//
//===----------------------------------------------------------------------===//
//
-// This pass eliminates machine instruction PHI nodes by inserting copy
-// instructions, using an intelligent copy-folding technique based on
-// dominator information. This is technique is derived from:
-//
-// Budimlic, et al. Fast copy coalescing and live-range identification.
-// In Proceedings of the ACM SIGPLAN 2002 Conference on Programming Language
-// Design and Implementation (Berlin, Germany, June 17 - 19, 2002).
-// PLDI '02. ACM, New York, NY, 25-32.
-// DOI= http://doi.acm.org/10.1145/512529.512534
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/RegisterCoalescer.h"
-#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
namespace {
- struct StrongPHIElimination : public MachineFunctionPass {
- static char ID; // Pass identification, replacement for typeid
- StrongPHIElimination() : MachineFunctionPass(ID) {
- initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
- }
-
- // Waiting stores, for each MBB, the set of copies that need to
- // be inserted into that MBB
- DenseMap<MachineBasicBlock*,
- std::multimap<unsigned, unsigned> > Waiting;
-
- // Stacks holds the renaming stack for each register
- std::map<unsigned, std::vector<unsigned> > Stacks;
-
- // Registers in UsedByAnother are PHI nodes that are themselves
- // used as operands to another PHI node
- std::set<unsigned> UsedByAnother;
-
- // RenameSets are the is a map from a PHI-defined register
- // to the input registers to be coalesced along with the
- // predecessor block for those input registers.
- std::map<unsigned, std::map<unsigned, MachineBasicBlock*> > RenameSets;
-
- // PhiValueNumber holds the ID numbers of the VNs for each phi that we're
- // eliminating, indexed by the register defined by that phi.
- std::map<unsigned, unsigned> PhiValueNumber;
-
- // Store the DFS-in number of each block
- DenseMap<MachineBasicBlock*, unsigned> preorder;
-
- // Store the DFS-out number of each block
- DenseMap<MachineBasicBlock*, unsigned> maxpreorder;
-
- bool runOnMachineFunction(MachineFunction &Fn);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
- AU.addRequired<MachineDominatorTree>();
- AU.addRequired<SlotIndexes>();
- AU.addPreserved<SlotIndexes>();
- AU.addRequired<LiveIntervals>();
-
- // TODO: Actually make this true.
- AU.addPreserved<LiveIntervals>();
- AU.addPreserved<RegisterCoalescer>();
- MachineFunctionPass::getAnalysisUsage(AU);
- }
-
- virtual void releaseMemory() {
- preorder.clear();
- maxpreorder.clear();
-
- Waiting.clear();
- Stacks.clear();
- UsedByAnother.clear();
- RenameSets.clear();
- }
+class StrongPHIElimination : public MachineFunctionPass {
+public:
+ static char ID; // Pass identification, replacement for typeid
+ StrongPHIElimination() : MachineFunctionPass(ID) {
+ initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
+ }
- private:
-
- /// DomForestNode - Represents a node in the "dominator forest". This is
- /// a forest in which the nodes represent registers and the edges
- /// represent a dominance relation in the block defining those registers.
- struct DomForestNode {
- private:
- // Store references to our children
- std::vector<DomForestNode*> children;
- // The register we represent
- unsigned reg;
-
- // Add another node as our child
- void addChild(DomForestNode* DFN) { children.push_back(DFN); }
-
- public:
- typedef std::vector<DomForestNode*>::iterator iterator;
-
- // Create a DomForestNode by providing the register it represents, and
- // the node to be its parent. The virtual root node has register 0
- // and a null parent.
- DomForestNode(unsigned r, DomForestNode* parent) : reg(r) {
- if (parent)
- parent->addChild(this);
- }
-
- ~DomForestNode() {
- for (iterator I = begin(), E = end(); I != E; ++I)
- delete *I;
- }
-
- /// getReg - Return the regiser that this node represents
- inline unsigned getReg() { return reg; }
-
- // Provide iterator access to our children
- inline DomForestNode::iterator begin() { return children.begin(); }
- inline DomForestNode::iterator end() { return children.end(); }
- };
-
- void computeDFS(MachineFunction& MF);
- void processBlock(MachineBasicBlock* MBB);
+private:
+ bool runOnMachineFunction(MachineFunction &Fn) {
+ llvm_unreachable("Strong phi elimination is not implemented");
+ }
- std::vector<DomForestNode*> computeDomForest(
- std::map<unsigned, MachineBasicBlock*>& instrs,
- MachineRegisterInfo& MRI);
- void processPHIUnion(MachineInstr* Inst,
- std::map<unsigned, MachineBasicBlock*>& PHIUnion,
- std::vector<StrongPHIElimination::DomForestNode*>& DF,
- std::vector<std::pair<unsigned, unsigned> >& locals);
- void ScheduleCopies(MachineBasicBlock* MBB, std::set<unsigned>& pushed);
- void InsertCopies(MachineDomTreeNode* MBB,
- SmallPtrSet<MachineBasicBlock*, 16>& v);
- bool mergeLiveIntervals(unsigned primary, unsigned secondary);
- };
-}
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ AU.addRequired<MachineDominatorTree>();
+ AU.addRequired<SlotIndexes>();
+ AU.addPreserved<SlotIndexes>();
+ AU.addRequired<LiveIntervals>();
+ AU.addPreserved<LiveIntervals>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+};
+} // namespace
char StrongPHIElimination::ID = 0;
INITIALIZE_PASS_BEGIN(StrongPHIElimination, "strong-phi-node-elimination",
char &llvm::StrongPHIEliminationID = StrongPHIElimination::ID;
-/// computeDFS - Computes the DFS-in and DFS-out numbers of the dominator tree
-/// of the given MachineFunction. These numbers are then used in other parts
-/// of the PHI elimination process.
