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llvm/lib/CodeGen/InlineSpiller.cpp
Duncan P. N. Exon Smith cc3610dedb CodeGen: Use MachineInstr& in InlineSpiller::rematerializeFor() 
InlineSpiller::rematerializeFor() never uses its parameter as an
iterator, so take it by reference instead.  This removes an implicit
conversion from MachineBasicBlock::iterator to MachineInstr*.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@262152 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-27 20:23:14 +00:00

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//===-------- InlineSpiller.cpp - Insert spills and restores inline -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The inline spiller modifies the machine function directly instead of
// inserting spills and restores in VirtRegMap.
//
//===----------------------------------------------------------------------===//
#include "Spiller.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveRangeEdit.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
#define DEBUG_TYPE "regalloc"
STATISTIC(NumSpilledRanges, "Number of spilled live ranges");
STATISTIC(NumSnippets, "Number of spilled snippets");
STATISTIC(NumSpills, "Number of spills inserted");
STATISTIC(NumSpillsRemoved, "Number of spills removed");
STATISTIC(NumReloads, "Number of reloads inserted");
STATISTIC(NumReloadsRemoved, "Number of reloads removed");
STATISTIC(NumFolded, "Number of folded stack accesses");
STATISTIC(NumFoldedLoads, "Number of folded loads");
STATISTIC(NumRemats, "Number of rematerialized defs for spilling");
STATISTIC(NumOmitReloadSpill, "Number of omitted spills of reloads");
STATISTIC(NumHoists, "Number of hoisted spills");
static cl::opt<bool> DisableHoisting("disable-spill-hoist", cl::Hidden,
cl::desc("Disable inline spill hoisting"));
namespace {
class InlineSpiller : public Spiller {
MachineFunction &MF;
LiveIntervals &LIS;
LiveStacks &LSS;
AliasAnalysis *AA;
MachineDominatorTree &MDT;
MachineLoopInfo &Loops;
VirtRegMap &VRM;
MachineFrameInfo &MFI;
MachineRegisterInfo &MRI;
const TargetInstrInfo &TII;
const TargetRegisterInfo &TRI;
const MachineBlockFrequencyInfo &MBFI;
// Variables that are valid during spill(), but used by multiple methods.
LiveRangeEdit *Edit;
LiveInterval *StackInt;
int StackSlot;
unsigned Original;
// All registers to spill to StackSlot, including the main register.
SmallVector<unsigned, 8> RegsToSpill;
// All COPY instructions to/from snippets.
// They are ignored since both operands refer to the same stack slot.
SmallPtrSet<MachineInstr*, 8> SnippetCopies;
// Values that failed to remat at some point.
SmallPtrSet<VNInfo*, 8> UsedValues;
public:
// Information about a value that was defined by a copy from a sibling
// register.
struct SibValueInfo {
// True when all reaching defs were reloads: No spill is necessary.
bool AllDefsAreReloads;
// True when value is defined by an original PHI not from splitting.
bool DefByOrigPHI;
// True when the COPY defining this value killed its source.
bool KillsSource;
// The preferred register to spill.
unsigned SpillReg;
// The value of SpillReg that should be spilled.
VNInfo *SpillVNI;
// The block where SpillVNI should be spilled. Currently, this must be the
// block containing SpillVNI->def.
MachineBasicBlock *SpillMBB;
// A defining instruction that is not a sibling copy or a reload, or NULL.
// This can be used as a template for rematerialization.
MachineInstr *DefMI;
// List of values that depend on this one. These values are actually the
// same, but live range splitting has placed them in different registers,
// or SSA update needed to insert PHI-defs to preserve SSA form. This is
// copies of the current value and phi-kills. Usually only phi-kills cause
// more than one dependent value.
TinyPtrVector<VNInfo*> Deps;
SibValueInfo(unsigned Reg, VNInfo *VNI)
: AllDefsAreReloads(true), DefByOrigPHI(false), KillsSource(false),
SpillReg(Reg), SpillVNI(VNI), SpillMBB(nullptr), DefMI(nullptr) {}
// Returns true when a def has been found.
bool hasDef() const { return DefByOrigPHI || DefMI; }
};
private:
// Values in RegsToSpill defined by sibling copies.
typedef DenseMap<VNInfo*, SibValueInfo> SibValueMap;
SibValueMap SibValues;
// Dead defs generated during spilling.
SmallVector<MachineInstr*, 8> DeadDefs;
~InlineSpiller() override {}
public:
InlineSpiller(MachineFunctionPass &pass, MachineFunction &mf, VirtRegMap &vrm)
: MF(mf), LIS(pass.getAnalysis<LiveIntervals>()),
LSS(pass.getAnalysis<LiveStacks>()),
AA(&pass.getAnalysis<AAResultsWrapperPass>().getAAResults()),
MDT(pass.getAnalysis<MachineDominatorTree>()),
Loops(pass.getAnalysis<MachineLoopInfo>()), VRM(vrm),
MFI(*mf.getFrameInfo()), MRI(mf.getRegInfo()),
TII(*mf.getSubtarget().getInstrInfo()),
TRI(*mf.getSubtarget().getRegisterInfo()),
MBFI(pass.getAnalysis<MachineBlockFrequencyInfo>()) {}
void spill(LiveRangeEdit &) override;
private:
bool isSnippet(const LiveInterval &SnipLI);
void collectRegsToSpill();
bool isRegToSpill(unsigned Reg) {
return std::find(RegsToSpill.begin(),
RegsToSpill.end(), Reg) != RegsToSpill.end();
}
bool isSibling(unsigned Reg);
MachineInstr *traceSiblingValue(unsigned, VNInfo*, VNInfo*);
void propagateSiblingValue(SibValueMap::iterator, VNInfo *VNI = nullptr);
void analyzeSiblingValues();
bool hoistSpill(LiveInterval &SpillLI, MachineInstr &CopyMI);
void eliminateRedundantSpills(LiveInterval &LI, VNInfo *VNI);
void markValueUsed(LiveInterval*, VNInfo*);
bool reMaterializeFor(LiveInterval &, MachineInstr &MI);
void reMaterializeAll();
bool coalesceStackAccess(MachineInstr *MI, unsigned Reg);
bool foldMemoryOperand(ArrayRef<std::pair<MachineInstr*, unsigned> >,
MachineInstr *LoadMI = nullptr);
void insertReload(unsigned VReg, SlotIndex, MachineBasicBlock::iterator MI);
void insertSpill(unsigned VReg, bool isKill, MachineBasicBlock::iterator MI);
void spillAroundUses(unsigned Reg);
void spillAll();
};
}
namespace llvm {
Spiller::~Spiller() { }
void Spiller::anchor() { }
Spiller *createInlineSpiller(MachineFunctionPass &pass,
MachineFunction &mf,
VirtRegMap &vrm) {
return new InlineSpiller(pass, mf, vrm);
}
}
//===----------------------------------------------------------------------===//
// Snippets
//===----------------------------------------------------------------------===//
// When spilling a virtual register, we also spill any snippets it is connected
// to. The snippets are small live ranges that only have a single real use,
// leftovers from live range splitting. Spilling them enables memory operand
// folding or tightens the live range around the single use.
