compiler.cpp

/* Copyright (c) 2008-2015, Avian Contributors

   Permission to use, copy, modify, and/or distribute this software
   for any purpose with or without fee is hereby granted, provided
   that the above copyright notice and this permission notice appear
   in all copies.

   There is NO WARRANTY for this software.  See license.txt for
   details. */

#include "avian/target.h"

#include <avian/util/runtime-array.h>

#include <avian/codegen/compiler.h>
#include <avian/codegen/assembler.h>
#include <avian/codegen/architecture.h>
#include <avian/codegen/promise.h>

#include "codegen/compiler/regalloc.h"
#include "codegen/compiler/context.h"
#include "codegen/compiler/resource.h"
#include "codegen/compiler/value.h"
#include "codegen/compiler/site.h"
#include "codegen/compiler/read.h"
#include "codegen/compiler/event.h"
#include "codegen/compiler/promise.h"
#include "codegen/compiler/frame.h"
#include "codegen/compiler/ir.h"

using namespace vm;

namespace avian {
namespace codegen {
namespace compiler {

const bool DebugAppend = false;
const bool DebugCompile = false;
const bool DebugResources = false;
const bool DebugFrame = false;
const bool DebugControl = false;
const bool DebugBuddies = false;

const unsigned StealRegisterReserveCount = 2;

// this should be equal to the largest number of registers used by a
// compare instruction:
const unsigned ResolveRegisterReserveCount = (TargetBytesPerWord == 8 ? 2 : 4);

void apply(Context* c,
           lir::UnaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High);

void apply(Context* c,
           lir::BinaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High,
           unsigned s2Size,
           Site* s2Low,
           Site* s2High);

void apply(Context* c,
           lir::TernaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High,
           unsigned s2Size,
           Site* s2Low,
           Site* s2High,
           unsigned s3Size,
           Site* s3Low,
           Site* s3High);

class ConstantPoolNode {
 public:
  ConstantPoolNode(Promise* promise) : promise(promise), next(0)
  {
  }

  Promise* promise;
  ConstantPoolNode* next;
};

Read* live(Context* c UNUSED, Value* v)
{
  assertT(c, v->buddy->hasBuddy(c, v));

  Value* p = v;
  do {
    if (valid(p->reads)) {
      return p->reads;
    }
    p = p->buddy;
  } while (p != v);

  return 0;
}

unsigned sitesToString(Context* c, Value* v, char* buffer, unsigned size);

void deadWord(Context* c, Value* v)
{
  Value* nextWord = v->nextWord;
  assertT(c, nextWord != v);

  for (SiteIterator it(c, v, true, false); it.hasMore();) {
    Site* s = it.next();

    if (s->registerSize(c) > TargetBytesPerWord) {
      it.remove(c);
      nextWord->addSite(c, s);
    }
  }
}

void deadBuddy(Context* c, Value* v, Read* r UNUSED)
{
  assertT(c, v->buddy != v);
  assertT(c, r);

  if (DebugBuddies) {
    fprintf(stderr, "remove dead buddy %p from", v);
    for (Value* p = v->buddy; p != v; p = p->buddy) {
      fprintf(stderr, " %p", p);
    }
    fprintf(stderr, "\n");
  }

  assertT(c, v->buddy);

  Value* next = v->buddy;
  v->buddy = v;
  Value* p = next;
  while (p->buddy != v)
    p = p->buddy;
  p->buddy = next;

  assertT(c, p->buddy);

  for (SiteIterator it(c, v, false, false); it.hasMore();) {
    Site* s = it.next();
    it.remove(c);

    next->addSite(c, s);
  }
}

void popRead(Context* c, Event* e UNUSED, Value* v)
{
  assertT(c, e == v->reads->event);

  if (DebugReads) {
    fprintf(stderr,
            "pop read %p from %p next %p event %p (%s)\n",
            v->reads,
            v,
            v->reads->next(c),
            e,
            (e ? e->name() : 0));
  }

  v->reads = v->reads->next(c);

  if (not valid(v->reads)) {
    Value* nextWord = v->nextWord;
    if (nextWord != v) {
      if (valid(nextWord->reads)) {
        deadWord(c, v);
      } else {
        deadWord(c, nextWord);
      }
    }

    Read* r = live(c, v);
    if (r) {
      deadBuddy(c, v, r);
    } else {
      v->clearSites(c);
    }
  }
}

void addBuddy(Value* original, Value* buddy)
{
  buddy->buddy = original;
  Value* p = original;
  while (p->buddy != original)
    p = p->buddy;
  p->buddy = buddy;

  if (DebugBuddies) {
    fprintf(stderr, "add buddy %p to", buddy);
    for (Value* p = buddy->buddy; p != buddy; p = p->buddy) {
      fprintf(stderr, " %p", p);
    }
    fprintf(stderr, "\n");
  }
}

void move(Context* c, Value* value, Site* src, Site* dst);

unsigned sitesToString(Context* c, Site* sites, char* buffer, unsigned size)
{
  unsigned total = 0;
  for (Site* s = sites; s; s = s->next) {
    total += s->toString(c, buffer + total, size - total);

    if (s->next) {
      assertT(c, size > total + 2);
      memcpy(buffer + total, ", ", 2);
      total += 2;
    }
  }

  assertT(c, size > total);
  buffer[total] = 0;

  return total;
}

unsigned sitesToString(Context* c, Value* v, char* buffer, unsigned size)
{
  unsigned total = 0;
  Value* p = v;
  do {
    if (total) {
      assertT(c, size > total + 2);
      memcpy(buffer + total, "; ", 2);
      total += 2;
    }

    if (p->sites) {
      total += vm::snprintf(buffer + total, size - total, "%p has ", p);
      total += sitesToString(c, p->sites, buffer + total, size - total);
    } else {
      total += vm::snprintf(buffer + total, size - total, "%p has nothing", p);
    }

    p = p->buddy;
  } while (p != v);

  return total;
}

Site* pickTargetSite(Context* c,
                     Read* read,
                     bool intersectRead = false,
                     unsigned registerReserveCount = 0,
                     CostCalculator* costCalculator = 0)
{
  Target target(
      pickTarget(c, read, intersectRead, registerReserveCount, costCalculator));

  expect(c, target.cost < Target::Impossible);

  if (target.type == lir::Operand::Type::Memory) {
    return frameSite(c, target.index);
  } else {
    return registerSite(c, Register(target.index));
  }
}

bool acceptMatch(Context* c, Site* s, Read*, const SiteMask& mask)
{
  return s->match(c, mask);
}

Site* pickSourceSite(Context* c,
                     Read* read,
                     Site* target = 0,
                     unsigned* cost = 0,
                     SiteMask* extraMask = 0,
                     bool intersectRead = true,
                     bool includeBuddies = true,
                     bool includeNextWord = true,
                     bool (*accept)(Context*, Site*, Read*, const SiteMask&)
                     = acceptMatch)
{
  SiteMask mask;

  if (extraMask) {
    mask = mask.intersectionWith(*extraMask);
  }

  if (intersectRead) {
    read->intersect(&mask);
  }

  Site* site = 0;
  unsigned copyCost = 0xFFFFFFFF;
  for (SiteIterator it(c, read->value, includeBuddies, includeNextWord);
       it.hasMore();) {
    Site* s = it.next();
    if (accept(c, s, read, mask)) {
      unsigned v = s->copyCost(c, target);
      if (v < copyCost) {
        site = s;
        copyCost = v;
      }
    }
  }

  if (DebugMoves and site and target) {
    char srcb[256];
    site->toString(c, srcb, 256);
    char dstb[256];
    target->toString(c, dstb, 256);
    fprintf(stderr,
            "pick source %s to %s for %p cost %d\n",
            srcb,
            dstb,
            read->value,
            copyCost);
  }

  if (cost)
    *cost = copyCost;
  return site;
}

Site* maybeMove(Context* c,
                Read* read,
                bool intersectRead,
                bool includeNextWord,
                unsigned registerReserveCount = 0)
{
  Value* value = read->value;
  unsigned size = value == value->nextWord ? TargetBytesPerWord : 8;

  class MyCostCalculator : public CostCalculator {
   public:
    MyCostCalculator(Value* value, unsigned size, bool includeNextWord)
        : value(value), size(size), includeNextWord(includeNextWord)
    {
    }

    virtual unsigned cost(Context* c, SiteMask dstMask)
    {
      OperandMask src;
      OperandMask tmp;
      c->arch->planMove(
          size, src, tmp, OperandMask(dstMask.typeMask, dstMask.registerMask, 0));

      SiteMask srcMask = SiteMask::lowPart(src);
      for (SiteIterator it(c, value, true, includeNextWord); it.hasMore();) {
        Site* s = it.next();
        if (s->match(c, srcMask) or s->match(c, dstMask)) {
          return 0;
        }
      }

      return Target::IndirectMovePenalty;
    }

    Value* value;
    unsigned size;
    bool includeNextWord;
  } costCalculator(value, size, includeNextWord);

  Site* dstSite = pickTargetSite(
      c, read, intersectRead, registerReserveCount, &costCalculator);

  OperandMask src;
  OperandMask tmp;
  c->arch->planMove(
      size,
      src,
      tmp,
      OperandMask(1 << (unsigned)dstSite->type(c), dstSite->registerMask(c), 0));

