llvm-6502/lib/Analysis/MemoryDependenceAnalysis.cpp
Owen Anderson 521a20207c When removing instructions from the analysis, be sure to check the confirmed
flag when determining what to do with dependencies.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40079 91177308-0d34-0410-b5e6-96231b3b80d8
2007-07-20 06:16:07 +00:00

281 lines
10 KiB
C++

//===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the Owen Anderson and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements an analysis that determines, for a given memory
// operation, what preceding memory operations it depends on. It builds on
// alias analysis information, and tries to provide a lazy, caching interface to
// a common kind of alias information query.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Target/TargetData.h"
using namespace llvm;
char MemoryDependenceAnalysis::ID = 0;
Instruction* MemoryDependenceAnalysis::NonLocal = (Instruction*)0;
Instruction* MemoryDependenceAnalysis::None = (Instruction*)~0;
// Register this pass...
static RegisterPass<MemoryDependenceAnalysis> X("memdep",
"Memory Dependence Analysis");
/// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
///
void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<AliasAnalysis>();
AU.addRequiredTransitive<TargetData>();
}
// Find the dependency of a CallSite
Instruction* MemoryDependenceAnalysis::getCallSiteDependency(CallSite C, Instruction* start,
bool local) {
assert(local && "Non-local memory dependence analysis not yet implemented");
AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
TargetData& TD = getAnalysis<TargetData>();
BasicBlock::iterator blockBegin = C.getInstruction()->getParent()->begin();
BasicBlock::iterator QI = C.getInstruction();
while (QI != blockBegin) {
--QI;
// If this inst is a memory op, get the pointer it accessed
Value* pointer = 0;
uint64_t pointerSize = 0;
if (StoreInst* S = dyn_cast<StoreInst>(QI)) {
pointer = S->getPointerOperand();
pointerSize = TD.getTypeSize(S->getOperand(0)->getType());
} else if (LoadInst* L = dyn_cast<LoadInst>(QI)) {
pointer = L->getPointerOperand();
pointerSize = TD.getTypeSize(L->getType());
} else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) {
pointer = AI;
if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize()))
pointerSize = C->getZExtValue() * TD.getTypeSize(AI->getAllocatedType());
else
pointerSize = ~0UL;
} else if (VAArgInst* V = dyn_cast<VAArgInst>(QI)) {
pointer = V->getOperand(0);
pointerSize = TD.getTypeSize(V->getType());
} else if (FreeInst* F = dyn_cast<FreeInst>(QI)) {
pointer = F->getPointerOperand();
// FreeInsts erase the entire structure
pointerSize = ~0UL;
} else if (CallSite::get(QI).getInstruction() != 0) {
if (AA.getModRefInfo(C, CallSite::get(QI)) != AliasAnalysis::NoModRef) {
depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(QI, true)));
reverseDep.insert(std::make_pair(QI, C.getInstruction()));
return QI;
} else {
continue;
}
} else
continue;
if (AA.getModRefInfo(C, pointer, pointerSize) != AliasAnalysis::NoModRef) {
depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(QI, true)));
reverseDep.insert(std::make_pair(QI, C.getInstruction()));
return QI;
}
}
// No dependence found
depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(NonLocal, true)));
reverseDep.insert(std::make_pair(NonLocal, C.getInstruction()));
return NonLocal;
}
/// getDependency - Return the instruction on which a memory operation
/// depends. The local paramter indicates if the query should only
/// evaluate dependencies within the same basic block.