//
// This minimizes register pressure and maximizes the store-to-load distance for
// spill slots which can be important in tight loops.
/// isFullCopyOf - If MI is a COPY to or from Reg, return the other register,
/// otherwise return 0.
static unsigned isFullCopyOf(const MachineInstr *MI, unsigned Reg) {
if (!MI->isFullCopy())
return 0;
if (MI->getOperand(0).getReg() == Reg)
return MI->getOperand(1).getReg();
if (MI->getOperand(1).getReg() == Reg)
return MI->getOperand(0).getReg();
return 0;
}
/// isSnippet - Identify if a live interval is a snippet that should be spilled.
/// It is assumed that SnipLI is a virtual register with the same original as
/// Edit->getReg().
bool InlineSpiller::isSnippet(const LiveInterval &SnipLI) {
unsigned Reg = Edit->getReg();
// A snippet is a tiny live range with only a single instruction using it
// besides copies to/from Reg or spills/fills. We accept:
//
// %snip = COPY %Reg / FILL fi#
// %snip = USE %snip
// %Reg = COPY %snip / SPILL %snip, fi#
//
if (SnipLI.getNumValNums() > 2 || !LIS.intervalIsInOneMBB(SnipLI))
return false;
MachineInstr *UseMI = nullptr;
// Check that all uses satisfy our criteria.
for (MachineRegisterInfo::reg_instr_nodbg_iterator
RI = MRI.reg_instr_nodbg_begin(SnipLI.reg),
E = MRI.reg_instr_nodbg_end(); RI != E; ) {
MachineInstr *MI = &*(RI++);
// Allow copies to/from Reg.
if (isFullCopyOf(MI, Reg))
continue;
// Allow stack slot loads.
int FI;
if (SnipLI.reg == TII.isLoadFromStackSlot(MI, FI) && FI == StackSlot)
continue;
// Allow stack slot stores.
if (SnipLI.reg == TII.isStoreToStackSlot(MI, FI) && FI == StackSlot)
continue;
// Allow a single additional instruction.
if (UseMI && MI != UseMI)
return false;
UseMI = MI;
}
return true;
}
/// collectRegsToSpill - Collect live range snippets that only have a single
/// real use.
void InlineSpiller::collectRegsToSpill() {
unsigned Reg = Edit->getReg();
// Main register always spills.
RegsToSpill.assign(1, Reg);
SnippetCopies.clear();
// Snippets all have the same original, so there can't be any for an original
// register.
if (Original == Reg)
return;
for (MachineRegisterInfo::reg_instr_iterator
RI = MRI.reg_instr_begin(Reg), E = MRI.reg_instr_end(); RI != E; ) {
MachineInstr *MI = &*(RI++);
unsigned SnipReg = isFullCopyOf(MI, Reg);
if (!isSibling(SnipReg))
continue;
LiveInterval &SnipLI = LIS.getInterval(SnipReg);
if (!isSnippet(SnipLI))
continue;
SnippetCopies.insert(MI);
if (isRegToSpill(SnipReg))
continue;
RegsToSpill.push_back(SnipReg);
DEBUG(dbgs() << "\talso spill snippet " << SnipLI << '\n');
++NumSnippets;
}
}
//===----------------------------------------------------------------------===//
// Sibling Values
//===----------------------------------------------------------------------===//
// After live range splitting, some values to be spilled may be defined by
// copies from sibling registers. We trace the sibling copies back to the
// original value if it still exists. We need it for rematerialization.
//
// Even when the value can't be rematerialized, we still want to determine if
// the value has already been spilled, or we may want to hoist the spill from a
// loop.
bool InlineSpiller::isSibling(unsigned Reg) {
return TargetRegisterInfo::isVirtualRegister(Reg) &&
VRM.getOriginal(Reg) == Original;
}
#ifndef NDEBUG
static raw_ostream &operator<<(raw_ostream &OS,
const InlineSpiller::SibValueInfo &SVI) {
OS << "spill " << PrintReg(SVI.SpillReg) << ':'
<< SVI.SpillVNI->id << '@' << SVI.SpillVNI->def;
if (SVI.SpillMBB)
OS << " in BB#" << SVI.SpillMBB->getNumber();
if (SVI.AllDefsAreReloads)
OS << " all-reloads";
if (SVI.DefByOrigPHI)
OS << " orig-phi";
if (SVI.KillsSource)
OS << " kill";
OS << " deps[";
for (VNInfo *Dep : SVI.Deps)
OS << ' ' << Dep->id << '@' << Dep->def;
OS << " ]";
if (SVI.DefMI)
OS << " def: " << *SVI.DefMI;
else
OS << '\n';
return OS;
}
#endif
/// propagateSiblingValue - Propagate the value in SVI to dependents if it is
/// known. Otherwise remember the dependency for later.
///
/// @param SVIIter SibValues entry to propagate.
/// @param VNI Dependent value, or NULL to propagate to all saved dependents.
void InlineSpiller::propagateSiblingValue(SibValueMap::iterator SVIIter,
VNInfo *VNI) {
SibValueMap::value_type *SVI = &*SVIIter;
// When VNI is non-NULL, add it to SVI's deps, and only propagate to that.
TinyPtrVector<VNInfo*> FirstDeps;
if (VNI) {
FirstDeps.push_back(VNI);
SVI->second.Deps.push_back(VNI);
}
// Has the value been completely determined yet? If not, defer propagation.
if (!SVI->second.hasDef())
return;
// Work list of values to propagate.
