coregrind/m_transtab.c

/*--------------------------------------------------------------------*/
/*--- Management of the translation table and cache.               ---*/
/*---                                                 m_transtab.c ---*/
/*--------------------------------------------------------------------*/

/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2000-2007 Julian Seward 
      jseward@acm.org

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

#include "pub_core_basics.h"
#include "pub_core_debuglog.h"
#include "pub_core_machine.h"    // For VG(machine_get_VexArchInfo)
#include "pub_core_libcbase.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcprint.h"
#include "pub_core_options.h"
#include "pub_core_tooliface.h"  // For VG_(details).avg_translation_sizeB
#include "pub_core_transtab.h"
#include "pub_core_aspacemgr.h"
#include "pub_core_mallocfree.h" // VG_(out_of_memory_NORETURN)

/* #define DEBUG_TRANSTAB */


/*-------------------------------------------------------------*/
/*--- Management of the FIFO-based translation table+cache. ---*/
/*-------------------------------------------------------------*/

/*------------------ CONSTANTS ------------------*/

/* Number of sectors the TC is divided into.  If you need a larger
   overall translation cache, increase this value. */
#define N_SECTORS 8

/* Number of TC entries in each sector.  This needs to be a prime
   number to work properly, it must be <= 65535 (so that a TT index
   fits in a UShort, leaving room for 0xFFFF(EC2TTE_DELETED) to denote
   'deleted') and it is strongly recommended not to change this.
   65521 is the largest prime <= 65535. */
#define N_TTES_PER_SECTOR /*30011*/ /*40009*/ 65521

/* Because each sector contains a hash table of TTEntries, we need to
   specify the maximum allowable loading, after which the sector is
   deemed full. */
#define SECTOR_TT_LIMIT_PERCENT 80

/* The sector is deemed full when this many entries are in it. */
#define N_TTES_PER_SECTOR_USABLE \
           ((N_TTES_PER_SECTOR * SECTOR_TT_LIMIT_PERCENT) / 100)

/* Equivalence classes for fast address range deletion.  There are 1 +
   2^ECLASS_WIDTH bins.  The highest one, ECLASS_MISC, describes an
   address range which does not fall cleanly within any specific bin.
   Note that ECLASS_SHIFT + ECLASS_WIDTH must be < 32. */
#define ECLASS_SHIFT 11
#define ECLASS_WIDTH 8
#define ECLASS_MISC  (1 << ECLASS_WIDTH)
#define ECLASS_N     (1 + ECLASS_MISC)

#define EC2TTE_DELETED  0xFFFF /* 16-bit special value */


/*------------------ TYPES ------------------*/

/* A translation-table entry.  This indicates precisely which areas of
   guest code are included in the translation, and contains all other
   auxiliary info too.  */
typedef
   struct {
      /* Profiling only: the count and weight (arbitrary meaning) for
         this translation.  Weight is a property of the translation
         itself and computed once when the translation is created.
         Count is an entry count for the translation and is
         incremented by 1 every time the translation is used, if we
         are profiling. */
      UInt     count;
      UShort   weight;

      /* Status of the slot.  Note, we need to be able to do lazy
         deletion, hence the Deleted state. */
      enum { InUse, Deleted, Empty } status;

      /* 64-bit aligned pointer to one or more 64-bit words containing
         the corresponding host code (must be in the same sector!)
         This is a pointer into the sector's tc (code) area. */
      ULong* tcptr;

      /* This is the original guest address that purportedly is the
         entry point of the translation.  You might think that .entry
         should be the same as .vge->base[0], and most of the time it
         is.  However, when doing redirections, that is not the case.
         .vge must always correctly describe the guest code sections
         from which this translation was made.  However, .entry may or
         may not be a lie, depending on whether or not we're doing
         redirection. */
      Addr64 entry;

      /* This structure describes precisely what ranges of guest code
         the translation covers, so we can decide whether or not to
         delete it when translations of a given address range are
         invalidated. */
      VexGuestExtents vge;

