313 lines
9.7 KiB
C++
313 lines
9.7 KiB
C++
//===- SafeStackColoring.cpp - SafeStack frame coloring -------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//===----------------------------------------------------------------------===//
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#include "SafeStackColoring.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/User.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.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 <cassert>
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#include <tuple>
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#include <utility>
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using namespace llvm;
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using namespace llvm::safestack;
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#define DEBUG_TYPE "safestackcoloring"
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// Disabled by default due to PR32143.
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static cl::opt<bool> ClColoring("safe-stack-coloring",
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cl::desc("enable safe stack coloring"),
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cl::Hidden, cl::init(false));
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const StackColoring::LiveRange &StackColoring::getLiveRange(AllocaInst *AI) {
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const auto IT = AllocaNumbering.find(AI);
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assert(IT != AllocaNumbering.end());
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return LiveRanges[IT->second];
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}
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bool StackColoring::readMarker(Instruction *I, bool *IsStart) {
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auto *II = dyn_cast<IntrinsicInst>(I);
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if (!II || (II->getIntrinsicID() != Intrinsic::lifetime_start &&
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II->getIntrinsicID() != Intrinsic::lifetime_end))
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return false;
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*IsStart = II->getIntrinsicID() == Intrinsic::lifetime_start;
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return true;
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}
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void StackColoring::removeAllMarkers() {
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for (auto *I : Markers) {
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auto *Op = dyn_cast<Instruction>(I->getOperand(1));
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I->eraseFromParent();
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// Remove the operand bitcast, too, if it has no more uses left.
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if (Op && Op->use_empty())
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Op->eraseFromParent();
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}
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}
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void StackColoring::collectMarkers() {
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InterestingAllocas.resize(NumAllocas);
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DenseMap<BasicBlock *, SmallDenseMap<Instruction *, Marker>> BBMarkerSet;
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// Compute the set of start/end markers per basic block.
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for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
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AllocaInst *AI = Allocas[AllocaNo];
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SmallVector<Instruction *, 8> WorkList;
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WorkList.push_back(AI);
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while (!WorkList.empty()) {
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Instruction *I = WorkList.pop_back_val();
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for (User *U : I->users()) {
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if (auto *BI = dyn_cast<BitCastInst>(U)) {
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WorkList.push_back(BI);
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continue;
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}
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auto *UI = dyn_cast<Instruction>(U);
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if (!UI)
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continue;
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bool IsStart;
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if (!readMarker(UI, &IsStart))
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continue;
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if (IsStart)
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InterestingAllocas.set(AllocaNo);
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BBMarkerSet[UI->getParent()][UI] = {AllocaNo, IsStart};
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Markers.push_back(UI);
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}
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}
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}
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// Compute instruction numbering. Only the following instructions are
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// considered:
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// * Basic block entries
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// * Lifetime markers
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// For each basic block, compute
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// * the list of markers in the instruction order
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// * the sets of allocas whose lifetime starts or ends in this BB
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LLVM_DEBUG(dbgs() << "Instructions:\n");
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unsigned InstNo = 0;
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for (BasicBlock *BB : depth_first(&F)) {
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LLVM_DEBUG(dbgs() << " " << InstNo << ": BB " << BB->getName() << "\n");
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unsigned BBStart = InstNo++;
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BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
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BlockInfo.Begin.resize(NumAllocas);
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BlockInfo.End.resize(NumAllocas);
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BlockInfo.LiveIn.resize(NumAllocas);
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BlockInfo.LiveOut.resize(NumAllocas);
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auto &BlockMarkerSet = BBMarkerSet[BB];
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if (BlockMarkerSet.empty()) {
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unsigned BBEnd = InstNo;
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BlockInstRange[BB] = std::make_pair(BBStart, BBEnd);
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continue;
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}
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auto ProcessMarker = [&](Instruction *I, const Marker &M) {
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LLVM_DEBUG(dbgs() << " " << InstNo << ": "
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<< (M.IsStart ? "start " : "end ") << M.AllocaNo
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<< ", " << *I << "\n");
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BBMarkers[BB].push_back({InstNo, M});
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InstructionNumbering[I] = InstNo++;
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if (M.IsStart) {
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if (BlockInfo.End.test(M.AllocaNo))
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BlockInfo.End.reset(M.AllocaNo);
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BlockInfo.Begin.set(M.AllocaNo);
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} else {
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if (BlockInfo.Begin.test(M.AllocaNo))
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BlockInfo.Begin.reset(M.AllocaNo);
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BlockInfo.End.set(M.AllocaNo);
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}
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};
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if (BlockMarkerSet.size() == 1) {
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ProcessMarker(BlockMarkerSet.begin()->getFirst(),
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BlockMarkerSet.begin()->getSecond());
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} else {
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// Scan the BB to determine the marker order.
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for (Instruction &I : *BB) {
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auto It = BlockMarkerSet.find(&I);
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if (It == BlockMarkerSet.end())
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continue;
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ProcessMarker(&I, It->getSecond());
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}
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}
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unsigned BBEnd = InstNo;
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BlockInstRange[BB] = std::make_pair(BBStart, BBEnd);
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}
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NumInst = InstNo;
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}
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void StackColoring::calculateLocalLiveness() {
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bool changed = true;
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while (changed) {
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changed = false;
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for (BasicBlock *BB : depth_first(&F)) {
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BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
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// Compute LiveIn by unioning together the LiveOut sets of all preds.
