//
//===----------------------------------------------------------------------===//
//
-// 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
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "strongphielim"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
-
namespace {
- struct VISIBILITY_HIDDEN StrongPHIElimination : public MachineFunctionPass {
- static char ID; // Pass identification, replacement for typeid
- StrongPHIElimination() : MachineFunctionPass((intptr_t)&ID) {}
-
- // Waiting stores, for each MBB, the set of copies that need to
- // be inserted into that MBB
- DenseMap<MachineBasicBlock*,
- std::map<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 another PHI node
- std::set<unsigned> UsedByAnother;
-
- // RenameSets are the sets of operands to a PHI (the defining instruction
- // of the key) that can be renamed without copies
- std::map<unsigned, std::set<unsigned> > RenameSets;
-
- // 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.addRequired<MachineDominatorTree>();
- AU.addRequired<LiveVariables>();
- MachineFunctionPass::getAnalysisUsage(AU);
- }
-
- virtual void releaseMemory() {
- preorder.clear();
- maxpreorder.clear();
-
- Waiting.clear();
- Stacks.clear();
- UsedByAnother.clear();
- RenameSets.clear();
- }
-
- 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);
-
- std::vector<DomForestNode*> computeDomForest(std::set<unsigned>& instrs);
- void processPHIUnion(MachineInstr* Inst,
- std::set<unsigned>& PHIUnion,
- std::vector<StrongPHIElimination::DomForestNode*>& DF,
- std::vector<std::pair<unsigned, unsigned> >& locals);
- void ScheduleCopies(MachineBasicBlock* MBB, std::set<unsigned>& pushed);
- void InsertCopies(MachineBasicBlock* MBB, std::set<MachineBasicBlock*>& v);
- };
-
- char StrongPHIElimination::ID = 0;
- RegisterPass<StrongPHIElimination> X("strong-phi-node-elimination",
- "Eliminate PHI nodes for register allocation, intelligently");
-}
-
-const PassInfo *llvm::StrongPHIEliminationID = X.getPassInfo();
-
-/// 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 = node->begin(), E = node->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();
- }
- }
-}
-
-/// 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;
- LiveVariables& LV;
-
+class StrongPHIElimination : public MachineFunctionPass {
public:
- PreorderSorter(DenseMap<MachineBasicBlock*, unsigned>& p,
- LiveVariables& L) : preorder(p), LV(L) { }
-
- bool operator()(unsigned A, unsigned B) {
- if (A == B)
- return false;
-
- MachineBasicBlock* ABlock = LV.getVarInfo(A).DefInst->getParent();
- MachineBasicBlock* BBlock = LV.getVarInfo(A).DefInst->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::set<unsigned>& regs) {
- LiveVariables& LV = getAnalysis<LiveVariables>();
-
- // 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::set<unsigned>::iterator I = regs.begin(), E = regs.end();
- I != E; ++I)
- worklist.push_back(*I);
-
- // Sort the registers by the DFS-in number of their defining block
- PreorderSorter PS(preorder, LV);
- 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[LV.getVarInfo(*I).DefInst->getParent()];
- MachineBasicBlock* parentBlock = CurrentParent->getReg() ?
- LV.getVarInfo(CurrentParent->getReg()).DefInst->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() ?
- LV.getVarInfo(CurrentParent->getReg()).DefInst->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 VarInfo, if a register
-/// is live into a block
-static bool isLiveIn(LiveVariables::VarInfo& V, MachineBasicBlock* MBB) {
- if (V.AliveBlocks.test(MBB->getNumber()))
- return true;
-
- if (V.DefInst->getParent() != MBB &&
- V.UsedBlocks.test(MBB->getNumber()))
- return true;
-
- return false;
-}
-
-/// isLiveOut - help method that determines, from a VarInfo, if a register is
-/// live out of a block.
