llvm/lib/Analysis/IPA/PgmDependenceGraph.cpp
2003-11-11 22:41:34 +00:00

259 lines
8.8 KiB
C++

//===- PgmDependenceGraph.cpp - Enumerate PDG for a function ----*- C++ -*-===//
//
// 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.
//
//===----------------------------------------------------------------------===//
//
// The Program Dependence Graph (PDG) for a single function represents all
// data and control dependences for the function. This file provides an
// iterator to enumerate all these dependences. In particular, it enumerates:
//
// -- Data dependences on memory locations, computed using the
// MemoryDepAnalysis pass;
// -- Data dependences on SSA registers, directly from Def-Use edges of Values;
// -- Control dependences, computed using postdominance frontiers
// (NOT YET IMPLEMENTED).
//
// Note that this file does not create an explicit dependence graph --
// it only provides an iterator to traverse the PDG conceptually.
// The MemoryDepAnalysis does build an explicit graph, which is used internally
// here. That graph could be augmented with the other dependences above if
// desired, but for most uses there will be little need to do that.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/PgmDependenceGraph.h"
#include "llvm/Analysis/MemoryDepAnalysis.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Function.h"
namespace llvm {
//----------------------------------------------------------------------------
// class DepIterState
//----------------------------------------------------------------------------
const DepIterState::IterStateFlags DepIterState::NoFlag = 0x0;
const DepIterState::IterStateFlags DepIterState::MemDone = 0x1;
const DepIterState::IterStateFlags DepIterState::SSADone = 0x2;
const DepIterState::IterStateFlags DepIterState::AllDone = 0x4;
const DepIterState::IterStateFlags DepIterState::FirstTimeFlag= 0x8;
// Find the first memory dependence for the current Mem In/Out iterators.
// Find the first memory dependence for the current Mem In/Out iterators.
// Sets dep to that dependence and returns true if one is found.
//
bool DepIterState::SetFirstMemoryDep()
{
if (! (depFlags & MemoryDeps))
return false;
bool doIncomingDeps = dep.getDepType() & IncomingFlag;
if (( doIncomingDeps && memDepIter == memDepGraph->inDepEnd( *depNode)) ||
(!doIncomingDeps && memDepIter == memDepGraph->outDepEnd(*depNode)))
{
iterFlags |= MemDone;
return false;
}
dep = *memDepIter; // simple copy from dependence in memory DepGraph
return true;
}
// Find the first valid data dependence for the current SSA In/Out iterators.
// A valid data dependence is one that is to/from an Instruction.
// E.g., an SSA edge from a formal parameter is not a valid dependence.
// Sets dep to that dependence and returns true if a valid one is found.
// Returns false and leaves dep unchanged otherwise.
//
bool DepIterState::SetFirstSSADep()
{
if (! (depFlags & SSADeps))
return false;
bool doIncomingDeps = dep.getDepType() & IncomingFlag;
Instruction* firstTarget = NULL;
// Increment the In or Out iterator till it runs out or we find a valid dep
if (doIncomingDeps)
for (Instruction::op_iterator E = depNode->getInstr().op_end();
ssaInEdgeIter != E &&
(firstTarget = dyn_cast<Instruction>(ssaInEdgeIter))== NULL; )
++ssaInEdgeIter;
else
for (Value::use_iterator E = depNode->getInstr().use_end();
ssaOutEdgeIter != E &&
(firstTarget = dyn_cast<Instruction>(*ssaOutEdgeIter)) == NULL; )
++ssaOutEdgeIter;
// If the iterator ran out before we found a valid dep, there isn't one.
if (!firstTarget)
{
iterFlags |= SSADone;
return false;
}
// Create a simple dependence object to represent this SSA dependence.
dep = Dependence(memDepGraph->getNode(*firstTarget, /*create*/ true),
TrueDependence, doIncomingDeps);
return true;
}
DepIterState::DepIterState(DependenceGraph* _memDepGraph,
Instruction& I,
bool incomingDeps,
PDGIteratorFlags whichDeps)
: memDepGraph(_memDepGraph),
depFlags(whichDeps),
iterFlags(NoFlag)
{
depNode = memDepGraph->getNode(I, /*create*/ true);
if (incomingDeps)
{
if (whichDeps & MemoryDeps) memDepIter= memDepGraph->inDepBegin(*depNode);
if (whichDeps & SSADeps) ssaInEdgeIter = I.op_begin();
/* Initialize control dependence iterator here. */
}
else
{
if (whichDeps & MemoryDeps) memDepIter=memDepGraph->outDepBegin(*depNode);
if (whichDeps & SSADeps) ssaOutEdgeIter = I.use_begin();
/* Initialize control dependence iterator here. */
}
// Set the dependence to the first of a memory dep or an SSA dep
// and set the done flag if either is found. Otherwise, set the
// init flag to indicate that the iterators have just been initialized.