  SiteMask srcMask = SiteMask::lowPart(src);
  unsigned cost = 0xFFFFFFFF;
  Site* srcSite = 0;
  for (SiteIterator it(c, value, true, includeNextWord); it.hasMore();) {
    Site* s = it.next();
    unsigned v = s->copyCost(c, dstSite);
    if (v == 0) {
      srcSite = s;
      cost = 0;
      break;
    }
    if (not s->match(c, srcMask)) {
      v += CopyPenalty;
    }
    if (v < cost) {
      srcSite = s;
      cost = v;
    }
  }

  if (cost) {
    if (DebugMoves) {
      char srcb[256];
      srcSite->toString(c, srcb, 256);
      char dstb[256];
      dstSite->toString(c, dstb, 256);
      fprintf(stderr,
              "maybe move %s to %s for %p to %p\n",
              srcb,
              dstb,
              value,
              value);
    }

    srcSite->freeze(c, value);

    value->addSite(c, dstSite);

    srcSite->thaw(c, value);

    if (not srcSite->match(c, srcMask)) {
      srcSite->freeze(c, value);
      dstSite->freeze(c, value);

      SiteMask tmpMask = SiteMask::lowPart(tmp);
      SingleRead tmpRead(tmpMask, 0);
      tmpRead.value = value;
      tmpRead.successor_ = value;

      Site* tmpSite = pickTargetSite(c, &tmpRead, true);

      value->addSite(c, tmpSite);

      move(c, value, srcSite, tmpSite);

      dstSite->thaw(c, value);
      srcSite->thaw(c, value);

      srcSite = tmpSite;
    }

    move(c, value, srcSite, dstSite);
  }

  return dstSite;
}

Site* maybeMove(Context* c,
                Value* v,
                const SiteMask& mask,
                bool intersectMask,
                bool includeNextWord,
                unsigned registerReserveCount = 0)
{
  SingleRead read(mask, 0);
  read.value = v;
  read.successor_ = v;

  return maybeMove(
      c, &read, intersectMask, includeNextWord, registerReserveCount);
}

Site* pickSiteOrMove(Context* c,
                     Read* read,
                     bool intersectRead,
                     bool includeNextWord,
                     unsigned registerReserveCount = 0)
{
  Site* s
      = pickSourceSite(c, read, 0, 0, 0, intersectRead, true, includeNextWord);

  if (s) {
    return s;
  } else {
    return maybeMove(
        c, read, intersectRead, includeNextWord, registerReserveCount);
  }
}

Site* pickSiteOrMove(Context* c,
                     Value* v,
                     const SiteMask& mask,
                     bool intersectMask,
                     bool includeNextWord,
                     unsigned registerReserveCount = 0)
{
  SingleRead read(mask, 0);
  read.value = v;
  read.successor_ = v;

  return pickSiteOrMove(
      c, &read, intersectMask, includeNextWord, registerReserveCount);
}

void steal(Context* c, Resource* r, Value* thief)
{
  if (DebugResources) {
    char resourceBuffer[256];
    r->toString(c, resourceBuffer, 256);
    char siteBuffer[1024];
    sitesToString(c, r->value, siteBuffer, 1024);
    fprintf(stderr,
            "%p steal %s from %p (%s)\n",
            thief,
            resourceBuffer,
            r->value,
            siteBuffer);
  }

  if ((not(thief and thief->isBuddyOf(r->value))
       and r->value->uniqueSite(c, r->site))) {
    r->site->freeze(c, r->value);

    maybeMove(c, live(c, r->value), false, true, StealRegisterReserveCount);

    r->site->thaw(c, r->value);
  }

  r->value->removeSite(c, r->site);
}

SiteMask generalRegisterMask(Context* c)
{
  return SiteMask(lir::Operand::RegisterPairMask,
                  c->regFile->generalRegisters,
                  NoFrameIndex);
}

SiteMask generalRegisterOrConstantMask(Context* c)
{
  return SiteMask(lir::Operand::RegisterPairMask | lir::Operand::ConstantMask,
                  c->regFile->generalRegisters,
                  NoFrameIndex);
}

MultiRead* multiRead(Context* c)
{
  return new (c->zone) MultiRead;
}

StubRead* stubRead(Context* c)
{
  return new (c->zone) StubRead;
}

Site* pickSite(Context* c,
               Value* v,
               Site* s,
               unsigned index,
               bool includeNextWord)
{
  for (SiteIterator it(c, v, true, includeNextWord); it.hasMore();) {
    Site* candidate = it.next();
    if (s->matchNextWord(c, candidate, index)) {
      return candidate;
    }
  }

  return 0;
}

Site* pickSiteOrMove(Context* c, Value* v, Site* s, unsigned index)
{
  Site* n = pickSite(c, v, s, index, false);
  if (n) {
    return n;
  }

  return maybeMove(c, v, s->nextWordMask(c, index), true, false);
}

Site* pickSiteOrMove(Context* c, Value* v, Site* s, Site** low, Site** high)
{
  if (v->wordIndex == 0) {
    *low = s;
    *high = pickSiteOrMove(c, v->nextWord, s, 1);
    return *high;
  } else {
    *low = pickSiteOrMove(c, v->nextWord, s, 0);
    *high = s;
    return *low;
  }
}

Site* pickSiteOrGrow(Context* c, Value* v, Site* s, unsigned index)
{
  Site* n = pickSite(c, v, s, index, false);
  if (n) {
    return n;
  }

  n = s->makeNextWord(c, index);
  v->addSite(c, n);
  return n;
}

Site* pickSiteOrGrow(Context* c, Value* v, Site* s, Site** low, Site** high)
{
  if (v->wordIndex == 0) {
    *low = s;
    *high = pickSiteOrGrow(c, v->nextWord, s, 1);
    return *high;
  } else {
    *low = pickSiteOrGrow(c, v->nextWord, s, 0);
    *high = s;
    return *low;
  }
}

bool isHome(Value* v, int frameIndex)
{
  Value* p = v;
  do {
    if (p->home == frameIndex) {
      return true;
    }
    p = p->buddy;
  } while (p != v);

  return false;
}

bool acceptForResolve(Context* c, Site* s, Read* read, const SiteMask& mask)
{
  if (acceptMatch(c, s, read, mask) and (not s->frozen(c))) {
    if (s->type(c) == lir::Operand::Type::RegisterPair) {
      return c->availableGeneralRegisterCount > ResolveRegisterReserveCount;
    } else {
      assertT(c,
              s->match(c, SiteMask(lir::Operand::MemoryMask, 0, AnyFrameIndex)));

      return isHome(read->value,
                    offsetToFrameIndex(c, static_cast<MemorySite*>(s)->offset));
    }
  } else {
    return false;
  }
}

void move(Context* c, Value* value, Site* src, Site* dst)
{
  if (DebugMoves) {
    char srcb[256];
    src->toString(c, srcb, 256);
    char dstb[256];
    dst->toString(c, dstb, 256);
    fprintf(stderr, "move %s to %s for %p to %p\n", srcb, dstb, value, value);
  }

  assertT(c, value->findSite(dst));

  src->freeze(c, value);
  dst->freeze(c, value);

  unsigned srcSize;
  unsigned dstSize;
  if (value->nextWord == value) {
    srcSize = TargetBytesPerWord;
    dstSize = TargetBytesPerWord;
  } else {
    srcSize = src->registerSize(c);
    dstSize = dst->registerSize(c);
  }

  if (srcSize == dstSize) {
    apply(c, lir::Move, srcSize, src, src, dstSize, dst, dst);
  } else if (srcSize > TargetBytesPerWord) {
    Site* low, *high, *other = pickSiteOrGrow(c, value, dst, &low, &high);
    other->freeze(c, value->nextWord);

    apply(c, lir::Move, srcSize, src, src, srcSize, low, high);

    other->thaw(c, value->nextWord);
  } else {
    Site* low, *high, *other = pickSiteOrMove(c, value, src, &low, &high);
    other->freeze(c, value->nextWord);

    apply(c, lir::Move, dstSize, low, high, dstSize, dst, dst);

    other->thaw(c, value->nextWord);
  }

  dst->thaw(c, value);
  src->thaw(c, value);
}

void asAssemblerOperand(Context* c, Site* low, Site* high, lir::Operand* result)
{
  low->asAssemblerOperand(c, high, result);
}

class OperandUnion : public lir::Operand {
 public:
  // must be large enough and aligned properly to hold any operand
  // type (we'd use an actual union type here, except that classes
  // with constructors cannot be used in a union):
  uintptr_t padding[4];
};

void apply(Context* c,
           lir::UnaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High)
{
  assertT(c, s1Low->type(c) == s1High->type(c));

  lir::Operand::Type s1Type = s1Low->type(c);
  OperandUnion s1Union;
  asAssemblerOperand(c, s1Low, s1High, &s1Union);

  c->assembler->apply(op, OperandInfo(s1Size, s1Type, &s1Union));
}

void apply(Context* c,
           lir::BinaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High,
           unsigned s2Size,
           Site* s2Low,
           Site* s2High)
{
  assertT(c, s1Low->type(c) == s1High->type(c));
  assertT(c, s2Low->type(c) == s2High->type(c));

  lir::Operand::Type s1Type = s1Low->type(c);
  OperandUnion s1Union;
  asAssemblerOperand(c, s1Low, s1High, &s1Union);

  lir::Operand::Type s2Type = s2Low->type(c);
  OperandUnion s2Union;
  asAssemblerOperand(c, s2Low, s2High, &s2Union);

  c->assembler->apply(op,
                      OperandInfo(s1Size, s1Type, &s1Union),
                      OperandInfo(s2Size, s2Type, &s2Union));
}

void apply(Context* c,
           lir::TernaryOperation op,
           unsigned s1Size,
           Site* s1Low,
           Site* s1High,
           unsigned s2Size,
           Site* s2Low,
           Site* s2High,
           unsigned s3Size,
           Site* s3Low,
           Site* s3High)
{
  assertT(c, s1Low->type(c) == s1High->type(c));
  assertT(c, s2Low->type(c) == s2High->type(c));
  assertT(c, s3Low->type(c) == s3High->type(c));

