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2fbfdcffd3
class. The Method class is obsolete (renamed) and all references to it are being converted over to Function. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2144 91177308-0d34-0410-b5e6-96231b3b80d8
73 lines
2.6 KiB
C++
73 lines
2.6 KiB
C++
//===-- GlobalDCE.cpp - DCE unreachable internal functions ----------------===//
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//
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// This transform is designed to eliminate unreachable internal globals
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO/GlobalDCE.h"
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Module.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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#include "Support/DepthFirstIterator.h"
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#include <set>
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static bool RemoveUnreachableFunctions(Module *M, CallGraph &CallGraph) {
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// Calculate which functions are reachable from the external functions in the
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// call graph.
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//
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std::set<CallGraphNode*> ReachableNodes(df_begin(&CallGraph),
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df_end(&CallGraph));
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// Loop over the functions in the module twice. The first time is used to
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// drop references that functions have to each other before they are deleted.
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// The second pass removes the functions that need to be removed.
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//
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std::vector<CallGraphNode*> FunctionsToDelete; // Track unused functions
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for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) {
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CallGraphNode *N = CallGraph[*I];
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if (!ReachableNodes.count(N)) { // Not reachable??
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(*I)->dropAllReferences();
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N->removeAllCalledMethods();
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FunctionsToDelete.push_back(N);
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}
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}
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// Nothing to do if no unreachable functions have been found...
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if (FunctionsToDelete.empty()) return false;
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// Unreachables functions have been found and should have no references to
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// them, delete them now.
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//
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for (std::vector<CallGraphNode*>::iterator I = FunctionsToDelete.begin(),
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E = FunctionsToDelete.end(); I != E; ++I)
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delete CallGraph.removeMethodFromModule(*I);
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return true;
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}
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namespace {
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struct GlobalDCE : public Pass {
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// run - Do the GlobalDCE pass on the specified module, optionally updating
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// the specified callgraph to reflect the changes.
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//
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bool run(Module *M) {
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return RemoveUnreachableFunctions(M, getAnalysis<CallGraph>());
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}
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// getAnalysisUsageInfo - This function works on the call graph of a module.
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// It is capable of updating the call graph to reflect the new state of the
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// module.
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//
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virtual void getAnalysisUsageInfo(Pass::AnalysisSet &Required,
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Pass::AnalysisSet &Destroyed,
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Pass::AnalysisSet &Provided) {
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Required.push_back(CallGraph::ID);
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// FIXME: This should update the callgraph, not destroy it!
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Destroyed.push_back(CallGraph::ID);
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}
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};
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}
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Pass *createGlobalDCEPass() { return new GlobalDCE(); }
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