llvm-6502/lib/Analysis/IPA/CallGraph.cpp
2003-11-11 22:41:34 +00:00

356 lines
11 KiB
C++

//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
//
// 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 interface is used to build and manipulate a call graph, which is a very
// useful tool for interprocedural optimization.
//
// Every function in a module is represented as a node in the call graph. The
// callgraph node keeps track of which functions the are called by the function
// corresponding to the node.
//
// A call graph will contain nodes where the function that they correspond to is
// null. This 'external' node is used to represent control flow that is not
// represented (or analyzable) in the module. As such, the external node will
// have edges to functions with the following properties:
// 1. All functions in the module without internal linkage, since they could
// be called by functions outside of the our analysis capability.
// 2. All functions whose address is used for something more than a direct
// call, for example being stored into a memory location. Since they may
// be called by an unknown caller later, they must be tracked as such.
//
// Similarly, functions have a call edge to the external node iff:
// 1. The function is external, reflecting the fact that they could call
// anything without internal linkage or that has its address taken.
// 2. The function contains an indirect function call.
//
// As an extension in the future, there may be multiple nodes with a null
// function. These will be used when we can prove (through pointer analysis)
// that an indirect call site can call only a specific set of functions.
//
// Because of these properties, the CallGraph captures a conservative superset
// of all of the caller-callee relationships, which is useful for
// transformations.
//
// The CallGraph class also attempts to figure out what the root of the
// CallGraph is, which is currently does by looking for a function named 'main'.
// If no function named 'main' is found, the external node is used as the entry
// node, reflecting the fact that any function without internal linkage could
// be called into (which is common for libraries).
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Constants.h" // Remove when ConstantPointerRefs are gone
#include "llvm/Module.h"
#include "llvm/iOther.h"
#include "llvm/iTerminators.h"
#include "llvm/Support/CallSite.h"
#include "Support/STLExtras.h"
namespace llvm {
static RegisterAnalysis<CallGraph> X("callgraph", "Call Graph Construction");
static const char * const KnownExternalFunctions[] = {
// Low-level system calls
"open",
"read",
"write",
"writev",
"lseek",
"poll",
"ioctl",
// Low-level stdc library functions
"abort", "exit",
"getenv", "putenv",
// Standard IO functions
"printf",
"sprintf",
"fopen",
"freopen",
"fclose",
"fwrite",
"puts",
"fputs",
"getc",
"ungetc",
"putc",
"putchar",
"fread",
"fileno",
"ftell",
"fflush",
"fseek",
"fileno",
"ferror",
"feof",
"fdopen",
"__fxstat",
"setbuf",
"setbuffer",
"etlinebuf",
"setvbuf",
// Memory functions
"malloc",
"free",
"realloc",
"calloc",
"memalign",
// String functions
"atoi",
"memmove",
"memset",
"memchr",
"memcmp",
"strchr",
"strncpy",
"strncmp",
"strcmp",
"strtok",
"__strcoll_l",
"__strxfrm_l",
"__strftime_l",
"__strtol_l",
"__strtoul_l",
"__strtoll_l",
"__strtoull_l",
"__strtof_l",
"__strtod_l",
"__strtold_l",
"isalpha",
// Math functions
"exp", "sqrt", "cbrt", "hypot",
"log", "log10", "pow",
"sin", "cos", "tan",
"asin", "acos", "atan", "atan2",
// Locale functions
"__uselocale",
"__newlocale",
"__freelocale",
"__duplocale",
"__nl_langinfo_l",
// gettext functions used by libstdc++
"gettext",
"dgettext",
"dcgettext",
"textdomain",
"bindtextdomain",
// Random stuff
"__assert_fail",
"__errno_location",
"clock", "time",
"__main",
};
/// ExternalFunctionDoesntCallIntoProgram - This hack is used to indicate to the
/// call graph that the specified external function is _KNOWN_ to not call back
/// into the program. This is important, because otherwise functions which call
/// "printf" for example, end up in a great big SCC that goes from the function
/// through main.
///
static bool ExternalFunctionDoesntCallIntoProgram(const std::string &Name) {
static std::vector<std::string> Funcs;
// First time this is called?
if (Funcs.empty()) {
// Add a whole bunch of functions which are often used...
Funcs.insert(Funcs.end(), KnownExternalFunctions,
KnownExternalFunctions+
sizeof(KnownExternalFunctions)/sizeof(KnownExternalFunctions[0]));
// Sort the list for efficient access
std::sort(Funcs.begin(), Funcs.end());
}
if (Name.size() > 7 && !memcmp("__llvm_", Name.c_str(), 7))
return true;
// Binary search for the function name...
std::vector<std::string>::iterator I =
std::lower_bound(Funcs.begin(), Funcs.end(), Name);
// Found it?
return I != Funcs.end() && *I == Name;
}
// getNodeFor - Return the node for the specified function or create one if it
// does not already exist.
