//===- MemoryDepAnalysis.cpp - Compute dep graph for memory ops -----------===//
//
// 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 implements a pass (MemoryDepAnalysis) that computes memory-based
// data dependences between instructions for each function in a module.
// Memory-based dependences occur due to load and store operations, but
// also the side-effects of call instructions.
//
// The result of this pass is a DependenceGraph for each function
// representing the memory-based data dependences between instructions.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/MemoryDepAnalysis.h"
#include "llvm/Module.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/Analysis/IPModRef.h"
#include "llvm/Analysis/DataStructure.h"
#include "llvm/Analysis/DSGraph.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CFG.h"
#include "Support/SCCIterator.h"
#include "Support/Statistic.h"
#include "Support/STLExtras.h"
#include "Support/hash_map"
#include "Support/hash_set"
namespace llvm {
///--------------------------------------------------------------------------
/// struct ModRefTable:
///
/// A data structure that tracks ModRefInfo for instructions:
/// -- modRefMap is a map of Instruction* -> ModRefInfo for the instr.
/// -- definers is a vector of instructions that define any node
/// -- users is a vector of instructions that reference any node
/// -- numUsersBeforeDef is a vector indicating that the number of users
/// seen before definers[i] is numUsersBeforeDef[i].
///
/// numUsersBeforeDef[] effectively tells us the exact interleaving of
/// definers and users within the ModRefTable.
/// This is only maintained when constructing the table for one SCC, and
/// not copied over from one table to another since it is no longer useful.
///--------------------------------------------------------------------------
struct ModRefTable {
typedef hash_map<Instruction*, ModRefInfo> ModRefMap;
typedef ModRefMap::const_iterator const_map_iterator;
typedef ModRefMap:: iterator map_iterator;
typedef std::vector<Instruction*>::const_iterator const_ref_iterator;
typedef std::vector<Instruction*>:: iterator ref_iterator;
ModRefMap modRefMap;
std::vector<Instruction*> definers;
std::vector<Instruction*> users;
std::vector<unsigned> numUsersBeforeDef;
// Iterators to enumerate all the defining instructions
const_ref_iterator defsBegin() const { return definers.begin(); }
ref_iterator defsBegin() { return definers.begin(); }
const_ref_iterator defsEnd() const { return definers.end(); }
ref_iterator defsEnd() { return definers.end(); }
// Iterators to enumerate all the user instructions
const_ref_iterator usersBegin() const { return users.begin(); }
ref_iterator usersBegin() { return users.begin(); }
const_ref_iterator usersEnd() const { return users.end(); }
ref_iterator usersEnd() { return users.end(); }
// Iterator identifying the last user that was seen *before* a
// specified def. In particular, all users in the half-closed range
// [ usersBegin(), usersBeforeDef_End(defPtr) )
// were seen *before* the specified def. All users in the half-closed range
// [ usersBeforeDef_End(defPtr), usersEnd() )
// were seen *after* the specified def.
//
ref_iterator usersBeforeDef_End(const_ref_iterator defPtr) {
unsigned defIndex = (unsigned) (defPtr - defsBegin());
assert(defIndex < numUsersBeforeDef.size());
assert(usersBegin() + numUsersBeforeDef[defIndex] <= usersEnd());
return usersBegin() + numUsersBeforeDef[defIndex];
}
const_ref_iterator usersBeforeDef_End(const_ref_iterator defPtr) const {
return const_cast<ModRefTable*>(this)->usersBeforeDef_End(defPtr);
}
//
// Modifier methods
//
void AddDef(Instruction* D) {
definers.push_back(D);
numUsersBeforeDef.push_back(users.size());
}
void AddUse(Instruction* U) {
users.push_back(U);
}
void Insert(const ModRefTable& fromTable) {
modRefMap.insert(fromTable.modRefMap.begin(), fromTable.modRefMap.end());
definers.insert(definers.end(),
fromTable.definers.begin(), fromTable.definers.end());
users.insert(users.end(),
fromTable.users.begin(), fromTable.users.end());
numUsersBeforeDef.clear(); /* fromTable.numUsersBeforeDef is ignored */
}
};
///--------------------------------------------------------------------------
/// class ModRefInfoBuilder:
///
/// A simple InstVisitor<> class that retrieves the Mod/Ref info for
/// Load/Store/Call instructions and inserts this information in
/// a ModRefTable. It also records all instructions that Mod any node
/// and all that use any node.
