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f4de63f65f
out how to run a collection of passes optimially given their behaviors and charactaristics. Convert code to use it. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1507 91177308-0d34-0410-b5e6-96231b3b80d8
81 lines
3.1 KiB
C++
81 lines
3.1 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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// 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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// mergeDuplicateConstants - Static accessor for clients that don't want to
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// deal with passes.
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//
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bool ConstantMerge::mergeDuplicateConstants(Module *M) {
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std::map<Constant*, GlobalVariable*> Constants;
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unsigned LastConstantSeen = 0;
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return ::mergeDuplicateConstants(M, LastConstantSeen, Constants);
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}
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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 ConstantMerge::doInitialization(Module *M) {
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return ::mergeDuplicateConstants(M, LastConstantSeen, Constants);
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}
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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 DynamicConstantMerge::runOnMethod(Method *M) {
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return ::mergeDuplicateConstants(M->getParent(), LastConstantSeen, Constants);
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}
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