      /* Address range summary info: these are pointers back to
         eclass[] entries in the containing Sector.  Those entries in
         turn point back here -- the two structures are mutually
         redundant but both necessary to make fast deletions work.
         The eclass info is similar to, and derived from, this entry's
         'vge' field, but it is not the same */
      UShort n_tte2ec;      // # tte2ec pointers (1 to 3)
      UShort tte2ec_ec[3];  // for each, the eclass #
      UInt   tte2ec_ix[3];  // and the index within the eclass.
      // for i in 0 .. n_tte2ec-1
      //    sec->ec2tte[ tte2ec_ec[i] ][ tte2ec_ix[i] ] 
      // should be the index 
      // of this TTEntry in the containing Sector's tt array.
   }
   TTEntry;


/* Finally, a sector itself.  Each sector contains an array of
   TCEntries, which hold code, and an array of TTEntries, containing
   all required administrative info.  Profiling is supported using the
   TTEntry .count and .weight fields, if required.  Each sector is
   independent in that no cross-sector references are allowed.

   If the sector is not in use, all three pointers are NULL and
   tt_n_inuse is zero.  
*/
typedef
   struct {
      /* The TCEntry area.  Size of this depends on the average
         translation size.  We try and size it so it becomes full
         precisely when this sector's translation table (tt) reaches
         its load limit (SECTOR_TT_LIMIT_PERCENT). */
      ULong* tc;

      /* The TTEntry array.  This is a fixed size, always containing
         exactly N_TTES_PER_SECTOR entries. */
      TTEntry* tt;

      /* This points to the current allocation point in tc. */
      ULong* tc_next;

      /* The count of tt entries with state InUse. */
      Int tt_n_inuse;

      /* Expandable arrays of tt indices for each of the ECLASS_N
         address range equivalence classes.  These hold indices into
         the containing sector's tt array, which in turn should point
         back here. */
      Int     ec2tte_size[ECLASS_N];
      Int     ec2tte_used[ECLASS_N];
      UShort* ec2tte[ECLASS_N];
   }
   Sector;


/*------------------ DECLS ------------------*/

/* The root data structure is an array of sectors.  The index of the
   youngest sector is recorded, and new translations are put into that
   sector.  When it fills up, we move along to the next sector and
   start to fill that up, wrapping around at the end of the array.
   That way, once all N_TC_SECTORS have been bought into use for the
   first time, and are full, we then re-use the oldest sector,
   endlessly. 

   When running, youngest sector should be between >= 0 and <
   N_TC_SECTORS.  The initial -1 value indicates the TT/TC system is
   not yet initialised. 
*/
static Sector sectors[N_SECTORS];
static Int    youngest_sector = -1;

/* The number of ULongs in each TCEntry area.  This is computed once
   at startup and does not change. */
static Int    tc_sector_szQ;


/* Fast helper for the TC.  A direct-mapped cache which holds a set of
   recently used (guest address, host address) pairs.  This array is
   referred to directly from m_dispatch/dispatch-<platform>.S.

   Entries in tt_fast may refer to any valid TC entry, regardless of
   which sector it's in.  Consequently we must be very careful to
   invalidate this cache when TC entries are changed or disappear.

   A special .guest address - TRANSTAB_BOGUS_GUEST_ADDR -- must be
   pointed at to cause that cache entry to miss.  This relies on the
   assumption that no guest code actually has that address, hence a
   value 0x1 seems good.  m_translate gives the client a synthetic
   segfault if it tries to execute at this address.
*/
/*
typedef
   struct { 
      Addr guest;
      Addr host;
   }
   FastCacheEntry;
*/
/*global*/ __attribute__((aligned(16)))
           FastCacheEntry VG_(tt_fast)[VG_TT_FAST_SIZE];
/*
#define TRANSTAB_BOGUS_GUEST_ADDR ((Addr)1)
*/

/* For profiling, we have a parallel array of pointers to .count
   fields in TT entries.  Again, these pointers must be invalidated
   when translations disappear.  A NULL pointer suffices to indicate
   an unused slot.

   When not profiling (the normal case, VG_(clo_profile_flags) == 0),
   all tt_fastN entries are set to NULL at startup and never read nor
   written after that.