-void StrongPHIElimination::computeDFS(MachineFunction& MF) {
- SmallPtrSet<MachineDomTreeNode*, 8> frontier;
- SmallPtrSet<MachineDomTreeNode*, 8> visited;
-
- unsigned time = 0;
-
- MachineDominatorTree& DT = getAnalysis<MachineDominatorTree>();
-
- MachineDomTreeNode* node = DT.getRootNode();
-
- std::vector<MachineDomTreeNode*> worklist;
- worklist.push_back(node);
-
- while (!worklist.empty()) {
- MachineDomTreeNode* currNode = worklist.back();
-
- if (!frontier.count(currNode)) {
- frontier.insert(currNode);
- ++time;
- preorder.insert(std::make_pair(currNode->getBlock(), time));
- }
-
- bool inserted = false;
- for (MachineDomTreeNode::iterator I = currNode->begin(), E = currNode->end();
- I != E; ++I)
- if (!frontier.count(*I) && !visited.count(*I)) {
- worklist.push_back(*I);
- inserted = true;
- break;
- }
-
- if (!inserted) {
- frontier.erase(currNode);
- visited.insert(currNode);
- maxpreorder.insert(std::make_pair(currNode->getBlock(), time));
-
- worklist.pop_back();
- }
- }
-}
-
-namespace {
-
-/// PreorderSorter - a helper class that is used to sort registers
-/// according to the preorder number of their defining blocks
-class PreorderSorter {
-private:
- DenseMap<MachineBasicBlock*, unsigned>& preorder;
- MachineRegisterInfo& MRI;
-
-public:
- PreorderSorter(DenseMap<MachineBasicBlock*, unsigned>& p,
- MachineRegisterInfo& M) : preorder(p), MRI(M) { }
-
- bool operator()(unsigned A, unsigned B) {
- if (A == B)
- return false;
-
- MachineBasicBlock* ABlock = MRI.getVRegDef(A)->getParent();
- MachineBasicBlock* BBlock = MRI.getVRegDef(B)->getParent();
-
- if (preorder[ABlock] < preorder[BBlock])
- return true;
- else if (preorder[ABlock] > preorder[BBlock])
- return false;
-
- return false;
- }
-};
-
-}
-
-/// computeDomForest - compute the subforest of the DomTree corresponding
-/// to the defining blocks of the registers in question
-std::vector<StrongPHIElimination::DomForestNode*>
-StrongPHIElimination::computeDomForest(
- std::map<unsigned, MachineBasicBlock*>& regs,
- MachineRegisterInfo& MRI) {
- // Begin by creating a virtual root node, since the actual results
- // may well be a forest. Assume this node has maximum DFS-out number.
- DomForestNode* VirtualRoot = new DomForestNode(0, 0);
- maxpreorder.insert(std::make_pair((MachineBasicBlock*)0, ~0UL));
-
- // Populate a worklist with the registers
- std::vector<unsigned> worklist;
- worklist.reserve(regs.size());
- for (std::map<unsigned, MachineBasicBlock*>::iterator I = regs.begin(),
- E = regs.end(); I != E; ++I)
- worklist.push_back(I->first);
-
- // Sort the registers by the DFS-in number of their defining block
- PreorderSorter PS(preorder, MRI);
- std::sort(worklist.begin(), worklist.end(), PS);
-
- // Create a "current parent" stack, and put the virtual root on top of it
- DomForestNode* CurrentParent = VirtualRoot;
- std::vector<DomForestNode*> stack;
- stack.push_back(VirtualRoot);
-
- // Iterate over all the registers in the previously computed order
- for (std::vector<unsigned>::iterator I = worklist.begin(), E = worklist.end();
- I != E; ++I) {
- unsigned pre = preorder[MRI.getVRegDef(*I)->getParent()];
- MachineBasicBlock* parentBlock = CurrentParent->getReg() ?
- MRI.getVRegDef(CurrentParent->getReg())->getParent() :
- 0;
-
- // If the DFS-in number of the register is greater than the DFS-out number
- // of the current parent, repeatedly pop the parent stack until it isn't.
- while (pre > maxpreorder[parentBlock]) {
- stack.pop_back();
- CurrentParent = stack.back();
-
- parentBlock = CurrentParent->getReg() ?
