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Code cleanups and added comments.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80781 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andreas Neustifter 2009-09-02 12:38:39 +00:00
parent 254bb831d8
commit 9341cdc217
1 changed files with 45 additions and 17 deletions
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62
lib/Transforms/Instrumentation/OptimalEdgeProfiling.cpp
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@ -14,14 +14,11 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "insert-optimal-edge-profiling"
#include "ProfilingUtils.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Instrumentation.h"
@ -75,8 +72,19 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
return false; // No main, no instrumentation!
}
// BlocksToInstrument stores all blocks that are in the function prior to
// instrumenting, since the spliting of critical edges adds new blocks (which
// have not to be instrumented), we have to remember them for later.
std::set<BasicBlock*> BlocksToInstrument;
// NumEdges counts all the edges that may be instrumented. Later on its
// decided which edges to actually instrument, to achieve optimal profiling.
// For the entry block a virtual edge (0,entry) is reserved, for each block
// with no successors an edge (BB,0) is reserved. These edges are necessary
// to calculate a truly optimal maximum spanning tree and thus an optimal
// instrumentation.
unsigned NumEdges = 0;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
if (F->isDeclaration()) continue;
// Reserve space for (0,entry) edge.
@ -95,6 +103,13 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
}
}
// In the profiling output a counter for each edge is reserved, but only few
// are used. This is done to be able to read back in the profile without
// calulating the maximum spanning tree again, instead each edge counter that
// is not used is initialised with -1 to signal that this edge counter has to
// be calculated from other edge counters on reading the profile info back
// in.
const Type *Int32 = Type::getInt32Ty(M.getContext());
const ArrayType *ATy = ArrayType::get(Int32, NumEdges);
GlobalVariable *Counters =
@ -112,13 +127,23 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
if (F->isDeclaration()) continue;
DEBUG(errs()<<"Working on "<<F->getNameStr()<<"\n");
PI = &getAnalysisID<ProfileInfo>(ProfileEstimatorPassID,*F);
MaximumSpanningTree MST = MaximumSpanningTree(&(*F),PI,true);
// Calculate a Maximum Spanning Tree with the edge weights determined by
// ProfileEstimator. ProfileEstimator also assign weights to the virtual
// edges (0,entry) and (BB,0) (for blocks with no successors) and this
// edges also participate in the maximum spanning tree calculation.
// The third parameter of MaximumSpanningTree() has the effect that not the
// actual MST is returned but the edges _not_ in the MST.
PI = &getAnalysisID<ProfileInfo>(ProfileEstimatorPassID, *F);
MaximumSpanningTree MST = MaximumSpanningTree(&(*F), PI, true);
// Check if (0,entry) not in the MST. If not, instrument edge
// (IncrementCounterInBlock()) and set the counter initially to zero, if
// the edge is in the MST the counter is initialised to -1.
// Create counter for (0,entry) edge.
BasicBlock *entry = &(F->getEntryBlock());
ProfileInfo::Edge edge = ProfileInfo::getEdge(0,entry);
if (std::binary_search(MST.begin(),MST.end(),edge)) {
if (std::binary_search(MST.begin(), MST.end(), edge)) {
printEdgeCounter(edge,entry,i);
IncrementCounterInBlock(entry, i, Counters); NumEdgesInserted++;
Initializer[i++] = (zeroc);
@ -127,15 +152,17 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
}
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
if (!BlocksToInstrument.count(BB)) continue; // Don't count new blocks
// Do not count blocks that where introduced by spliting critical edges.
if (!BlocksToInstrument.count(BB)) continue;
// Okay, we have to add a counter of each outgoing edge not in MST. If
// the outgoing edge is not critical don't split it, just insert the
// counter in the source or destination of the edge.
// counter in the source or destination of the edge. Also, if the block
// has no successors, the virtual edge (BB,0) is processed.
TerminatorInst *TI = BB->getTerminator();
if (TI->getNumSuccessors() == 0) {
// Create counter for (BB,0), edge.
ProfileInfo::Edge edge = ProfileInfo::getEdge(BB,0);
if (std::binary_search(MST.begin(),MST.end(),edge)) {
if (std::binary_search(MST.begin(), MST.end(), edge)) {
printEdgeCounter(edge,BB,i);
IncrementCounterInBlock(BB, i, Counters); NumEdgesInserted++;
Initializer[i++] = (zeroc);
@ -146,14 +173,14 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) {
BasicBlock *Succ = TI->getSuccessor(s);
ProfileInfo::Edge edge = ProfileInfo::getEdge(BB,Succ);
if (std::binary_search(MST.begin(),MST.end(),edge)) {
if (std::binary_search(MST.begin(), MST.end(), edge)) {
// If the edge is critical, split it.
SplitCriticalEdge(TI,s,this);
Succ = TI->getSuccessor(s);
// Okay, we are guaranteed that the edge is no longer critical. If we
// only have a single successor, insert the counter in this block,
// Okay, we are guaranteed that the edge is no longer critical. If
// we only have a single successor, insert the counter in this block,
// otherwise insert it in the successor block.
if (TI->getNumSuccessors() == 1) {
// Insert counter at the start of the block
@ -172,10 +199,11 @@ bool OptimalEdgeProfiler::runOnModule(Module &M) {
}
}
// check if indeed all counters have been used
// Check if the number of edges counted at first was the number of edges we
// considered for instrumentation.
assert(i==NumEdges && "the number of edges in counting array is wrong");
// assign initialiser to array
// Assing the now completely defined initialiser to the array.
Constant *init = ConstantArray::get(ATy, Initializer);
Counters->setInitializer(init);