SmallSetVector<SibValueMap::value_type *, 8> WorkList;
WorkList.insert(SVI);
do {
SVI = WorkList.pop_back_val();
TinyPtrVector<VNInfo*> *Deps = VNI ? &FirstDeps : &SVI->second.Deps;
VNI = nullptr;
SibValueInfo &SV = SVI->second;
if (!SV.SpillMBB)
SV.SpillMBB = LIS.getMBBFromIndex(SV.SpillVNI->def);
DEBUG(dbgs() << " prop to " << Deps->size() << ": "
<< SVI->first->id << '@' << SVI->first->def << ":\t" << SV);
assert(SV.hasDef() && "Propagating undefined value");
// Should this value be propagated as a preferred spill candidate? We don't
// propagate values of registers that are about to spill.
bool PropSpill = !DisableHoisting && !isRegToSpill(SV.SpillReg);
unsigned SpillDepth = ~0u;
for (VNInfo *Dep : *Deps) {
SibValueMap::iterator DepSVI = SibValues.find(Dep);
assert(DepSVI != SibValues.end() && "Dependent value not in SibValues");
SibValueInfo &DepSV = DepSVI->second;
if (!DepSV.SpillMBB)
DepSV.SpillMBB = LIS.getMBBFromIndex(DepSV.SpillVNI->def);
bool Changed = false;
// Propagate defining instruction.
if (!DepSV.hasDef()) {
Changed = true;
DepSV.DefMI = SV.DefMI;
DepSV.DefByOrigPHI = SV.DefByOrigPHI;
}
// Propagate AllDefsAreReloads. For PHI values, this computes an AND of
// all predecessors.
if (!SV.AllDefsAreReloads && DepSV.AllDefsAreReloads) {
Changed = true;
DepSV.AllDefsAreReloads = false;
}
// Propagate best spill value.
if (PropSpill && SV.SpillVNI != DepSV.SpillVNI) {
if (SV.SpillMBB == DepSV.SpillMBB) {
// DepSV is in the same block. Hoist when dominated.
if (DepSV.KillsSource && SV.SpillVNI->def < DepSV.SpillVNI->def) {
// This is an alternative def earlier in the same MBB.
// Hoist the spill as far as possible in SpillMBB. This can ease
// register pressure:
//
// x = def
// y = use x
// s = copy x
//
// Hoisting the spill of s to immediately after the def removes the
// interference between x and y:
//
// x = def
// spill x
// y = use x<kill>
//
// This hoist only helps when the DepSV copy kills its source.
Changed = true;
DepSV.SpillReg = SV.SpillReg;
DepSV.SpillVNI = SV.SpillVNI;
DepSV.SpillMBB = SV.SpillMBB;
}
} else {
// DepSV is in a different block.
if (SpillDepth == ~0u)
SpillDepth = Loops.getLoopDepth(SV.SpillMBB);
// Also hoist spills to blocks with smaller loop depth, but make sure
// that the new value dominates. Non-phi dependents are always
// dominated, phis need checking.
const BranchProbability MarginProb(4, 5); // 80%
// Hoist a spill to outer loop if there are multiple dependents (it
// can be beneficial if more than one dependents are hoisted) or
// if DepSV (the hoisting source) is hotter than SV (the hoisting
// destination) (we add a 80% margin to bias a little towards
// loop depth).
bool HoistCondition =
(MBFI.getBlockFreq(DepSV.SpillMBB) >=
(MBFI.getBlockFreq(SV.SpillMBB) * MarginProb)) ||
Deps->size() > 1;
if ((Loops.getLoopDepth(DepSV.SpillMBB) > SpillDepth) &&
HoistCondition &&
(!DepSVI->first->isPHIDef() ||
MDT.dominates(SV.SpillMBB, DepSV.SpillMBB))) {
Changed = true;
DepSV.SpillReg = SV.SpillReg;
DepSV.SpillVNI = SV.SpillVNI;
DepSV.SpillMBB = SV.SpillMBB;
}
}
}
if (!Changed)
continue;
// Something changed in DepSVI. Propagate to dependents.
WorkList.insert(&*DepSVI);
DEBUG(dbgs() << " update " << DepSVI->first->id << '@'
<< DepSVI->first->def << " to:\t" << DepSV);
}
} while (!WorkList.empty());
}
/// traceSiblingValue - Trace a value that is about to be spilled back to the
/// real defining instructions by looking through sibling copies. Always stay
/// within the range of OrigVNI so the registers are known to carry the same
/// value.
///
/// Determine if the value is defined by all reloads, so spilling isn't
/// necessary - the value is already in the stack slot.
///
/// Return a defining instruction that may be a candidate for rematerialization.
///
MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
VNInfo *OrigVNI) {
// Check if a cached value already exists.
SibValueMap::iterator SVI;
bool Inserted;
std::tie(SVI, Inserted) =
SibValues.insert(std::make_pair(UseVNI, SibValueInfo(UseReg, UseVNI)));
if (!Inserted) {
DEBUG(dbgs() << "Cached value " << PrintReg(UseReg) << ':'
<< UseVNI->id << '@' << UseVNI->def << ' ' << SVI->second);
return SVI->second.DefMI;
}
DEBUG(dbgs() << "Tracing value " << PrintReg(UseReg) << ':'
<< UseVNI->id << '@' << UseVNI->def << '\n');
// List of (Reg, VNI) that have been inserted into SibValues, but need to be
// processed.
SmallVector<std::pair<unsigned, VNInfo*>, 8> WorkList;
WorkList.push_back(std::make_pair(UseReg, UseVNI));
LiveInterval &OrigLI = LIS.getInterval(Original);
do {
unsigned Reg;
VNInfo *VNI;
std::tie(Reg, VNI) = WorkList.pop_back_val();
DEBUG(dbgs() << " " << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def
<< ":\t");
// First check if this value has already been computed.
SVI = SibValues.find(VNI);
assert(SVI != SibValues.end() && "Missing SibValues entry");
// Trace through PHI-defs created by live range splitting.
if (VNI->isPHIDef()) {
// Stop at original PHIs. We don't know the value at the
// predecessors. Look up the VNInfo for the current definition
// in OrigLI, to properly determine whether or not this phi was
// added by splitting.
if (VNI->def == OrigLI.getVNInfoAt(VNI->def)->def) {
DEBUG(dbgs() << "orig phi value\n");
SVI->second.DefByOrigPHI = true;
SVI->second.AllDefsAreReloads = false;
propagateSiblingValue(SVI);
continue;
}
// This is a PHI inserted by live range splitting. We could trace the
// live-out value from predecessor blocks, but that search can be very
// expensive if there are many predecessors and many more PHIs as
// generated by tail-dup when it sees an indirectbr. Instead, look at
// all the non-PHI defs that have the same value as OrigVNI. They must
// jointly dominate VNI->def. This is not optimal since VNI may actually
// be jointly dominated by a smaller subset of defs, so there is a change
// we will miss a AllDefsAreReloads optimization.
