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7a9eb848cd
* Add new RegisterOpt/RegisterAnalysis templates for registering passes that are to show up in opt or analyze * Register Analyses now * Change optimizations to use RegisterOpt instead of RegisterPass * Add support for different "PassType's" * Add new RegisterOpt/RegisterAnalysis templates for registering passes that are to show up in opt or analyze * Register Analyses now * Change optimizations to use RegisterOpt instead of RegisterPass * Remove getPassName implementations from various subclasses llvm-svn: 3113
69 lines
2.2 KiB
C++
69 lines
2.2 KiB
C++
//===- ConstantProp.cpp - Code to perform Simple Constant Propogation -----===//
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//
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// This file implements constant propogation and merging:
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//
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// Specifically, this:
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// * Converts instructions like "add int 1, 2" into 3
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//
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// Notice that:
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// * This pass has a habit of making definitions be dead. It is a good idea
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// to to run a DIE pass sometime after running this pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ConstantHandling.h"
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#include "llvm/Instruction.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstIterator.h"
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#include "Support/StatisticReporter.h"
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#include <set>
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static Statistic<> NumInstKilled("constprop - Number of instructions killed");
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namespace {
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struct ConstantPropogation : public FunctionPass {
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bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.preservesCFG();
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}
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};
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RegisterOpt<ConstantPropogation> X("constprop","Simple constant propogation");
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}
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Pass *createConstantPropogationPass() {
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return new ConstantPropogation();
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}
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bool ConstantPropogation::runOnFunction(Function &F) {
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// Initialize the worklist to all of the instructions ready to process...
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std::set<Instruction*> WorkList(inst_begin(F), inst_end(F));
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bool Changed = false;
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while (!WorkList.empty()) {
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Instruction *I = *WorkList.begin();
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WorkList.erase(WorkList.begin()); // Get an element from the worklist...
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if (!I->use_empty()) // Don't muck with dead instructions...
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if (Constant *C = ConstantFoldInstruction(I)) {
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// Add all of the users of this instruction to the worklist, they might
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// be constant propogatable now...
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for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
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UI != UE; ++UI)
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WorkList.insert(cast<Instruction>(*UI));
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// Replace all of the uses of a variable with uses of the constant.
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I->replaceAllUsesWith(C);
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// We made a change to the function...
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Changed = true;
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++NumInstKilled;
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}
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}
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return Changed;
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}
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