  lir::Operand::Type s1Type = s1Low->type(c);
  OperandUnion s1Union;
  asAssemblerOperand(c, s1Low, s1High, &s1Union);

  lir::Operand::Type s2Type = s2Low->type(c);
  OperandUnion s2Union;
  asAssemblerOperand(c, s2Low, s2High, &s2Union);

  lir::Operand::Type s3Type = s3Low->type(c);
  OperandUnion s3Union;
  asAssemblerOperand(c, s3Low, s3High, &s3Union);

  c->assembler->apply(op,
                      OperandInfo(s1Size, s1Type, &s1Union),
                      OperandInfo(s2Size, s2Type, &s2Union),
                      OperandInfo(s3Size, s3Type, &s3Union));
}

void append(Context* c, Event* e);

void saveLocals(Context* c, Event* e)
{
  for (unsigned li = 0; li < c->localFootprint; ++li) {
    Local* local = e->localsBefore + li;
    if (local->value) {
      if (DebugReads) {
        fprintf(stderr,
                "local save read %p at %d of %d\n",
                local->value,
                compiler::frameIndex(c, li),
                totalFrameSize(c));
      }

      e->addRead(
          c,
          local->value,
          SiteMask(lir::Operand::MemoryMask, 0, compiler::frameIndex(c, li)));
    }
  }
}

void maybeMove(Context* c,
               lir::BinaryOperation op,
               unsigned srcSize,
               unsigned srcSelectSize,
               Value* srcValue,
               unsigned dstSize,
               Value* dstValue,
               const SiteMask& dstMask)
{
  Read* read = live(c, dstValue);
  bool isStore = read == 0;

  Site* target;
  if (dstValue->target) {
    target = dstValue->target;
  } else if (isStore) {
    return;
  } else {
    target = pickTargetSite(c, read);
  }

  unsigned cost = srcValue->source->copyCost(c, target);

  if (srcSelectSize < dstSize)
    cost = 1;

  if (cost) {
    // todo: let c->arch->planMove decide this:
    bool useTemporary = ((target->type(c) == lir::Operand::Type::Memory
                          and srcValue->source->type(c) == lir::Operand::Type::Memory)
                         or (srcSelectSize < dstSize
                             and target->type(c) != lir::Operand::Type::RegisterPair));

    srcValue->source->freeze(c, srcValue);

    dstValue->addSite(c, target);

    srcValue->source->thaw(c, srcValue);

    bool addOffset = srcSize != srcSelectSize and c->arch->bigEndian()
                     and srcValue->source->type(c) == lir::Operand::Type::Memory;

    if (addOffset) {
      static_cast<MemorySite*>(srcValue->source)->offset
          += (srcSize - srcSelectSize);
    }

    target->freeze(c, dstValue);

    if (target->match(c, dstMask) and not useTemporary) {
      if (DebugMoves) {
        char srcb[256];
        srcValue->source->toString(c, srcb, 256);
        char dstb[256];
        target->toString(c, dstb, 256);
        fprintf(stderr,
                "move %s to %s for %p to %p\n",
                srcb,
                dstb,
                srcValue,
                dstValue);
      }

      srcValue->source->freeze(c, srcValue);

      apply(c,
            op,
            min(srcSelectSize, dstSize),
            srcValue->source,
            srcValue->source,
            dstSize,
            target,
            target);

      srcValue->source->thaw(c, srcValue);
    } else {
      // pick a temporary register which is valid as both a
      // destination and a source for the moves we need to perform:

      dstValue->removeSite(c, target);

      bool thunk;
      OperandMask src;

      c->arch->planSource(op, dstSize, src, dstSize, &thunk);

      if (isGeneralValue(srcValue)) {
        src.lowRegisterMask &= c->regFile->generalRegisters;
      }

      assertT(c, thunk == 0);
      assertT(c, dstMask.typeMask & src.typeMask & lir::Operand::RegisterPairMask);

      Site* tmpTarget
          = freeRegisterSite(c, dstMask.registerMask & src.lowRegisterMask);

      srcValue->source->freeze(c, srcValue);

      dstValue->addSite(c, tmpTarget);

      tmpTarget->freeze(c, dstValue);

      if (DebugMoves) {
        char srcb[256];
        srcValue->source->toString(c, srcb, 256);
        char dstb[256];
        tmpTarget->toString(c, dstb, 256);
        fprintf(stderr,
                "move %s to %s for %p to %p\n",
                srcb,
                dstb,
                srcValue,
                dstValue);
      }

      apply(c,
            op,
            srcSelectSize,
            srcValue->source,
            srcValue->source,
            dstSize,
            tmpTarget,
            tmpTarget);

      tmpTarget->thaw(c, dstValue);

      srcValue->source->thaw(c, srcValue);

      if (useTemporary or isStore) {
        if (DebugMoves) {
          char srcb[256];
          tmpTarget->toString(c, srcb, 256);
          char dstb[256];
          target->toString(c, dstb, 256);
          fprintf(stderr,
                  "move %s to %s for %p to %p\n",
                  srcb,
                  dstb,
                  srcValue,
                  dstValue);
        }

        dstValue->addSite(c, target);

        tmpTarget->freeze(c, dstValue);

        apply(c,
              lir::Move,
              dstSize,
              tmpTarget,
              tmpTarget,
              dstSize,
              target,
              target);

        tmpTarget->thaw(c, dstValue);

        if (isStore) {
          dstValue->removeSite(c, tmpTarget);
        }
      }
    }

    target->thaw(c, dstValue);

    if (addOffset) {
      static_cast<MemorySite*>(srcValue->source)->offset
          -= (srcSize - srcSelectSize);
    }
  } else {
    target = srcValue->source;

    if (DebugMoves) {
      char dstb[256];
      target->toString(c, dstb, 256);
      fprintf(
          stderr, "null move in %s for %p to %p\n", dstb, srcValue, dstValue);
    }
  }

  if (isStore) {
    dstValue->removeSite(c, target);
  }
}

Site* pickMatchOrMove(Context* c,
                      Read* r,
                      Site* nextWord,
                      unsigned index,
                      bool intersectRead)
{
  Site* s = pickSite(c, r->value, nextWord, index, true);
  SiteMask mask;
  if (intersectRead) {
    r->intersect(&mask);
  }
  if (s and s->match(c, mask)) {
    return s;
  }

  return pickSiteOrMove(c,
                        r->value,
                        mask.intersectionWith(nextWord->nextWordMask(c, index)),
                        true,
                        true);
}

Site* pickSiteOrMove(Context* c,
                     Value* src,
                     Value* dst,
                     Site* nextWord,
                     unsigned index)
{
  if (live(c, dst)) {
    Read* read = live(c, src);
    Site* s;
    if (nextWord) {
      s = pickMatchOrMove(c, read, nextWord, index, false);
    } else {
      s = pickSourceSite(c, read, 0, 0, 0, false, true, true);

      if (s == 0 or s->isVolatile(c)) {
        s = maybeMove(c, read, false, true);
      }
    }
    assertT(c, s);

    addBuddy(src, dst);

    if (src->source->isVolatile(c)) {
      src->removeSite(c, src->source);
    }

    return s;
  } else {
    return 0;
  }
}

ConstantSite* findConstantSite(Context* c, Value* v);

Site* getTarget(Context* c,
                Value* value,
                Value* result,
                const SiteMask& resultMask);

void freezeSource(Context* c, unsigned size, Value* v);

void thawSource(Context* c, unsigned size, Value* v);

void removeBuddy(Context* c, Value* v)
{
  if (v->buddy != v) {
    if (DebugBuddies) {
      fprintf(stderr, "remove buddy %p from", v);
      for (Value* p = v->buddy; p != v; p = p->buddy) {
        fprintf(stderr, " %p", p);
      }
      fprintf(stderr, "\n");
    }

    assertT(c, v->buddy);

    Value* next = v->buddy;
    v->buddy = v;
    Value* p = next;
    while (p->buddy != v)
      p = p->buddy;
    p->buddy = next;

    assertT(c, p->buddy);

    if (not live(c, next)) {
      next->clearSites(c);
    }

    if (not live(c, v)) {
      v->clearSites(c);
    }
  }
}

Site* copy(Context* c, Site* s)
{
  Site* start = 0;
  Site* end = 0;
  for (; s; s = s->next) {
    Site* n = s->copy(c);
    if (end) {
      end->next = n;
    } else {
      start = n;
    }
    end = n;
  }
  return start;
}

class Snapshot {
 public:
  Snapshot(Context* c, Value* value, Snapshot* next)
      : value(value),
        buddy(value->buddy),
        sites(copy(c, value->sites)),
        next(next)
  {
  }

  Value* value;
  Value* buddy;
  Site* sites;
  Snapshot* next;
};

Snapshot* snapshot(Context* c, Value* value, Snapshot* next)
{
  if (DebugControl) {
    char buffer[256];
    sitesToString(c, value->sites, buffer, 256);
    fprintf(
        stderr, "snapshot %p buddy %p sites %s\n", value, value->buddy, buffer);
  }

  return new (c->zone) Snapshot(c, value, next);
}

Snapshot* makeSnapshots(Context* c, Value* value, Snapshot* next)
{
  next = snapshot(c, value, next);
  for (Value* p = value->buddy; p != value; p = p->buddy) {
    next = snapshot(c, p, next);
  }
  return next;
}

Value* maybeBuddy(Context* c, Value* v);

Value* pushWord(Context* c, Value* v)
{
  if (v) {
    v = maybeBuddy(c, v);
  }

  Stack* s = stack(c, v, c->stack);

  if (DebugFrame) {
    fprintf(stderr, "push %p\n", v);
  }

  if (v) {
    v->home = frameIndex(c, s->index + c->localFootprint);
  }
  c->stack = s;

  return v;
}

void push(Context* c, unsigned footprint, Value* v)
{
  assertT(c, footprint);

  bool bigEndian = c->arch->bigEndian();