- MRI.getVRegDef(CurrentParent->getReg())->getParent() :
- 0;
- }
-
- // Now that we've found the appropriate parent, create a DomForestNode for
- // this register and attach it to the forest
- DomForestNode* child = new DomForestNode(*I, CurrentParent);
-
- // Push this new node on the "current parent" stack
- stack.push_back(child);
- CurrentParent = child;
- }
-
- // Return a vector containing the children of the virtual root node
- std::vector<DomForestNode*> ret;
- ret.insert(ret.end(), VirtualRoot->begin(), VirtualRoot->end());
- return ret;
-}
-
-/// isLiveIn - helper method that determines, from a regno, if a register
-/// is live into a block
-static bool isLiveIn(unsigned r, MachineBasicBlock* MBB,
- LiveIntervals& LI) {
- LiveInterval& I = LI.getOrCreateInterval(r);
- SlotIndex idx = LI.getMBBStartIdx(MBB);
- return I.liveAt(idx);
-}
-
-/// isLiveOut - help method that determines, from a regno, if a register is
-/// live out of a block.
-static bool isLiveOut(unsigned r, MachineBasicBlock* MBB,
- LiveIntervals& LI) {
- for (MachineBasicBlock::succ_iterator PI = MBB->succ_begin(),
- E = MBB->succ_end(); PI != E; ++PI)
- if (isLiveIn(r, *PI, LI))
- return true;
-
- return false;
-}
-
-/// interferes - checks for local interferences by scanning a block. The only
-/// trick parameter is 'mode' which tells it the relationship of the two
-/// registers. 0 - defined in the same block, 1 - first properly dominates
-/// second, 2 - second properly dominates first
-static bool interferes(unsigned a, unsigned b, MachineBasicBlock* scan,
- LiveIntervals& LV, unsigned mode) {
- MachineInstr* def = 0;
- MachineInstr* kill = 0;
-
- // The code is still in SSA form at this point, so there is only one
- // definition per VReg. Thus we can safely use MRI->getVRegDef().
- const MachineRegisterInfo* MRI = &scan->getParent()->getRegInfo();
-
- bool interference = false;
-
- // Wallk the block, checking for interferences
- for (MachineBasicBlock::iterator MBI = scan->begin(), MBE = scan->end();
- MBI != MBE; ++MBI) {
- MachineInstr* curr = MBI;
-
- // Same defining block...
- if (mode == 0) {
- if (curr == MRI->getVRegDef(a)) {
- // If we find our first definition, save it
- if (!def) {
- def = curr;
- // If there's already an unkilled definition, then
- // this is an interference
- } else if (!kill) {
- interference = true;
- break;
- // If there's a definition followed by a KillInst, then
- // they can't interfere
- } else {
- interference = false;
- break;
- }
- // Symmetric with the above
- } else if (curr == MRI->getVRegDef(b)) {
- if (!def) {
- def = curr;
- } else if (!kill) {
- interference = true;
- break;
- } else {
- interference = false;
- break;
- }
- // Store KillInsts if they match up with the definition
- } else if (curr->killsRegister(a)) {
- if (def == MRI->getVRegDef(a)) {
- kill = curr;
- } else if (curr->killsRegister(b)) {
- if (def == MRI->getVRegDef(b)) {
- kill = curr;
- }
- }
- }
- // First properly dominates second...
- } else if (mode == 1) {
- if (curr == MRI->getVRegDef(b)) {
- // Definition of second without kill of first is an interference
- if (!kill) {
- interference = true;
- break;
- // Definition after a kill is a non-interference
- } else {
- interference = false;
- break;
- }
- // Save KillInsts of First
- } else if (curr->killsRegister(a)) {
- kill = curr;
- }
- // Symmetric with the above
- } else if (mode == 2) {
- if (curr == MRI->getVRegDef(a)) {
- if (!kill) {
- interference = true;
- break;
- } else {
- interference = false;
- break;
- }
- } else if (curr->killsRegister(b)) {
- kill = curr;
- }
- }
- }
-
- return interference;
-}
-
-/// processBlock - Determine how to break up PHIs in the current block. Each
-/// PHI is broken up by some combination of renaming its operands and inserting
-/// copies. This method is responsible for determining which operands receive
-/// which treatment.
-void StrongPHIElimination::processBlock(MachineBasicBlock* MBB) {
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
- MachineRegisterInfo& MRI = MBB->getParent()->getRegInfo();
-
- // Holds names that have been added to a set in any PHI within this block
- // before the current one.
- std::set<unsigned> ProcessedNames;
-
- // Iterate over all the PHI nodes in this block
- MachineBasicBlock::iterator P = MBB->begin();
- while (P != MBB->end() && P->isPHI()) {
- unsigned DestReg = P->getOperand(0).getReg();
-
- // Don't both doing PHI elimination for dead PHI's.
