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//===- llvm/Analysis/MemoryDependenceAnalysis.h - Memory Deps --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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2007-12-29 19:59:42 +00:00
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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2007-07-06 23:14:35 +00:00
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MemoryDependenceAnalysis analysis pass.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_MEMORY_DEPENDENCE_H
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#define LLVM_ANALYSIS_MEMORY_DEPENDENCE_H
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#include "llvm/BasicBlock.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/PointerIntPair.h"
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namespace llvm {
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class Function;
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class FunctionPass;
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class Instruction;
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class CallSite;
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/// MemDepResult - A memory dependence query can return one of three different
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/// answers:
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/// Normal : The query is dependent on a specific instruction.
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/// NonLocal: The query does not depend on anything inside this block, but
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/// we haven't scanned beyond the block to find out what.
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/// None : The query does not depend on anything: we found the entry
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/// block or the allocation site of the memory.
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class MemDepResult {
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enum DepType {
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Invalid = 0, Normal, NonLocal, None
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};
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typedef PointerIntPair<Instruction*, 2, DepType> PairTy;
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PairTy Value;
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explicit MemDepResult(PairTy V) : Value(V) {}
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public:
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MemDepResult() : Value(0, Invalid) {}
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/// get methods: These are static ctor methods for creating various
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/// MemDepResult kinds.
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static MemDepResult get(Instruction *Inst) {
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return MemDepResult(PairTy(Inst, Normal));
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}
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static MemDepResult getNonLocal() {
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return MemDepResult(PairTy(0, NonLocal));
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}
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static MemDepResult getNone() {
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return MemDepResult(PairTy(0, None));
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}
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/// isNormal - Return true if this MemDepResult represents a query that is
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/// a normal instruction dependency.
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bool isNormal() const { return Value.getInt() == Normal; }
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/// isNonLocal - Return true if this MemDepResult represents an query that
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/// is transparent to the start of the block, but where a non-local hasn't
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/// been done.
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bool isNonLocal() const { return Value.getInt() == NonLocal; }
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/// isNone - Return true if this MemDepResult represents a query that
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/// doesn't depend on any instruction.
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bool isNone() const { return Value.getInt() == None; }
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/// getInst() - If this is a normal dependency, return the instruction that
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/// is depended on. Otherwise, return null.
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Instruction *getInst() const { return isNormal() ? Value.getPointer() : 0; }
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bool operator==(const MemDepResult &M) { return M.Value == Value; }
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bool operator!=(const MemDepResult &M) { return M.Value != Value; }
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};
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/// MemoryDependenceAnalysis - This is an analysis that determines, for a
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/// given memory operation, what preceding memory operations it depends on.
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/// It builds on alias analysis information, and tries to provide a lazy,
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/// caching interface to a common kind of alias information query.
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///
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/// The dependency information returned is somewhat unusual, but is pragmatic.
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/// If queried about a store or call that might modify memory, the analysis
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/// will return the instruction[s] that may either load from that memory or
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/// store to it. If queried with a load or call that can never modify memory,
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/// the analysis will return calls and stores that might modify the pointer,
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/// but generally does not return loads unless a) they are volatile, or
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/// b) they load from *must-aliased* pointers. Returning a dependence on
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/// must-alias'd pointers instead of all pointers interacts well with the
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/// internal caching mechanism.
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///
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class MemoryDependenceAnalysis : public FunctionPass {
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/// DepType - This enum is used to indicate what flavor of dependence this
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/// is. If the type is Normal, there is an associated instruction pointer.
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enum DepType {
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/// Dirty - Entries with this marker occur in a LocalDeps map or
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/// NonLocalDeps map when the instruction they previously referenced was
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/// removed from MemDep. In either case, the entry may include an
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/// instruction pointer. If so, the pointer is an instruction in the
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/// block where scanning can start from, saving some work.
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///
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/// In a default-constructed DepResultTy object, the type will be Dirty
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/// and the instruction pointer will be null.
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///
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Dirty = 0,
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/// Normal - This is a normal instruction dependence. The pointer member
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/// of the DepResultTy pair holds the instruction.
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Normal,
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/// None - This dependence type indicates that the query does not depend
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/// on any instructions, either because it is not a memory instruction or
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/// because it scanned to the definition of the memory (alloca/malloc)
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/// being accessed.
