//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#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)
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
}
}
}
- // 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;
}
"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
-/// header of the loop is the preheader node. The "preheaders" pass can be
-/// "Required" to ensure that there is always a preheader node for every loop.
+/// header of the loop is the preheader node.
///
-/// This method returns null if there is no preheader for the loop (either
-/// because the loop is dead or because multiple blocks branch to the header
-/// node of this loop).
+/// This method returns null if there is no preheader for the loop.
///
BasicBlock *Loop::getLoopPreheader() const {
// Keep track of nodes outside the loop branching to the header...
return Out;
}
+/// 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
+/// to it.
+///
+PHINode *Loop::getCanonicalInductionVariable() const {
+ BasicBlock *H = getHeader();
+
+ BasicBlock *Incoming = 0, *Backedge = 0;
+ pred_iterator PI = pred_begin(H);
+ assert(PI != pred_end(H) && "Loop must have at least one backedge!");
+ Backedge = *PI++;
+ if (PI == pred_end(H)) return 0; // dead loop
+ Incoming = *PI++;
+ if (PI != pred_end(H)) return 0; // multiple backedges?
+
+ if (contains(Incoming)) {
+ if (contains(Backedge))
+ return 0;
+ std::swap(Incoming, Backedge);
+ } else if (!contains(Backedge))
+ return 0;
+
+ // Loop over all of the PHI nodes, looking for a canonical indvar.
+ 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;
+}
+
+/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
+/// the canonical induction variable value for the "next" iteration of the loop.
+/// This always succeeds if getCanonicalInductionVariable succeeds.
+///
+Instruction *Loop::getCanonicalInductionVariableIncrement() const {
+ if (PHINode *PN = getCanonicalInductionVariable()) {
+ bool P1InLoop = contains(PN->getIncomingBlock(1));
+ return cast<Instruction>(PN->getIncomingValue(P1InLoop));
+ }
+ return 0;
+}
+
+/// getTripCount - Return a loop-invariant LLVM value indicating the number of
+/// times the loop will be executed. Note that this means that the backedge of
+/// the loop executes N-1 times. If the trip-count cannot be determined, this
+/// returns null.
+///
+Value *Loop::getTripCount() const {
+ // 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 (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);
+ }
+
+ return 0;
+}
+
+
+//===-------------------------------------------------------------------===//
+// APIs for updating loop information after changing the CFG
+//
+
/// addBasicBlockToLoop - This function is used by other analyses to update loop
/// information. NewBB is set to be a new member of the current loop. Because
/// of this, it is added as a member of all parent loops, and is added to the
}
}
-/// 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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