- if (P->registerDefIsDead(DestReg)) {
- ++P;
- continue;
- }
-
- LiveInterval& PI = LI.getOrCreateInterval(DestReg);
- SlotIndex pIdx = LI.getInstructionIndex(P).getDefIndex();
- VNInfo* PVN = PI.getLiveRangeContaining(pIdx)->valno;
- PhiValueNumber.insert(std::make_pair(DestReg, PVN->id));
-
- // PHIUnion is the set of incoming registers to the PHI node that
- // are going to be renames rather than having copies inserted. This set
- // is refinded over the course of this function. UnionedBlocks is the set
- // of corresponding MBBs.
- std::map<unsigned, MachineBasicBlock*> PHIUnion;
- SmallPtrSet<MachineBasicBlock*, 8> UnionedBlocks;
-
- // Iterate over the operands of the PHI node
- for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
- unsigned SrcReg = P->getOperand(i-1).getReg();
-
- // Don't need to try to coalesce a register with itself.
- if (SrcReg == DestReg) {
- ProcessedNames.insert(SrcReg);
- continue;
- }
-
- // We don't need to insert copies for implicit_defs.
- MachineInstr* DefMI = MRI.getVRegDef(SrcReg);
- if (DefMI->isImplicitDef())
- ProcessedNames.insert(SrcReg);
-
- // Check for trivial interferences via liveness information, allowing us
- // to avoid extra work later. Any registers that interfere cannot both
- // be in the renaming set, so choose one and add copies for it instead.
- // The conditions are:
- // 1) if the operand is live into the PHI node's block OR
- // 2) if the PHI node is live out of the operand's defining block OR
- // 3) if the operand is itself a PHI node and the original PHI is
- // live into the operand's defining block OR
- // 4) if the operand is already being renamed for another PHI node
- // in this block OR
- // 5) if any two operands are defined in the same block, insert copies
- // for one of them
- if (isLiveIn(SrcReg, P->getParent(), LI) ||
- isLiveOut(P->getOperand(0).getReg(),
- MRI.getVRegDef(SrcReg)->getParent(), LI) ||
- ( MRI.getVRegDef(SrcReg)->isPHI() &&
- isLiveIn(P->getOperand(0).getReg(),
- MRI.getVRegDef(SrcReg)->getParent(), LI) ) ||
- ProcessedNames.count(SrcReg) ||
- UnionedBlocks.count(MRI.getVRegDef(SrcReg)->getParent())) {
-
- // Add a copy for the selected register
- MachineBasicBlock* From = P->getOperand(i).getMBB();
- Waiting[From].insert(std::make_pair(SrcReg, DestReg));
- UsedByAnother.insert(SrcReg);
- } else {
- // Otherwise, add it to the renaming set
- PHIUnion.insert(std::make_pair(SrcReg,P->getOperand(i).getMBB()));
- UnionedBlocks.insert(MRI.getVRegDef(SrcReg)->getParent());
- }
- }
-
- // Compute the dominator forest for the renaming set. This is a forest
- // where the nodes are the registers and the edges represent dominance
- // relations between the defining blocks of the registers
- std::vector<StrongPHIElimination::DomForestNode*> DF =
- computeDomForest(PHIUnion, MRI);
-
- // Walk DomForest to resolve interferences at an inter-block level. This
- // will remove registers from the renaming set (and insert copies for them)
- // if interferences are found.
- std::vector<std::pair<unsigned, unsigned> > localInterferences;
- processPHIUnion(P, PHIUnion, DF, localInterferences);
-
- // If one of the inputs is defined in the same block as the current PHI
- // then we need to check for a local interference between that input and
- // the PHI.
- for (std::map<unsigned, MachineBasicBlock*>::iterator I = PHIUnion.begin(),
- E = PHIUnion.end(); I != E; ++I)
- if (MRI.getVRegDef(I->first)->getParent() == P->getParent())
- localInterferences.push_back(std::make_pair(I->first,
- P->getOperand(0).getReg()));
-
- // The dominator forest walk may have returned some register pairs whose
- // interference cannot be determined from dominator analysis. We now
- // examine these pairs for local interferences.
