Add a stack slot coloring pass. Not yet enabled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51934 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/StackSlotColoring.cpp

@@ -0,0 +1,271 @@
+//===-- StackSlotColoring.cpp - Sinking for machine instructions ----------===//
+//
+//                     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/LiveStackAnalysis.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/Passes.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"));
+
+static cl::opt<int>
+DeleteLimit("slot-delete-limit", cl::init(-1), cl::Hidden,
+             cl::desc("Stack coloring slot deletion limit"));
+
+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((intptr_t)&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 &&
+      (DeleteLimit == -1 || (int)NumEliminated < DeleteLimit)) {
+    // 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);
+  SlotMapping.resize(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;
+}