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First try at implementing the AliasSetTracker class. I'm sure it will need

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revision as I start to use it though.

llvm-svn: 3954
This commit is contained in:
Chris Lattner 2002-09-26 21:49:07 +00:00
parent e96e0a72c4
commit a9bc408104
2 changed files with 281 additions and 0 deletions
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109
include/llvm/Analysis/AliasSetTracker.h Normal file
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//===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- C++ -*-===//
//
// This file defines two classes: AliasSetTracker and AliasSet. These interface
// are used to classify a collection of pointer references into a maximal number
// of disjoint sets. Each AliasSet object constructed by the AliasSetTracker
// object refers to memory disjoint from the other sets.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_ALIASSETTRACKER_H
#define LLVM_ANALYSIS_ALIASSETTRACKER_H
#include <vector>
class AliasAnalysis;
class LoadInst;
class StoreInst;
class CallInst;
class InvokeInst;
class Value;
class AliasSetTracker;
class AliasSet {
friend class AliasSetTracker;
std::vector<LoadInst*> Loads;
std::vector<StoreInst*> Stores;
std::vector<CallInst*> Calls;
std::vector<InvokeInst*> Invokes;
public:
/// AccessType - Keep track of whether this alias set merely refers to the
/// locations of memory, whether it modifies the memory, or whether it does
/// both. The lattice goes from "None" (alias set not present) to either Refs
/// or Mods, then to ModRef as neccesary.
///
enum AccessType {
Refs, Mods, ModRef
};
/// AliasType - Keep track the relationships between the pointers in the set.
/// Lattice goes from MustAlias to MayAlias.
///
enum AliasType {
MustAlias, MayAlias
};
private:
enum AccessType AccessTy;
enum AliasType AliasTy;
public:
/// Accessors...
enum AccessType getAccessType() const { return AccessTy; }
enum AliasType getAliasType() const { return AliasTy; }
// TODO: in the future, add a fixed size (4? 2?) cache of pointers that we
// know are in the alias set, to cut down time answering "pointeraliasesset"
// queries.
/// pointerAliasesSet - Return true if the specified pointer "may" (or must)
/// alias one of the members in the set.
///
bool pointerAliasesSet(const Value *Ptr, AliasAnalysis &AA) const;
/// mergeSetIn - Merge the specified alias set into this alias set...
///
void mergeSetIn(const AliasSet &AS);
const std::vector<LoadInst*> &getLoads() const { return Loads; }
const std::vector<StoreInst*> &getStores() const { return Stores; }
const std::vector<CallInst*> &getCalls() const { return Calls; }
const std::vector<InvokeInst*> &getInvokes() const { return Invokes; }
private:
AliasSet() : AliasTy(MustAlias) {} // Can only be created by AliasSetTracker
void updateAccessType();
Value *getSomePointer() const;
};
class AliasSetTracker {
AliasAnalysis &AA;
std::vector<AliasSet> AliasSets;
public:
/// AliasSetTracker ctor - Create an empty collection of AliasSets, and use
/// the specified alias analysis object to disambiguate load and store
/// addresses.
AliasSetTracker(AliasAnalysis &aa) : AA(aa) {}
/// add methods - These methods are used to add different types of
/// instructions to the alias sets. Adding a new instruction can result in
/// one of three actions happening:
///
/// 1. If the instruction doesn't alias any other sets, create a new set.
/// 2. If the instruction aliases exactly one set, add it to the set
/// 3. If the instruction aliases multiple sets, merge the sets, and add
/// the instruction to the result.
///
void add(LoadInst *LI);
void add(StoreInst *SI);
void add(CallInst *CI);
void add(InvokeInst *II);
/// getAliasSets - Return the alias sets that are active.
const std::vector<AliasSet> &getAliasSets() const { return AliasSets; }
private:
AliasSet *findAliasSetForPointer(const Value *Ptr);
void mergeAllSets();
};
#endif