- for (std::vector<std::pair<unsigned, unsigned> >::iterator I =
- localInterferences.begin(), E = localInterferences.end(); I != E; ++I) {
- std::pair<unsigned, unsigned> p = *I;
-
- MachineDominatorTree& MDT = getAnalysis<MachineDominatorTree>();
-
- // Determine the block we need to scan and the relationship between
- // the two registers
- MachineBasicBlock* scan = 0;
- unsigned mode = 0;
- if (MRI.getVRegDef(p.first)->getParent() ==
- MRI.getVRegDef(p.second)->getParent()) {
- scan = MRI.getVRegDef(p.first)->getParent();
- mode = 0; // Same block
- } else if (MDT.dominates(MRI.getVRegDef(p.first)->getParent(),
- MRI.getVRegDef(p.second)->getParent())) {
- scan = MRI.getVRegDef(p.second)->getParent();
- mode = 1; // First dominates second
- } else {
- scan = MRI.getVRegDef(p.first)->getParent();
- mode = 2; // Second dominates first
- }
-
- // If there's an interference, we need to insert copies
- if (interferes(p.first, p.second, scan, LI, mode)) {
- // Insert copies for First
- for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
- if (P->getOperand(i-1).getReg() == p.first) {
- unsigned SrcReg = p.first;
- MachineBasicBlock* From = P->getOperand(i).getMBB();
-
- Waiting[From].insert(std::make_pair(SrcReg,
- P->getOperand(0).getReg()));
- UsedByAnother.insert(SrcReg);
-
- PHIUnion.erase(SrcReg);
- }
- }
- }
- }
-
- // Add the renaming set for this PHI node to our overall renaming information
- for (std::map<unsigned, MachineBasicBlock*>::iterator QI = PHIUnion.begin(),
- QE = PHIUnion.end(); QI != QE; ++QI) {
- DEBUG(dbgs() << "Adding Renaming: " << QI->first << " -> "
- << P->getOperand(0).getReg() << "\n");
- }
-
- RenameSets.insert(std::make_pair(P->getOperand(0).getReg(), PHIUnion));
-
- // Remember which registers are already renamed, so that we don't try to
- // rename them for another PHI node in this block
- for (std::map<unsigned, MachineBasicBlock*>::iterator I = PHIUnion.begin(),
- E = PHIUnion.end(); I != E; ++I)
- ProcessedNames.insert(I->first);
-
- ++P;
- }
-}
-
-/// processPHIUnion - Take a set of candidate registers to be coalesced when
-/// decomposing the PHI instruction. Use the DominanceForest to remove the ones
-/// that are known to interfere, and flag others that need to be checked for
-/// local interferences.
-void StrongPHIElimination::processPHIUnion(MachineInstr* Inst,
- std::map<unsigned, MachineBasicBlock*>& PHIUnion,
- std::vector<StrongPHIElimination::DomForestNode*>& DF,
- std::vector<std::pair<unsigned, unsigned> >& locals) {
-
- std::vector<DomForestNode*> worklist(DF.begin(), DF.end());
- SmallPtrSet<DomForestNode*, 4> visited;
-
- // Code is still in SSA form, so we can use MRI::getVRegDef()
- MachineRegisterInfo& MRI = Inst->getParent()->getParent()->getRegInfo();
-
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
- unsigned DestReg = Inst->getOperand(0).getReg();
-
- // DF walk on the DomForest
- while (!worklist.empty()) {
- DomForestNode* DFNode = worklist.back();
-
- visited.insert(DFNode);
-
- bool inserted = false;
- for (DomForestNode::iterator CI = DFNode->begin(), CE = DFNode->end();
- CI != CE; ++CI) {
- DomForestNode* child = *CI;
-
- // If the current node is live-out of the defining block of one of its
- // children, insert a copy for it. NOTE: The paper actually calls for
- // a more elaborate heuristic for determining whether to insert copies
- // for the child or the parent. In the interest of simplicity, we're
- // just always choosing the parent.
- if (isLiveOut(DFNode->getReg(),
- MRI.getVRegDef(child->getReg())->getParent(), LI)) {
- // Insert copies for parent
- for (int i = Inst->getNumOperands() - 1; i >= 2; i-=2) {
- if (Inst->getOperand(i-1).getReg() == DFNode->getReg()) {
- unsigned SrcReg = DFNode->getReg();
- MachineBasicBlock* From = Inst->getOperand(i).getMBB();
-
- Waiting[From].insert(std::make_pair(SrcReg, DestReg));
- UsedByAnother.insert(SrcReg);
-
- PHIUnion.erase(SrcReg);
- }
- }
-
- // If a node is live-in to the defining block of one of its children, but
- // not live-out, then we need to scan that block for local interferences.
- } else if (isLiveIn(DFNode->getReg(),
- MRI.getVRegDef(child->getReg())->getParent(), LI) ||
- MRI.getVRegDef(DFNode->getReg())->getParent() ==
- MRI.getVRegDef(child->getReg())->getParent()) {
- // Add (p, c) to possible local interferences
- locals.push_back(std::make_pair(DFNode->getReg(), child->getReg()));
- }
-
- if (!visited.count(child)) {
- worklist.push_back(child);
- inserted = true;
- }
- }
-
- if (!inserted) worklist.pop_back();
- }
-}
-
-/// ScheduleCopies - Insert copies into predecessor blocks, scheduling
-/// them properly so as to avoid the 'lost copy' and the 'virtual swap'
-/// problems.
-///
-/// Based on "Practical Improvements to the Construction and Destruction
-/// of Static Single Assignment Form" by Briggs, et al.