// Separate all values dominated by OrigVNI into PHIs and non-PHIs.
SmallVector<VNInfo*, 8> PHIs, NonPHIs;
LiveInterval &LI = LIS.getInterval(Reg);
for (LiveInterval::vni_iterator VI = LI.vni_begin(), VE = LI.vni_end();
VI != VE; ++VI) {
VNInfo *VNI2 = *VI;
if (VNI2->isUnused())
continue;
if (!OrigLI.containsOneValue() &&
OrigLI.getVNInfoAt(VNI2->def) != OrigVNI)
continue;
if (VNI2->isPHIDef() && VNI2->def != OrigVNI->def)
PHIs.push_back(VNI2);
else
NonPHIs.push_back(VNI2);
}
DEBUG(dbgs() << "split phi value, checking " << PHIs.size()
<< " phi-defs, and " << NonPHIs.size()
<< " non-phi/orig defs\n");
// Create entries for all the PHIs. Don't add them to the worklist, we
// are processing all of them in one go here.
for (VNInfo *PHI : PHIs)
SibValues.insert(std::make_pair(PHI, SibValueInfo(Reg, PHI)));
// Add every PHI as a dependent of all the non-PHIs.
for (VNInfo *NonPHI : NonPHIs) {
// Known value? Try an insertion.
std::tie(SVI, Inserted) =
SibValues.insert(std::make_pair(NonPHI, SibValueInfo(Reg, NonPHI)));
// Add all the PHIs as dependents of NonPHI.
SVI->second.Deps.insert(SVI->second.Deps.end(), PHIs.begin(),
PHIs.end());
// This is the first time we see NonPHI, add it to the worklist.
if (Inserted)
WorkList.push_back(std::make_pair(Reg, NonPHI));
else
// Propagate to all inserted PHIs, not just VNI.
propagateSiblingValue(SVI);
}
// Next work list item.
continue;
}
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
assert(MI && "Missing def");
// Trace through sibling copies.
if (unsigned SrcReg = isFullCopyOf(MI, Reg)) {
if (isSibling(SrcReg)) {
LiveInterval &SrcLI = LIS.getInterval(SrcReg);
LiveQueryResult SrcQ = SrcLI.Query(VNI->def);
assert(SrcQ.valueIn() && "Copy from non-existing value");
// Check if this COPY kills its source.
SVI->second.KillsSource = SrcQ.isKill();
VNInfo *SrcVNI = SrcQ.valueIn();
DEBUG(dbgs() << "copy of " << PrintReg(SrcReg) << ':'
<< SrcVNI->id << '@' << SrcVNI->def
<< " kill=" << unsigned(SVI->second.KillsSource) << '\n');
// Known sibling source value? Try an insertion.
std::tie(SVI, Inserted) = SibValues.insert(
std::make_pair(SrcVNI, SibValueInfo(SrcReg, SrcVNI)));
// This is the first time we see Src, add it to the worklist.
if (Inserted)
WorkList.push_back(std::make_pair(SrcReg, SrcVNI));
propagateSiblingValue(SVI, VNI);
// Next work list item.
continue;
}
}
// Track reachable reloads.
SVI->second.DefMI = MI;
SVI->second.SpillMBB = MI->getParent();
int FI;
if (Reg == TII.isLoadFromStackSlot(MI, FI) && FI == StackSlot) {
DEBUG(dbgs() << "reload\n");
propagateSiblingValue(SVI);
// Next work list item.
continue;
}
// Potential remat candidate.
DEBUG(dbgs() << "def " << *MI);
SVI->second.AllDefsAreReloads = false;
propagateSiblingValue(SVI);
} while (!WorkList.empty());
// Look up the value we were looking for. We already did this lookup at the
// top of the function, but SibValues may have been invalidated.
SVI = SibValues.find(UseVNI);
assert(SVI != SibValues.end() && "Didn't compute requested info");
DEBUG(dbgs() << " traced to:\t" << SVI->second);
return SVI->second.DefMI;
}
/// analyzeSiblingValues - Trace values defined by sibling copies back to
/// something that isn't a sibling copy.
///
/// Keep track of values that may be rematerializable.
void InlineSpiller::analyzeSiblingValues() {
SibValues.clear();
// No siblings at all?
if (Edit->getReg() == Original)
return;
LiveInterval &OrigLI = LIS.getInterval(Original);
for (unsigned Reg : RegsToSpill) {
LiveInterval &LI = LIS.getInterval(Reg);
for (LiveInterval::const_vni_iterator VI = LI.vni_begin(),
VE = LI.vni_end(); VI != VE; ++VI) {
VNInfo *VNI = *VI;
if (VNI->isUnused())
continue;
MachineInstr *DefMI = nullptr;
if (!VNI->isPHIDef()) {
DefMI = LIS.getInstructionFromIndex(VNI->def);
assert(DefMI && "No defining instruction");
}
// Check possible sibling copies.
if (VNI->isPHIDef() || DefMI->isCopy()) {
VNInfo *OrigVNI = OrigLI.getVNInfoAt(VNI->def);
assert(OrigVNI && "Def outside original live range");
if (OrigVNI->def != VNI->def)
DefMI = traceSiblingValue(Reg, VNI, OrigVNI);
}
if (DefMI && Edit->checkRematerializable(VNI, DefMI, AA)) {
DEBUG(dbgs() << "Value " << PrintReg(Reg) << ':' << VNI->id << '@'
<< VNI->def << " may remat from " << *DefMI);
}
}
}
}
/// hoistSpill - Given a sibling copy that defines a value to be spilled, insert
/// a spill at a better location.
bool InlineSpiller::hoistSpill(LiveInterval &SpillLI, MachineInstr &CopyMI) {
SlotIndex Idx = LIS.getInstructionIndex(CopyMI);
VNInfo *VNI = SpillLI.getVNInfoAt(Idx.getRegSlot());
assert(VNI && VNI->def == Idx.getRegSlot() && "Not defined by copy");
SibValueMap::iterator I = SibValues.find(VNI);
if (I == SibValues.end())
return false;
const SibValueInfo &SVI = I->second;
// Let the normal folding code deal with the boring case.
if (!SVI.AllDefsAreReloads && SVI.SpillVNI == VNI)
return false;
// SpillReg may have been deleted by remat and DCE.