///--------------------------------------------------------------------------
class ModRefInfoBuilder : public InstVisitor<ModRefInfoBuilder> {
const DSGraph& funcGraph;
const FunctionModRefInfo& funcModRef;
struct ModRefTable& modRefTable;
ModRefInfoBuilder(); // DO NOT IMPLEMENT
ModRefInfoBuilder(const ModRefInfoBuilder&); // DO NOT IMPLEMENT
void operator=(const ModRefInfoBuilder&); // DO NOT IMPLEMENT
public:
ModRefInfoBuilder(const DSGraph& _funcGraph,
const FunctionModRefInfo& _funcModRef,
ModRefTable& _modRefTable)
: funcGraph(_funcGraph), funcModRef(_funcModRef), modRefTable(_modRefTable)
{
}
// At a call instruction, retrieve the ModRefInfo using IPModRef results.
// Add the call to the defs list if it modifies any nodes and to the uses
// list if it refs any nodes.
//
void visitCallInst(CallInst& callInst) {
ModRefInfo safeModRef(funcGraph.getGraphSize());
const ModRefInfo* callModRef = funcModRef.getModRefInfo(callInst);
if (callModRef == NULL) {
// call to external/unknown function: mark all nodes as Mod and Ref
safeModRef.getModSet().set();
safeModRef.getRefSet().set();
callModRef = &safeModRef;
}
modRefTable.modRefMap.insert(std::make_pair(&callInst,
ModRefInfo(*callModRef)));
if (callModRef->getModSet().any())
modRefTable.AddDef(&callInst);
if (callModRef->getRefSet().any())
modRefTable.AddUse(&callInst);
}
// At a store instruction, add to the mod set the single node pointed to
// by the pointer argument of the store. Interestingly, if there is no
// such node, that would be a null pointer reference!
void visitStoreInst(StoreInst& storeInst) {
const DSNodeHandle& ptrNode =
funcGraph.getNodeForValue(storeInst.getPointerOperand());
if (const DSNode* target = ptrNode.getNode()) {
unsigned nodeId = funcModRef.getNodeId(target);
ModRefInfo& minfo =
modRefTable.modRefMap.insert(
std::make_pair(&storeInst,
ModRefInfo(funcGraph.getGraphSize()))).first->second;
minfo.setNodeIsMod(nodeId);
modRefTable.AddDef(&storeInst);
} else
std::cerr << "Warning: Uninitialized pointer reference!\n";
}
// At a load instruction, add to the ref set the single node pointed to
// by the pointer argument of the load. Interestingly, if there is no
// such node, that would be a null pointer reference!
void visitLoadInst(LoadInst& loadInst) {
const DSNodeHandle& ptrNode =
funcGraph.getNodeForValue(loadInst.getPointerOperand());
if (const DSNode* target = ptrNode.getNode()) {
unsigned nodeId = funcModRef.getNodeId(target);
ModRefInfo& minfo =
modRefTable.modRefMap.insert(
std::make_pair(&loadInst,
ModRefInfo(funcGraph.getGraphSize()))).first->second;
minfo.setNodeIsRef(nodeId);
modRefTable.AddUse(&loadInst);
} else
std::cerr << "Warning: Uninitialized pointer reference!\n";
}
};
//----------------------------------------------------------------------------
// class MemoryDepAnalysis: A dep. graph for load/store/call instructions
//----------------------------------------------------------------------------
/// getAnalysisUsage - This does not modify anything. It uses the Top-Down DS
/// Graph and IPModRef.
///
void MemoryDepAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<TDDataStructures>();
AU.addRequired<IPModRef>();
}
/// Basic dependence gathering algorithm, using scc_iterator on CFG:
///
/// for every SCC S in the CFG in PostOrder on the SCC DAG
/// {
/// for every basic block BB in S in *postorder*
/// for every instruction I in BB in reverse
/// Add (I, ModRef[I]) to ModRefCurrent
/// if (Mod[I] != NULL)
/// Add I to DefSetCurrent: { I \in S : Mod[I] != NULL }
/// if (Ref[I] != NULL)
/// Add I to UseSetCurrent: { I : Ref[I] != NULL }
///
/// for every def D in DefSetCurrent
///
/// // NOTE: D comes after itself iff S contains a loop
/// if (HasLoop(S) && D & D)
/// Add output-dep: D -> D2
///
/// for every def D2 *after* D in DefSetCurrent
/// // NOTE: D2 comes before D in execution order
/// if (D & D2)
/// Add output-dep: D2 -> D
/// if (HasLoop(S))
/// Add output-dep: D -> D2
///
/// for every use U in UseSetCurrent that was seen *before* D
/// // NOTE: U comes after D in execution order