-void StrongPHIElimination::ScheduleCopies(MachineBasicBlock* MBB,
- std::set<unsigned>& pushed) {
- // FIXME: This function needs to update LiveIntervals
- std::multimap<unsigned, unsigned>& copy_set= Waiting[MBB];
-
- std::multimap<unsigned, unsigned> worklist;
- std::map<unsigned, unsigned> map;
-
- // Setup worklist of initial copies
- for (std::multimap<unsigned, unsigned>::iterator I = copy_set.begin(),
- E = copy_set.end(); I != E; ) {
- map.insert(std::make_pair(I->first, I->first));
- map.insert(std::make_pair(I->second, I->second));
-
- if (!UsedByAnother.count(I->second)) {
- worklist.insert(*I);
-
- // Avoid iterator invalidation
- std::multimap<unsigned, unsigned>::iterator OI = I;
- ++I;
- copy_set.erase(OI);
- } else {
- ++I;
- }
- }
-
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
- MachineFunction* MF = MBB->getParent();
- MachineRegisterInfo& MRI = MF->getRegInfo();
- const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
-
- SmallVector<std::pair<unsigned, MachineInstr*>, 4> InsertedPHIDests;
-
- // Iterate over the worklist, inserting copies
- while (!worklist.empty() || !copy_set.empty()) {
- while (!worklist.empty()) {
- std::multimap<unsigned, unsigned>::iterator WI = worklist.begin();
- std::pair<unsigned, unsigned> curr = *WI;
- worklist.erase(WI);
-
- const TargetRegisterClass *RC = MF->getRegInfo().getRegClass(curr.first);
-
- if (isLiveOut(curr.second, MBB, LI)) {
- // Create a temporary
- unsigned t = MF->getRegInfo().createVirtualRegister(RC);
-
- // Insert copy from curr.second to a temporary at
- // the Phi defining curr.second
- MachineBasicBlock::iterator PI = MRI.getVRegDef(curr.second);
- BuildMI(*PI->getParent(), PI, DebugLoc(), TII->get(TargetOpcode::COPY),
- t).addReg(curr.second);
- DEBUG(dbgs() << "Inserted copy from " << curr.second << " to " << t
- << "\n");
-
- // Push temporary on Stacks
- Stacks[curr.second].push_back(t);
-
- // Insert curr.second in pushed
- pushed.insert(curr.second);
-
- // Create a live interval for this temporary
- InsertedPHIDests.push_back(std::make_pair(t, --PI));
- }
-
- // Insert copy from map[curr.first] to curr.second
- BuildMI(*MBB, MBB->getFirstTerminator(), DebugLoc(),
- TII->get(TargetOpcode::COPY), curr.second).addReg(map[curr.first]);
- map[curr.first] = curr.second;
- DEBUG(dbgs() << "Inserted copy from " << curr.first << " to "
- << curr.second << "\n");
-
- // Push this copy onto InsertedPHICopies so we can
- // update LiveIntervals with it.
- MachineBasicBlock::iterator MI = MBB->getFirstTerminator();
- InsertedPHIDests.push_back(std::make_pair(curr.second, --MI));
-
- // If curr.first is a destination in copy_set...
- for (std::multimap<unsigned, unsigned>::iterator I = copy_set.begin(),
- E = copy_set.end(); I != E; )
- if (curr.first == I->second) {
- std::pair<unsigned, unsigned> temp = *I;
- worklist.insert(temp);
-
- // Avoid iterator invalidation
- std::multimap<unsigned, unsigned>::iterator OI = I;
- ++I;
- copy_set.erase(OI);
-
- break;
- } else {
- ++I;
- }
- }
-
- if (!copy_set.empty()) {
- std::multimap<unsigned, unsigned>::iterator CI = copy_set.begin();
- std::pair<unsigned, unsigned> curr = *CI;
- worklist.insert(curr);
- copy_set.erase(CI);
-
- LiveInterval& I = LI.getInterval(curr.second);
- MachineBasicBlock::iterator term = MBB->getFirstTerminator();
- SlotIndex endIdx = SlotIndex();
- if (term != MBB->end())
- endIdx = LI.getInstructionIndex(term);
- else
- endIdx = LI.getMBBEndIdx(MBB);
-
- if (I.liveAt(endIdx)) {
- const TargetRegisterClass *RC =
- MF->getRegInfo().getRegClass(curr.first);
-
- // Insert a copy from dest to a new temporary t at the end of b
- unsigned t = MF->getRegInfo().createVirtualRegister(RC);
- BuildMI(*MBB, MBB->getFirstTerminator(), DebugLoc(),
- TII->get(TargetOpcode::COPY), t).addReg(curr.second);
- map[curr.second] = t;
-
- MachineBasicBlock::iterator TI = MBB->getFirstTerminator();
- InsertedPHIDests.push_back(std::make_pair(t, --TI));
- }
- }
- }
-
- // Renumber the instructions so that we can perform the index computations
- // needed to create new live intervals.
- LI.renumber();
-
- // For copies that we inserted at the ends of predecessors, we construct
- // live intervals. This is pretty easy, since we know that the destination
- // register cannot have be in live at that point previously. We just have
- // to make sure that, for registers that serve as inputs to more than one
- // PHI, we don't create multiple overlapping live intervals.
