#include "llvm/CodeGen/MachineInstr.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/Support/Compiler.h"
using namespace llvm;
-
namespace {
struct VISIBILITY_HIDDEN StrongPHIElimination : public MachineFunctionPass {
static char ID; // Pass identification, replacement for typeid
// used as operands to another another PHI node
std::set<unsigned> UsedByAnother;
- // RenameSets are the sets of operands (and their VNInfo IDs) to a PHI
- // (the defining instruction of the key) that can be renamed without copies.
- std::map<unsigned, std::map<unsigned, unsigned> > RenameSets;
+ // 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.
// TODO: Actually make this true.
AU.addPreserved<LiveIntervals>();
+ AU.addPreserved<RegisterCoalescer>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void computeDFS(MachineFunction& MF);
void processBlock(MachineBasicBlock* MBB);
- std::vector<DomForestNode*> computeDomForest(std::map<unsigned, unsigned>& instrs,
+ std::vector<DomForestNode*> computeDomForest(
+ std::map<unsigned, MachineBasicBlock*>& instrs,
MachineRegisterInfo& MRI);
void processPHIUnion(MachineInstr* Inst,
- std::map<unsigned, unsigned>& PHIUnion,
+ 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(MachineBasicBlock* MBB,
SmallPtrSet<MachineBasicBlock*, 16>& v);
- void mergeLiveIntervals(unsigned primary, unsigned secondary, unsigned VN);
+ void mergeLiveIntervals(unsigned primary, unsigned secondary,
+ MachineBasicBlock* pred);
};
-
- char StrongPHIElimination::ID = 0;
- RegisterPass<StrongPHIElimination> X("strong-phi-node-elimination",
- "Eliminate PHI nodes for register allocation, intelligently");
}
-const PassInfo *llvm::StrongPHIEliminationID = X.getPassInfo();
+char StrongPHIElimination::ID = 0;
+static RegisterPass<StrongPHIElimination>
+X("strong-phi-node-elimination",
+ "Eliminate PHI nodes for register allocation, intelligently");
+
+const PassInfo *const llvm::StrongPHIEliminationID = &X;
/// 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
}
}
+namespace {
+
/// PreorderSorter - a helper class that is used to sort registers
/// according to the preorder number of their defining blocks
class PreorderSorter {
}
};
+}
+
/// 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, unsigned>& regs,
+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.
// Populate a worklist with the registers
std::vector<unsigned> worklist;
worklist.reserve(regs.size());
- for (std::map<unsigned, unsigned>::iterator I = regs.begin(), E = regs.end();
- I != E; ++I)
+ 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
// Iterate over all the PHI nodes in this block
MachineBasicBlock::iterator P = MBB->begin();
- while (P->getOpcode() == TargetInstrInfo::PHI) {
+ while (P != MBB->end() && P->getOpcode() == TargetInstrInfo::PHI) {
unsigned DestReg = P->getOperand(0).getReg();
// Don't both doing PHI elimination for dead PHI's.
// 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, unsigned> PHIUnion;
+ std::map<unsigned, MachineBasicBlock*> PHIUnion;
SmallPtrSet<MachineBasicBlock*, 8> UnionedBlocks;
// Iterate over the operands of the PHI node
UsedByAnother.insert(SrcReg);
} else {
// Otherwise, add it to the renaming set
- LiveInterval& I = LI.getOrCreateInterval(SrcReg);
- unsigned idx = LI.getMBBEndIdx(P->getOperand(i).getMBB());
- VNInfo* VN = I.getLiveRangeContaining(idx)->valno;
-
- assert(VN && "No VNInfo for register?");
-
- PHIUnion.insert(std::make_pair(SrcReg, VN->id));
+ PHIUnion.insert(std::make_pair(SrcReg,P->getOperand(i).getMBB()));
UnionedBlocks.insert(MRI.getVRegDef(SrcReg)->getParent());
}
}
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 determines from dominator analysis. We now
+ // 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) {
}
}
- // Add the renaming set for this PHI node to our overal renaming information
+ // Add the renaming set for this PHI node to our overall 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
- for (std::map<unsigned, unsigned>::iterator I = PHIUnion.begin(),
+ for (std::map<unsigned, MachineBasicBlock*>::iterator I = PHIUnion.begin(),
E = PHIUnion.end(); I != E; ++I)
ProcessedNames.insert(I->first);
/// that are known to interfere, and flag others that need to be checked for
/// local interferences.
