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//===-- GlobalDCE.cpp - DCE unreachable internal methods ---------*- C++ -*--=//
//
// This transform is designed to eliminate unreachable internal globals
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO/GlobalDCE.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Module.h"
#include "llvm/Method.h"
#include "Support/DepthFirstIterator.h"
#include <set>
static bool RemoveUnreachableMethods(Module *M, cfg::CallGraph &CallGraph) {
// Calculate which methods are reachable from the external methods in the call
// graph.
//
std::set<cfg::CallGraphNode*> ReachableNodes(df_begin(&CallGraph),
df_end(&CallGraph));
// Loop over the methods in the module twice. The first time is used to drop
// references that methods have to each other before they are deleted. The
// second pass removes the methods that need to be removed.
//
std::vector<cfg::CallGraphNode*> MethodsToDelete; // Track unused methods
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) {
cfg::CallGraphNode *N = CallGraph[*I];
if (!ReachableNodes.count(N)) { // Not reachable??
(*I)->dropAllReferences();
N->removeAllCalledMethods();
MethodsToDelete.push_back(N);
}
}
// Nothing to do if no unreachable methods have been found...
if (MethodsToDelete.empty()) return false;
// Unreachables methods have been found and should have no references to them,
// delete them now.
//
for (std::vector<cfg::CallGraphNode*>::iterator I = MethodsToDelete.begin(),
E = MethodsToDelete.end(); I != E; ++I)
delete CallGraph.removeMethodFromModule(*I);
return true;
}
bool GlobalDCE::run(Module *M) {
// TODO: FIXME: GET THE CALL GRAPH FROM THE PASS!
// Create a call graph if one is not already available...
cfg::CallGraph CallGraph(M);
return RemoveUnreachableMethods(M, CallGraph);
}
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