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