//
CallGraphNode *CallGraph::getNodeFor(Function *F) {
CallGraphNode *&CGN = FunctionMap[F];
if (CGN) return CGN;
assert((!F || F->getParent() == Mod) && "Function not in current module!");
return CGN = new CallGraphNode(F);
}
static bool isOnlyADirectCall(Function *F, CallSite CS) {
if (!CS.getInstruction()) return false;
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); I != E; ++I)
if (*I == F) return false;
return true;
}
// addToCallGraph - Add a function to the call graph, and link the node to all
// of the functions that it calls.
//
void CallGraph::addToCallGraph(Function *F) {
CallGraphNode *Node = getNodeFor(F);
// If this function has external linkage, anything could call it...
if (!F->hasInternalLinkage()) {
ExternalNode->addCalledFunction(Node);
// Found the entry point?
if (F->getName() == "main") {
if (Root)
Root = ExternalNode; // Found multiple external mains? Don't pick one.
else
Root = Node; // Found a main, keep track of it!
}
}
// If this function is not defined in this translation unit, it could call
// anything.
if (F->isExternal() && !F->getIntrinsicID() &&
!ExternalFunctionDoesntCallIntoProgram(F->getName()))
Node->addCalledFunction(ExternalNode);
// Loop over all of the users of the function... looking for callers...
//
bool isUsedExternally = false;
for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I) {
if (Instruction *Inst = dyn_cast<Instruction>(*I)) {
if (isOnlyADirectCall(F, CallSite::get(Inst)))
getNodeFor(Inst->getParent()->getParent())->addCalledFunction(Node);
else
isUsedExternally = true;
} else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(*I)) {
// THIS IS A DISGUSTING HACK. Brought to you by the power of
// ConstantPointerRefs!
for (Value::use_iterator I = CPR->use_begin(), E = CPR->use_end();
I != E; ++I)
if (Instruction *Inst = dyn_cast<Instruction>(*I)) {
if (isOnlyADirectCall(F, CallSite::get(Inst)))
getNodeFor(Inst->getParent()->getParent())->addCalledFunction(Node);
else
isUsedExternally = true;
} else {
isUsedExternally = true;
}
} else { // Can't classify the user!
isUsedExternally = true;
}
}
if (isUsedExternally)
ExternalNode->addCalledFunction(Node);
// Look for an indirect function call...
for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II){
CallSite CS = CallSite::get(II);
if (CS.getInstruction() && !CS.getCalledFunction())
Node->addCalledFunction(ExternalNode);
}
}
bool CallGraph::run(Module &M) {
destroy();
Mod = &M;
ExternalNode = getNodeFor(0);
Root = 0;
// Add every function to the call graph...
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
addToCallGraph(I);
// If we didn't find a main function, use the external call graph node
if (Root == 0) Root = ExternalNode;
return false;
}
void CallGraph::destroy() {
for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
I != E; ++I)
delete I->second;
FunctionMap.clear();
}
static void WriteToOutput(const CallGraphNode *CGN, std::ostream &o) {
if (CGN->getFunction())
o << "Call graph node for function: '"
<< CGN->getFunction()->getName() <<"'\n";
else
o << "Call graph node <<null function: 0x" << CGN << ">>:\n";
for (unsigned i = 0; i < CGN->size(); ++i)
if ((*CGN)[i]->getFunction())
o << " Calls function '" << (*CGN)[i]->getFunction()->getName() << "'\n";
else
o << " Calls external node\n";
o << "\n";
}
void CallGraph::print(std::ostream &o, const Module *M) const {
o << "CallGraph Root is: ";
if (getRoot()->getFunction())
o << getRoot()->getFunction()->getName() << "\n";
else
o << "<<null function: 0x" << getRoot() << ">>\n";
for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
WriteToOutput(I->second, o);
}
//===----------------------------------------------------------------------===//
// Implementations of public modification methods
//
// Functions to keep a call graph up to date with a function that has been
// modified
//
void CallGraph::addFunctionToModule(Function *Meth) {
assert(0 && "not implemented");
abort();
}
// removeFunctionFromModule - Unlink the function from this module, returning
// it. Because this removes the function from the module, the call graph node
// is destroyed. This is only valid if the function does not call any other
// functions (ie, there are no edges in it's CGN). The easiest way to do this
// is to dropAllReferences before calling this.
//
Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
assert(CGN->CalledFunctions.empty() && "Cannot remove function from call "
"graph if it references other functions!");
Function *F = CGN->getFunction(); // Get the function for the call graph node
delete CGN; // Delete the call graph node for this func
FunctionMap.erase(F); // Remove the call graph node from the map
Mod->getFunctionList().remove(F);
return F;
}
void CallGraph::stub() {}
} // End llvm namespace