  Value* low = v;

  if (bigEndian) {
    v = pushWord(c, v);
  }

  Value* high;
  if (footprint > 1) {
    assertT(c, footprint == 2);

    if (TargetBytesPerWord == 4) {
      low->maybeSplit(c);
      high = pushWord(c, low->nextWord);
    } else {
      high = pushWord(c, 0);
    }
  } else {
    high = 0;
  }

  if (not bigEndian) {
    v = pushWord(c, v);
  }

  if (high) {
    v->nextWord = high;
    high->nextWord = v;
    high->wordIndex = 1;
  }
}

void popWord(Context* c)
{
  Stack* s = c->stack;
  assertT(c, s->value == 0 or s->value->home >= 0);

  if (DebugFrame) {
    fprintf(stderr, "pop %p\n", s->value);
  }

  c->stack = s->next;
}

Value* pop(Context* c, unsigned footprint)
{
  assertT(c, footprint);

  Stack* s = 0;

  bool bigEndian = c->arch->bigEndian();

  if (not bigEndian) {
    s = c->stack;
  }

  if (footprint > 1) {
    assertT(c, footprint == 2);

#ifndef NDEBUG
    Stack* low;
    Stack* high;
    if (bigEndian) {
      high = c->stack;
      low = high->next;
    } else {
      low = c->stack;
      high = low->next;
    }

    assertT(
        c,
        (TargetBytesPerWord == 8 and low->value->nextWord == low->value
         and high->value == 0)
        or (TargetBytesPerWord == 4 and low->value->nextWord == high->value));
#endif  // not NDEBUG

    popWord(c);
  }

  if (bigEndian) {
    s = c->stack;
  }

  popWord(c);

  return s->value;
}

Value* storeLocal(Context* c,
                  unsigned footprint,
                  Value* v,
                  unsigned index,
                  bool copy)
{
  assertT(c, index + footprint <= c->localFootprint);

  if (copy) {
    unsigned sizeInBytes = sizeof(Local) * c->localFootprint;
    Local* newLocals = static_cast<Local*>(c->zone->allocate(sizeInBytes));
    memcpy(newLocals, c->locals, sizeInBytes);
    c->locals = newLocals;
  }

  Value* high;
  if (footprint > 1) {
    assertT(c, footprint == 2);

    unsigned highIndex;
    unsigned lowIndex;
    if (c->arch->bigEndian()) {
      highIndex = index + 1;
      lowIndex = index;
    } else {
      lowIndex = index + 1;
      highIndex = index;
    }

    if (TargetBytesPerWord == 4) {
      assertT(c, v->nextWord != v);

      high = storeLocal(c, 1, v->nextWord, highIndex, false);
    } else {
      high = 0;
    }

    index = lowIndex;
  } else {
    high = 0;
  }

  v = maybeBuddy(c, v);

  if (high != 0) {
    v->nextWord = high;
    high->nextWord = v;
    high->wordIndex = 1;
  }

  Local* local = c->locals + index;
  local->value = v;

  if (DebugFrame) {
    fprintf(stderr, "store local %p at %d\n", local->value, index);
  }

  local->value->home = frameIndex(c, index);

  return v;
}

unsigned typeFootprint(Context* c, ir::Type type)
{
  // TODO: this function is very Java-specific in nature. Generalize.
  switch (type.flavor()) {
  case ir::Type::Float:
  case ir::Type::Integer:
    return type.rawSize() / 4;
  case ir::Type::Object:
  case ir::Type::Address:
    return 1;
  case ir::Type::Void:
    return 0;
  default:
    abort(c);
  }
}

Value* loadLocal(Context* c, ir::Type type, unsigned index)
{
  unsigned footprint = typeFootprint(c, type);
  assertT(c, index + footprint <= c->localFootprint);

  if (footprint > 1) {
    assertT(c, footprint == 2);

    if (not c->arch->bigEndian()) {
      ++index;
    }
  }

  assertT(c, c->locals[index].value);
  assertT(c, c->locals[index].value->home >= 0);

  if (DebugFrame) {
    fprintf(stderr, "load local %p at %d\n", c->locals[index].value, index);
  }

  return c->locals[index].value;
}

Value* threadRegister(Context* c)
{
  Site* s = registerSite(c, c->arch->thread());
  return value(c, ir::Type::addr(), s, s);
}

unsigned frameFootprint(Context* c, Stack* s)
{
  return c->localFootprint + (s ? (s->index + 1) : 0);
}

void visit(Context* c, Link* link)
{
  if (false) {
    fprintf(stderr,
            "visit link from %d to %d fork %p junction %p\n",
            link->predecessor->logicalInstruction->index,
            link->successor->logicalInstruction->index,
            link->forkState,
            link->junctionState);
  }

  ForkState* forkState = link->forkState;
  if (forkState) {
    for (unsigned i = 0; i < forkState->readCount; ++i) {
      ForkElement* p = forkState->elements + i;
      Value* v = p->value;
      v->reads = p->read->nextTarget();
      if (false) {
        fprintf(stderr, "next read %p for %p from %p\n", v->reads, v, p->read);
      }
      if (not live(c, v)) {
        v->clearSites(c);
      }
    }
  }

  JunctionState* junctionState = link->junctionState;
  if (junctionState) {
    for (unsigned i = 0; i < junctionState->frameFootprint; ++i) {
      StubReadPair* p = junctionState->reads + i;

      if (p->value and p->value->reads) {
        assertT(c, p->value->reads == p->read);
        popRead(c, 0, p->value);
      }
    }
  }
}

class BuddyEvent : public Event {
 public:
  BuddyEvent(Context* c, Value* original, Value* buddy)
      : Event(c), original(original), buddy(buddy)
  {
    this->addRead(c, original, SiteMask(~0, ~0, AnyFrameIndex), buddy);
  }

  virtual const char* name()
  {
    return "BuddyEvent";
  }

  virtual void compile(Context* c)
  {
    if (DebugBuddies) {
      fprintf(stderr, "original %p buddy %p\n", original, buddy);
    }

    assertT(c, original->hasSite(c));

    assertT(c, original);
    assertT(c, buddy);

    addBuddy(original, buddy);

    popRead(c, this, original);
  }

  Value* original;
  Value* buddy;
};

void appendBuddy(Context* c, Value* original, Value* buddy)
{
  append(c, new (c->zone) BuddyEvent(c, original, buddy));
}

void append(Context* c, Event* e)
{
  LogicalInstruction* i = c->logicalCode[c->logicalIp];
  if (c->stack != i->stack or c->locals != i->locals) {
    appendDummy(c);
  }

  if (DebugAppend) {
    fprintf(stderr,
            " -- append %s at %d with %d stack before\n",
            e->name(),
            e->logicalInstruction->index,
            c->stack ? c->stack->index + 1 : 0);
  }

  if (c->lastEvent) {
    c->lastEvent->next = e;
  } else {
    c->firstEvent = e;
  }
  c->lastEvent = e;

  Event* p = c->predecessor;
  if (p) {
    if (DebugAppend) {
      fprintf(stderr,
              "%d precedes %d\n",
              p->logicalInstruction->index,
              e->logicalInstruction->index);
    }

    Link* link
        = compiler::link(c, p, e->predecessors, e, p->successors, c->forkState);
    e->predecessors = link;
    p->successors = link;
  }
  c->forkState = 0;

  c->predecessor = e;

  if (e->logicalInstruction->firstEvent == 0) {
    e->logicalInstruction->firstEvent = e;
  }
  e->logicalInstruction->lastEvent = e;
}

Site* readSource(Context* c, Read* r)
{
  Value* v = r->value;

  if (DebugReads) {
    char buffer[1024];
    sitesToString(c, v, buffer, 1024);
    fprintf(stderr, "read source for %p from %s\n", v, buffer);
  }

  if (not v->hasSite(c)) {
    if (DebugReads) {
      fprintf(stderr, "no sites found for %p\n", v);
    }
    return 0;
  }

  Value* high = r->high(c);
  if (high) {
    return pickMatchOrMove(c, r, high->source, 0, true);
  } else {
    return pickSiteOrMove(c, r, true, true);
  }
}

void propagateJunctionSites(Context* c, Event* e, Site** sites)
{
  for (Link* pl = e->predecessors; pl; pl = pl->nextPredecessor) {
    Event* p = pl->predecessor;
    if (p->junctionSites == 0) {
      p->junctionSites = sites;
      for (Link* sl = p->successors; sl; sl = sl->nextSuccessor) {
        Event* s = sl->successor;
        propagateJunctionSites(c, s, sites);
      }
    }
  }
}

void propagateJunctionSites(Context* c, Event* e)
{
  for (Link* sl = e->successors; sl; sl = sl->nextSuccessor) {
    Event* s = sl->successor;
    if (s->predecessors->nextPredecessor) {
      unsigned size = sizeof(Site*) * frameFootprint(c, e->stackAfter);
      Site** junctionSites = static_cast<Site**>(c->zone->allocate(size));
      memset(junctionSites, 0, size);

      propagateJunctionSites(c, s, junctionSites);
      break;
    }
  }
}

class SiteRecord {
 public:
  Site* site;
  Value* value;
};

void init(SiteRecord* r, Site* s, Value* v)
{
  r->site = s;
  r->value = v;
}

class SiteRecordList {
 public:
  SiteRecordList(SiteRecord* records, unsigned capacity)
      : records(records), index(0), capacity(capacity)
  {
  }