-static bool isLiveOut(LiveVariables::VarInfo& V, MachineBasicBlock* MBB) {
- if (MBB == V.DefInst->getParent() ||
- V.UsedBlocks.test(MBB->getNumber())) {
- for (std::vector<MachineInstr*>::iterator I = V.Kills.begin(),
- E = V.Kills.end(); I != E; ++I)
- if ((*I)->getParent() == MBB)
- return false;
-
- return true;
+ static char ID; // Pass identification, replacement for typeid
+ StrongPHIElimination() : MachineFunctionPass(ID) {
+ initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
}
-
- return false;
-}
-
-/// isKillInst - helper method that determines, from a VarInfo, if an
-/// instruction kills a given register
-static bool isKillInst(LiveVariables::VarInfo& V, MachineInstr* MI) {
- return std::find(V.Kills.begin(), V.Kills.end(), MI) != V.Kills.end();
-}
-
-/// 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(LiveVariables::VarInfo& First,
- LiveVariables::VarInfo& Second,
- MachineBasicBlock* scan, unsigned mode) {
- MachineInstr* def = 0;
- MachineInstr* kill = 0;
-
- 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 == First.DefInst) {
- // If we find our first DefInst, save it
- if (!def) {
- def = curr;
- // If there's already an unkilled DefInst, then
- // this is an interference
- } else if (!kill) {
- interference = true;
- break;
- // If there's a DefInst followed by a KillInst, then
- // they can't interfere
- } else {
- interference = false;
- break;
- }
- // Symmetric with the above
- } else if (curr == Second.DefInst ) {
- if (!def) {
- def = curr;
- } else if (!kill) {
- interference = true;
- break;
- } else {
- interference = false;
- break;
- }
- // Store KillInsts if they match up with the DefInst
- } else if (isKillInst(First, curr)) {
- if (def == First.DefInst) {
- kill = curr;
- } else if (isKillInst(Second, curr)) {
- if (def == Second.DefInst) {
- kill = curr;
- }
- }
- }
- // First properly dominates second...
- } else if (mode == 1) {
- if (curr == Second.DefInst) {
- // DefInst of second without kill of first is an interference
- if (!kill) {
- interference = true;
- break;
- // DefInst after a kill is a non-interference
- } else {
- interference = false;
- break;
- }
- // Save KillInsts of First
- } else if (isKillInst(First, curr)) {
- kill = curr;
- }
- // Symmetric with the above
- } else if (mode == 2) {
- if (curr == First.DefInst) {
- if (!kill) {
- interference = true;
- break;
- } else {
- interference = false;
- break;
- }
- } else if (isKillInst(Second, curr)) {
- kill = curr;
- }
- }
- }
-
- return interference;
-}
-
-/// processBlock - Eliminate PHIs in the given block
-void StrongPHIElimination::processBlock(MachineBasicBlock* MBB) {
- LiveVariables& LV = getAnalysis<LiveVariables>();
-
- // Holds names that have been added to a set in any PHI within this block
- // before the current one.
- std::set<unsigned> ProcessedNames;
-
- MachineBasicBlock::iterator P = MBB->begin();
- while (P != MBB->end() && P->getOpcode() == TargetInstrInfo::PHI) {
- LiveVariables::VarInfo& PHIInfo = LV.getVarInfo(P->getOperand(0).getReg());
-
- unsigned DestReg = P->getOperand(0).getReg();
- // Hold the names that are currently in the candidate set.