/// if (U & D)
/// if (U != D || HasLoop(S))
/// Add true-dep: D -> U
/// if (HasLoop(S))
/// Add anti-dep: U -> D
///
/// for every use U in UseSetCurrent that was seen *after* D
/// // NOTE: U comes before D in execution order
/// if (U & D)
/// if (U != D || HasLoop(S))
/// Add anti-dep: U -> D
/// if (HasLoop(S))
/// Add true-dep: D -> U
///
/// for every def Dnext in DefSetAfter
/// // NOTE: Dnext comes after D in execution order
/// if (Dnext & D)
/// Add output-dep: D -> Dnext
///
/// for every use Unext in UseSetAfter
/// // NOTE: Unext comes after D in execution order
/// if (Unext & D)
/// Add true-dep: D -> Unext
///
/// for every use U in UseSetCurrent
/// for every def Dnext in DefSetAfter
/// // NOTE: Dnext comes after U in execution order
/// if (Dnext & D)
/// Add anti-dep: U -> Dnext
///
/// Add ModRefCurrent to ModRefAfter: { (I, ModRef[I] ) }
/// Add DefSetCurrent to DefSetAfter: { I : Mod[I] != NULL }
/// Add UseSetCurrent to UseSetAfter: { I : Ref[I] != NULL }
/// }
///
///
void MemoryDepAnalysis::ProcessSCC(std::vector<BasicBlock*> &S,
ModRefTable& ModRefAfter, bool hasLoop) {
ModRefTable ModRefCurrent;
ModRefTable::ModRefMap& mapCurrent = ModRefCurrent.modRefMap;
ModRefTable::ModRefMap& mapAfter = ModRefAfter.modRefMap;
// Builder class fills out a ModRefTable one instruction at a time.
// To use it, we just invoke it's visit function for each basic block:
//
// for each basic block BB in the SCC in *postorder*
// for each instruction I in BB in *reverse*
// ModRefInfoBuilder::visit(I)
// : Add (I, ModRef[I]) to ModRefCurrent.modRefMap
// : Add I to ModRefCurrent.definers if it defines any node
// : Add I to ModRefCurrent.users if it uses any node
//
ModRefInfoBuilder builder(*funcGraph, *funcModRef, ModRefCurrent);
for (std::vector<BasicBlock*>::iterator BI = S.begin(), BE = S.end();
BI != BE; ++BI)
// Note: BBs in the SCC<> created by scc_iterator are in postorder.
for (BasicBlock::reverse_iterator II=(*BI)->rbegin(), IE=(*BI)->rend();
II != IE; ++II)
builder.visit(*II);
/// for every def D in DefSetCurrent
///
for (ModRefTable::ref_iterator II=ModRefCurrent.defsBegin(),
IE=ModRefCurrent.defsEnd(); II != IE; ++II)
{
/// // NOTE: D comes after itself iff S contains a loop
/// if (HasLoop(S))
/// Add output-dep: D -> D2
if (hasLoop)
funcDepGraph->AddSimpleDependence(**II, **II, OutputDependence);
/// for every def D2 *after* D in DefSetCurrent
/// // NOTE: D2 comes before D in execution order
/// if (D2 & D)
/// Add output-dep: D2 -> D
/// if (HasLoop(S))
/// Add output-dep: D -> D2
for (ModRefTable::ref_iterator JI=II+1; JI != IE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
mapCurrent.find(*JI)->second.getModSet()))
{
funcDepGraph->AddSimpleDependence(**JI, **II, OutputDependence);
if (hasLoop)
funcDepGraph->AddSimpleDependence(**II, **JI, OutputDependence);
}
/// for every use U in UseSetCurrent that was seen *before* D
/// // NOTE: U comes after D in execution order
/// if (U & D)
/// if (U != D || HasLoop(S))
/// Add true-dep: U -> D
/// if (HasLoop(S))
/// Add anti-dep: D -> U
ModRefTable::ref_iterator JI=ModRefCurrent.usersBegin();
ModRefTable::ref_iterator JE = ModRefCurrent.usersBeforeDef_End(II);
for ( ; JI != JE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
mapCurrent.find(*JI)->second.getRefSet()))
{
if (*II != *JI || hasLoop)
funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
if (hasLoop)
funcDepGraph->AddSimpleDependence(**JI, **II, AntiDependence);
}
/// for every use U in UseSetCurrent that was seen *after* D
/// // NOTE: U comes before D in execution order
/// if (U & D)
/// if (U != D || HasLoop(S))
/// Add anti-dep: U -> D
/// if (HasLoop(S))
/// Add true-dep: D -> U
for (/*continue JI*/ JE = ModRefCurrent.usersEnd(); JI != JE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
mapCurrent.find(*JI)->second.getRefSet()))
{
if (*II != *JI || hasLoop)
funcDepGraph->AddSimpleDependence(**JI, **II, AntiDependence);
if (hasLoop)
funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
}
/// for every def Dnext in DefSetPrev