Instruction* MemoryDependenceAnalysis::getDependency(Instruction* query,
Instruction* start,
bool local) {
if (!local)
assert(0 && "Non-local memory dependence is not yet supported.");
// Start looking for dependencies with the queried inst
BasicBlock::iterator QI = query;
// Check for a cached result
std::pair<Instruction*, bool> cachedResult = depGraphLocal[query];
// If we have a _confirmed_ cached entry, return it
if (cachedResult.second)
return cachedResult.first;
else if (cachedResult.first != NonLocal)
// If we have an unconfirmed cached entry, we can start our search from there
QI = cachedResult.first;
if (start)
QI = start;
AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
TargetData& TD = getAnalysis<TargetData>();
// Get the pointer value for which dependence will be determined
Value* dependee = 0;
uint64_t dependeeSize = 0;
bool queryIsVolatile = false;
if (StoreInst* S = dyn_cast<StoreInst>(query)) {
dependee = S->getPointerOperand();
dependeeSize = TD.getTypeSize(S->getOperand(0)->getType());
queryIsVolatile = S->isVolatile();
} else if (LoadInst* L = dyn_cast<LoadInst>(query)) {
dependee = L->getPointerOperand();
dependeeSize = TD.getTypeSize(L->getType());
queryIsVolatile = L->isVolatile();
} else if (VAArgInst* V = dyn_cast<VAArgInst>(query)) {
dependee = V->getOperand(0);
dependeeSize = TD.getTypeSize(V->getType());
} else if (FreeInst* F = dyn_cast<FreeInst>(query)) {
dependee = F->getPointerOperand();
// FreeInsts erase the entire structure, not just a field
dependeeSize = ~0UL;
} else if (CallSite::get(query).getInstruction() != 0)
return getCallSiteDependency(CallSite::get(query), start);
else if (isa<AllocationInst>(query))
return None;
else
return None;
BasicBlock::iterator blockBegin = query->getParent()->begin();
while (QI != blockBegin) {
--QI;
// If this inst is a memory op, get the pointer it accessed
Value* pointer = 0;
uint64_t pointerSize = 0;
if (StoreInst* S = dyn_cast<StoreInst>(QI)) {
// All volatile loads/stores depend on each other
if (queryIsVolatile && S->isVolatile()) {
if (!start) {
depGraphLocal.insert(std::make_pair(query, std::make_pair(S, true)));
reverseDep.insert(std::make_pair(S, query));
}
return S;
}
pointer = S->getPointerOperand();
pointerSize = TD.getTypeSize(S->getOperand(0)->getType());
} else if (LoadInst* L = dyn_cast<LoadInst>(QI)) {
// All volatile loads/stores depend on each other
if (queryIsVolatile && L->isVolatile()) {
if (!start) {
depGraphLocal.insert(std::make_pair(query, std::make_pair(L, true)));
reverseDep.insert(std::make_pair(L, query));
}
return L;
}
pointer = L->getPointerOperand();
pointerSize = TD.getTypeSize(L->getType());
} else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) {
pointer = AI;
if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize()))
pointerSize = C->getZExtValue() * TD.getTypeSize(AI->getAllocatedType());
else
pointerSize = ~0UL;
} else if (VAArgInst* V = dyn_cast<VAArgInst>(QI)) {
pointer = V->getOperand(0);
pointerSize = TD.getTypeSize(V->getType());
} else if (FreeInst* F = dyn_cast<FreeInst>(QI)) {
pointer = F->getPointerOperand();
// FreeInsts erase the entire structure
pointerSize = ~0UL;
} else if (CallSite::get(QI).getInstruction() != 0) {
// Call insts need special handling. Check is they can modify our pointer
if (AA.getModRefInfo(CallSite::get(QI), dependee, dependeeSize) !=
AliasAnalysis::NoModRef) {
if (!start) {
depGraphLocal.insert(std::make_pair(query, std::make_pair(QI, true)));
reverseDep.insert(std::make_pair(QI, query));
}
return QI;
} else {
continue;
}
}
// If we found a pointer, check if it could be the same as our pointer
if (pointer) {
AliasAnalysis::AliasResult R = AA.alias(pointer, pointerSize,
dependee, dependeeSize);
if (R != AliasAnalysis::NoAlias) {
if (!start) {
depGraphLocal.insert(std::make_pair(query, std::make_pair(QI, true)));
reverseDep.insert(std::make_pair(QI, query));
}
return QI;
}
}
}
// If we found nothing, return the non-local flag
if (!start) {
depGraphLocal.insert(std::make_pair(query,
std::make_pair(NonLocal, true)));
reverseDep.insert(std::make_pair(NonLocal, query));
}
return NonLocal;
}
/// removeInstruction - Remove an instruction from the dependence analysis,
/// updating the dependence of instructions that previously depended on it.
void MemoryDependenceAnalysis::removeInstruction(Instruction* rem) {
// Figure out the new dep for things that currently depend on rem
Instruction* newDep = NonLocal;
if (depGraphLocal[rem].first != NonLocal &&
depGraphLocal[rem].second) {
// If we have dep info for rem, set them to it
BasicBlock::iterator RI = depGraphLocal[rem].first;
RI++;
newDep = RI;
} else if (depGraphLocal[rem].first == NonLocal &&
depGraphLocal[rem].second ) {
// If we have a confirmed non-local flag, use it
newDep = NonLocal;
} else {
// Otherwise, use the immediate successor of rem
// NOTE: This is because, when getDependence is called, it will first check
// the immediate predecessor of what is in the cache.
BasicBlock::iterator RI = rem;
RI++;
newDep = RI;
}
std::multimap<Instruction*, Instruction*>::iterator I = reverseDep.find(rem);
while (I->first == rem) {
// Insert the new dependencies
// Mark it as unconfirmed as long as it is not the non-local flag
depGraphLocal[I->second] = std::make_pair(newDep, !newDep);
reverseDep.erase(I);
I = reverseDep.find(rem);
}
getAnalysis<AliasAnalysis>().deleteValue(rem);
}