//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Owen Anderson and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#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"
using namespace llvm;
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.addPreserved<LiveVariables>();
- AU.addPreservedID(PHIEliminationID);
AU.addRequired<MachineDominatorTree>();
AU.addRequired<LiveVariables>();
- AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
preorder.clear();
maxpreorder.clear();
- waiting.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);
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(); }
};
- DenseMap<MachineBasicBlock*, unsigned> preorder;
- DenseMap<MachineBasicBlock*, unsigned> maxpreorder;
-
- DenseMap<MachineBasicBlock*, std::vector<MachineInstr*> > waiting;
-
-
void computeDFS(MachineFunction& MF);
- void processPHI(MachineInstr* P);
-
- std::vector<DomForestNode*> computeDomForest(std::set<unsigned>& instrs);
+ void processBlock(MachineBasicBlock* MBB);
+ std::vector<DomForestNode*> computeDomForest(std::set<unsigned>& instrs,
+ MachineRegisterInfo& MRI);
+ 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;
}
}
+/// 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;
+ MachineRegisterInfo& MRI;
public:
PreorderSorter(DenseMap<MachineBasicBlock*, unsigned>& p,
- LiveVariables& L) : preorder(p), LV(L) { }
+ MachineRegisterInfo& M) : preorder(p), MRI(M) { }
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();
+ 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;
- assert(0 && "Error sorting by dominance!");
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>();
-
+StrongPHIElimination::computeDomForest(std::set<unsigned>& 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::set<unsigned>::iterator I = regs.begin(), E = regs.end();
I != E; ++I)
worklist.push_back(*I);
- PreorderSorter PS(preorder, LV);
+ // 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[LV.getVarInfo(*I).DefInst->getParent()];
- MachineBasicBlock* parentBlock =
- LV.getVarInfo(CurrentParent->getReg()).DefInst->getParent();
+ 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 = LV.getVarInfo(CurrentParent->getReg()).DefInst->getParent();
+ 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;
}
-void StrongPHIElimination::processPHI(MachineInstr* P) {
+/// isLiveIn - helper method that determines, from a VarInfo, if a register
+/// is live into a block
+static bool isLiveIn(unsigned r, MachineBasicBlock* MBB,
+ MachineRegisterInfo& MRI, LiveVariables& LV) {
+ LiveVariables::VarInfo V = LV.getVarInfo(r);
+ if (V.AliveBlocks.test(MBB->getNumber()))
+ return true;
+
+ if (MRI.getVRegDef(r)->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(unsigned r, MachineBasicBlock* MBB,
+ MachineRegisterInfo& MRI, LiveVariables& LV) {
+ LiveVariables::VarInfo& V = LV.getVarInfo(r);
+ if (MBB == MRI.getVRegDef(r)->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;
+ }
+
+ 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,
+ LiveVariables& 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 (LV.KillsRegister(curr, a)) {
+ if (def == MRI->getVRegDef(a)) {
+ kill = curr;
+ } else if (LV.KillsRegister(curr, 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 (LV.KillsRegister(curr, 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 (LV.KillsRegister(curr, 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) {
+ LiveVariables& LV = getAnalysis<LiveVariables>();
+ 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->getOpcode() == TargetInstrInfo::PHI) {
+ unsigned DestReg = P->getOperand(0).getReg();
+
+ // 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::set<unsigned> PHIUnion;
+ std::set<MachineBasicBlock*> 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();
+
+ // 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(), MRI, LV) ||
+ isLiveOut(P->getOperand(0).getReg(),
+ MRI.getVRegDef(SrcReg)->getParent(), MRI, LV) ||
+ ( MRI.getVRegDef(SrcReg)->getOpcode() == TargetInstrInfo::PHI &&
+ isLiveIn(P->getOperand(0).getReg(),
+ MRI.getVRegDef(SrcReg)->getParent(), MRI, LV) ) ||
+ 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(SrcReg);
+ 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);
+
+ // The dominator forest walk may have returned some register pairs whose
+ // interference cannot be determines 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, LV, 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 overal renaming information
+ 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
+ ProcessedNames.insert(PHIUnion.begin(), PHIUnion.end());
+
+ ++P;
+ }
+}
+
+/// 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;
+
+ // Code is still in SSA form, so we can use MRI::getVRegDef()
+ MachineRegisterInfo& MRI = Inst->getParent()->getParent()->getRegInfo();
+
+ LiveVariables& LV = getAnalysis<LiveVariables>();
+ 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(), MRI, LV)) {
+ // 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(),
+ MRI, LV) ||
+ 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 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();
+ MachineRegisterInfo& MRI = MF->getRegInfo();
+ 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(curr.second, MBB, MRI, LV)) {
+ // 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);
+ TII->copyRegToReg(*PI->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->getFirstTerminator(), 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->getFirstTerminator(), t,
+ curr.second, RC, RC);
+ map[curr.second] = t;
+
+ worklist.insert(curr);
+ }
+ }
+}
+
+/// 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();
}
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
+ 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) {
+ for (MachineBasicBlock::iterator BI = I->begin(), BE = I->end();
+ BI != BE; ++BI)
if (BI->getOpcode() == TargetInstrInfo::PHI)
- processPHI(BI);
- else
- break;
- }
+ phis.push_back(BI);
}
+ for (std::vector<MachineInstr*>::iterator I = phis.begin(), E = phis.end();
+ I != E; ++I)
+ (*I)->eraseFromParent();
+
return false;
}
projects / oota-llvm.git / blobdiff