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changing the stack slots on an instruction, to keep them consistent with the actual memory addresses. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60584 91177308-0d34-0410-b5e6-96231b3b80d8
285 lines
8.9 KiB
C++
285 lines
8.9 KiB
C++
//===-- StackSlotColoring.cpp - Stack slot coloring pass. -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the stack slot coloring pass.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "stackcoloring"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/LiveStackAnalysis.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/PseudoSourceValue.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include <vector>
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using namespace llvm;
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static cl::opt<bool>
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DisableSharing("no-stack-slot-sharing",
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cl::init(false), cl::Hidden,
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cl::desc("Surpress slot sharing during stack coloring"));
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STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
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namespace {
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class VISIBILITY_HIDDEN StackSlotColoring : public MachineFunctionPass {
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LiveStacks* LS;
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MachineFrameInfo *MFI;
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// SSIntervals - Spill slot intervals.
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std::vector<LiveInterval*> SSIntervals;
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// OrigAlignments - Alignments of stack objects before coloring.
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SmallVector<unsigned, 16> OrigAlignments;
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// OrigSizes - Sizess of stack objects before coloring.
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SmallVector<unsigned, 16> OrigSizes;
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// AllColors - If index is set, it's a spill slot, i.e. color.
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// FIXME: This assumes PEI locate spill slot with smaller indices
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// closest to stack pointer / frame pointer. Therefore, smaller
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// index == better color.
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BitVector AllColors;
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// NextColor - Next "color" that's not yet used.
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int NextColor;
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// UsedColors - "Colors" that have been assigned.
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BitVector UsedColors;
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// Assignments - Color to intervals mapping.
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SmallVector<SmallVector<LiveInterval*,4>,16> Assignments;
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public:
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static char ID; // Pass identification
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StackSlotColoring() : MachineFunctionPass(&ID), NextColor(-1) {}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<LiveStacks>();
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AU.addPreservedID(MachineLoopInfoID);
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AU.addPreservedID(MachineDominatorsID);
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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virtual bool runOnMachineFunction(MachineFunction &MF);
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virtual const char* getPassName() const {
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return "Stack Slot Coloring";
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}
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private:
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bool InitializeSlots();
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bool OverlapWithAssignments(LiveInterval *li, int Color) const;
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int ColorSlot(LiveInterval *li);
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bool ColorSlots(MachineFunction &MF);
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};
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} // end anonymous namespace
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char StackSlotColoring::ID = 0;
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static RegisterPass<StackSlotColoring>
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X("stack-slot-coloring", "Stack Slot Coloring");
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FunctionPass *llvm::createStackSlotColoringPass() {
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return new StackSlotColoring();
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}
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namespace {
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// IntervalSorter - Comparison predicate that sort live intervals by
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// their weight.
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struct IntervalSorter {
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bool operator()(LiveInterval* LHS, LiveInterval* RHS) const {
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return LHS->weight > RHS->weight;
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}
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};
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}
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/// InitializeSlots - Process all spill stack slot liveintervals and add them
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/// to a sorted (by weight) list.
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bool StackSlotColoring::InitializeSlots() {
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if (LS->getNumIntervals() < 2)
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return false;
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int LastFI = MFI->getObjectIndexEnd();
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OrigAlignments.resize(LastFI);
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OrigSizes.resize(LastFI);
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AllColors.resize(LastFI);
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UsedColors.resize(LastFI);
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Assignments.resize(LastFI);
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// Gather all spill slots into a list.
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for (LiveStacks::iterator i = LS->begin(), e = LS->end(); i != e; ++i) {
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LiveInterval &li = i->second;
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int FI = li.getStackSlotIndex();
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if (MFI->isDeadObjectIndex(FI))
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continue;
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SSIntervals.push_back(&li);
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OrigAlignments[FI] = MFI->getObjectAlignment(FI);
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OrigSizes[FI] = MFI->getObjectSize(FI);
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AllColors.set(FI);
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}
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// Sort them by weight.
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std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
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// Get first "color".
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NextColor = AllColors.find_first();
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return true;
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}
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/// OverlapWithAssignments - Return true if LiveInterval overlaps with any
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/// LiveIntervals that have already been assigned to the specified color.
