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creation functions in their public header file, unless they can help it. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1816 91177308-0d34-0410-b5e6-96231b3b80d8
100 lines
3.6 KiB
C++
100 lines
3.6 KiB
C++
//===- ConstantMerge.cpp - Merge duplicate global constants -----------------=//
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//
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// This file defines the interface to a pass that merges duplicate global
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// constants together into a single constant that is shared. This is useful
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// because some passes (ie TraceValues) insert a lot of string constants into
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// the program, regardless of whether or not they duplicate an existing string.
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//
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// Algorithm: ConstantMerge is designed to build up a map of available constants
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// and elminate duplicates when it is initialized.
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//
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// The DynamicConstantMerge method is a superset of the ConstantMerge algorithm
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// that checks for each method to see if constants have been added to the
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// constant pool since it was last run... if so, it processes them.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/ConstantMerge.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/Module.h"
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#include "llvm/Method.h"
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#include "llvm/Pass.h"
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// mergeDuplicateConstants - Workhorse for the pass. This eliminates duplicate
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// constants, starting at global ConstantNo, and adds vars to the map if they
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// are new and unique.
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//
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static inline
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bool mergeDuplicateConstants(Module *M, unsigned &ConstantNo,
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std::map<Constant*, GlobalVariable*> &CMap) {
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Module::GlobalListType &GList = M->getGlobalList();
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if (GList.size() <= ConstantNo) return false; // No new constants
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bool MadeChanges = false;
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for (; ConstantNo < GList.size(); ++ConstantNo) {
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GlobalVariable *GV = GList[ConstantNo];
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if (GV->isConstant()) { // Only process constants
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assert(GV->hasInitializer() && "Globals constants must have inits!");
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Constant *Init = GV->getInitializer();
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// Check to see if the initializer is already known...
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std::map<Constant*, GlobalVariable*>::iterator I = CMap.find(Init);
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if (I == CMap.end()) { // Nope, add it to the map
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CMap.insert(std::make_pair(Init, GV));
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} else { // Yup, this is a duplicate!
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// Make all uses of the duplicate constant use the cannonical version...
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GV->replaceAllUsesWith(I->second);
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// Remove and delete the global value from the module...
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delete GList.remove(GList.begin()+ConstantNo);
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--ConstantNo; // Don't skip the next constant.
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MadeChanges = true;
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}
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}
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}
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return MadeChanges;
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}
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namespace {
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// FIXME: ConstantMerge should not be a methodPass!!!
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class ConstantMerge : public MethodPass {
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protected:
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std::map<Constant*, GlobalVariable*> Constants;
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unsigned LastConstantSeen;
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public:
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inline ConstantMerge() : LastConstantSeen(0) {}
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// doInitialization - For this pass, process all of the globals in the
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// module, eliminating duplicate constants.
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//
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bool doInitialization(Module *M) {
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return ::mergeDuplicateConstants(M, LastConstantSeen, Constants);
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}
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bool runOnMethod(Method*) { return false; }
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// doFinalization - Clean up internal state for this module
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//
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bool doFinalization(Module *M) {
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LastConstantSeen = 0;
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Constants.clear();
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return false;
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}
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};
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struct DynamicConstantMerge : public ConstantMerge {
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// doPerMethodWork - Check to see if any globals have been added to the
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// global list for the module. If so, eliminate them.
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//
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bool runOnMethod(Method *M) {
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return ::mergeDuplicateConstants(M->getParent(), LastConstantSeen,
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Constants);
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}
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};
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}
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Pass *createConstantMergePass() { return new ConstantMerge(); }
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Pass *createDynamicConstantMergePass() { return new DynamicConstantMerge(); }
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