   When profiling (VG_(clo_profile_flags) > 0), tt_fast and tt_fastN
   change together: if tt_fast[i].guest is TRANSTAB_BOGUS_GUEST_ADDR
   then the corresponding tt_fastN[i] must be null.  If
   tt_fast[i].guest is any other value, then tt_fastN[i] *must* point
   to the .count field of the corresponding TT entry.

   tt_fast and tt_fastN are referred to from assembly code
   (dispatch.S).
*/
/*global*/ UInt* VG_(tt_fastN)[VG_TT_FAST_SIZE];


/* Make sure we're not used before initialisation. */
static Bool init_done = False;


/*------------------ STATS DECLS ------------------*/

/* Number of fast-cache updates and flushes done. */
ULong n_fast_flushes = 0;
ULong n_fast_updates = 0;

/* Number of full lookups done. */
ULong n_full_lookups = 0;
ULong n_lookup_probes = 0;

/* Number/osize/tsize of translations entered; also the number of
   those for which self-checking was requested. */
ULong n_in_count    = 0;
ULong n_in_osize    = 0;
ULong n_in_tsize    = 0;
ULong n_in_sc_count = 0;

/* Number/osize of translations discarded due to lack of space. */
ULong n_dump_count = 0;
ULong n_dump_osize = 0;

/* Number/osize of translations discarded due to requests to do so. */
ULong n_disc_count = 0;
ULong n_disc_osize = 0;


/*-------------------------------------------------------------*/
/*--- Address-range equivalence class stuff                 ---*/
/*-------------------------------------------------------------*/

/* Return equivalence class number for a range. */

static Int range_to_eclass ( Addr64 start, UInt len )
{
   UInt mask   = (1 << ECLASS_WIDTH) - 1;
   UInt lo     = (UInt)start;
   UInt hi     = lo + len - 1;
   UInt loBits = (lo >> ECLASS_SHIFT) & mask;
   UInt hiBits = (hi >> ECLASS_SHIFT) & mask;
   if (loBits == hiBits) {
      vg_assert(loBits < ECLASS_N-1);
      return loBits;
   } else {
      return ECLASS_MISC;
   }
}


/* Calculates the equivalence class numbers for any VexGuestExtent.
   These are written in *eclasses, which must be big enough to hold 3
   Ints.  The number written, between 1 and 3, is returned.  The
   eclasses are presented in order, and any duplicates are removed.
*/

static 
Int vexGuestExtents_to_eclasses ( /*OUT*/Int* eclasses,
                                  VexGuestExtents* vge )
{
#  define SWAP(_lv1,_lv2) \
      do { Int t = _lv1; _lv1 = _lv2; _lv2 = t; } while (0)

   Int i, j, n_ec, r;

   vg_assert(vge->n_used >= 1 && vge->n_used <= 3);

   n_ec = 0;
   for (i = 0; i < vge->n_used; i++) {
      r = range_to_eclass( vge->base[i], (UInt)vge->len[i] );
      if (r == ECLASS_MISC) 
         goto bad;
      /* only add if we haven't already seen it */
      for (j = 0; j < n_ec; j++)
         if (eclasses[j] == r)
            break;
      if (j == n_ec)
         eclasses[n_ec++] = r;
   }

   if (n_ec == 1)
      return 1;

   if (n_ec == 2) {
      /* sort */
      if (eclasses[0] > eclasses[1])
         SWAP(eclasses[0], eclasses[1]);
      return 2;
   }

   if (n_ec == 3) {
      /* sort */
      if (eclasses[0] > eclasses[2])
         SWAP(eclasses[0], eclasses[2]);
      if (eclasses[0] > eclasses[1])
         SWAP(eclasses[0], eclasses[1]);
      if (eclasses[1] > eclasses[2])
         SWAP(eclasses[1], eclasses[2]);
      return 3;
   }

   /* NOTREACHED */
   vg_assert(0);

  bad:
   eclasses[0] = ECLASS_MISC;
   return 1;

#  undef SWAP
}


/* Add tteno to the set of entries listed for equivalence class ec in
   this sector.  Returns used location in eclass array. */

static 
UInt addEClassNo ( /*MOD*/Sector* sec, Int ec, UShort tteno )
{
   Int    old_sz, new_sz, i, r;
   UShort *old_ar, *new_ar;

   vg_assert(ec >= 0 && ec < ECLASS_N);
   vg_assert(tteno < N_TTES_PER_SECTOR);

   if (0) VG_(printf)("ec %d  gets %d\n", ec, (Int)tteno);

   if (sec->ec2tte_used[ec] >= sec->ec2tte_size[ec]) {

      vg_assert(sec->ec2tte_used[ec] == sec->ec2tte_size[ec]);

