//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
-//
+//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+//
//===----------------------------------------------------------------------===//
//
// This file defines the LoopInfo class that is used to identify natural loops
#include "llvm/Analysis/Dominators.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CFG.h"
-#include "Support/DepthFirstIterator.h"
+#include "llvm/ADT/DepthFirstIterator.h"
#include <algorithm>
+#include <iostream>
using namespace llvm;
static RegisterAnalysis<LoopInfo>
// Loop implementation
//
bool Loop::contains(const BasicBlock *BB) const {
- return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
+ return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
bool Loop::isLoopExit(const BasicBlock *BB) const {
return NumBackEdges;
}
+/// isLoopInvariant - Return true if the specified value is loop invariant
+///
+bool Loop::isLoopInvariant(Value *V) const {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ return !contains(I->getParent());
+ return true; // All non-instructions are loop invariant
+}
+
void Loop::print(std::ostream &OS, unsigned Depth) const {
OS << std::string(Depth*2, ' ') << "Loop Containing: ";
if (i) OS << ",";
WriteAsOperand(OS, getBlocks()[i], false);
}
- if (!ExitBlocks.empty()) {
- OS << "\tExitBlocks: ";
- for (unsigned i = 0; i < getExitBlocks().size(); ++i) {
- if (i) OS << ",";
- WriteAsOperand(OS, getExitBlocks()[i], false);
- }
- }
-
OS << "\n";
for (iterator I = begin(), E = end(); I != E; ++I)
BasicBlock *RootNode = DS.getRoot();
for (df_iterator<BasicBlock*> NI = df_begin(RootNode),
- NE = df_end(RootNode); NI != NE; ++NI)
+ NE = df_end(RootNode); NI != NE; ++NI)
if (Loop *L = ConsiderForLoop(*NI, DS))
TopLevelLoops.push_back(L);
-
- for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
- TopLevelLoops[i]->setLoopDepth(1);
}
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorSet>();
}
-void LoopInfo::print(std::ostream &OS) const {
+void LoopInfo::print(std::ostream &OS, const Module* ) const {
for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
TopLevelLoops[i]->print(OS);
#if 0
for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
E = BBMap.end(); I != E; ++I)
OS << "BB '" << I->first->getName() << "' level = "
- << I->second->LoopDepth << "\n";
+ << I->second->getLoopDepth() << "\n";
#endif
}
std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?");
SLP->SubLoops.erase(I); // Remove from parent...
-
+
// Add the subloop to THIS loop...
SubLoop->ParentLoop = L;
L->SubLoops.push_back(SubLoop);
// Normal case, add the block to our loop...
L->Blocks.push_back(X);
-
+
// Add all of the predecessors of X to the end of the work stack...
TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X));
}
// If there are any loops nested within this loop, create them now!
for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(),
- E = L->Blocks.end(); I != E; ++I)
+ E = L->Blocks.end(); I != E; ++I)
if (Loop *NewLoop = ConsiderForLoop(*I, DS)) {
L->SubLoops.push_back(NewLoop);
NewLoop->ParentLoop = L;
// loop can be found for them.
//
for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(),
- E = L->Blocks.end(); I != E; ++I) {
+ E = L->Blocks.end(); I != E; ++I) {
std::map<BasicBlock*, Loop*>::iterator BBMI = BBMap.lower_bound(*I);
if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet...
BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
--i; // We just shrunk the SubLoops list.
}
}
- }
+ }
}
}
- // Now that we know all of the blocks that make up this loop, see if there are
- // any branches to outside of the loop... building the ExitBlocks list.
- for (std::vector<BasicBlock*>::iterator BI = L->Blocks.begin(),
- BE = L->Blocks.end(); BI != BE; ++BI)
- for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I)
- if (!L->contains(*I)) // Not in current loop?
- L->ExitBlocks.push_back(*I); // It must be an exit block...
-
return L;
}
assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
OldParent->SubLoops.erase(I); // Remove from parent's subloops list
NewChild->ParentLoop = 0;
-
- InsertLoopInto(NewChild, NewParent);
+
+ InsertLoopInto(NewChild, NewParent);
}
/// InsertLoopInto - This inserts loop L into the specified parent loop. If the
void LoopInfo::InsertLoopInto(Loop *L, Loop *Parent) {
BasicBlock *LHeader = L->getHeader();
assert(Parent->contains(LHeader) && "This loop should not be inserted here!");
-
+
// Check to see if it belongs in a child loop...
for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i)
if (Parent->SubLoops[i]->contains(LHeader)) {
InsertLoopInto(L, Parent->SubLoops[i]);
return;
- }
+ }
// If not, insert it here!
Parent->SubLoops.push_back(L);
"Loops already embedded into a subloop!");
}
+/// removeLoop - This removes the specified top-level loop from this loop info
+/// object. The loop is not deleted, as it will presumably be inserted into
+/// another loop.
+Loop *LoopInfo::removeLoop(iterator I) {
+ assert(I != end() && "Cannot remove end iterator!");
+ Loop *L = *I;
+ assert(L->getParentLoop() == 0 && "Not a top-level loop!");
+ TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
+ return L;
+}
+
+/// removeBlock - This method completely removes BB from all data structures,
+/// including all of the Loop objects it is nested in and our mapping from
+/// BasicBlocks to loops.