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BitVector LocalLiveIn;
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for (auto *PredBB : predecessors(BB)) {
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LivenessMap::const_iterator I = BlockLiveness.find(PredBB);
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// If a predecessor is unreachable, ignore it.
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if (I == BlockLiveness.end())
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continue;
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LocalLiveIn |= I->second.LiveOut;
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}
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// Compute LiveOut by subtracting out lifetimes that end in this
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// block, then adding in lifetimes that begin in this block. If
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// we have both BEGIN and END markers in the same basic block
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// then we know that the BEGIN marker comes after the END,
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// because we already handle the case where the BEGIN comes
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// before the END when collecting the markers (and building the
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// BEGIN/END vectors).
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BitVector LocalLiveOut = LocalLiveIn;
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LocalLiveOut.reset(BlockInfo.End);
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LocalLiveOut |= BlockInfo.Begin;
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// Update block LiveIn set, noting whether it has changed.
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if (LocalLiveIn.test(BlockInfo.LiveIn)) {
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changed = true;
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BlockInfo.LiveIn |= LocalLiveIn;
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}
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// Update block LiveOut set, noting whether it has changed.
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if (LocalLiveOut.test(BlockInfo.LiveOut)) {
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changed = true;
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BlockInfo.LiveOut |= LocalLiveOut;
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}
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}
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} // while changed.
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}
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void StackColoring::calculateLiveIntervals() {
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for (auto IT : BlockLiveness) {
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BasicBlock *BB = IT.getFirst();
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BlockLifetimeInfo &BlockInfo = IT.getSecond();
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unsigned BBStart, BBEnd;
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std::tie(BBStart, BBEnd) = BlockInstRange[BB];
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BitVector Started, Ended;
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Started.resize(NumAllocas);
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Ended.resize(NumAllocas);
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SmallVector<unsigned, 8> Start;
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Start.resize(NumAllocas);
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// LiveIn ranges start at the first instruction.
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for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
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if (BlockInfo.LiveIn.test(AllocaNo)) {
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Started.set(AllocaNo);
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Start[AllocaNo] = BBStart;
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}
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}
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for (auto &It : BBMarkers[BB]) {
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unsigned InstNo = It.first;
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bool IsStart = It.second.IsStart;
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unsigned AllocaNo = It.second.AllocaNo;
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if (IsStart) {
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assert(!Started.test(AllocaNo) || Start[AllocaNo] == BBStart);
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if (!Started.test(AllocaNo)) {
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Started.set(AllocaNo);
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Ended.reset(AllocaNo);
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Start[AllocaNo] = InstNo;
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}
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} else {
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assert(!Ended.test(AllocaNo));
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if (Started.test(AllocaNo)) {
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LiveRanges[AllocaNo].AddRange(Start[AllocaNo], InstNo);
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Started.reset(AllocaNo);
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}
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Ended.set(AllocaNo);
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}
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}
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for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
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if (Started.test(AllocaNo))
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LiveRanges[AllocaNo].AddRange(Start[AllocaNo], BBEnd);
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}
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void StackColoring::dumpAllocas() {
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dbgs() << "Allocas:\n";
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for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
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dbgs() << " " << AllocaNo << ": " << *Allocas[AllocaNo] << "\n";
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}
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LLVM_DUMP_METHOD void StackColoring::dumpBlockLiveness() {
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dbgs() << "Block liveness:\n";
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for (auto IT : BlockLiveness) {
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BasicBlock *BB = IT.getFirst();
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BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
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auto BlockRange = BlockInstRange[BB];
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dbgs() << " BB [" << BlockRange.first << ", " << BlockRange.second
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<< "): begin " << BlockInfo.Begin << ", end " << BlockInfo.End
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<< ", livein " << BlockInfo.LiveIn << ", liveout "
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<< BlockInfo.LiveOut << "\n";
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}
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}
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LLVM_DUMP_METHOD void StackColoring::dumpLiveRanges() {
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dbgs() << "Alloca liveness:\n";
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for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
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LiveRange &Range = LiveRanges[AllocaNo];
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dbgs() << " " << AllocaNo << ": " << Range << "\n";
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}
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}
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#endif
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void StackColoring::run() {
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LLVM_DEBUG(dumpAllocas());
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for (unsigned I = 0; I < NumAllocas; ++I)
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AllocaNumbering[Allocas[I]] = I;
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LiveRanges.resize(NumAllocas);
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collectMarkers();
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if (!ClColoring) {
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for (auto &R : LiveRanges) {
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R.SetMaximum(1);
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R.AddRange(0, 1);
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}
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return;
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}
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for (auto &R : LiveRanges)
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R.SetMaximum(NumInst);
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for (unsigned I = 0; I < NumAllocas; ++I)
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if (!InterestingAllocas.test(I))
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LiveRanges[I] = getFullLiveRange();
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calculateLocalLiveness();
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LLVM_DEBUG(dumpBlockLiveness());
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calculateLiveIntervals();
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LLVM_DEBUG(dumpLiveRanges());
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}
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