dbgs() << "NOT unswitching loop %"
+ << currentLoop->getHeader()->getName()
+ << " at non-trivial condition '" << *Val
+ << "' == " << *LoopCond << "\n"
+ << ". Cost too high.\n");
+ return false;
+ }
// Do not do non-trivial unswitch while optimizing for size.
+ // FIXME: Use Function::optForSize().
if (OptimizeForSize || F->hasFnAttribute(Attribute::OptimizeForSize))
return false;
return true;
}
-/// CloneLoop - Recursively clone the specified loop and all of its children,
+/// Recursively clone the specified loop and all of its children,
/// mapping the blocks with the specified map.
static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
LoopInfo *LI, LPPassManager *LPM) {
}
}
// fallthrough.
+ case LLVMContext::MD_make_implicit:
case LLVMContext::MD_dbg:
DstInst->setMetadata(MD.first, MD.second);
}
}
}
-/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values
-/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the
-/// code immediately before InsertPt.
+/// Emit a conditional branch on two values if LIC == Val, branch to TrueDst,
+/// otherwise branch to FalseDest. Insert the code immediately before InsertPt.
void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
BasicBlock *TrueDest,
BasicBlock *FalseDest,
SplitCriticalEdge(BI, 1, Options);
}
-/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable
-/// condition in it (a cond branch from its header block to its latch block,
-/// where the path through the loop that doesn't execute its body has no
-/// side-effects), unswitch it. This doesn't involve any code duplication, just
-/// moving the conditional branch outside of the loop and updating loop info.
+/// Given a loop that has a trivial unswitchable condition in it (a cond branch
+/// from its header block to its latch block, where the path through the loop
+/// that doesn't execute its body has no side-effects), unswitch it. This
+/// doesn't involve any code duplication, just moving the conditional branch
+/// outside of the loop and updating loop info.
void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
BasicBlock *ExitBlock,
TerminatorInst *TI) {
++NumTrivial;
}
-/// SplitExitEdges - Split all of the edges from inside the loop to their exit
-/// blocks. Update the appropriate Phi nodes as we do so.
+/// Check if the first non-constant condition starting from the loop header is
+/// a trivial unswitch condition: that is, a condition controls whether or not
+/// the loop does anything at all. If it is a trivial condition, unswitching
+/// produces no code duplications (equivalently, it produces a simpler loop and
+/// a new empty loop, which gets deleted). Therefore always unswitch trivial
+/// condition.
+bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) {
+ BasicBlock *CurrentBB = currentLoop->getHeader();
+ TerminatorInst *CurrentTerm = CurrentBB->getTerminator();
+ LLVMContext &Context = CurrentBB->getContext();
+
+ // If loop header has only one reachable successor (currently via an
+ // unconditional branch or constant foldable conditional branch, but
+ // should also consider adding constant foldable switch instruction in
+ // future), we should keep looking for trivial condition candidates in
+ // the successor as well. An alternative is to constant fold conditions
+ // and merge successors into loop header (then we only need to check header's
+ // terminator). The reason for not doing this in LoopUnswitch pass is that
+ // it could potentially break LoopPassManager's invariants. Folding dead
+ // branches could either eliminate the current loop or make other loops
+ // unreachable. LCSSA form might also not be preserved after deleting
+ // branches. The following code keeps traversing loop header's successors
+ // until it finds the trivial condition candidate (condition that is not a
+ // constant). Since unswitching generates branches with constant conditions,
+ // this scenario could be very common in practice.
+ SmallSet<BasicBlock*, 8> Visited;
+
+ while (true) {
+ // If we exit loop or reach a previous visited block, then
+ // we can not reach any trivial condition candidates (unfoldable
+ // branch instructions or switch instructions) and no unswitch
+ // can happen. Exit and return false.
+ if (!currentLoop->contains(CurrentBB) || !Visited.insert(CurrentBB).second)
+ return false;
+
+ // Check 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. Check the header first.
+ for (BasicBlock::iterator I : *CurrentBB)
+ if (I->mayHaveSideEffects())
+ return false;
+
+ // FIXME: add check for constant foldable switch instructions.
+ if (BranchInst *BI = dyn_cast<BranchInst>(CurrentTerm)) {
+ if (BI->isUnconditional()) {
+ CurrentBB = BI->getSuccessor(0);
+ } else if (BI->getCondition() == ConstantInt::getTrue(Context)) {
+ CurrentBB = BI->getSuccessor(0);
+ } else if (BI->getCondition() == ConstantInt::getFalse(Context)) {
+ CurrentBB = BI->getSuccessor(1);
+ } else {
+ // Found a trivial condition candidate: non-foldable conditional branch.
