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94 lines
3.6 KiB
C++
94 lines
3.6 KiB
C++
//===- EdgeProfiling.cpp - Insert counters for edge profiling -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass instruments the specified program with counters for edge profiling.
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// Edge profiling can give a reasonable approximation of the hot paths through a
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// program, and is used for a wide variety of program transformations.
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//
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// Note that this implementation is very naive. We insert a counter for *every*
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// edge in the program, instead of using control flow information to prune the
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// number of counters inserted.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "ProfilingUtils.h"
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#include <iostream>
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#include <set>
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using namespace llvm;
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namespace {
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class EdgeProfiler : public Pass {
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bool run(Module &M);
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};
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RegisterOpt<EdgeProfiler> X("insert-edge-profiling",
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"Insert instrumentation for edge profiling");
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}
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bool EdgeProfiler::run(Module &M) {
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Function *Main = M.getMainFunction();
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if (Main == 0) {
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std::cerr << "WARNING: cannot insert edge profiling into a module"
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<< " with no main function!\n";
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return false; // No main, no instrumentation!
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}
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std::set<BasicBlock*> BlocksToInstrument;
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unsigned NumEdges = 0;
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for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
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for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
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// Keep track of which blocks need to be instrumented. We don't want to
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// instrument blocks that are added as the result of breaking critical
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// edges!
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BlocksToInstrument.insert(BB);
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NumEdges += BB->getTerminator()->getNumSuccessors();
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}
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const Type *ATy = ArrayType::get(Type::UIntTy, NumEdges);
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GlobalVariable *Counters =
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new GlobalVariable(ATy, false, GlobalValue::InternalLinkage,
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Constant::getNullValue(ATy), "EdgeProfCounters", &M);
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// Instrument all of the edges...
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unsigned i = 0;
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for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
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for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
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if (BlocksToInstrument.count(BB)) { // Don't instrument inserted blocks
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// Okay, we have to add a counter of each outgoing edge. If the
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// outgoing edge is not critical don't split it, just insert the counter
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// in the source or destination of the edge.
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TerminatorInst *TI = BB->getTerminator();
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for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) {
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// If the edge is critical, split it.
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SplitCriticalEdge(TI, s, this);
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// Okay, we are guaranteed that the edge is no longer critical. If we
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// only have a single successor, insert the counter in this block,
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// otherwise insert it in the successor block.
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if (TI->getNumSuccessors() == 0) {
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// Insert counter at the start of the block
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IncrementCounterInBlock(BB, i++, Counters);
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} else {
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// Insert counter at the start of the block
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IncrementCounterInBlock(TI->getSuccessor(s), i++, Counters);
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}
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}
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}
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// Add the initialization call to main.
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InsertProfilingInitCall(Main, "llvm_start_edge_profiling", Counters);
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return true;
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}
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