  SiteRecord* records;
  unsigned index;
  unsigned capacity;
};

void freeze(Context* c, SiteRecordList* frozen, Site* s, Value* v)
{
  assertT(c, frozen->index < frozen->capacity);

  s->freeze(c, v);
  init(new (frozen->records + (frozen->index++)) SiteRecord, s, v);
}

void thaw(Context* c, SiteRecordList* frozen)
{
  while (frozen->index) {
    SiteRecord* sr = frozen->records + (--frozen->index);
    sr->site->thaw(c, sr->value);
  }
}

bool resolveOriginalSites(Context* c,
                          Event* e,
                          SiteRecordList* frozen,
                          Site** sites)
{
  bool complete = true;
  for (FrameIterator it(c, e->stackAfter, e->localsAfter, true);
       it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    Value* v = el.value;
    Read* r = v ? live(c, v) : 0;
    Site* s = sites[el.localIndex];

    if (r) {
      if (s) {
        if (DebugControl) {
          char buffer[256];
          s->toString(c, buffer, 256);
          fprintf(stderr,
                  "resolve original %s for %p local %d frame %d\n",
                  buffer,
                  v,
                  el.localIndex,
                  el.frameIndex(c));
        }

        Site* target = pickSiteOrMove(
            c, v, s->mask(c), true, true, ResolveRegisterReserveCount);

        freeze(c, frozen, target, v);
      } else {
        complete = false;
      }
    } else if (s) {
      if (DebugControl) {
        char buffer[256];
        s->toString(c, buffer, 256);
        fprintf(stderr,
                "freeze original %s for %p local %d frame %d\n",
                buffer,
                v,
                el.localIndex,
                el.frameIndex(c));
      }

      Value dummy(0, 0, ir::Type::addr());
      dummy.addSite(c, s);
      dummy.removeSite(c, s);
      freeze(c, frozen, s, 0);
    }
  }

  return complete;
}

bool resolveSourceSites(Context* c,
                        Event* e,
                        SiteRecordList* frozen,
                        Site** sites)
{
  bool complete = true;
  for (FrameIterator it(c, e->stackAfter, e->localsAfter); it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    Value* v = el.value;
    Read* r = live(c, v);

    if (r and sites[el.localIndex] == 0) {
      SiteMask mask(lir::Operand::RegisterPairMask | lir::Operand::MemoryMask,
                    c->regFile->generalRegisters,
                    AnyFrameIndex);

      Site* s = pickSourceSite(
          c, r, 0, 0, &mask, true, false, true, acceptForResolve);

      if (s) {
        if (DebugControl) {
          char buffer[256];
          s->toString(c, buffer, 256);
          fprintf(stderr,
                  "resolve source %s from %p local %d frame %d\n",
                  buffer,
                  v,
                  el.localIndex,
                  el.frameIndex(c));
        }

        freeze(c, frozen, s, v);

        sites[el.localIndex] = s->copy(c);
      } else {
        complete = false;
      }
    }
  }

  return complete;
}

void resolveTargetSites(Context* c,
                        Event* e,
                        SiteRecordList* frozen,
                        Site** sites)
{
  for (FrameIterator it(c, e->stackAfter, e->localsAfter); it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    Value* v = el.value;
    Read* r = live(c, v);

    if (r and sites[el.localIndex] == 0) {
      SiteMask mask(lir::Operand::RegisterPairMask | lir::Operand::MemoryMask,
                    c->regFile->generalRegisters,
                    AnyFrameIndex);

      Site* s = pickSourceSite(
          c, r, 0, 0, &mask, false, true, true, acceptForResolve);

      if (s == 0) {
        s = maybeMove(c, v, mask, false, true, ResolveRegisterReserveCount);
      }

      freeze(c, frozen, s, v);

      sites[el.localIndex] = s->copy(c);

      if (DebugControl) {
        char buffer[256];
        sites[el.localIndex]->toString(c, buffer, 256);
        fprintf(stderr,
                "resolve target %s for %p local %d frame %d\n",
                buffer,
                el.value,
                el.localIndex,
                el.frameIndex(c));
      }
    }
  }
}

void resolveJunctionSites(Context* c, Event* e, SiteRecordList* frozen)
{
  bool complete;
  if (e->junctionSites) {
    complete = resolveOriginalSites(c, e, frozen, e->junctionSites);
  } else {
    propagateJunctionSites(c, e);
    complete = false;
  }

  if (e->junctionSites) {
    if (not complete) {
      complete = resolveSourceSites(c, e, frozen, e->junctionSites);
      if (not complete) {
        resolveTargetSites(c, e, frozen, e->junctionSites);
      }
    }

    if (DebugControl) {
      fprintf(stderr,
              "resolved junction sites %p at %d\n",
              e->junctionSites,
              e->logicalInstruction->index);
    }
  }
}

void resolveBranchSites(Context* c, Event* e, SiteRecordList* frozen)
{
  if (e->successors->nextSuccessor and e->junctionSites == 0) {
    unsigned footprint = frameFootprint(c, e->stackAfter);
    RUNTIME_ARRAY(Site*, branchSites, footprint);
    memset(RUNTIME_ARRAY_BODY(branchSites), 0, sizeof(Site*) * footprint);

    if (not resolveSourceSites(c, e, frozen, RUNTIME_ARRAY_BODY(branchSites))) {
      resolveTargetSites(c, e, frozen, RUNTIME_ARRAY_BODY(branchSites));
    }
  }
}

void captureBranchSnapshots(Context* c, Event* e)
{
  if (e->successors->nextSuccessor) {
    for (FrameIterator it(c, e->stackAfter, e->localsAfter); it.hasMore();) {
      FrameIterator::Element el = it.next(c);
      e->snapshots = makeSnapshots(c, el.value, e->snapshots);
    }

    for (List<Value*>* sv = e->successors->forkState->saved; sv;
         sv = sv->next) {
      e->snapshots = makeSnapshots(c, sv->item, e->snapshots);
    }

    if (DebugControl) {
      fprintf(stderr,
              "captured snapshots %p at %d\n",
              e->snapshots,
              e->logicalInstruction->index);
    }
  }
}

void populateSiteTables(Context* c, Event* e, SiteRecordList* frozen)
{
  resolveJunctionSites(c, e, frozen);

  resolveBranchSites(c, e, frozen);
}

void setSites(Context* c, Value* v, Site* s)
{
  assertT(c, live(c, v));

  for (; s; s = s->next) {
    v->addSite(c, s->copy(c));
  }

  if (DebugControl) {
    char buffer[256];
    sitesToString(c, v->sites, buffer, 256);
    fprintf(stderr, "set sites %s for %p\n", buffer, v);
  }
}

void resetFrame(Context* c, Event* e)
{
  for (FrameIterator it(c, e->stackBefore, e->localsBefore); it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    el.value->clearSites(c);
  }

  while (c->acquiredResources) {
    c->acquiredResources->value->clearSites(c);
  }
}

void setSites(Context* c, Event* e, Site** sites)
{
  resetFrame(c, e);

  for (FrameIterator it(c, e->stackBefore, e->localsBefore); it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    if (sites[el.localIndex]) {
      if (live(c, el.value)) {
        setSites(c, el.value, sites[el.localIndex]);
      } else if (DebugControl) {
        char buffer[256];
        sitesToString(c, sites[el.localIndex], buffer, 256);
        fprintf(stderr,
                "skip sites %s for %p local %d frame %d\n",
                buffer,
                el.value,
                el.localIndex,
                el.frameIndex(c));
      }
    } else if (DebugControl) {
      fprintf(stderr,
              "no sites for %p local %d frame %d\n",
              el.value,
              el.localIndex,
              el.frameIndex(c));
    }
  }
}

void removeBuddies(Context* c)
{
  for (FrameIterator it(c, c->stack, c->locals); it.hasMore();) {
    FrameIterator::Element el = it.next(c);
    removeBuddy(c, el.value);
  }
}

void restore(Context* c, Event* e, Snapshot* snapshots)
{
  for (Snapshot* s = snapshots; s; s = s->next) {
    Value* v = s->value;
    Value* next = v->buddy;
    if (v != next) {
      v->buddy = v;
      Value* p = next;
      while (p->buddy != v)
        p = p->buddy;
      p->buddy = next;
    }
  }

  for (Snapshot* s = snapshots; s; s = s->next) {
    assertT(c, s->buddy);

    s->value->buddy = s->buddy;
  }

  resetFrame(c, e);

  for (Snapshot* s = snapshots; s; s = s->next) {
    if (live(c, s->value)) {
      if (live(c, s->value) and s->sites and s->value->sites == 0) {
        setSites(c, s->value, s->sites);
      }
    }

    if (false) {
      char buffer[256];
      sitesToString(c, s->sites, buffer, 256);
      fprintf(stderr,
              "restore %p buddy %p sites %s live %p\n",
              s->value,
              s->value->buddy,
              buffer,
              live(c, s->value));
    }
  }
}

void populateSources(Context* c, Event* e)
{
  RUNTIME_ARRAY(SiteRecord, frozenRecords, e->readCount);
  SiteRecordList frozen(RUNTIME_ARRAY_BODY(frozenRecords), e->readCount);

  for (Read* r = e->reads; r; r = r->eventNext) {
    r->value->source = readSource(c, r);
    if (r->value->source) {
      if (DebugReads) {
        char buffer[256];
        r->value->source->toString(c, buffer, 256);
        fprintf(stderr, "freeze source %s for %p\n", buffer, r->value);
      }

      freeze(c, &frozen, r->value->source, r->value);
    }
  }

  thaw(c, &frozen);
}

void setStubRead(Context* c, StubReadPair* p, Value* v)
{
  if (v) {
    StubRead* r = stubRead(c);
    if (DebugReads) {
      fprintf(stderr, "add stub read %p to %p\n", r, v);
    }
    finishAddRead(c, v, r);