- std::set<unsigned> PHIUnion;
- std::set<MachineBasicBlock*> UnionedBlocks;
-
- for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
- unsigned SrcReg = P->getOperand(i-1).getReg();
- LiveVariables::VarInfo& SrcInfo = LV.getVarInfo(SrcReg);
-
- // Check for trivial interferences
- if (isLiveIn(SrcInfo, P->getParent()) ||
- isLiveOut(PHIInfo, SrcInfo.DefInst->getParent()) ||
- ( PHIInfo.DefInst->getOpcode() == TargetInstrInfo::PHI &&
- isLiveIn(PHIInfo, SrcInfo.DefInst->getParent()) ) ||
- ProcessedNames.count(SrcReg) ||
- UnionedBlocks.count(SrcInfo.DefInst->getParent())) {
-
- // add a copy from a_i to p in Waiting[From[a_i]]
- MachineBasicBlock* From = P->getOperand(i).getMBB();
- Waiting[From].insert(std::make_pair(SrcReg, DestReg));
- UsedByAnother.insert(SrcReg);
- } else {
- PHIUnion.insert(SrcReg);
- UnionedBlocks.insert(SrcInfo.DefInst->getParent());
- }
- }
-
- std::vector<StrongPHIElimination::DomForestNode*> DF =
- computeDomForest(PHIUnion);
-
- // Walk DomForest to resolve interferences
- std::vector<std::pair<unsigned, unsigned> > localInterferences;
- processPHIUnion(P, PHIUnion, DF, localInterferences);
-
- // Check 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;
-
- LiveVariables::VarInfo& FirstInfo = LV.getVarInfo(p.first);
- LiveVariables::VarInfo& SecondInfo = LV.getVarInfo(p.second);
-
- 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 (FirstInfo.DefInst->getParent() == SecondInfo.DefInst->getParent()) {
- scan = FirstInfo.DefInst->getParent();
- mode = 0; // Same block
- } else if (MDT.dominates(FirstInfo.DefInst->getParent(),
- SecondInfo.DefInst->getParent())) {
- scan = SecondInfo.DefInst->getParent();
- mode = 1; // First dominates second
- } else {
- scan = FirstInfo.DefInst->getParent();
- mode = 2; // Second dominates first
- }
-
- // If there's an interference, we need to insert copies
- if (interferes(FirstInfo, SecondInfo, scan, 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);
- }
- }
- }
- }
-
- // Cache renaming information
- RenameSets.insert(std::make_pair(P->getOperand(0).getReg(), PHIUnion));
-
- ProcessedNames.insert(PHIUnion.begin(), PHIUnion.end());
- ++P;
+private:
+ bool runOnMachineFunction(MachineFunction &Fn) {
+ llvm_unreachable("Strong phi elimination is not implemented");
}
-}
-
-/// processPHIUnion - Take a set of candidate registers to be coallesced 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::set<unsigned>& 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;
-
- LiveVariables& LV = getAnalysis<LiveVariables>();
- unsigned DestReg = Inst->getOperand(0).getReg();
-
- // DF walk on the DomForest
- while (!worklist.empty()) {
- DomForestNode* DFNode = worklist.back();
-
- LiveVariables::VarInfo& Info = LV.getVarInfo(DFNode->getReg());
- visited.insert(DFNode);
- bool inserted = false;
- for (DomForestNode::iterator CI = DFNode->begin(), CE = DFNode->end();
- CI != CE; ++CI) {
- DomForestNode* child = *CI;
- LiveVariables::VarInfo& CInfo = LV.getVarInfo(child->getReg());
-
- if (isLiveOut(Info, CInfo.DefInst->getParent())) {
- // 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);
- }
- }
- } else if (isLiveIn(Info, CInfo.DefInst->getParent()) ||
- Info.DefInst->getParent() == CInfo.DefInst->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();
+ 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
-/// 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 LiveVariables
- std::map<unsigned, unsigned>& copy_set= Waiting[MBB];
-
- std::map<unsigned, unsigned> worklist;
- std::map<unsigned, unsigned> map;
-
- // Setup worklist of initial copies
- for (std::map<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->first)) {
- worklist.insert(*I);
-
- // Avoid iterator invalidation
- unsigned first = I->first;
- ++I;
- copy_set.erase(first);
- } else {
- ++I;
- }
- }
-
- LiveVariables& LV = getAnalysis<LiveVariables>();
- MachineFunction* MF = MBB->getParent();
- const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
-
- // Iterate over the worklist, inserting copies
- while (!worklist.empty() || !copy_set.empty()) {
- while (!worklist.empty()) {
- std::pair<unsigned, unsigned> curr = *worklist.begin();
- worklist.erase(curr.first);
-
- const TargetRegisterClass *RC = MF->getRegInfo().getRegClass(curr.first);
-
- if (isLiveOut(LV.getVarInfo(curr.second), MBB)) {
- // Create a temporary
- unsigned t = MF->getRegInfo().createVirtualRegister(RC);
-
- // Insert copy from curr.second to a temporary at
- // the Phi defining curr.second
- LiveVariables::VarInfo VI = LV.getVarInfo(curr.second);
- MachineBasicBlock::iterator PI = VI.DefInst;
- TII->copyRegToReg(*VI.DefInst->getParent(), PI, t,
- curr.second, RC, RC);
-
- // Push temporary on Stacks
- Stacks[curr.second].push_back(t);
-
- // Insert curr.second in pushed
- pushed.insert(curr.second);
- }
-
- // Insert copy from map[curr.first] to curr.second
- TII->copyRegToReg(*MBB, MBB->end(), curr.second,
- map[curr.first], RC, RC);
- map[curr.first] = curr.second;
-
- // If curr.first is a destination in copy_set...