if (!LIS.hasInterval(SVI.SpillReg)) {
DEBUG(dbgs() << "Stale interval: " << PrintReg(SVI.SpillReg) << '\n');
SibValues.erase(I);
return false;
}
LiveInterval &SibLI = LIS.getInterval(SVI.SpillReg);
if (!SibLI.containsValue(SVI.SpillVNI)) {
DEBUG(dbgs() << "Stale value: " << PrintReg(SVI.SpillReg) << '\n');
SibValues.erase(I);
return false;
}
// Conservatively extend the stack slot range to the range of the original
// value. We may be able to do better with stack slot coloring by being more
// careful here.
assert(StackInt && "No stack slot assigned yet.");
LiveInterval &OrigLI = LIS.getInterval(Original);
VNInfo *OrigVNI = OrigLI.getVNInfoAt(Idx);
StackInt->MergeValueInAsValue(OrigLI, OrigVNI, StackInt->getValNumInfo(0));
DEBUG(dbgs() << "\tmerged orig valno " << OrigVNI->id << ": "
<< *StackInt << '\n');
// Already spilled everywhere.
if (SVI.AllDefsAreReloads) {
DEBUG(dbgs() << "\tno spill needed: " << SVI);
++NumOmitReloadSpill;
return true;
}
// We are going to spill SVI.SpillVNI immediately after its def, so clear out
// any later spills of the same value.
eliminateRedundantSpills(SibLI, SVI.SpillVNI);
MachineBasicBlock *MBB = LIS.getMBBFromIndex(SVI.SpillVNI->def);
MachineBasicBlock::iterator MII;
if (SVI.SpillVNI->isPHIDef())
MII = MBB->SkipPHIsAndLabels(MBB->begin());
else {
MachineInstr *DefMI = LIS.getInstructionFromIndex(SVI.SpillVNI->def);
assert(DefMI && "Defining instruction disappeared");
MII = DefMI;
++MII;
}
// Insert spill without kill flag immediately after def.
TII.storeRegToStackSlot(*MBB, MII, SVI.SpillReg, false, StackSlot,
MRI.getRegClass(SVI.SpillReg), &TRI);
--MII; // Point to store instruction.
LIS.InsertMachineInstrInMaps(*MII);
DEBUG(dbgs() << "\thoisted: " << SVI.SpillVNI->def << '\t' << *MII);
++NumSpills;
++NumHoists;
return true;
}
/// eliminateRedundantSpills - SLI:VNI is known to be on the stack. Remove any
/// redundant spills of this value in SLI.reg and sibling copies.
void InlineSpiller::eliminateRedundantSpills(LiveInterval &SLI, VNInfo *VNI) {
assert(VNI && "Missing value");
SmallVector<std::pair<LiveInterval*, VNInfo*>, 8> WorkList;
WorkList.push_back(std::make_pair(&SLI, VNI));
assert(StackInt && "No stack slot assigned yet.");
do {
LiveInterval *LI;
std::tie(LI, VNI) = WorkList.pop_back_val();
unsigned Reg = LI->reg;
DEBUG(dbgs() << "Checking redundant spills for "
<< VNI->id << '@' << VNI->def << " in " << *LI << '\n');
// Regs to spill are taken care of.
if (isRegToSpill(Reg))
continue;
// Add all of VNI's live range to StackInt.
StackInt->MergeValueInAsValue(*LI, VNI, StackInt->getValNumInfo(0));
DEBUG(dbgs() << "Merged to stack int: " << *StackInt << '\n');
// Find all spills and copies of VNI.
for (MachineRegisterInfo::use_instr_nodbg_iterator
UI = MRI.use_instr_nodbg_begin(Reg), E = MRI.use_instr_nodbg_end();
UI != E; ) {
MachineInstr *MI = &*(UI++);
if (!MI->isCopy() && !MI->mayStore())
continue;
SlotIndex Idx = LIS.getInstructionIndex(*MI);
if (LI->getVNInfoAt(Idx) != VNI)
continue;
// Follow sibling copies down the dominator tree.
if (unsigned DstReg = isFullCopyOf(MI, Reg)) {
if (isSibling(DstReg)) {
LiveInterval &DstLI = LIS.getInterval(DstReg);
VNInfo *DstVNI = DstLI.getVNInfoAt(Idx.getRegSlot());
assert(DstVNI && "Missing defined value");
assert(DstVNI->def == Idx.getRegSlot() && "Wrong copy def slot");
WorkList.push_back(std::make_pair(&DstLI, DstVNI));
}
continue;
}
// Erase spills.
int FI;
if (Reg == TII.isStoreToStackSlot(MI, FI) && FI == StackSlot) {
DEBUG(dbgs() << "Redundant spill " << Idx << '\t' << *MI);
// eliminateDeadDefs won't normally remove stores, so switch opcode.
MI->setDesc(TII.get(TargetOpcode::KILL));
DeadDefs.push_back(MI);
++NumSpillsRemoved;
--NumSpills;
}
}
} while (!WorkList.empty());
}
//===----------------------------------------------------------------------===//
// Rematerialization
//===----------------------------------------------------------------------===//
/// markValueUsed - Remember that VNI failed to rematerialize, so its defining
/// instruction cannot be eliminated. See through snippet copies
void InlineSpiller::markValueUsed(LiveInterval *LI, VNInfo *VNI) {
SmallVector<std::pair<LiveInterval*, VNInfo*>, 8> WorkList;
WorkList.push_back(std::make_pair(LI, VNI));
do {
std::tie(LI, VNI) = WorkList.pop_back_val();
if (!UsedValues.insert(VNI).second)
continue;
if (VNI->isPHIDef()) {
MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
for (MachineBasicBlock *P : MBB->predecessors()) {
VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(P));
if (PVNI)
WorkList.push_back(std::make_pair(LI, PVNI));
}
continue;
}
// Follow snippet copies.
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
if (!SnippetCopies.count(MI))
continue;
LiveInterval &SnipLI = LIS.getInterval(MI->getOperand(1).getReg());
assert(isRegToSpill(SnipLI.reg) && "Unexpected register in copy");
VNInfo *SnipVNI = SnipLI.getVNInfoAt(VNI->def.getRegSlot(true));
assert(SnipVNI && "Snippet undefined before copy");
WorkList.push_back(std::make_pair(&SnipLI, SnipVNI));
} while (!WorkList.empty());
}
/// reMaterializeFor - Attempt to rematerialize before MI instead of reloading.
bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg, MachineInstr &MI) {
// Analyze instruction
SmallVector<std::pair<MachineInstr *, unsigned>, 8> Ops;
MIBundleOperands::VirtRegInfo RI =
MIBundleOperands(MI).analyzeVirtReg(VirtReg.reg, &Ops);
if (!RI.Reads)
return false;
SlotIndex UseIdx = LIS.getInstructionIndex(MI).getRegSlot(true);
VNInfo *ParentVNI = VirtReg.getVNInfoAt(UseIdx.getBaseIndex());
if (!ParentVNI) {
DEBUG(dbgs() << "\tadding <undef> flags: ");
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (MO.isReg() && MO.isUse() && MO.getReg() == VirtReg.reg)
MO.setIsUndef();
}
DEBUG(dbgs() << UseIdx << '\t' << MI);
return true;
}
if (SnippetCopies.count(&MI))
return false;
// Use an OrigVNI from traceSiblingValue when ParentVNI is a sibling copy.