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bool
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StackSlotColoring::OverlapWithAssignments(LiveInterval *li, int Color) const {
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const SmallVector<LiveInterval*,4> &OtherLIs = Assignments[Color];
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for (unsigned i = 0, e = OtherLIs.size(); i != e; ++i) {
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LiveInterval *OtherLI = OtherLIs[i];
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if (OtherLI->overlaps(*li))
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return true;
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}
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return false;
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}
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/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
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///
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int StackSlotColoring::ColorSlot(LiveInterval *li) {
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int Color = -1;
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bool Share = false;
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if (!DisableSharing) {
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// Check if it's possible to reuse any of the used colors.
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Color = UsedColors.find_first();
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while (Color != -1) {
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if (!OverlapWithAssignments(li, Color)) {
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Share = true;
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++NumEliminated;
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break;
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}
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Color = UsedColors.find_next(Color);
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}
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}
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// Assign it to the first available color (assumed to be the best) if it's
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// not possible to share a used color with other objects.
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if (!Share) {
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assert(NextColor != -1 && "No more spill slots?");
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Color = NextColor;
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UsedColors.set(Color);
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NextColor = AllColors.find_next(NextColor);
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}
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// Record the assignment.
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Assignments[Color].push_back(li);
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int FI = li->getStackSlotIndex();
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DOUT << "Assigning fi#" << FI << " to fi#" << Color << "\n";
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// Change size and alignment of the allocated slot. If there are multiple
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// objects sharing the same slot, then make sure the size and alignment
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// are large enough for all.
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unsigned Align = OrigAlignments[FI];
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if (!Share || Align > MFI->getObjectAlignment(Color))
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MFI->setObjectAlignment(Color, Align);
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int64_t Size = OrigSizes[FI];
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if (!Share || Size > MFI->getObjectSize(Color))
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MFI->setObjectSize(Color, Size);
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return Color;
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}
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/// Colorslots - Color all spill stack slots and rewrite all frameindex machine
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/// operands in the function.
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bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
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unsigned NumObjs = MFI->getObjectIndexEnd();
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std::vector<int> SlotMapping(NumObjs, -1);
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bool Changed = false;
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for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
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LiveInterval *li = SSIntervals[i];
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int SS = li->getStackSlotIndex();
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int NewSS = ColorSlot(li);
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SlotMapping[SS] = NewSS;
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Changed |= (SS != NewSS);
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}
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if (!Changed)
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return false;
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// Rewrite all MO_FrameIndex operands.
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// FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
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for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
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MBB != E; ++MBB) {
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for (MachineBasicBlock::iterator MII = MBB->begin(), EE = MBB->end();
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MII != EE; ++MII) {
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MachineInstr &MI = *MII;
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for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
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MachineOperand &MO = MI.getOperand(i);
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if (!MO.isFI())
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continue;
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int FI = MO.getIndex();
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if (FI < 0)
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continue;
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int NewFI = SlotMapping[FI];
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if (NewFI == -1)
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continue;
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MO.setIndex(NewFI);
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// Update the MachineMemOperand for the new memory location.
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// FIXME: We need a better method of managing these too.
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SmallVector<MachineMemOperand, 2> MMOs(MI.memoperands_begin(),
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MI.memoperands_end());
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MI.clearMemOperands(MF);
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const Value *OldSV = PseudoSourceValue::getFixedStack(FI);
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for (unsigned i = 0, e = MMOs.size(); i != e; ++i) {
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if (MMOs[i].getValue() == OldSV) {
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MachineMemOperand MMO(PseudoSourceValue::getFixedStack(NewFI),
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MMOs[i].getFlags(), MMOs[i].getOffset(),
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MMOs[i].getSize(), MMOs[i].getAlignment());
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MI.addMemOperand(MF, MMO);
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} else
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MI.addMemOperand(MF, MMOs[i]);
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}
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}
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}
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}
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// Delete unused stack slots.
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while (NextColor != -1) {
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DOUT << "Removing unused stack object fi#" << NextColor << "\n";
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MFI->RemoveStackObject(NextColor);
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NextColor = AllColors.find_next(NextColor);
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}
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return true;
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}
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bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
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DOUT << "********** Stack Slot Coloring **********\n";
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MFI = MF.getFrameInfo();
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LS = &getAnalysis<LiveStacks>();
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bool Changed = false;
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if (InitializeSlots())
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Changed = ColorSlots(MF);
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NextColor = -1;
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SSIntervals.clear();
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OrigAlignments.clear();
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OrigSizes.clear();
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AllColors.clear();
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UsedColors.clear();
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for (unsigned i = 0, e = Assignments.size(); i != e; ++i)
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Assignments[i].clear();
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Assignments.clear();
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return Changed;
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}
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