- for (std::map<unsigned, unsigned>::iterator I = copy_set.begin(),
- E = copy_set.end(); I != E; )
- if (curr.first == I->second) {
- std::pair<unsigned, unsigned> temp = *I;
-
- // Avoid iterator invalidation
- ++I;
- copy_set.erase(temp.first);
- worklist.insert(temp);
-
- break;
- } else {
- ++I;
- }
- }
-
- if (!copy_set.empty()) {
- std::pair<unsigned, unsigned> curr = *copy_set.begin();
- copy_set.erase(curr.first);
-
- 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);
- TII->copyRegToReg(*MBB, MBB->end(), t,
- curr.second, RC, RC);
- map[curr.second] = t;
-
- worklist.insert(curr);
- }
- }
-}
+char StrongPHIElimination::ID = 0;
+INITIALIZE_PASS_BEGIN(StrongPHIElimination, "strong-phi-node-elimination",
+ "Eliminate PHI nodes for register allocation, intelligently", false, false)
+INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
+INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
+INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
+INITIALIZE_PASS_END(StrongPHIElimination, "strong-phi-node-elimination",
+ "Eliminate PHI nodes for register allocation, intelligently", false, false)
-/// InsertCopies - insert copies into MBB and all of its successors
-void StrongPHIElimination::InsertCopies(MachineBasicBlock* MBB,
- std::set<MachineBasicBlock*>& visited) {
- visited.insert(MBB);
-
- std::set<unsigned> pushed;
-
- // Rewrite register uses from Stacks
- for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
- I != E; ++I)
- for (unsigned i = 0; i < I->getNumOperands(); ++i)
- if (I->getOperand(i).isRegister() &&
- Stacks[I->getOperand(i).getReg()].size()) {
- I->getOperand(i).setReg(Stacks[I->getOperand(i).getReg()].back());
- }
-
- // Schedule the copies for this block
- ScheduleCopies(MBB, pushed);
-
- // Recur to our successors
- for (GraphTraits<MachineBasicBlock*>::ChildIteratorType I =
- GraphTraits<MachineBasicBlock*>::child_begin(MBB), E =
- GraphTraits<MachineBasicBlock*>::child_end(MBB); I != E; ++I)
- if (!visited.count(*I))
- 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();
-}
+char &llvm::StrongPHIEliminationID = StrongPHIElimination::ID;
-bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
- // 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()->getOpcode() == TargetInstrInfo::PHI)
- processBlock(I);
-
- // Insert copies
- // FIXME: This process should probably preserve LiveVariables
- std::set<MachineBasicBlock*> visited;
- InsertCopies(Fn.begin(), visited);
-
- // Perform renaming
- typedef std::map<unsigned, std::set<unsigned> > RenameSetType;
- for (RenameSetType::iterator I = RenameSets.begin(), E = RenameSets.end();
- I != E; ++I)
- for (std::set<unsigned>::iterator SI = I->second.begin(),
- SE = I->second.end(); SI != SE; ++SI)
- Fn.getRegInfo().replaceRegWith(*SI, I->first);
-
- // FIXME: Insert last-minute copies
-
- // Remove 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->getOpcode() == TargetInstrInfo::PHI)
- BI->eraseFromParent();
-
- return false;
-}
projects / oota-llvm.git / blobdiff