LiveRangeEdit::Remat RM(ParentVNI);
SibValueMap::const_iterator SibI = SibValues.find(ParentVNI);
if (SibI != SibValues.end())
RM.OrigMI = SibI->second.DefMI;
if (!Edit->canRematerializeAt(RM, UseIdx, false)) {
markValueUsed(&VirtReg, ParentVNI);
DEBUG(dbgs() << "\tcannot remat for " << UseIdx << '\t' << MI);
return false;
}
// If the instruction also writes VirtReg.reg, it had better not require the
// same register for uses and defs.
if (RI.Tied) {
markValueUsed(&VirtReg, ParentVNI);
DEBUG(dbgs() << "\tcannot remat tied reg: " << UseIdx << '\t' << MI);
return false;
}
// Before rematerializing into a register for a single instruction, try to
// fold a load into the instruction. That avoids allocating a new register.
if (RM.OrigMI->canFoldAsLoad() &&
foldMemoryOperand(Ops, RM.OrigMI)) {
Edit->markRematerialized(RM.ParentVNI);
++NumFoldedLoads;
return true;
}
// Alocate a new register for the remat.
unsigned NewVReg = Edit->createFrom(Original);
// Finally we can rematerialize OrigMI before MI.
SlotIndex DefIdx =
Edit->rematerializeAt(*MI.getParent(), MI, NewVReg, RM, TRI);
(void)DefIdx;
DEBUG(dbgs() << "\tremat: " << DefIdx << '\t'
<< *LIS.getInstructionFromIndex(DefIdx));
// Replace operands
for (const auto &OpPair : Ops) {
MachineOperand &MO = OpPair.first->getOperand(OpPair.second);
if (MO.isReg() && MO.isUse() && MO.getReg() == VirtReg.reg) {
MO.setReg(NewVReg);
MO.setIsKill();
}
}
DEBUG(dbgs() << "\t " << UseIdx << '\t' << MI << '\n');
++NumRemats;
return true;
}
/// reMaterializeAll - Try to rematerialize as many uses as possible,
/// and trim the live ranges after.
void InlineSpiller::reMaterializeAll() {
// analyzeSiblingValues has already tested all relevant defining instructions.
if (!Edit->anyRematerializable(AA))
return;
UsedValues.clear();
// Try to remat before all uses of snippets.
bool anyRemat = false;
for (unsigned Reg : RegsToSpill) {
LiveInterval &LI = LIS.getInterval(Reg);
for (MachineRegisterInfo::reg_bundle_iterator
RegI = MRI.reg_bundle_begin(Reg), E = MRI.reg_bundle_end();
RegI != E; ) {
MachineInstr &MI = *RegI++;
// Debug values are not allowed to affect codegen.
if (MI.isDebugValue())
continue;
anyRemat |= reMaterializeFor(LI, MI);
}
}
if (!anyRemat)
return;
// Remove any values that were completely rematted.
for (unsigned Reg : RegsToSpill) {
LiveInterval &LI = LIS.getInterval(Reg);
for (LiveInterval::vni_iterator I = LI.vni_begin(), E = LI.vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused() || VNI->isPHIDef() || UsedValues.count(VNI))
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
MI->addRegisterDead(Reg, &TRI);
if (!MI->allDefsAreDead())
continue;
DEBUG(dbgs() << "All defs dead: " << *MI);
DeadDefs.push_back(MI);
}
}
// Eliminate dead code after remat. Note that some snippet copies may be
// deleted here.
if (DeadDefs.empty())
return;
DEBUG(dbgs() << "Remat created " << DeadDefs.size() << " dead defs.\n");
Edit->eliminateDeadDefs(DeadDefs, RegsToSpill);
// LiveRangeEdit::eliminateDeadDef is used to remove dead define instructions
// after rematerialization. To remove a VNI for a vreg from its LiveInterval,
// LiveIntervals::removeVRegDefAt is used. However, after non-PHI VNIs are all
// removed, PHI VNI are still left in the LiveInterval.
// So to get rid of unused reg, we need to check whether it has non-dbg
// reference instead of whether it has non-empty interval.
unsigned ResultPos = 0;
for (unsigned Reg : RegsToSpill) {
if (MRI.reg_nodbg_empty(Reg)) {
Edit->eraseVirtReg(Reg);
continue;
}
assert((LIS.hasInterval(Reg) && !LIS.getInterval(Reg).empty()) &&
"Reg with empty interval has reference");
RegsToSpill[ResultPos++] = Reg;
}
RegsToSpill.erase(RegsToSpill.begin() + ResultPos, RegsToSpill.end());
DEBUG(dbgs() << RegsToSpill.size() << " registers to spill after remat.\n");
}
//===----------------------------------------------------------------------===//
// Spilling
//===----------------------------------------------------------------------===//
/// If MI is a load or store of StackSlot, it can be removed.
bool InlineSpiller::coalesceStackAccess(MachineInstr *MI, unsigned Reg) {
int FI = 0;
unsigned InstrReg = TII.isLoadFromStackSlot(MI, FI);
bool IsLoad = InstrReg;
if (!IsLoad)
InstrReg = TII.isStoreToStackSlot(MI, FI);
// We have a stack access. Is it the right register and slot?
if (InstrReg != Reg || FI != StackSlot)
return false;
DEBUG(dbgs() << "Coalescing stack access: " << *MI);
LIS.RemoveMachineInstrFromMaps(*MI);
MI->eraseFromParent();
if (IsLoad) {
++NumReloadsRemoved;
--NumReloads;
} else {
++NumSpillsRemoved;
--NumSpills;
}
return true;
}
#if !defined(NDEBUG)
// Dump the range of instructions from B to E with their slot indexes.
static void dumpMachineInstrRangeWithSlotIndex(MachineBasicBlock::iterator B,
MachineBasicBlock::iterator E,
LiveIntervals const &LIS,
const char *const header,
unsigned VReg =0) {
char NextLine = '\n';
char SlotIndent = '\t';
if (std::next(B) == E) {
NextLine = ' ';
SlotIndent = ' ';
}
dbgs() << '\t' << header << ": " << NextLine;
for (MachineBasicBlock::iterator I = B; I != E; ++I) {
SlotIndex Idx = LIS.getInstructionIndex(*I).getRegSlot();
// If a register was passed in and this instruction has it as a
// destination that is marked as an early clobber, print the
// early-clobber slot index.
if (VReg) {
MachineOperand *MO = I->findRegisterDefOperand(VReg);
if (MO && MO->isEarlyClobber())
Idx = Idx.getRegSlot(true);
}
dbgs() << SlotIndent << Idx << '\t' << *I;
}
}
#endif
/// foldMemoryOperand - Try folding stack slot references in Ops into their
/// instructions.