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None,
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/// NonLocal - This marker indicates that the query has no dependency in
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/// the specified block. To find out more, the client should query other
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/// predecessor blocks.
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NonLocal
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};
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typedef PointerIntPair<Instruction*, 2, DepType> DepResultTy;
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// A map from instructions to their dependency.
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typedef DenseMap<Instruction*, DepResultTy> LocalDepMapType;
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LocalDepMapType LocalDeps;
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// A map from instructions to their non-local dependencies.
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typedef DenseMap<Instruction*,
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// This is an owning pointer.
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DenseMap<BasicBlock*, DepResultTy>*> NonLocalDepMapType;
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NonLocalDepMapType NonLocalDeps;
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// A reverse mapping from dependencies to the dependees. This is
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// used when removing instructions to keep the cache coherent.
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typedef DenseMap<Instruction*,
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SmallPtrSet<Instruction*, 4> > ReverseDepMapType;
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ReverseDepMapType ReverseLocalDeps;
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// A reverse mapping form dependencies to the non-local dependees.
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ReverseDepMapType ReverseNonLocalDeps;
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public:
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MemoryDependenceAnalysis() : FunctionPass(&ID) {}
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static char ID;
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/// Pass Implementation stuff. This doesn't do any analysis.
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///
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bool runOnFunction(Function &) {return false; }
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/// Clean up memory in between runs
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void releaseMemory() {
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LocalDeps.clear();
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for (NonLocalDepMapType::iterator I = NonLocalDeps.begin(),
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E = NonLocalDeps.end(); I != E; ++I)
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delete I->second;
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NonLocalDeps.clear();
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ReverseLocalDeps.clear();
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ReverseNonLocalDeps.clear();
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}
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/// getAnalysisUsage - Does not modify anything. It uses Value Numbering
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/// and Alias Analysis.
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///
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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/// getDependency - Return the instruction on which a memory operation
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/// depends. See the class comment for more details.
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MemDepResult getDependency(Instruction *QueryInst);
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/// getDependencyFrom - Return the instruction on which the memory operation
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/// 'QueryInst' depends. This starts scanning from the instruction before
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/// the position indicated by ScanIt.
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///
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/// Note that this method does no caching at all. You should use
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/// getDependency where possible.
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MemDepResult getDependencyFrom(Instruction *QueryInst,
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BasicBlock::iterator ScanIt, BasicBlock *BB){
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return ConvToResult(getDependencyFromInternal(QueryInst, ScanIt, BB));
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}
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/// getNonLocalDependency - Perform a full dependency query for the
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/// specified instruction, returning the set of blocks that the value is
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/// potentially live across. The returned set of results will include a
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/// "NonLocal" result for all blocks where the value is live across.
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///
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/// This method assumes the instruction returns a "nonlocal" dependency
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/// within its own block.
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void getNonLocalDependency(Instruction *QueryInst,
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SmallVectorImpl<std::pair<BasicBlock*,
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MemDepResult> > &Result);
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/// removeInstruction - Remove an instruction from the dependence analysis,
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/// updating the dependence of instructions that previously depended on it.
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void removeInstruction(Instruction *InstToRemove);
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private:
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MemDepResult ConvToResult(DepResultTy R) {
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if (R.getInt() == Normal)
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return MemDepResult::get(R.getPointer());
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if (R.getInt() == NonLocal)
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return MemDepResult::getNonLocal();
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assert(R.getInt() == None && "Unknown MemDepResult!");
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return MemDepResult::getNone();
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}
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/// verifyRemoved - Verify that the specified instruction does not occur
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/// in our internal data structures.
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void verifyRemoved(Instruction *Inst) const;
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/// getDependencyFromInternal - Return the instruction on which the memory
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/// operation 'QueryInst' depends. This starts scanning from the
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/// instruction before the position indicated by ScanIt.
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DepResultTy getDependencyFromInternal(Instruction *QueryInst,
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BasicBlock::iterator ScanIt, BasicBlock *BB);
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DepResultTy getCallSiteDependency(CallSite C, BasicBlock::iterator ScanIt,
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BasicBlock *BB);
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};
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} // End llvm namespace
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#endif
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