    p->value = v;
    p->read = r;
  }
}

void populateJunctionReads(Context* c, Link* link)
{
  JunctionState* state = new (
      c->zone->allocate(sizeof(JunctionState)
                        + (sizeof(StubReadPair) * frameFootprint(c, c->stack))))
      JunctionState(frameFootprint(c, c->stack));

  memset(state->reads, 0, sizeof(StubReadPair) * frameFootprint(c, c->stack));

  link->junctionState = state;

  for (FrameIterator it(c, c->stack, c->locals); it.hasMore();) {
    FrameIterator::Element e = it.next(c);
    setStubRead(c, state->reads + e.localIndex, e.value);
  }
}

void updateJunctionReads(Context* c, JunctionState* state)
{
  for (FrameIterator it(c, c->stack, c->locals); it.hasMore();) {
    FrameIterator::Element e = it.next(c);
    StubReadPair* p = state->reads + e.localIndex;
    if (p->value and p->read->read == 0) {
      Read* r = live(c, e.value);
      if (r) {
        if (DebugReads) {
          fprintf(
              stderr, "stub read %p for %p valid: %p\n", p->read, p->value, r);
        }
        p->read->read = r;
      }
    }
  }

  for (unsigned i = 0; i < frameFootprint(c, c->stack); ++i) {
    StubReadPair* p = state->reads + i;
    if (p->value and p->read->read == 0) {
      if (DebugReads) {
        fprintf(stderr, "stub read %p for %p invalid\n", p->read, p->value);
      }
      p->read->valid_ = false;
    }
  }
}

void compile(Context* c,
             uintptr_t stackOverflowHandler,
             unsigned stackLimitOffset)
{
  if (c->logicalCode[c->logicalIp]->lastEvent == 0) {
    appendDummy(c);
  }

  Assembler* a = c->assembler;

  Block* firstBlock = block(c, c->firstEvent);
  Block* block = firstBlock;

  if (stackOverflowHandler) {
    a->checkStackOverflow(stackOverflowHandler, stackLimitOffset);
  }

  a->allocateFrame(c->alignedFrameSize);

  for (Event* e = c->firstEvent; e; e = e->next) {
    if (DebugCompile) {
      fprintf(stderr,
              " -- compile %s at %d with %d preds %d succs %d stack\n",
              e->name(),
              e->logicalInstruction->index,
              e->predecessors->countPredecessors(),
              e->successors->countSuccessors(),
              e->stackBefore ? e->stackBefore->index + 1 : 0);
    }

    e->block = block;

    c->stack = e->stackBefore;
    c->locals = e->localsBefore;

    if (e->logicalInstruction->machineOffset == 0) {
      e->logicalInstruction->machineOffset = a->offset();
    }

    if (e->predecessors) {
      visit(c, e->predecessors->lastPredecessor());

      Event* first = e->predecessors->predecessor;
      if (e->predecessors->nextPredecessor) {
        for (Link* pl = e->predecessors; pl->nextPredecessor;
             pl = pl->nextPredecessor) {
          updateJunctionReads(c, pl->junctionState);
        }

        if (DebugControl) {
          fprintf(stderr,
                  "set sites to junction sites %p at %d\n",
                  first->junctionSites,
                  first->logicalInstruction->index);
        }

        setSites(c, e, first->junctionSites);
        removeBuddies(c);
      } else if (first->successors->nextSuccessor) {
        if (DebugControl) {
          fprintf(stderr,
                  "restore snapshots %p at %d\n",
                  first->snapshots,
                  first->logicalInstruction->index);
        }

        restore(c, e, first->snapshots);
      }
    }

    unsigned footprint = frameFootprint(c, e->stackAfter);
    RUNTIME_ARRAY(SiteRecord, frozenRecords, footprint);
    SiteRecordList frozen(RUNTIME_ARRAY_BODY(frozenRecords), footprint);

    bool branch = e->isBranch();
    if (branch and e->successors) {
      populateSiteTables(c, e, &frozen);
    }

    populateSources(c, e);

    if (branch and e->successors) {
      captureBranchSnapshots(c, e);
    }

    thaw(c, &frozen);

    e->compile(c);

    if ((not branch) and e->successors) {
      populateSiteTables(c, e, &frozen);
      captureBranchSnapshots(c, e);
      thaw(c, &frozen);
    }

    if (e->visitLinks) {
      for (List<Link*>* cell = reverseDestroy(e->visitLinks); cell;
           cell = cell->next) {
        visit(c, cell->item);
      }
      e->visitLinks = 0;
    }

    for (CodePromise* p = e->promises; p; p = p->next) {
      p->offset = a->offset();
    }

    a->endEvent();

    LogicalInstruction* nextInstruction = e->logicalInstruction->next(c);
    if (e->next == 0 or (e->next->logicalInstruction != e->logicalInstruction
                         and (e->next->logicalInstruction != nextInstruction
                              or e != e->logicalInstruction->lastEvent))) {
      Block* b = e->logicalInstruction->firstEvent->block;

      while (b->nextBlock) {
        b = b->nextBlock;
      }

      if (b != block) {
        b->nextBlock = block;
      }

      block->nextInstruction = nextInstruction;
      block->assemblerBlock = a->endBlock(e->next != 0);

      if (e->next) {
        block = compiler::block(c, e->next);
      }
    }
  }

  c->firstBlock = firstBlock;
}

void restore(Context* c, ForkState* state)
{
  for (unsigned i = 0; i < state->readCount; ++i) {
    ForkElement* p = state->elements + i;
    p->value->lastRead = p->read;
    p->read->allocateTarget(c);
  }
}

void addForkElement(Context* c, Value* v, ForkState* state, unsigned index)
{
  MultiRead* r = multiRead(c);
  if (DebugReads) {
    fprintf(stderr, "add multi read %p to %p\n", r, v);
  }
  finishAddRead(c, v, r);

  ForkElement* p = state->elements + index;
  p->value = v;
  p->read = r;
}

ForkState* saveState(Context* c)
{
  if (c->logicalCode[c->logicalIp]->lastEvent == 0) {
    appendDummy(c);
  }

  unsigned elementCount = frameFootprint(c, c->stack) + c->saved->count();

  ForkState* state = new (c->zone->allocate(
      sizeof(ForkState) + (sizeof(ForkElement) * elementCount)))
      ForkState(c->stack, c->locals, c->saved, c->predecessor, c->logicalIp);

  if (c->predecessor) {
    c->forkState = state;

    unsigned count = 0;

    for (FrameIterator it(c, c->stack, c->locals); it.hasMore();) {
      FrameIterator::Element e = it.next(c);
      addForkElement(c, e.value, state, count++);
    }

    for (List<Value*>* sv = c->saved; sv; sv = sv->next) {
      addForkElement(c, sv->item, state, count++);
    }

    state->readCount = count;
  }

  c->saved = 0;

  return state;
}

void restoreState(Context* c, ForkState* s)
{
  if (c->logicalCode[c->logicalIp]->lastEvent == 0) {
    appendDummy(c);
  }

  c->stack = s->stack;
  c->locals = s->locals;
  c->predecessor = s->predecessor;
  c->logicalIp = s->logicalIp;

  if (c->predecessor) {
    c->forkState = s;
    restore(c, s);
  }
}

Value* maybeBuddy(Context* c, Value* v)
{
  if (v->home >= 0) {
    Value* n = value(c, v->type);
    appendBuddy(c, v, n);
    return n;
  } else {
    return v;
  }
}

void linkLocals(Context* c, Local* oldLocals, Local* newLocals)
{
  for (int i = 0; i < static_cast<int>(c->localFootprint); ++i) {
    Local* local = oldLocals + i;
    if (local->value) {
      int highOffset = c->arch->bigEndian() ? 1 : -1;

      if (i + highOffset >= 0
          and i + highOffset < static_cast<int>(c->localFootprint)
          and local->value->nextWord == local[highOffset].value) {
        Value* v = newLocals[i].value;
        Value* next = newLocals[i + highOffset].value;
        v->nextWord = next;
        next->nextWord = v;
        next->wordIndex = 1;
      }
    }
  }
}

class Client : public Assembler::Client {
 public:
  Client(Context* c) : c(c)
  {
  }

  virtual Register acquireTemporary(RegisterMask mask)
  {
    unsigned cost;
    Register r = pickRegisterTarget(c, 0, mask, &cost);
    expect(c, cost < Target::Impossible);
    save(r);
    c->registerResources[r.index()].increment(c);
    return r;
  }

  virtual void releaseTemporary(Register r)
  {
    c->registerResources[r.index()].decrement(c);
  }

  virtual void save(Register r)
  {
    RegisterResource* reg = c->registerResources + r.index();

    assertT(c, reg->referenceCount == 0);
    assertT(c, reg->freezeCount == 0);
    assertT(c, not reg->reserved);

    if (reg->value) {
      steal(c, reg, 0);
    }
  }

  Context* c;
};

class MyCompiler : public Compiler {
 public:
  MyCompiler(System* s,
             Assembler* assembler,
             Zone* zone,
             Compiler::Client* compilerClient)
      : c(s, assembler, zone, compilerClient), client(&c)
  {
    assembler->setClient(&client);
  }

  virtual State* saveState()
  {
    State* s = compiler::saveState(&c);
    restoreState(s);
    return s;
  }

  virtual void restoreState(State* state)
  {
    compiler::restoreState(&c, static_cast<ForkState*>(state));
  }

  virtual void init(unsigned logicalCodeLength,
                    unsigned parameterFootprint,
                    unsigned localFootprint,
                    unsigned alignedFrameSize)
  {
    c.parameterFootprint = parameterFootprint;
    c.localFootprint = localFootprint;
    c.alignedFrameSize = alignedFrameSize;

    unsigned frameResourceCount = totalFrameSize(&c);

    c.frameResources = static_cast<FrameResource*>(
        c.zone->allocate(sizeof(FrameResource) * frameResourceCount));

    for (unsigned i = 0; i < frameResourceCount; ++i) {
      new (c.frameResources + i) FrameResource;
    }

    unsigned base = frameBase(&c);
    c.frameResources[base + c.arch->returnAddressOffset()].reserved = true;
    c.frameResources[base + c.arch->framePointerOffset()].reserved
        = UseFramePointer;

    c.logicalCode.init(c.zone, logicalCodeLength);

    c.logicalCode[-1] = new (c.zone) LogicalInstruction(-1, c.stack, c.locals);

    c.locals
        = static_cast<Local*>(c.zone->allocate(sizeof(Local) * localFootprint));

    memset(c.locals, 0, sizeof(Local) * localFootprint);
  }

  virtual void extendLogicalCode(unsigned more)
  {
    c.logicalCode.extend(c.zone, more);
  }

  virtual void visitLogicalIp(unsigned logicalIp)
  {
    assertT(&c, logicalIp < c.logicalCode.count());

    if (c.logicalCode[c.logicalIp]->lastEvent == 0) {
      appendDummy(&c);
    }

    Event* e = c.logicalCode[logicalIp]->firstEvent;