///
/// @param Ops Operand indices from analyzeVirtReg().
/// @param LoadMI Load instruction to use instead of stack slot when non-null.
/// @return True on success.
bool InlineSpiller::
foldMemoryOperand(ArrayRef<std::pair<MachineInstr*, unsigned> > Ops,
MachineInstr *LoadMI) {
if (Ops.empty())
return false;
// Don't attempt folding in bundles.
MachineInstr *MI = Ops.front().first;
if (Ops.back().first != MI || MI->isBundled())
return false;
bool WasCopy = MI->isCopy();
unsigned ImpReg = 0;
bool SpillSubRegs = (MI->getOpcode() == TargetOpcode::STATEPOINT ||
MI->getOpcode() == TargetOpcode::PATCHPOINT ||
MI->getOpcode() == TargetOpcode::STACKMAP);
// TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
// operands.
SmallVector<unsigned, 8> FoldOps;
for (const auto &OpPair : Ops) {
unsigned Idx = OpPair.second;
assert(MI == OpPair.first && "Instruction conflict during operand folding");
MachineOperand &MO = MI->getOperand(Idx);
if (MO.isImplicit()) {
ImpReg = MO.getReg();
continue;
}
// FIXME: Teach targets to deal with subregs.
if (!SpillSubRegs && MO.getSubReg())
return false;
// We cannot fold a load instruction into a def.
if (LoadMI && MO.isDef())
return false;
// Tied use operands should not be passed to foldMemoryOperand.
if (!MI->isRegTiedToDefOperand(Idx))
FoldOps.push_back(Idx);
}
MachineInstrSpan MIS(MI);
MachineInstr *FoldMI =
LoadMI ? TII.foldMemoryOperand(MI, FoldOps, LoadMI)
: TII.foldMemoryOperand(MI, FoldOps, StackSlot);
if (!FoldMI)
return false;
// Remove LIS for any dead defs in the original MI not in FoldMI.
for (MIBundleOperands MO(*MI); MO.isValid(); ++MO) {
if (!MO->isReg())
continue;
unsigned Reg = MO->getReg();
if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg) ||
MRI.isReserved(Reg)) {
continue;
}
// Skip non-Defs, including undef uses and internal reads.
if (MO->isUse())
continue;
MIBundleOperands::PhysRegInfo RI =
MIBundleOperands(*FoldMI).analyzePhysReg(Reg, &TRI);
if (RI.FullyDefined)
continue;
// FoldMI does not define this physreg. Remove the LI segment.
assert(MO->isDead() && "Cannot fold physreg def");
SlotIndex Idx = LIS.getInstructionIndex(*MI).getRegSlot();
LIS.removePhysRegDefAt(Reg, Idx);
}
LIS.ReplaceMachineInstrInMaps(*MI, *FoldMI);
MI->eraseFromParent();
// Insert any new instructions other than FoldMI into the LIS maps.
assert(!MIS.empty() && "Unexpected empty span of instructions!");
for (MachineInstr &MI : MIS)
if (&MI != FoldMI)
LIS.InsertMachineInstrInMaps(MI);
// TII.foldMemoryOperand may have left some implicit operands on the
// instruction. Strip them.
if (ImpReg)
for (unsigned i = FoldMI->getNumOperands(); i; --i) {
MachineOperand &MO = FoldMI->getOperand(i - 1);
if (!MO.isReg() || !MO.isImplicit())
break;
if (MO.getReg() == ImpReg)
FoldMI->RemoveOperand(i - 1);
}
DEBUG(dumpMachineInstrRangeWithSlotIndex(MIS.begin(), MIS.end(), LIS,
"folded"));
if (!WasCopy)
++NumFolded;
else if (Ops.front().second == 0)
++NumSpills;
else
++NumReloads;
return true;
}
void InlineSpiller::insertReload(unsigned NewVReg,
SlotIndex Idx,
MachineBasicBlock::iterator MI) {
MachineBasicBlock &MBB = *MI->getParent();
MachineInstrSpan MIS(MI);
TII.loadRegFromStackSlot(MBB, MI, NewVReg, StackSlot,
MRI.getRegClass(NewVReg), &TRI);
LIS.InsertMachineInstrRangeInMaps(MIS.begin(), MI);
DEBUG(dumpMachineInstrRangeWithSlotIndex(MIS.begin(), MI, LIS, "reload",
NewVReg));
++NumReloads;
}
/// insertSpill - Insert a spill of NewVReg after MI.
void InlineSpiller::insertSpill(unsigned NewVReg, bool isKill,
MachineBasicBlock::iterator MI) {
MachineBasicBlock &MBB = *MI->getParent();
MachineInstrSpan MIS(MI);
TII.storeRegToStackSlot(MBB, std::next(MI), NewVReg, isKill, StackSlot,
MRI.getRegClass(NewVReg), &TRI);
LIS.InsertMachineInstrRangeInMaps(std::next(MI), MIS.end());
DEBUG(dumpMachineInstrRangeWithSlotIndex(std::next(MI), MIS.end(), LIS,
"spill"));
++NumSpills;
}
/// spillAroundUses - insert spill code around each use of Reg.
void InlineSpiller::spillAroundUses(unsigned Reg) {
DEBUG(dbgs() << "spillAroundUses " << PrintReg(Reg) << '\n');
LiveInterval &OldLI = LIS.getInterval(Reg);
// Iterate over instructions using Reg.
for (MachineRegisterInfo::reg_bundle_iterator
RegI = MRI.reg_bundle_begin(Reg), E = MRI.reg_bundle_end();
RegI != E; ) {
MachineInstr *MI = &*(RegI++);
// Debug values are not allowed to affect codegen.
if (MI->isDebugValue()) {
// Modify DBG_VALUE now that the value is in a spill slot.
bool IsIndirect = MI->isIndirectDebugValue();
uint64_t Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
const MDNode *Var = MI->getDebugVariable();
const MDNode *Expr = MI->getDebugExpression();
DebugLoc DL = MI->getDebugLoc();
DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
MachineBasicBlock *MBB = MI->getParent();
assert(cast<DILocalVariable>(Var)->isValidLocationForIntrinsic(DL) &&
"Expected inlined-at fields to agree");
BuildMI(*MBB, MBB->erase(MI), DL, TII.get(TargetOpcode::DBG_VALUE))
.addFrameIndex(StackSlot)
.addImm(Offset)
.addMetadata(Var)
.addMetadata(Expr);
continue;
}
// Ignore copies to/from snippets. We'll delete them.
if (SnippetCopies.count(MI))
continue;
// Stack slot accesses may coalesce away.
if (coalesceStackAccess(MI, Reg))
continue;
// Analyze instruction.