+ break;
+ }
+ } else {
+ break;
+ }
+
+ CurrentTerm = CurrentBB->getTerminator();
+ }
+
+ // CondVal is the condition that controls the trivial condition.
+ // LoopExitBB is the BasicBlock that loop exits when meets trivial condition.
+ Constant *CondVal = nullptr;
+ BasicBlock *LoopExitBB = nullptr;
+
+ if (BranchInst *BI = dyn_cast<BranchInst>(CurrentTerm)) {
+ // If this isn't branching on an invariant condition, we can't unswitch it.
+ if (!BI->isConditional())
+ return false;
+
+ Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
+ currentLoop, Changed);
+
+ // Unswitch only if the trivial condition itself is an LIV (not
+ // partial LIV which could occur in and/or)
+ if (!LoopCond || LoopCond != BI->getCondition())
+ 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)))) {
+ CondVal = ConstantInt::getTrue(Context);
+ } else if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop,
+ BI->getSuccessor(1)))) {
+ CondVal = ConstantInt::getFalse(Context);
+ }
+
+ // 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.
+
+ UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, LoopExitBB,
+ CurrentTerm);
+ ++NumBranches;
+ return true;
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurrentTerm)) {
+ // If this isn't switching on an invariant condition, we can't unswitch it.
+ Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
+ currentLoop, Changed);
+
+ // Unswitch only if the trivial condition itself is an LIV (not
+ // partial LIV which could occur in and/or)
+ if (!LoopCond || LoopCond != SI->getCondition())
+ 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;
+ CondVal = 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.
+
+ UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, LoopExitBB,
+ nullptr);
+ ++NumSwitches;
+ return true;
+ }
+ return false;
+}
+
+/// Split all of the edges from inside the loop to their exit blocks.
+/// Update the appropriate Phi nodes as we do so.
void LoopUnswitch::SplitExitEdges(Loop *L,
const SmallVectorImpl<BasicBlock *> &ExitBlocks){
// Although SplitBlockPredecessors doesn't preserve loop-simplify in
// general, if we call it on all predecessors of all exits then it does.
- SplitBlockPredecessors(ExitBlock, Preds, ".us-lcssa",
- /*AliasAnalysis*/ nullptr, DT, LI,
+ SplitBlockPredecessors(ExitBlock, Preds, ".us-lcssa", DT, LI,
/*PreserveLCSSA*/ true);
}
}
-/// UnswitchNontrivialCondition - We determined that the loop is profitable
-/// to unswitch when LIC equal Val. Split it into loop versions and test the
-/// condition outside of either loop. Return the loops created as Out1/Out2.
+/// We determined that the loop is profitable to unswitch when LIC equal Val.
+/// Split it into loop versions and test the condition outside of either loop.
+/// Return the loops created as Out1/Out2.
void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
Loop *L, TerminatorInst *TI) {
Function *F = loopHeader->getParent();
RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true);
}
-/// RemoveFromWorklist - Remove all instances of I from the worklist vector
-/// specified.
+/// Remove all instances of I from the worklist vector specified.
static void RemoveFromWorklist(Instruction *I,
std::vector<Instruction*> &Worklist) {
Worklist.end());
}
-/// ReplaceUsesOfWith - When we find that I really equals V, remove I from the
+/// When we find that I really equals V, remove I from the
/// program, replacing all uses with V and update the worklist.
static void ReplaceUsesOfWith(Instruction *I, Value *V,
std::vector<Instruction*> &Worklist,
++NumSimplify;
}
-// 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.
+/// 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) {
SimplifyCode(Worklist, L);
}
-/// SimplifyCode - Okay, now that we have simplified some instructions in the
-/// loop, walk over it and constant prop, dce, and fold control flow where
-/// possible. Note that this is effectively a very simple loop-structure-aware
-/// optimizer. During processing of this loop, L could very well be deleted, so
-/// it must not be used.
+/// Now that we have simplified some instructions in the loop, walk over it and
+/// constant prop, dce, and fold control flow where possible. Note that this is
+/// effectively a very simple loop-structure-aware optimizer. During processing
+/// of this loop, L could very well be deleted, so it must not be used.
///
/// FIXME: When the loop optimizer is more mature, separate this out to a new
/// pass.