    Event* p = c.predecessor;
    if (p) {
      if (DebugAppend) {
        fprintf(stderr,
                "visit %d pred %d\n",
                logicalIp,
                p->logicalInstruction->index);
      }

      p->stackAfter = c.stack;
      p->localsAfter = c.locals;

      Link* link = compiler::link(
          &c, p, e->predecessors, e, p->successors, c.forkState);
      e->predecessors = link;
      p->successors = link;
      c.lastEvent->visitLinks = cons(&c, link, c.lastEvent->visitLinks);

      if (DebugAppend) {
        fprintf(stderr,
                "populate junction reads for %d to %d\n",
                p->logicalInstruction->index,
                logicalIp);
      }

      populateJunctionReads(&c, link);
    }

    c.forkState = 0;
  }

  virtual void startLogicalIp(unsigned logicalIp)
  {
    assertT(&c, logicalIp < c.logicalCode.count());
    assertT(&c, c.logicalCode[logicalIp] == 0);

    if (c.logicalCode[c.logicalIp]->lastEvent == 0) {
      appendDummy(&c);
    }

    Event* p = c.predecessor;
    if (p) {
      p->stackAfter = c.stack;
      p->localsAfter = c.locals;
    }

    c.logicalCode[logicalIp] = new (c.zone)
        LogicalInstruction(logicalIp, c.stack, c.locals);

    c.logicalIp = logicalIp;
  }

  virtual Promise* machineIp(unsigned logicalIp)
  {
    return ipPromise(&c, logicalIp);
  }

  virtual Promise* poolAppend(intptr_t value)
  {
    return poolAppendPromise(resolvedPromise(&c, value));
  }

  virtual Promise* poolAppendPromise(Promise* value)
  {
    Promise* p = poolPromise(&c, c.constantCount);

    ConstantPoolNode* constant = new (c.zone) ConstantPoolNode(value);

    if (c.firstConstant) {
      c.lastConstant->next = constant;
    } else {
      c.firstConstant = constant;
    }
    c.lastConstant = constant;
    ++c.constantCount;

    return p;
  }

  virtual ir::Value* constant(int64_t value, ir::Type type)
  {
    return promiseConstant(resolvedPromise(&c, value), type);
  }

  virtual ir::Value* promiseConstant(Promise* value, ir::Type type)
  {
    return compiler::value(&c, type, compiler::constantSite(&c, value));
  }

  virtual ir::Value* address(ir::Type type, Promise* address)
  {
    return value(&c, type, compiler::addressSite(&c, address));
  }

  virtual ir::Value* memory(ir::Value* base,
                            ir::Type type,
                            int displacement = 0,
                            ir::Value* index = 0)
  {
    Value* result = value(&c, type);

    appendMemory(&c,
                 static_cast<Value*>(base),
                 displacement,
                 static_cast<Value*>(index),
                 index == 0 ? 1 : type.size(c.targetInfo),
                 result);

    return result;
  }

  virtual ir::Value* threadRegister()
  {
    return compiler::threadRegister(&c);
  }

  Promise* machineIp()
  {
    return c.logicalCode[c.logicalIp]->lastEvent->makeCodePromise(&c);
  }

  virtual void push(ir::Type type, ir::Value* value)
  {
    // TODO: once type information is flowed properly, enable this assertT.
    // Some time later, we can remove the parameter.
    // assertT(&c, value->type == type);
    compiler::push(&c, typeFootprint(&c, type), static_cast<Value*>(value));
  }

  virtual void save(ir::Type type, ir::Value* value)
  {
    // TODO: once type information is flowed properly, enable this assertT.
    // Some time later, we can remove the parameter.
    // assertT(&c, value->type == type);
    unsigned footprint = typeFootprint(&c, type);
    c.saved = cons(&c, static_cast<Value*>(value), c.saved);
    if (TargetBytesPerWord == 4 and footprint > 1) {
      assertT(&c, footprint == 2);
      assertT(&c, static_cast<Value*>(value)->nextWord);

      save(ir::Type::i4(), static_cast<Value*>(value)->nextWord);
    }
  }

  virtual ir::Value* pop(ir::Type type)
  {
    ir::Value* value = compiler::pop(&c, typeFootprint(&c, type));
    // TODO: once type information is flowed properly, enable this assertT.
    // Some time later, we can remove the parameter.
    // assertT(&c, static_cast<Value*>(value)->type == type);
    return value;
  }

  virtual void pushed(ir::Type type)
  {
    Value* v = value(&c, type);
    appendFrameSite(
        &c,
        v,
        frameIndex(&c, (c.stack ? c.stack->index : 0) + c.localFootprint));

    Stack* s = compiler::stack(&c, v, c.stack);
    v->home = frameIndex(&c, s->index + c.localFootprint);
    c.stack = s;
  }

  virtual void popped(unsigned footprint)
  {
    for (; footprint; --footprint) {
      assertT(&c, c.stack->value == 0 or c.stack->value->home >= 0);

      if (DebugFrame) {
        fprintf(stderr, "popped %p\n", c.stack->value);
      }

      c.stack = c.stack->next;
    }
  }

  virtual unsigned topOfStack()
  {
    return c.stack->index;
  }

  virtual ir::Value* peek(unsigned footprint, unsigned index)
  {
    Stack* s = c.stack;
    for (unsigned i = index; i > 0; --i) {
      s = s->next;
    }

    if (footprint > 1) {
      assertT(&c, footprint == 2);

      bool bigEndian = c.arch->bigEndian();

#ifndef NDEBUG
      Stack* low;
      Stack* high;
      if (bigEndian) {
        high = s;
        low = s->next;
      } else {
        low = s;
        high = s->next;
      }

      assertT(
          &c,
          (TargetBytesPerWord == 8 and low->value->nextWord == low->value
           and high->value == 0)
          or (TargetBytesPerWord == 4 and low->value->nextWord == high->value));
#endif  // not NDEBUG

      if (bigEndian) {
        s = s->next;
      }
    }

    return s->value;
  }

  virtual ir::Value* nativeCall(ir::Value* address,
                                unsigned flags,
                                TraceHandler* traceHandler,
                                ir::Type resultType,
                                util::Slice<ir::Value*> arguments)
  {
    bool bigEndian = c.arch->bigEndian();

    unsigned footprint = 0;
    unsigned size = TargetBytesPerWord;
    RUNTIME_ARRAY(ir::Value*, args, arguments.count);
    int index = 0;
    for (unsigned i = 0; i < arguments.count; ++i) {
      Value* o = static_cast<Value*>(arguments[i]);
      if (o) {
        if (bigEndian and size > TargetBytesPerWord) {
          RUNTIME_ARRAY_BODY(args)[index++] = o->nextWord;
        }
        RUNTIME_ARRAY_BODY(args)[index] = o;
        if ((not bigEndian) and size > TargetBytesPerWord) {
          RUNTIME_ARRAY_BODY(args)[++index] = o->nextWord;
        }
        size = TargetBytesPerWord;
        ++index;
      } else {
        size = 8;
      }
      ++footprint;
    }

    Value* result = value(&c, resultType);
    appendCall(&c,
               static_cast<Value*>(address),
               ir::CallingConvention::Native,
               flags,
               traceHandler,
               result,
               util::Slice<ir::Value*>(RUNTIME_ARRAY_BODY(args), index));

    return result;
  }

  virtual ir::Value* stackCall(ir::Value* address,
                               unsigned flags,
                               TraceHandler* traceHandler,
                               ir::Type resultType,
                               Slice<ir::Value*> arguments)
  {
    Value* result = value(&c, resultType);
    Stack* b UNUSED = c.stack;
    appendCall(&c,
               static_cast<Value*>(address),
               ir::CallingConvention::Avian,
               flags,
               traceHandler,
               result,
               arguments);
    assertT(&c, c.stack == b);
    return result;
  }

  virtual void return_(ir::Value* a)
  {
    assertT(&c, a);
    appendReturn(&c, static_cast<Value*>(a));
  }

  virtual void return_()
  {
    appendReturn(&c, 0);
  }

  void initLocalPart(unsigned index, ir::Type type)
  {
    Value* v = value(&c, type);

    if (DebugFrame) {
      fprintf(stderr,
              "init local %p at %d (%d)\n",
              v,
              index,
              frameIndex(&c, index));
    }

    appendFrameSite(&c, v, frameIndex(&c, index));

    Local* local = c.locals + index;
    local->value = v;
    v->home = frameIndex(&c, index);
  }

  virtual void initLocal(unsigned index, ir::Type type)
  {
    unsigned footprint = typeFootprint(&c, type);

    assertT(&c, index + footprint <= c.localFootprint);