void StrongPHIElimination::processPHIUnion(MachineInstr* Inst,
- std::map<unsigned, unsigned>& PHIUnion,
+ std::map<unsigned, MachineBasicBlock*>& PHIUnion,
std::vector<StrongPHIElimination::DomForestNode*>& DF,
std::vector<std::pair<unsigned, unsigned> >& locals) {
/// 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
+ // FIXME: This function needs to update LiveIntervals
std::map<unsigned, unsigned>& copy_set= Waiting[MBB];
std::map<unsigned, unsigned> worklist;
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()) {
map[curr.first], RC, RC);
map[curr.first] = curr.second;
+ // 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::map<unsigned, unsigned>::iterator I = copy_set.begin(),
E = copy_set.end(); I != E; )
worklist.insert(curr);
}
}
+
+ // Renumber the instructions so that we can perform the index computations
+ // needed to create new live intervals.
+ LI.computeNumbering();
+
+ // 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)
+ LI.addLiveRangeToEndOfBlock(I->first, I->second);
}
/// InsertCopies - insert copies into MBB and all of its successors
Stacks[*I].pop_back();
}
-/// ComputeUltimateVN - Assuming we are going to join two live intervals,
-/// compute what the resultant value numbers for each value in the input two
-/// ranges will be. This is complicated by copies between the two which can
-/// and will commonly cause multiple value numbers to be merged into one.
-///
-/// VN is the value number that we're trying to resolve. InstDefiningValue
-/// keeps track of the new InstDefiningValue assignment for the result
-/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
-/// whether a value in this or other is a copy from the opposite set.
-/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
-/// already been assigned.
-///
-/// ThisFromOther[x] - If x is defined as a copy from the other interval, this
-/// contains the value number the copy is from.
-///
-static unsigned ComputeUltimateVN(VNInfo *VNI,
- SmallVector<VNInfo*, 16> &NewVNInfo,
- DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
- DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
- SmallVector<int, 16> &ThisValNoAssignments,
- SmallVector<int, 16> &OtherValNoAssignments) {
- unsigned VN = VNI->id;
-
- // If the VN has already been computed, just return it.
- if (ThisValNoAssignments[VN] >= 0)
- return ThisValNoAssignments[VN];
-// assert(ThisValNoAssignments[VN] != -2 && "Cyclic case?");
-
- // If this val is not a copy from the other val, then it must be a new value
- // number in the destination.
- DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
- if (I == ThisFromOther.end()) {
- NewVNInfo.push_back(VNI);
- return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
- }
- VNInfo *OtherValNo = I->second;
-
- // Otherwise, this *is* a copy from the RHS. If the other side has already
- // been computed, return it.
- if (OtherValNoAssignments[OtherValNo->id] >= 0)
- return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
-
- // Mark this value number as currently being computed, then ask what the
- // ultimate value # of the other value is.
- ThisValNoAssignments[VN] = -2;
- unsigned UltimateVN =
- ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
- OtherValNoAssignments, ThisValNoAssignments);
- return ThisValNoAssignments[VN] = UltimateVN;
-}
-
void StrongPHIElimination::mergeLiveIntervals(unsigned primary,
unsigned secondary,
- unsigned secondaryVN) {
+ MachineBasicBlock* pred) {
LiveIntervals& LI = getAnalysis<LiveIntervals>();
LiveInterval& LHS = LI.getOrCreateInterval(primary);
LiveInterval& RHS = LI.getOrCreateInterval(secondary);
- // Compute the final value assignment, assuming that the live ranges can be
- // coalesced.