      old_sz = sec->ec2tte_size[ec];
      old_ar = sec->ec2tte[ec];
      new_sz = old_sz==0 ? 8 : old_sz<64 ? 2*old_sz : (3*old_sz)/2;
      new_ar = VG_(arena_malloc)(VG_AR_TTAUX, new_sz * sizeof(UShort));
      for (i = 0; i < old_sz; i++)
         new_ar[i] = old_ar[i];
      if (old_ar)
         VG_(arena_free)(VG_AR_TTAUX, old_ar);
      sec->ec2tte_size[ec] = new_sz;
      sec->ec2tte[ec] = new_ar;

      if (0) VG_(printf)("expand ec %d to %d\n", ec, new_sz);
   }

   /* Common case */
   r = sec->ec2tte_used[ec]++;
   vg_assert(r >= 0 && r < sec->ec2tte_size[ec]);
   sec->ec2tte[ec][r] = tteno;
   return (UInt)r;
}


/* 'vge' is being added to 'sec' at TT entry 'tteno'.  Add appropriate
   eclass entries to 'sec'. */

static 
void upd_eclasses_after_add ( /*MOD*/Sector* sec, Int tteno )
{
   Int i, r, eclasses[3];
   TTEntry* tte;
   vg_assert(tteno >= 0 && tteno < N_TTES_PER_SECTOR);

   tte = &sec->tt[tteno];
   r = vexGuestExtents_to_eclasses( eclasses, &tte->vge );

   vg_assert(r >= 1 && r <= 3);
   tte->n_tte2ec = r;

   for (i = 0; i < r; i++) {
      tte->tte2ec_ec[i] = eclasses[i];
      tte->tte2ec_ix[i] = addEClassNo( sec, eclasses[i], (UShort)tteno );
   }
}


/* Check the eclass info in 'sec' to ensure it is consistent.  Returns
   True if OK, False if something's not right.  Expensive. */

static Bool sanity_check_eclasses_in_sector ( Sector* sec )
{
#  define BAD(_str) do { whassup = (_str); goto bad; } while (0)

   HChar*   whassup = NULL;
   Int      i, j, k, n, ec_num, ec_idx;
   TTEntry* tte;
   UShort   tteno;
   ULong*   tce;

   /* Basic checks on this sector */
   if (sec->tt_n_inuse < 0 || sec->tt_n_inuse > N_TTES_PER_SECTOR_USABLE)
      BAD("invalid sec->tt_n_inuse");
   tce = sec->tc_next;
   if (tce < &sec->tc[0] || tce > &sec->tc[tc_sector_szQ])
      BAD("sec->tc_next points outside tc");

   /* For each eclass ... */
   for (i = 0; i < ECLASS_N; i++) {
      if (sec->ec2tte_size[i] == 0 && sec->ec2tte[i] != NULL)
         BAD("ec2tte_size/ec2tte mismatch(1)");
      if (sec->ec2tte_size[i] != 0 && sec->ec2tte[i] == NULL)
         BAD("ec2tte_size/ec2tte mismatch(2)");
      if (sec->ec2tte_used[i] < 0 
          || sec->ec2tte_used[i] > sec->ec2tte_size[i])
         BAD("implausible ec2tte_used");
      if (sec->ec2tte_used[i] == 0)
         continue;

      /* For each tt reference in each eclass .. ensure the reference
         is to a valid tt entry, and that the entry's address ranges
         really include this eclass. */

      for (j = 0; j < sec->ec2tte_used[i]; j++) {
         tteno = sec->ec2tte[i][j];
         if (tteno == EC2TTE_DELETED)
            continue;
         if (tteno >= N_TTES_PER_SECTOR)
            BAD("implausible tteno");
         tte = &sec->tt[tteno];
         if (tte->status != InUse)
            BAD("tteno points to non-inuse tte");
         if (tte->n_tte2ec < 1 || tte->n_tte2ec > 3)
            BAD("tte->n_tte2ec out of range");
         /* Exactly least one of tte->eclasses[0 .. tte->n_eclasses-1]
            must equal i.  Inspect tte's eclass info. */
         n = 0;
         for (k = 0; k < tte->n_tte2ec; k++) {
            if (k < tte->n_tte2ec-1
                && tte->tte2ec_ec[k] >= tte->tte2ec_ec[k+1])
               BAD("tte->tte2ec_ec[..] out of order");
            ec_num = tte->tte2ec_ec[k];
            if (ec_num < 0 || ec_num >= ECLASS_N)
               BAD("tte->tte2ec_ec[..] out of range");
            if (ec_num != i)
               continue;
            ec_idx = tte->tte2ec_ix[k];
            if (ec_idx < 0 || ec_idx >= sec->ec2tte_used[i])
               BAD("tte->tte2ec_ix[..] out of range");
            if (ec_idx == j)
               n++;
         }
         if (n != 1)
            BAD("tteno does not point back at eclass");
      }
   }