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lib/Analysis/AliasSetTracker.cpp Normal file
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//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
//
// This file implements the AliasSetTracker and AliasSet classes.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/iTerminators.h"
/// updateAccessTypes - Depending on what type of accesses are in this set,
/// decide whether the set contains just references, just modifications, or a
/// mix.
///
void AliasSet::updateAccessType() {
if (!Calls.empty() || !Invokes.empty()) {
AccessTy = ModRef;
} else if (!Loads.empty()) {
if (Stores.empty())
AccessTy = Refs;
else
AccessTy = ModRef;
} else {
AccessTy = Mods;
}
}
/// mergeSetIn - Merge the specified alias set into this alias set...
///
void AliasSet::mergeSetIn(const AliasSet &AS) {
// Merge instruction sets...
Loads.insert( Loads.end(), AS.Loads.begin() , AS.Loads.end());
Stores.insert( Stores.end(), AS.Stores.begin() , AS.Stores.end());
Calls.insert( Calls.end(), AS.Calls.begin() , AS.Calls.end());
Invokes.insert(Invokes.end(), AS.Invokes.begin(), AS.Invokes.end());
// Update the alias and access types of this set...
if (AS.getAliasType() == MayAlias)
AliasTy = MayAlias;
updateAccessType();
}
/// pointerAliasesSet - Return true if the specified pointer "may" (or must)
/// alias one of the members in the set.
///
bool AliasSet::pointerAliasesSet(const Value *Ptr, AliasAnalysis &AA) const {
if (!Calls.empty() || !Invokes.empty())
return true;
for (unsigned i = 0, e = Loads.size(); i != e; ++i)
if (AA.alias(Ptr, Loads[i]->getOperand(0)))
return true;
for (unsigned i = 0, e = Stores.size(); i != e; ++i)
if (AA.alias(Ptr, Stores[i]->getOperand(1)))
return true;
return false;
}
/// getSomePointer - This method may only be called when the AliasType of the
/// set is MustAlias. This is used to return any old pointer (which must alias
/// all other pointers in the set) so that the caller can decide whether to turn
/// this set into a may alias set or not.
///
Value *AliasSet::getSomePointer() const {
assert(getAliasType() == MustAlias &&
"Cannot call getSomePointer on a 'MayAlias' set!");
assert(Calls.empty() && Invokes.empty() && "Call/invokes mean may alias!");
if (!Loads.empty())
return Loads[0]->getOperand(0);
assert(!Stores.empty() && "There are no instructions in this set!");
return Stores[0]->getOperand(1);
}
/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
/// instruction referring to the pointer into. If there are multiple alias sets
/// that may alias the pointer, merge them together and return the unified set.
///
AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr) {
AliasSet *FoundSet = 0;
for (unsigned i = 0; i != AliasSets.size(); ++i) {
if (AliasSets[i].pointerAliasesSet(Ptr, AA)) {
if (FoundSet == 0) { // If this is the first alias set ptr can go into...
FoundSet = &AliasSets[i]; // Remember it.
} else { // Otherwise, we must merge the sets...
FoundSet->mergeSetIn(AliasSets[i]); // Merge in contents...
AliasSets.erase(AliasSets.begin()+i); // Remove the set...
--i; // Don't skip the next set
}
}
}
return FoundSet;
}
void AliasSetTracker::add(LoadInst *LI) {
Value *Pointer = LI->getOperand(0);
// Check to see if the loaded pointer aliases any sets...
AliasSet *AS = findAliasSetForPointer(Pointer);
if (AS) {
AS->Loads.push_back(LI);
// Check to see if we need to change this into a MayAlias set now...
if (AS->getAliasType() == AliasSet::MustAlias)
if (AA.alias(AS->getSomePointer(), Pointer) != AliasAnalysis::MustAlias)
AS->AliasTy = AliasSet::MayAlias;
AS->updateAccessType();
} else {
// Otherwise create a new alias set to hold the load...
AliasSets.push_back(AliasSet());
AliasSets.back().Loads.push_back(LI);
AliasSets.back().AccessTy = AliasSet::Refs;
}
}
void AliasSetTracker::add(StoreInst *SI) {
Value *Pointer = SI->getOperand(1);
// Check to see if the loaded pointer aliases any sets...
AliasSet *AS = findAliasSetForPointer(Pointer);
if (AS) {
AS->Stores.push_back(SI);
// Check to see if we need to change this into a MayAlias set now...
if (AS->getAliasType() == AliasSet::MustAlias)
if (AA.alias(AS->getSomePointer(), Pointer) != AliasAnalysis::MustAlias)
AS->AliasTy = AliasSet::MayAlias;
AS->updateAccessType();
} else {
// Otherwise create a new alias set to hold the load...
AliasSets.push_back(AliasSet());
AliasSets.back().Stores.push_back(SI);
AliasSets.back().AccessTy = AliasSet::Mods;
}
}
void AliasSetTracker::mergeAllSets() {
if (AliasSets.size() < 2) return; // Noop
// Merge all of the sets into set #0
for (unsigned i = 1, e = AliasSets.size(); i != e; ++i)
AliasSets[0].mergeSetIn(AliasSets[i]);
// Delete extraneous sets...
AliasSets.erase(AliasSets.begin()+1, AliasSets.end());
}
void AliasSetTracker::add(CallInst *CI) {
if (!AliasSets.empty()) {
mergeAllSets();
} else {
AliasSets.push_back(AliasSet());
}
AliasSets[0].AccessTy = AliasSet::ModRef;
AliasSets[0].AliasTy = AliasSet::MayAlias;
AliasSets[0].Calls.push_back(CI);
}
void AliasSetTracker::add(InvokeInst *II) {
if (!AliasSets.empty()) {
mergeAllSets();
} else {
AliasSets.push_back(AliasSet());
}
AliasSets[0].AccessTy = AliasSet::ModRef;
AliasSets[0].AliasTy = AliasSet::MayAlias;
AliasSets[0].Invokes.push_back(II);
}