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//===-- SlotIndexes.cpp - Slot Indexes Pass ------------------------------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "slotindexes"
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#include "llvm/CodeGen/SlotIndexes.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/ManagedStatic.h"
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#include "llvm/Target/TargetInstrInfo.h"
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// Yep - these are thread safe. See the header for details.
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class EmptyIndexListEntry : public IndexListEntry {
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EmptyIndexListEntry() : IndexListEntry(EMPTY_KEY) {}
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class TombstoneIndexListEntry : public IndexListEntry {
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TombstoneIndexListEntry() : IndexListEntry(TOMBSTONE_KEY) {}
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// The following statics are thread safe. They're read only, and you
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// can't step from them to any other list entries.
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ManagedStatic<EmptyIndexListEntry> IndexListEntryEmptyKey;
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ManagedStatic<TombstoneIndexListEntry> IndexListEntryTombstoneKey;
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char SlotIndexes::ID = 0;
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static RegisterPass<SlotIndexes> X("slotindexes", "Slot index numbering");
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IndexListEntry* IndexListEntry::getEmptyKeyEntry() {
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return &*IndexListEntryEmptyKey;
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IndexListEntry* IndexListEntry::getTombstoneKeyEntry() {
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return &*IndexListEntryTombstoneKey;
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void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
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MachineFunctionPass::getAnalysisUsage(au);
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void SlotIndexes::releaseMemory() {
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terminatorGaps.clear();
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bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
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// Compute numbering as follows:
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// Grab an iterator to the start of the index list.
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// Iterate over all MBBs, and within each MBB all MIs, keeping the MI
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// iterator in lock-step (though skipping it over indexes which have
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// null pointers in the instruction field).
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// At each iteration assert that the instruction pointed to in the index
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// is the same one pointed to by the MI iterator. This
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// FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
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// only need to be set up once after the first numbering is computed.
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// Check that the list contains only the sentinal.
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assert(indexListHead->getNext() == 0 &&
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"Index list non-empty at initial numbering?");
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assert(idx2MBBMap.empty() &&
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"Index -> MBB mapping non-empty at initial numbering?");
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assert(mbb2IdxMap.empty() &&
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"MBB -> Index mapping non-empty at initial numbering?");
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assert(mi2iMap.empty() &&
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"MachineInstr -> Index mapping non-empty at initial numbering?");
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push_back(createEntry(0, index));
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// Iterate over the function.
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for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
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mbbItr != mbbEnd; ++mbbItr) {
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MachineBasicBlock *mbb = &*mbbItr;
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// Insert an index for the MBB start.
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SlotIndex blockStartIndex(back(), SlotIndex::LOAD);
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index += SlotIndex::NUM;
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for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
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miItr != miEnd; ++miItr) {
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MachineInstr *mi = miItr;
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if (mi->isDebugValue())
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if (miItr == mbb->getFirstTerminator()) {
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push_back(createEntry(0, index));
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terminatorGaps.insert(
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std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
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index += SlotIndex::NUM;
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// Insert a store index for the instr.
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push_back(createEntry(mi, index));
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// Save this base index in the maps.
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std::make_pair(mi, SlotIndex(back(), SlotIndex::LOAD)));
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unsigned Slots = mi->getDesc().getNumDefs();
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index += (Slots + 1) * SlotIndex::NUM;
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if (mbb->getFirstTerminator() == mbb->end()) {
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push_back(createEntry(0, index));
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terminatorGaps.insert(
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std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
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index += SlotIndex::NUM;
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// One blank instruction at the end.
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push_back(createEntry(0, index));
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SlotIndex blockEndIndex(back(), SlotIndex::LOAD);
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std::make_pair(mbb, std::make_pair(blockStartIndex, blockEndIndex)));
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idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
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// Sort the Idx2MBBMap
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std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
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void SlotIndexes::renumberIndexes() {
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// Renumber updates the index of every element of the index list.
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// If all instrs in the function have been allocated an index (which has been
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// placed in the index list in the order of instruction iteration) then the
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// resulting numbering will match what would have been generated by the
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// pass during the initial numbering of the function if the new instructions
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for (IndexListEntry *curEntry = front(); curEntry != getTail();
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curEntry = curEntry->getNext()) {
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curEntry->setIndex(index);
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if (curEntry->getInstr() == 0) {
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// MBB start entry or terminator gap. Just step index by 1.
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index += SlotIndex::NUM;
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unsigned Slots = curEntry->getInstr()->getDesc().getNumDefs();
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index += (Slots + 1) * SlotIndex::NUM;
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void SlotIndexes::dump() const {
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for (const IndexListEntry *itr = front(); itr != getTail();
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itr = itr->getNext()) {
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dbgs() << itr->getIndex() << " ";
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if (itr->getInstr() != 0) {
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dbgs() << *itr->getInstr();
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for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
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itr != mbb2IdxMap.end(); ++itr) {
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dbgs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
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<< itr->second.first << ", " << itr->second.second << "]\n";
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// Print a SlotIndex to a raw_ostream.
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void SlotIndex::print(raw_ostream &os) const {
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// Dump a SlotIndex to stderr.
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void SlotIndex::dump() const {