   /* That establishes that for each forward pointer from TTEntrys
      there is a corresponding backward pointer from the eclass[]
      arrays.  However, it doesn't rule out the possibility of other,
      bogus pointers in the eclass[] arrays.  So do those similarly:
      scan through them and check the TTEntryies they point at point
      back. */

   for (i = 0; i < N_TTES_PER_SECTOR_USABLE; i++) {

      tte = &sec->tt[i];
      if (tte->status == Empty || tte->status == Deleted) {
         if (tte->n_tte2ec != 0)
            BAD("tte->n_eclasses nonzero for unused tte");
         continue;
      }

      vg_assert(tte->status == InUse);

      if (tte->n_tte2ec < 1 || tte->n_tte2ec > 3)
         BAD("tte->n_eclasses out of range(2)");

      for (j = 0; j < tte->n_tte2ec; j++) {
         ec_num = tte->tte2ec_ec[j];
         if (ec_num < 0 || ec_num >= ECLASS_N)
            BAD("tte->eclass[..] out of range");
         ec_idx = tte->tte2ec_ix[j];
         if (ec_idx < 0 || ec_idx >= sec->ec2tte_used[ec_num])
            BAD("tte->ec_idx[..] out of range(2)");
         if (sec->ec2tte[ec_num][ec_idx] != i)
            BAD("ec2tte does not point back to tte");
      }
   }

   return True;

  bad:
   if (whassup)
      VG_(debugLog)(0, "transtab", "eclass sanity fail: %s\n", whassup);

#  if 0
   VG_(printf)("eclass = %d\n", i);
   VG_(printf)("tteno = %d\n", (Int)tteno);
   switch (tte->status) {
      case InUse:   VG_(printf)("InUse\n"); break;
      case Deleted: VG_(printf)("Deleted\n"); break;
      case Empty:   VG_(printf)("Empty\n"); break;
   }
   if (tte->status != Empty) {
      for (k = 0; k < tte->vge.n_used; k++)
         VG_(printf)("0x%llx %d\n", tte->vge.base[k], 
                                    (Int)tte->vge.len[k]);
   }
#  endif

   return False;

#  undef BAD
}


/* Sanity check absolutely everything.  True == check passed. */

/* forwards */
static Bool sanity_check_redir_tt_tc ( void );
static Bool sanity_check_fastcache ( void );

static Bool sanity_check_all_sectors ( void )
{
   Int     sno;
   Bool    sane;
   Sector* sec;
   for (sno = 0; sno < N_SECTORS; sno++) {
      sec = &sectors[sno];
      if (sec->tc == NULL)
         continue;
      sane = sanity_check_eclasses_in_sector( sec );
      if (!sane)
         return False;
   }
   if ( !sanity_check_redir_tt_tc() )
      return False;
   if ( !sanity_check_fastcache() )
      return False;
   return True;
}


/*-------------------------------------------------------------*/
/*--- Add/find translations                                 ---*/
/*-------------------------------------------------------------*/

static UInt vge_osize ( VexGuestExtents* vge )
{
   UInt i, n = 0;
   for (i = 0; i < vge->n_used; i++)
      n += (UInt)vge->len[i];
   return n;
}

static Bool isValidSector ( Int sector )
{
   if (sector < 0 || sector >= N_SECTORS)
      return False;
   return True;
}

static inline UInt HASH_TT ( Addr64 key )
{
   UInt kHi = (UInt)(key >> 32);
   UInt kLo = (UInt)key;
   UInt k32 = kHi ^ kLo;
   UInt ror = 7;
   if (ror > 0)
      k32 = (k32 >> ror) | (k32 << (32-ror));
   return k32 % N_TTES_PER_SECTOR;
}