+void LoopInfo::removeBlock(BasicBlock *BB) {
+ std::map<BasicBlock *, Loop*>::iterator I = BBMap.find(BB);
+ if (I != BBMap.end()) {
+ for (Loop *L = I->second; L; L = L->getParentLoop())
+ L->removeBlockFromLoop(BB);
+
+ BBMap.erase(I);
+ }
+}
+
+
//===----------------------------------------------------------------------===//
// APIs for simple analysis of the loop.
//
+/// getExitBlocks - Return all of the successor blocks of this loop. These
+/// are the blocks _outside of the current loop_ which are branched to.
+///
+void Loop::getExitBlocks(std::vector<BasicBlock*> &ExitBlocks) const {
+ for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(),
+ BE = Blocks.end(); BI != BE; ++BI)
+ for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I)
+ if (!contains(*I)) // Not in current loop?
+ ExitBlocks.push_back(*I); // It must be an exit block...
+}
+
+
/// getLoopPreheader - If there is a preheader for this loop, return it. A
/// loop has a preheader if there is only one edge to the header of the loop
/// from outside of the loop. If this is the case, the block branching to the
return 0; // Multiple predecessors outside the loop
Out = *PI;
}
-
+
// Make sure there is only one exit out of the preheader...
succ_iterator SI = succ_begin(Out);
++SI;
if (SI != succ_end(Out))
return 0; // Multiple exits from the block, must not be a preheader.
-
// If there is exactly one preheader, return it. If there was zero, then Out
// is still null.
return Out;
}
+/// getLoopLatch - If there is a latch block for this loop, return it. A
+/// latch block is the canonical backedge for a loop. A loop header in normal
+/// form has two edges into it: one from a preheader and one from a latch
+/// block.
+BasicBlock *Loop::getLoopLatch() const {
+ BasicBlock *Header = getHeader();
+ pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
+ if (PI == PE) return 0; // no preds?
+
+ BasicBlock *Latch = 0;
+ if (contains(*PI))
+ Latch = *PI;
+ ++PI;
+ if (PI == PE) return 0; // only one pred?
+
+ if (contains(*PI)) {
+ if (Latch) return 0; // multiple backedges
+ Latch = *PI;
+ }
+ ++PI;
+ if (PI != PE) return 0; // more than two preds
+
+ return Latch;
+}
+
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
/// induction variable: an integer recurrence that starts at 0 and increments by
/// one each time through the loop. If so, return the phi node that corresponds
return 0;
// Loop over all of the PHI nodes, looking for a canonical indvar.
- for (BasicBlock::iterator I = H->begin();
- PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
+ PHINode *PN = cast<PHINode>(I);
if (Instruction *Inc =
dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
if (CI->equalsInt(1))
return PN;
-
+ }
return 0;
}
// Canonical loops will end with a 'setne I, V', where I is the incremented
// canonical induction variable and V is the trip count of the loop.
Instruction *Inc = getCanonicalInductionVariableIncrement();
+ if (Inc == 0) return 0;
PHINode *IV = cast<PHINode>(Inc->getOperand(0));
-
+
BasicBlock *BackedgeBlock =
IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
- if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition()))
- if (SCI->getOperand(0) == Inc)
- if (BI->getSuccessor(0) == getHeader()) {
- if (SCI->getOpcode() == Instruction::SetNE)
+ if (BI->isConditional())
+ if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition()))
+ if (SCI->getOperand(0) == Inc)
+ if (BI->getSuccessor(0) == getHeader()) {
+ if (SCI->getOpcode() == Instruction::SetNE)
+ return SCI->getOperand(1);
+ } else if (SCI->getOpcode() == Instruction::SetEQ) {
return SCI->getOperand(1);
- } else if (SCI->getOpcode() == Instruction::SetEQ) {
- return SCI->getOperand(1);
- }
-
+ }
+
return 0;
}
}
}
-/// changeExitBlock - This method is used to update loop information. All
-/// instances of the specified Old basic block are removed from the exit list
-/// and replaced with New.
-///
-void Loop::changeExitBlock(BasicBlock *Old, BasicBlock *New) {
- assert(Old != New && "Cannot changeExitBlock to the same thing!");
- assert(Old && New && "Cannot changeExitBlock to or from a null node!");
- assert(hasExitBlock(Old) && "Old exit block not found!");
- std::vector<BasicBlock*>::iterator
- I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old);
- while (I != ExitBlocks.end()) {
- *I = New;
- I = std::find(I+1, ExitBlocks.end(), Old);
- }
-}
-
/// replaceChildLoopWith - This is used when splitting loops up. It replaces
/// the OldChild entry in our children list with NewChild, and updates the
/// parent pointers of the two loops as appropriate.
*I = NewChild;
OldChild->ParentLoop = 0;
NewChild->ParentLoop = this;
-
- // Update the loop depth of the new child.
- NewChild->setLoopDepth(LoopDepth+1);
}
/// addChildLoop - Add the specified loop to be a child of this loop.
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
NewChild->ParentLoop = this;
SubLoops.push_back(NewChild);
-
- // Update the loop depth of the new child.
- NewChild->setLoopDepth(LoopDepth+1);
}
template<typename T>
/// does not update the mapping in the LoopInfo class.
void Loop::removeBlockFromLoop(BasicBlock *BB) {
RemoveFromVector(Blocks, BB);
-
- // If this block branched out of this loop, remove any exit blocks entries due
- // to it.
- for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
- if (!contains(*SI) && *SI != BB)
- RemoveFromVector(ExitBlocks, *SI);
-
- // If any blocks in this loop branch to BB, add it to the exit blocks set.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- if (contains(*PI))
- ExitBlocks.push_back(BB);
}
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