    Value* v = value(&c, type);

    if (footprint > 1) {
      assertT(&c, footprint == 2);

      unsigned highIndex;
      unsigned lowIndex;
      if (c.arch->bigEndian()) {
        highIndex = index + 1;
        lowIndex = index;
      } else {
        lowIndex = index + 1;
        highIndex = index;
      }

      if (TargetBytesPerWord == 4) {
        initLocalPart(highIndex, type);
        Value* next = c.locals[highIndex].value;
        v->nextWord = next;
        next->nextWord = v;
        next->wordIndex = 1;
      }

      index = lowIndex;
    }

    if (DebugFrame) {
      fprintf(stderr,
              "init local %p at %d (%d)\n",
              v,
              index,
              frameIndex(&c, index));
    }

    appendFrameSite(&c, v, frameIndex(&c, index));

    Local* local = c.locals + index;
    local->value = v;
    v->home = frameIndex(&c, index);
  }

  virtual void initLocalsFromLogicalIp(unsigned logicalIp)
  {
    assertT(&c, logicalIp < c.logicalCode.count());

    unsigned footprint = sizeof(Local) * c.localFootprint;
    Local* newLocals = static_cast<Local*>(c.zone->allocate(footprint));
    memset(newLocals, 0, footprint);
    c.locals = newLocals;

    Event* e = c.logicalCode[logicalIp]->firstEvent;
    for (int i = 0; i < static_cast<int>(c.localFootprint); ++i) {
      Local* local = e->locals() + i;
      if (local->value) {
        initLocalPart(i, local->value->type);
      }
    }

    linkLocals(&c, e->locals(), newLocals);
  }

  virtual void storeLocal(ir::Value* src, unsigned index)
  {
    compiler::storeLocal(&c,
                         typeFootprint(&c, src->type),
                         static_cast<Value*>(src),
                         index,
                         true);
  }

  virtual ir::Value* loadLocal(ir::Type type, unsigned index)
  {
    return compiler::loadLocal(&c, type, index);
  }

  virtual void saveLocals()
  {
    int oldIp UNUSED = c.logicalIp;
    appendSaveLocals(&c);
    assertT(&c, oldIp == c.logicalIp);
  }

  virtual void checkBounds(ir::Value* object,
                           unsigned lengthOffset,
                           ir::Value* index,
                           intptr_t handler)
  {
    appendBoundsCheck(&c,
                      static_cast<Value*>(object),
                      lengthOffset,
                      static_cast<Value*>(index),
                      handler);
  }

  virtual ir::Value* truncate(ir::Type type, ir::Value* src)
  {
    assertT(&c, src->type.flavor() == type.flavor());
    assertT(&c, type.flavor() != ir::Type::Float);
    assertT(&c, type.rawSize() < src->type.rawSize());
    Value* dst = value(&c, type);
    appendMove(&c,
               lir::Move,
               src->type.size(c.targetInfo),
               src->type.size(c.targetInfo),
               static_cast<Value*>(src),
               type.size(c.targetInfo),
               dst);
    return dst;
  }

  virtual ir::Value* truncateThenExtend(ir::ExtendMode extendMode,
                                        ir::Type extendType,
                                        ir::Type truncateType,
                                        ir::Value* src)
  {
    Value* dst = value(&c, extendType);
    appendMove(&c,
               extendMode == ir::ExtendMode::Signed ? lir::Move : lir::MoveZ,
               TargetBytesPerWord,
               truncateType.size(c.targetInfo),
               static_cast<Value*>(src),
               extendType.size(c.targetInfo) < TargetBytesPerWord
                   ? TargetBytesPerWord
                   : extendType.size(c.targetInfo),
               dst);
    return dst;
  }

  virtual void store(ir::Value* src, ir::Value* dst)
  {
    assertT(&c, src->type.flavor() == dst->type.flavor());

    appendMove(&c,
               lir::Move,
               src->type.size(c.targetInfo),
               src->type.size(c.targetInfo),
               static_cast<Value*>(src),
               dst->type.size(c.targetInfo),
               static_cast<Value*>(dst));
  }

  virtual ir::Value* load(ir::ExtendMode extendMode,
                          ir::Value* src,
                          ir::Type dstType)
  {
    assertT(&c, src->type.flavor() == dstType.flavor());

    Value* dst = value(&c, dstType);
    appendMove(&c,
               extendMode == ir::ExtendMode::Signed ? lir::Move : lir::MoveZ,
               src->type.size(c.targetInfo),
               src->type.size(c.targetInfo),
               static_cast<Value*>(src),
               dstType.size(c.targetInfo) < TargetBytesPerWord
                   ? TargetBytesPerWord
                   : dstType.size(c.targetInfo),
               dst);
    return dst;
  }

  virtual void condJump(lir::TernaryOperation op,
                        ir::Value* a,
                        ir::Value* b,
                        ir::Value* addr)
  {
    assertT(&c,
            (isGeneralBranch(op) and isGeneralValue(a) and isGeneralValue(b))
            or (isFloatBranch(op) and isFloatValue(a) and isFloatValue(b)));

    assertT(&c, a->type == b->type);
    assertT(&c, addr->type == ir::Type::iptr());

    appendBranch(&c,
                 op,
                 static_cast<Value*>(a),
                 static_cast<Value*>(b),
                 static_cast<Value*>(addr));
  }

  virtual void jmp(ir::Value* addr)
  {
    appendJump(&c, lir::Jump, static_cast<Value*>(addr));
  }

  virtual void exit(ir::Value* addr)
  {
    appendJump(&c, lir::Jump, static_cast<Value*>(addr), true);
  }

  virtual ir::Value* binaryOp(lir::TernaryOperation op,
                              ir::Type type,
                              ir::Value* a,
                              ir::Value* b)
  {
    assertT(&c,
            (isGeneralBinaryOp(op) and isGeneralValue(a) and isGeneralValue(b))
            or (isFloatBinaryOp(op) and isFloatValue(a) and isFloatValue(b)));

    Value* result = value(&c, type);

    appendCombine(
        &c, op, static_cast<Value*>(a), static_cast<Value*>(b), result);
    return result;
  }

  virtual ir::Value* unaryOp(lir::BinaryOperation op, ir::Value* a)
  {
    assertT(&c,
            (isGeneralUnaryOp(op) and isGeneralValue(a))
            or (isFloatUnaryOp(op) and isFloatValue(a)));
    Value* result = value(&c, a->type);
    appendTranslate(&c, op, static_cast<Value*>(a), result);
    return result;
  }

  virtual ir::Value* f2f(ir::Type resType, ir::Value* a)
  {
    assertT(&c, isFloatValue(a));
    assertT(&c, resType.flavor() == ir::Type::Float);
    Value* result = value(&c, resType);
    appendTranslate(&c, lir::Float2Float, static_cast<Value*>(a), result);
    return result;
  }

  virtual ir::Value* f2i(ir::Type resType, ir::Value* a)
  {
    assertT(&c, isFloatValue(a));
    assertT(&c, resType.flavor() != ir::Type::Float);
    Value* result = value(&c, resType);
    appendTranslate(&c, lir::Float2Int, static_cast<Value*>(a), result);
    return result;
  }

  virtual ir::Value* i2f(ir::Type resType, ir::Value* a)
  {
    assertT(&c, isGeneralValue(a));
    assertT(&c, resType.flavor() == ir::Type::Float);
    Value* result = value(&c, resType);
    appendTranslate(&c, lir::Int2Float, static_cast<Value*>(a), result);
    return result;
  }

  virtual void nullaryOp(lir::Operation op)
  {
    appendOperation(&c, op);
  }

  virtual void compile(uintptr_t stackOverflowHandler,
                       unsigned stackLimitOffset)
  {
    compiler::compile(&c, stackOverflowHandler, stackLimitOffset);
  }

  virtual unsigned resolve(uint8_t* dst)
  {
    c.machineCode = dst;
    c.assembler->setDestination(dst);

    Block* block = c.firstBlock;
    while (block->nextBlock or block->nextInstruction) {
      Block* next = block->nextBlock
                        ? block->nextBlock
                        : block->nextInstruction->firstEvent->block;

      next->start
          = block->assemblerBlock->resolve(block->start, next->assemblerBlock);

      block = next;
    }

    return c.machineCodeSize = block->assemblerBlock->resolve(block->start, 0)
                               + c.assembler->footerSize();
  }

  virtual unsigned poolSize()
  {
    return c.constantCount * TargetBytesPerWord;
  }

  virtual void write()
  {
    c.assembler->write();

    int i = 0;
    for (ConstantPoolNode* n = c.firstConstant; n; n = n->next) {
      target_intptr_t* target = reinterpret_cast<target_intptr_t*>(
          c.machineCode + pad(c.machineCodeSize, TargetBytesPerWord) + i);

      if (n->promise->resolved()) {
        *target = targetVW(n->promise->value());
      } else {
        class Listener : public Promise::Listener {
         public:
          Listener(target_intptr_t* target) : target(target)
          {
          }

          virtual bool resolve(int64_t value, void** location)
          {
            *target = targetVW(value);
            if (location)
              *location = target;
            return true;
          }

          target_intptr_t* target;
        };
        new (n->promise->listen(sizeof(Listener))) Listener(target);
      }

      i += TargetBytesPerWord;
    }
  }

  virtual void dispose()
  {
    // ignore
  }

  Context c;
  compiler::Client client;
};

}  // namespace compiler

Compiler* makeCompiler(System* system,
                       Assembler* assembler,
                       Zone* zone,
                       Compiler::Client* client)
{
  return new (zone) compiler::MyCompiler(system, assembler, zone, client);
}

}  // namespace codegen
}  // namespace avian