- std::set<unsigned> RegHandled;
- for (SmallVector<std::pair<unsigned, MachineInstr*>, 4>::iterator I =
- InsertedPHIDests.begin(), E = InsertedPHIDests.end(); I != E; ++I) {
- if (RegHandled.insert(I->first).second) {
- LiveInterval& Int = LI.getOrCreateInterval(I->first);
- SlotIndex instrIdx = LI.getInstructionIndex(I->second);
- if (Int.liveAt(instrIdx.getDefIndex()))
- Int.removeRange(instrIdx.getDefIndex(),
- LI.getMBBEndIdx(I->second->getParent()).getNextSlot(),
- true);
-
- LiveRange R = LI.addLiveRangeToEndOfBlock(I->first, I->second);
- R.valno->setCopy(I->second);
- R.valno->def = LI.getInstructionIndex(I->second).getDefIndex();
- }
- }
-}
-
-/// InsertCopies - insert copies into MBB and all of its successors
-void StrongPHIElimination::InsertCopies(MachineDomTreeNode* MDTN,
- SmallPtrSet<MachineBasicBlock*, 16>& visited) {
- MachineBasicBlock* MBB = MDTN->getBlock();
- visited.insert(MBB);
-
- std::set<unsigned> pushed;
-
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
- // Rewrite register uses from Stacks
- for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
- I != E; ++I) {
- if (I->isPHI())
- continue;
-
- for (unsigned i = 0; i < I->getNumOperands(); ++i)
- if (I->getOperand(i).isReg() &&
- Stacks[I->getOperand(i).getReg()].size()) {
- // Remove the live range for the old vreg.
- LiveInterval& OldInt = LI.getInterval(I->getOperand(i).getReg());
- LiveInterval::iterator OldLR =
- OldInt.FindLiveRangeContaining(LI.getInstructionIndex(I).getUseIndex());
- if (OldLR != OldInt.end())
- OldInt.removeRange(*OldLR, true);
-
- // Change the register
- I->getOperand(i).setReg(Stacks[I->getOperand(i).getReg()].back());
-
- // Add a live range for the new vreg
- LiveInterval& Int = LI.getInterval(I->getOperand(i).getReg());
- VNInfo* FirstVN = *Int.vni_begin();
- FirstVN->setHasPHIKill(false);
- LiveRange LR (LI.getMBBStartIdx(I->getParent()),
- LI.getInstructionIndex(I).getUseIndex().getNextSlot(),
- FirstVN);
-
- Int.addRange(LR);
- }
- }
-
- // Schedule the copies for this block
- ScheduleCopies(MBB, pushed);
-
- // Recur down the dominator tree.
- for (MachineDomTreeNode::iterator I = MDTN->begin(),
- E = MDTN->end(); I != E; ++I)
- if (!visited.count((*I)->getBlock()))
- InsertCopies(*I, visited);
-
- // As we exit this block, pop the names we pushed while processing it
- for (std::set<unsigned>::iterator I = pushed.begin(),
- E = pushed.end(); I != E; ++I)
- Stacks[*I].pop_back();
-}
-
-bool StrongPHIElimination::mergeLiveIntervals(unsigned primary,
- unsigned secondary) {
-
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
- LiveInterval& LHS = LI.getOrCreateInterval(primary);
- LiveInterval& RHS = LI.getOrCreateInterval(secondary);
-
- LI.renumber();
-
- DenseMap<VNInfo*, VNInfo*> VNMap;
- for (LiveInterval::iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
- LiveRange R = *I;
-
- SlotIndex Start = R.start;
- SlotIndex End = R.end;
- if (LHS.getLiveRangeContaining(Start))
- return false;
-
- if (LHS.getLiveRangeContaining(End))
- return false;
-
- LiveInterval::iterator RI = std::upper_bound(LHS.begin(), LHS.end(), R);
- if (RI != LHS.end() && RI->start < End)
- return false;
- }
-
- for (LiveInterval::iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
- LiveRange R = *I;
- VNInfo* OldVN = R.valno;
- VNInfo*& NewVN = VNMap[OldVN];
- if (!NewVN) {
- NewVN = LHS.createValueCopy(OldVN, LI.getVNInfoAllocator());
- }
-
- LiveRange LR (R.start, R.end, NewVN);
- LHS.addRange(LR);
- }
-
- LI.removeInterval(RHS.reg);
-
- return true;
-}
-
-bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
-
- // Compute DFS numbers of each block
- computeDFS(Fn);
-
- // Determine which phi node operands need copies
- for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
- if (!I->empty() && I->begin()->isPHI())
- processBlock(I);
-
- // Break interferences where two different phis want to coalesce
- // in the same register.
