llvm-6502/lib/CodeGen/StackSlotColoring.cpp
2008-09-04 17:05:41 +00:00

266 lines
7.9 KiB
C++

//===-- StackSlotColoring.cpp - Stack slot coloring pass. -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the stack slot coloring pass.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "stackcoloring"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include <vector>
using namespace llvm;
static cl::opt<bool>
DisableSharing("no-stack-slot-sharing",
cl::init(false), cl::Hidden,
cl::desc("Surpress slot sharing during stack coloring"));
STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
namespace {
class VISIBILITY_HIDDEN StackSlotColoring : public MachineFunctionPass {
LiveStacks* LS;
MachineFrameInfo *MFI;
// SSIntervals - Spill slot intervals.
std::vector<LiveInterval*> SSIntervals;
// OrigAlignments - Alignments of stack objects before coloring.
SmallVector<unsigned, 16> OrigAlignments;
// OrigSizes - Sizess of stack objects before coloring.
SmallVector<unsigned, 16> OrigSizes;
// AllColors - If index is set, it's a spill slot, i.e. color.
// FIXME: This assumes PEI locate spill slot with smaller indices
// closest to stack pointer / frame pointer. Therefore, smaller
// index == better color.
BitVector AllColors;
// NextColor - Next "color" that's not yet used.
int NextColor;
// UsedColors - "Colors" that have been assigned.
BitVector UsedColors;
// Assignments - Color to intervals mapping.
SmallVector<SmallVector<LiveInterval*,4>,16> Assignments;
public:
static char ID; // Pass identification
StackSlotColoring() : MachineFunctionPass(&ID), NextColor(-1) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveStacks>();
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual const char* getPassName() const {
return "Stack Slot Coloring";
}
private:
bool InitializeSlots();
bool OverlapWithAssignments(LiveInterval *li, int Color) const;
int ColorSlot(LiveInterval *li);
bool ColorSlots(MachineFunction &MF);
};
} // end anonymous namespace
char StackSlotColoring::ID = 0;
static RegisterPass<StackSlotColoring>
X("stack-slot-coloring", "Stack Slot Coloring");
FunctionPass *llvm::createStackSlotColoringPass() {
return new StackSlotColoring();
}
namespace {
// IntervalSorter - Comparison predicate that sort live intervals by
// their weight.
struct IntervalSorter {
bool operator()(LiveInterval* LHS, LiveInterval* RHS) const {
return LHS->weight > RHS->weight;
}
};
}
/// InitializeSlots - Process all spill stack slot liveintervals and add them
/// to a sorted (by weight) list.
bool StackSlotColoring::InitializeSlots() {
if (LS->getNumIntervals() < 2)
return false;
int LastFI = MFI->getObjectIndexEnd();
OrigAlignments.resize(LastFI);
OrigSizes.resize(LastFI);
AllColors.resize(LastFI);
UsedColors.resize(LastFI);
Assignments.resize(LastFI);
// Gather all spill slots into a list.
for (LiveStacks::iterator i = LS->begin(), e = LS->end(); i != e; ++i) {
LiveInterval &li = i->second;
int FI = li.getStackSlotIndex();
if (MFI->isDeadObjectIndex(FI))
continue;
SSIntervals.push_back(&li);
OrigAlignments[FI] = MFI->getObjectAlignment(FI);
OrigSizes[FI] = MFI->getObjectSize(FI);
AllColors.set(FI);
}
// Sort them by weight.
std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
// Get first "color".
NextColor = AllColors.find_first();
return true;
}
/// OverlapWithAssignments - Return true if LiveInterval overlaps with any
/// LiveIntervals that have already been assigned to the specified color.
bool
StackSlotColoring::OverlapWithAssignments(LiveInterval *li, int Color) const {
const SmallVector<LiveInterval*,4> &OtherLIs = Assignments[Color];
for (unsigned i = 0, e = OtherLIs.size(); i != e; ++i) {
LiveInterval *OtherLI = OtherLIs[i];
if (OtherLI->overlaps(*li))
return true;
}
return false;
}
/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
///
int StackSlotColoring::ColorSlot(LiveInterval *li) {
int Color = -1;
bool Share = false;
if (!DisableSharing) {
// Check if it's possible to reuse any of the used colors.
Color = UsedColors.find_first();
while (Color != -1) {
if (!OverlapWithAssignments(li, Color)) {
Share = true;
++NumEliminated;
break;
}
Color = UsedColors.find_next(Color);
}
}
// Assign it to the first available color (assumed to be the best) if it's
// not possible to share a used color with other objects.
if (!Share) {
assert(NextColor != -1 && "No more spill slots?");
Color = NextColor;
UsedColors.set(Color);
NextColor = AllColors.find_next(NextColor);
}
// Record the assignment.
Assignments[Color].push_back(li);
int FI = li->getStackSlotIndex();
DOUT << "Assigning fi #" << FI << " to fi #" << Color << "\n";
// Change size and alignment of the allocated slot. If there are multiple
// objects sharing the same slot, then make sure the size and alignment
// are large enough for all.
unsigned Align = OrigAlignments[FI];
if (!Share || Align > MFI->getObjectAlignment(Color))
MFI->setObjectAlignment(Color, Align);
int64_t Size = OrigSizes[FI];
if (!Share || Size > MFI->getObjectSize(Color))
MFI->setObjectSize(Color, Size);
return Color;
}
/// Colorslots - Color all spill stack slots and rewrite all frameindex machine
/// operands in the function.
bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
unsigned NumObjs = MFI->getObjectIndexEnd();
std::vector<int> SlotMapping(NumObjs, -1);
bool Changed = false;
for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
LiveInterval *li = SSIntervals[i];
int SS = li->getStackSlotIndex();
int NewSS = ColorSlot(li);
SlotMapping[SS] = NewSS;
Changed |= (SS != NewSS);
}
if (!Changed)
return false;
// Rewrite all MO_FrameIndex operands.
// FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
MBB != E; ++MBB) {
for (MachineBasicBlock::iterator MII = MBB->begin(), EE = MBB->end();
MII != EE; ++MII) {
MachineInstr &MI = *MII;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isFrameIndex())
continue;
int FI = MO.getIndex();
if (FI < 0)
continue;
FI = SlotMapping[FI];
if (FI == -1)
continue;
MO.setIndex(FI);
}
}
}
// Delete unused stack slots.
while (NextColor != -1) {
DOUT << "Removing unused stack object fi #" << NextColor << "\n";
MFI->RemoveStackObject(NextColor);
NextColor = AllColors.find_next(NextColor);
}
return true;
}
bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
DOUT << "********** Stack Slot Coloring **********\n";
MFI = MF.getFrameInfo();
LS = &getAnalysis<LiveStacks>();
bool Changed = false;
if (InitializeSlots())
Changed = ColorSlots(MF);
NextColor = -1;
SSIntervals.clear();
OrigAlignments.clear();
OrigSizes.clear();
AllColors.clear();
UsedColors.clear();
for (unsigned i = 0, e = Assignments.size(); i != e; ++i)
Assignments[i].clear();
Assignments.clear();
return Changed;
}