SmallVector<std::pair<MachineInstr*, unsigned>, 8> Ops;
MIBundleOperands::VirtRegInfo RI =
MIBundleOperands(*MI).analyzeVirtReg(Reg, &Ops);
// Find the slot index where this instruction reads and writes OldLI.
// This is usually the def slot, except for tied early clobbers.
SlotIndex Idx = LIS.getInstructionIndex(*MI).getRegSlot();
if (VNInfo *VNI = OldLI.getVNInfoAt(Idx.getRegSlot(true)))
if (SlotIndex::isSameInstr(Idx, VNI->def))
Idx = VNI->def;
// Check for a sibling copy.
unsigned SibReg = isFullCopyOf(MI, Reg);
if (SibReg && isSibling(SibReg)) {
// This may actually be a copy between snippets.
if (isRegToSpill(SibReg)) {
DEBUG(dbgs() << "Found new snippet copy: " << *MI);
SnippetCopies.insert(MI);
continue;
}
if (RI.Writes) {
// Hoist the spill of a sib-reg copy.
if (hoistSpill(OldLI, *MI)) {
// This COPY is now dead, the value is already in the stack slot.
MI->getOperand(0).setIsDead();
DeadDefs.push_back(MI);
continue;
}
} else {
// This is a reload for a sib-reg copy. Drop spills downstream.
LiveInterval &SibLI = LIS.getInterval(SibReg);
eliminateRedundantSpills(SibLI, SibLI.getVNInfoAt(Idx));
// The COPY will fold to a reload below.
}
}
// Attempt to fold memory ops.
if (foldMemoryOperand(Ops))
continue;
// Create a new virtual register for spill/fill.
// FIXME: Infer regclass from instruction alone.
unsigned NewVReg = Edit->createFrom(Reg);
if (RI.Reads)
insertReload(NewVReg, Idx, MI);
// Rewrite instruction operands.
bool hasLiveDef = false;
for (const auto &OpPair : Ops) {
MachineOperand &MO = OpPair.first->getOperand(OpPair.second);
MO.setReg(NewVReg);
if (MO.isUse()) {
if (!OpPair.first->isRegTiedToDefOperand(OpPair.second))
MO.setIsKill();
} else {
if (!MO.isDead())
hasLiveDef = true;
}
}
DEBUG(dbgs() << "\trewrite: " << Idx << '\t' << *MI << '\n');
// FIXME: Use a second vreg if instruction has no tied ops.
if (RI.Writes)
if (hasLiveDef)
insertSpill(NewVReg, true, MI);
}
}
/// spillAll - Spill all registers remaining after rematerialization.
void InlineSpiller::spillAll() {
// Update LiveStacks now that we are committed to spilling.
if (StackSlot == VirtRegMap::NO_STACK_SLOT) {
StackSlot = VRM.assignVirt2StackSlot(Original);
StackInt = &LSS.getOrCreateInterval(StackSlot, MRI.getRegClass(Original));
StackInt->getNextValue(SlotIndex(), LSS.getVNInfoAllocator());
} else
StackInt = &LSS.getInterval(StackSlot);
if (Original != Edit->getReg())
VRM.assignVirt2StackSlot(Edit->getReg(), StackSlot);
assert(StackInt->getNumValNums() == 1 && "Bad stack interval values");
for (unsigned Reg : RegsToSpill)
StackInt->MergeSegmentsInAsValue(LIS.getInterval(Reg),
StackInt->getValNumInfo(0));
DEBUG(dbgs() << "Merged spilled regs: " << *StackInt << '\n');
// Spill around uses of all RegsToSpill.
for (unsigned Reg : RegsToSpill)
spillAroundUses(Reg);
// Hoisted spills may cause dead code.
if (!DeadDefs.empty()) {
DEBUG(dbgs() << "Eliminating " << DeadDefs.size() << " dead defs\n");
Edit->eliminateDeadDefs(DeadDefs, RegsToSpill);
}
// Finally delete the SnippetCopies.
for (unsigned Reg : RegsToSpill) {
for (MachineRegisterInfo::reg_instr_iterator
RI = MRI.reg_instr_begin(Reg), E = MRI.reg_instr_end();
RI != E; ) {
MachineInstr &MI = *(RI++);
assert(SnippetCopies.count(&MI) && "Remaining use wasn't a snippet copy");
// FIXME: Do this with a LiveRangeEdit callback.
LIS.RemoveMachineInstrFromMaps(MI);
MI.eraseFromParent();
}
}
// Delete all spilled registers.
for (unsigned Reg : RegsToSpill)
Edit->eraseVirtReg(Reg);
}
void InlineSpiller::spill(LiveRangeEdit &edit) {
++NumSpilledRanges;
Edit = &edit;
assert(!TargetRegisterInfo::isStackSlot(edit.getReg())
&& "Trying to spill a stack slot.");
// Share a stack slot among all descendants of Original.
Original = VRM.getOriginal(edit.getReg());
StackSlot = VRM.getStackSlot(Original);
StackInt = nullptr;
DEBUG(dbgs() << "Inline spilling "
<< TRI.getRegClassName(MRI.getRegClass(edit.getReg()))
<< ':' << edit.getParent()
<< "\nFrom original " << PrintReg(Original) << '\n');
assert(edit.getParent().isSpillable() &&
"Attempting to spill already spilled value.");
assert(DeadDefs.empty() && "Previous spill didn't remove dead defs");
collectRegsToSpill();
analyzeSiblingValues();
reMaterializeAll();
// Remat may handle everything.
if (!RegsToSpill.empty())
spillAll();
Edit->calculateRegClassAndHint(MF, Loops, MBFI);
}
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