- std::set<unsigned> seen;
- typedef std::map<unsigned, std::map<unsigned, MachineBasicBlock*> >
- RenameSetType;
- for (RenameSetType::iterator I = RenameSets.begin(), E = RenameSets.end();
- I != E; ++I) {
- for (std::map<unsigned, MachineBasicBlock*>::iterator
- OI = I->second.begin(), OE = I->second.end(); OI != OE; ) {
- if (!seen.count(OI->first)) {
- seen.insert(OI->first);
- ++OI;
- } else {
- Waiting[OI->second].insert(std::make_pair(OI->first, I->first));
- unsigned reg = OI->first;
- ++OI;
- I->second.erase(reg);
- DEBUG(dbgs() << "Removing Renaming: " << reg << " -> " << I->first
- << "\n");
- }
- }
- }
-
- // Insert copies
- // FIXME: This process should probably preserve LiveIntervals
- SmallPtrSet<MachineBasicBlock*, 16> visited;
- MachineDominatorTree& MDT = getAnalysis<MachineDominatorTree>();
- InsertCopies(MDT.getRootNode(), visited);
-
- // Perform renaming
- for (RenameSetType::iterator I = RenameSets.begin(), E = RenameSets.end();
- I != E; ++I)
- while (I->second.size()) {
- std::map<unsigned, MachineBasicBlock*>::iterator SI = I->second.begin();
-
- DEBUG(dbgs() << "Renaming: " << SI->first << " -> " << I->first << "\n");
-
- if (SI->first != I->first) {
- if (mergeLiveIntervals(I->first, SI->first)) {
- Fn.getRegInfo().replaceRegWith(SI->first, I->first);
-
- if (RenameSets.count(SI->first)) {
- I->second.insert(RenameSets[SI->first].begin(),
- RenameSets[SI->first].end());
- RenameSets.erase(SI->first);
- }
- } else {
- // Insert a last-minute copy if a conflict was detected.
- const TargetInstrInfo *TII = Fn.getTarget().getInstrInfo();
- BuildMI(*SI->second, SI->second->getFirstTerminator(), DebugLoc(),
- TII->get(TargetOpcode::COPY), I->first).addReg(SI->first);
-
- LI.renumber();
-
- LiveInterval& Int = LI.getOrCreateInterval(I->first);
- SlotIndex instrIdx =
- LI.getInstructionIndex(--SI->second->getFirstTerminator());
- if (Int.liveAt(instrIdx.getDefIndex()))
- Int.removeRange(instrIdx.getDefIndex(),
- LI.getMBBEndIdx(SI->second).getNextSlot(), true);
-
- LiveRange R = LI.addLiveRangeToEndOfBlock(I->first,
- --SI->second->getFirstTerminator());
- R.valno->setCopy(--SI->second->getFirstTerminator());
- R.valno->def = instrIdx.getDefIndex();
-
- DEBUG(dbgs() << "Renaming failed: " << SI->first << " -> "
- << I->first << "\n");
- }
- }
-
- LiveInterval& Int = LI.getOrCreateInterval(I->first);
- const LiveRange* LR =
- Int.getLiveRangeContaining(LI.getMBBEndIdx(SI->second));
- LR->valno->setHasPHIKill(true);
-
- I->second.erase(SI->first);
- }
-
- // Remove PHIs
- std::vector<MachineInstr*> phis;
- for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
- for (MachineBasicBlock::iterator BI = I->begin(), BE = I->end();
- BI != BE; ++BI)
- if (BI->isPHI())
- phis.push_back(BI);
- }
-
- for (std::vector<MachineInstr*>::iterator I = phis.begin(), E = phis.end();
- I != E; ) {
- MachineInstr* PInstr = *(I++);
-
- // If this is a dead PHI node, then remove it from LiveIntervals.
- unsigned DestReg = PInstr->getOperand(0).getReg();
- LiveInterval& PI = LI.getInterval(DestReg);
- if (PInstr->registerDefIsDead(DestReg)) {
- if (PI.containsOneValue()) {
- LI.removeInterval(DestReg);
- } else {
- SlotIndex idx = LI.getInstructionIndex(PInstr).getDefIndex();
- PI.removeRange(*PI.getLiveRangeContaining(idx), true);
- }
- } else {
- // Trim live intervals of input registers. They are no longer live into
- // this block if they died after the PHI. If they lived after it, don't
- // trim them because they might have other legitimate uses.
- for (unsigned i = 1; i < PInstr->getNumOperands(); i += 2) {
- unsigned reg = PInstr->getOperand(i).getReg();
-
- MachineBasicBlock* MBB = PInstr->getOperand(i+1).getMBB();
- LiveInterval& InputI = LI.getInterval(reg);
- if (MBB != PInstr->getParent() &&
- InputI.liveAt(LI.getMBBStartIdx(PInstr->getParent())) &&
- InputI.expiredAt(LI.getInstructionIndex(PInstr).getNextIndex()))
- InputI.removeRange(LI.getMBBStartIdx(PInstr->getParent()),
- LI.getInstructionIndex(PInstr),
- true);
- }
-
- // If the PHI is not dead, then the valno defined by the PHI
- // now has an unknown def.
- SlotIndex idx = LI.getInstructionIndex(PInstr).getDefIndex();
- const LiveRange* PLR = PI.getLiveRangeContaining(idx);
- PLR->valno->setIsPHIDef(true);
- LiveRange R (LI.getMBBStartIdx(PInstr->getParent()),
- PLR->start, PLR->valno);
- PI.addRange(R);
- }
-
- LI.RemoveMachineInstrFromMaps(PInstr);
- PInstr->eraseFromParent();
- }
-
- LI.renumber();
-
- return true;
-}
projects / oota-llvm.git / commitdiff