- SmallVector<int, 16> LHSValNoAssignments;
- SmallVector<int, 16> RHSValNoAssignments;
- SmallVector<VNInfo*, 16> NewVNInfo;
+ LI.computeNumbering();
- LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
- RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
- NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
+ const LiveRange* RangeMergingIn =
+ RHS.getLiveRangeContaining(LI.getMBBEndIdx(pred));
+ VNInfo* NewVN = LHS.getNextValue(RangeMergingIn->valno->def,
+ RangeMergingIn->valno->copy,
+ LI.getVNInfoAllocator());
+ NewVN->hasPHIKill = true;
+ LiveRange NewRange(RangeMergingIn->start, RangeMergingIn->end, NewVN);
- for (LiveInterval::vni_iterator I = LHS.vni_begin(), E = LHS.vni_end();
- I != E; ++I) {
- VNInfo *VNI = *I;
- unsigned VN = VNI->id;
- if (LHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
- continue;
-
- NewVNInfo.push_back(VNI);
- LHSValNoAssignments[VN] = NewVNInfo.size()-1;
- }
+ if (RHS.containsOneValue())
+ LI.removeInterval(RHS.reg);
+ else
+ RHS.removeRange(RangeMergingIn->start, RangeMergingIn->end, true);
- for (LiveInterval::vni_iterator I = RHS.vni_begin(), E = RHS.vni_end();
- I != E; ++I) {
- VNInfo *VNI = *I;
- unsigned VN = VNI->id;
- if (RHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
- continue;
-
- NewVNInfo.push_back(VNI);
- RHSValNoAssignments[VN] = NewVNInfo.size()-1;
- }
-
- // If we get here, we know that we can coalesce the live ranges. Ask the
- // intervals to coalesce themselves now.
-
- LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo);
- LI.removeInterval(secondary);
-
- // The valno that was previously the input to the PHI node
- // now has a PHIKill.
- LHS.getValNumInfo(RHSValNoAssignments[secondaryVN])->hasPHIKill = true;
+ LHS.addRange(NewRange);
}
bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
-
LiveIntervals& LI = getAnalysis<LiveIntervals>();
// Compute DFS numbers of each block
processBlock(I);
// Insert copies
- // FIXME: This process should probably preserve LiveVariables
+ // FIXME: This process should probably preserve LiveIntervals
SmallPtrSet<MachineBasicBlock*, 16> visited;
InsertCopies(Fn.begin(), visited);
// Perform renaming
- typedef std::map<unsigned, std::map<unsigned, unsigned> > RenameSetType;
+ 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, unsigned>::iterator SI = I->second.begin(),
- SE = I->second.end(); SI != SE; ++SI) {
+ for (std::map<unsigned, MachineBasicBlock*>::iterator SI =
+ I->second.begin(), SE = I->second.end(); SI != SE; ++SI) {
mergeLiveIntervals(I->first, SI->first, SI->second);
Fn.getRegInfo().replaceRegWith(SI->first, I->first);
}
I != E; ) {
MachineInstr* PInstr = *(I++);
+ // Trim live intervals of input registers. They are no longer live into
+ // this block.
+ 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.removeRange(LI.getMBBStartIdx(PInstr->getParent()),
+ LI.getInstructionIndex(PInstr),
+ true);
+ }
+
// 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)) {
- LiveInterval& PI = LI.getInterval(DestReg);
-
if (PI.containsOneValue()) {
LI.removeInterval(DestReg);
} else {
unsigned idx = LI.getDefIndex(LI.getInstructionIndex(PInstr));
PI.removeRange(*PI.getLiveRangeContaining(idx), true);
}
+ } else {
+ // If the PHI is not dead, then the valno defined by the PHI
+ // now has an unknown def.
+ unsigned idx = LI.getDefIndex(LI.getInstructionIndex(PInstr));
+ const LiveRange* PLR = PI.getLiveRangeContaining(idx);
+ PLR->valno->def = ~0U;
+ LiveRange R (LI.getMBBStartIdx(PInstr->getParent()),
+ PLR->start, PLR->valno);
+ PI.addRange(R);
}
-
+
LI.RemoveMachineInstrFromMaps(PInstr);
PInstr->eraseFromParent();
}
+ LI.computeNumbering();
+
return true;
}
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