/// // NOTE: Dnext comes after D in execution order
/// if (Dnext & D)
/// Add output-dep: D -> Dnext
for (ModRefTable::ref_iterator JI=ModRefAfter.defsBegin(),
JE=ModRefAfter.defsEnd(); JI != JE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
mapAfter.find(*JI)->second.getModSet()))
funcDepGraph->AddSimpleDependence(**II, **JI, OutputDependence);
/// for every use Unext in UseSetAfter
/// // NOTE: Unext comes after D in execution order
/// if (Unext & D)
/// Add true-dep: D -> Unext
for (ModRefTable::ref_iterator JI=ModRefAfter.usersBegin(),
JE=ModRefAfter.usersEnd(); JI != JE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
mapAfter.find(*JI)->second.getRefSet()))
funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
}
///
/// for every use U in UseSetCurrent
/// for every def Dnext in DefSetAfter
/// // NOTE: Dnext comes after U in execution order
/// if (Dnext & D)
/// Add anti-dep: U -> Dnext
for (ModRefTable::ref_iterator II=ModRefCurrent.usersBegin(),
IE=ModRefCurrent.usersEnd(); II != IE; ++II)
for (ModRefTable::ref_iterator JI=ModRefAfter.defsBegin(),
JE=ModRefAfter.defsEnd(); JI != JE; ++JI)
if (!Disjoint(mapCurrent.find(*II)->second.getRefSet(),
mapAfter.find(*JI)->second.getModSet()))
funcDepGraph->AddSimpleDependence(**II, **JI, AntiDependence);
/// Add ModRefCurrent to ModRefAfter: { (I, ModRef[I] ) }
/// Add DefSetCurrent to DefSetAfter: { I : Mod[I] != NULL }
/// Add UseSetCurrent to UseSetAfter: { I : Ref[I] != NULL }
ModRefAfter.Insert(ModRefCurrent);
}
/// Debugging support methods
///
void MemoryDepAnalysis::print(std::ostream &O) const
{
// TEMPORARY LOOP
for (hash_map<Function*, DependenceGraph*>::const_iterator
I = funcMap.begin(), E = funcMap.end(); I != E; ++I)
{
Function* func = I->first;
DependenceGraph* depGraph = I->second;
O << "\n================================================================\n";
O << "DEPENDENCE GRAPH FOR MEMORY OPERATIONS IN FUNCTION " << func->getName();
O << "\n================================================================\n\n";
depGraph->print(*func, O);
}
}
///
/// Run the pass on a function
///
bool MemoryDepAnalysis::runOnFunction(Function &F) {
assert(!F.isExternal());
// Get the FunctionModRefInfo holding IPModRef results for this function.
// Use the TD graph recorded within the FunctionModRefInfo object, which
// may not be the same as the original TD graph computed by DS analysis.
//
funcModRef = &getAnalysis<IPModRef>().getFunctionModRefInfo(F);
funcGraph = &funcModRef->getFuncGraph();
// TEMPORARY: ptr to depGraph (later just becomes "this").
assert(!funcMap.count(&F) && "Analyzing function twice?");
funcDepGraph = funcMap[&F] = new DependenceGraph();
ModRefTable ModRefAfter;
for (scc_iterator<Function*> I = scc_begin(&F), E = scc_end(&F); I != E; ++I)
ProcessSCC(*I, ModRefAfter, I.hasLoop());
return true;
}
//-------------------------------------------------------------------------
// TEMPORARY FUNCTIONS TO MAKE THIS A MODULE PASS ---
// These functions will go away once this class becomes a FunctionPass.
//
// Driver function to compute dependence graphs for every function.
// This is temporary and will go away once this is a FunctionPass.
//
bool MemoryDepAnalysis::run(Module& M)
{
for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
if (! FI->isExternal())
runOnFunction(*FI); // automatically inserts each depGraph into funcMap
return true;
}
// Release all the dependence graphs in the map.
void MemoryDepAnalysis::releaseMemory()
{
for (hash_map<Function*, DependenceGraph*>::const_iterator
I = funcMap.begin(), E = funcMap.end(); I != E; ++I)
delete I->second;
funcMap.clear();
// Clear pointers because the pass constructor will not be invoked again.
funcDepGraph = NULL;
funcGraph = NULL;
funcModRef = NULL;
}
MemoryDepAnalysis::~MemoryDepAnalysis()
{
releaseMemory();
}
//----END TEMPORARY FUNCTIONS----------------------------------------------
void MemoryDepAnalysis::dump() const
{
this->print(std::cerr);
}
static RegisterAnalysis<MemoryDepAnalysis>
Z("memdep", "Memory Dependence Analysis");
} // End llvm namespace