//
if (!SetFirstMemoryDep() && !SetFirstSSADep())
iterFlags |= AllDone;
else
iterFlags |= FirstTimeFlag;
}
// Helper function for ++ operator that bumps iterator by 1 (to next
// dependence) and resets the dep field to represent the new dependence.
//
void DepIterState::Next()
{
// firstMemDone and firstSsaDone are used to indicate when the memory or
// SSA iterators just ran out, or when this is the very first increment.
// In either case, the next iterator (if any) should not be incremented.
//
bool firstMemDone = iterFlags & FirstTimeFlag;
bool firstSsaDone = iterFlags & FirstTimeFlag;
bool doIncomingDeps = dep.getDepType() & IncomingFlag;
if (depFlags & MemoryDeps && ! (iterFlags & MemDone))
{
iterFlags &= ~FirstTimeFlag; // clear "firstTime" flag
++memDepIter;
if (SetFirstMemoryDep())
return;
firstMemDone = true; // flags that we _just_ rolled over
}
if (depFlags & SSADeps && ! (iterFlags & SSADone))
{
// Don't increment the SSA iterator if we either just rolled over from
// the memory dep iterator, or if the SSA iterator is already done.
iterFlags &= ~FirstTimeFlag; // clear "firstTime" flag
if (! firstMemDone)
if (doIncomingDeps) ++ssaInEdgeIter;
else ++ssaOutEdgeIter;
if (SetFirstSSADep())
return;
firstSsaDone = true; // flags if we just rolled over
}
if (depFlags & ControlDeps != 0)
{
assert(0 && "Cannot handle control deps");
// iterFlags &= ~FirstTimeFlag; // clear "firstTime" flag
}
// This iterator is now complete.
iterFlags |= AllDone;
}
//----------------------------------------------------------------------------
// class PgmDependenceGraph
//----------------------------------------------------------------------------
// MakeIterator -- Create and initialize an iterator as specified.
//
PDGIterator PgmDependenceGraph::MakeIterator(Instruction& I,
bool incomingDeps,
PDGIteratorFlags whichDeps)
{
assert(memDepGraph && "Function not initialized!");
return PDGIterator(new DepIterState(memDepGraph, I, incomingDeps, whichDeps));
}
void PgmDependenceGraph::printOutgoingSSADeps(Instruction& I,
std::ostream &O)
{
iterator SI = this->outDepBegin(I, SSADeps);
iterator SE = this->outDepEnd(I, SSADeps);
if (SI == SE)
return;
O << "\n Outgoing SSA dependences:\n";
for ( ; SI != SE; ++SI)
{
O << "\t";
SI->print(O);
O << " to instruction:";
O << SI->getSink()->getInstr();
}
}
void PgmDependenceGraph::print(std::ostream &O) const
{
MemoryDepAnalysis& graphSet = getAnalysis<MemoryDepAnalysis>();
// TEMPORARY LOOP
for (hash_map<Function*, DependenceGraph*>::iterator
I = graphSet.funcMap.begin(), E = graphSet.funcMap.end();
I != E; ++I)
{
Function* func = I->first;
DependenceGraph* depGraph = I->second;
const_cast<PgmDependenceGraph*>(this)->runOnFunction(*func);
O << "DEPENDENCE GRAPH FOR FUNCTION " << func->getName() << ":\n";
for (Function::iterator BB=func->begin(), FE=func->end(); BB != FE; ++BB)
for (BasicBlock::iterator II=BB->begin(), IE=BB->end(); II !=IE; ++II)
{
DepGraphNode* dgNode = depGraph->getNode(*II, /*create*/ true);
dgNode->print(O);
const_cast<PgmDependenceGraph*>(this)->printOutgoingSSADeps(*II, O);
}
} // END TEMPORARY LOOP
}
void PgmDependenceGraph::dump() const
{
this->print(std::cerr);
}
static RegisterAnalysis<PgmDependenceGraph>
Z("pgmdep", "Enumerate Program Dependence Graph (data and control)");
} // End llvm namespace