static void setFastCacheEntry ( Addr64 key, ULong* tcptr, UInt* count )
{
   UInt cno = (UInt)VG_TT_FAST_HASH(key);
   VG_(tt_fast)[cno].guest = (Addr)key;
   VG_(tt_fast)[cno].host  = (Addr)tcptr;
   if (VG_(clo_profile_flags) > 0)
      VG_(tt_fastN)[cno] = count;
   n_fast_updates++;
   /* This shouldn't fail.  It should be assured by m_translate
      which should reject any attempt to make translation of code
      starting at TRANSTAB_BOGUS_GUEST_ADDR. */
   vg_assert(VG_(tt_fast)[cno].guest != TRANSTAB_BOGUS_GUEST_ADDR);
}

/* Invalidate the fast cache's counter array, VG_(tt_fastN). */
static void invalidateFastNCache ( void )
{
   UInt j;
   vg_assert(VG_TT_FAST_SIZE > 0 && (VG_TT_FAST_SIZE % 4) == 0);
   for (j = 0; j < VG_TT_FAST_SIZE; j += 4) {
      VG_(tt_fastN)[j+0] = NULL;
      VG_(tt_fastN)[j+1] = NULL;
      VG_(tt_fastN)[j+2] = NULL;
      VG_(tt_fastN)[j+3] = NULL;
   }
   vg_assert(j == VG_TT_FAST_SIZE);
}

/* Invalidate the fast cache VG_(tt_fast).  If profiling, also
   invalidate the fast cache's counter array VG_(tt_fastN), otherwise
   don't touch it. */
static void invalidateFastCache ( void )
{
   UInt j;
   /* This loop is popular enough to make it worth unrolling a
      bit, at least on ppc32. */
   vg_assert(VG_TT_FAST_SIZE > 0 && (VG_TT_FAST_SIZE % 4) == 0);
   for (j = 0; j < VG_TT_FAST_SIZE; j += 4) {
      VG_(tt_fast)[j+0].guest = TRANSTAB_BOGUS_GUEST_ADDR;
      VG_(tt_fast)[j+1].guest = TRANSTAB_BOGUS_GUEST_ADDR;
      VG_(tt_fast)[j+2].guest = TRANSTAB_BOGUS_GUEST_ADDR;
      VG_(tt_fast)[j+3].guest = TRANSTAB_BOGUS_GUEST_ADDR;
   }

   if (VG_(clo_profile_flags) > 0)
      invalidateFastNCache();

   vg_assert(j == VG_TT_FAST_SIZE);
   n_fast_flushes++;
}

static Bool sanity_check_fastcache ( void )
{
   UInt j;
   if (0) VG_(printf)("sanity check fastcache\n");
   if (VG_(clo_profile_flags) > 0) {
      /* profiling */
      for (j = 0; j < VG_TT_FAST_SIZE; j++) {
         if (VG_(tt_fastN)[j] == NULL 
             && VG_(tt_fast)[j].guest != TRANSTAB_BOGUS_GUEST_ADDR)
            return False;
         if (VG_(tt_fastN)[j] != NULL 
             && VG_(tt_fast)[j].guest == TRANSTAB_BOGUS_GUEST_ADDR)
            return False;
      }
   } else {
      /* not profiling */
      for (j = 0; j < VG_TT_FAST_SIZE; j++) {
         if (VG_(tt_fastN)[j] != NULL)
            return False;
      }
   }
   return True;
}

static void initialiseSector ( Int sno )
{
   Int    i;
   SysRes sres;
   Sector* sec;
   vg_assert(isValidSector(sno));

   sec = &sectors[sno];

   if (sec->tc == NULL) {

      /* Sector has never been used before.  Need to allocate tt and
         tc. */
      vg_assert(sec->tt == NULL);
      vg_assert(sec->tc_next == NULL);
      vg_assert(sec->tt_n_inuse == 0);
      for (i = 0; i < ECLASS_N; i++) {
         vg_assert(sec->ec2tte_size[i] == 0);
         vg_assert(sec->ec2tte_used[i] == 0);
         vg_assert(sec->ec2tte[i] == NULL);
      }

      VG_(debugLog)(1,"transtab", "allocate sector %d\n", sno);

      sres = VG_(am_mmap_anon_float_valgrind)( 8 * tc_sector_szQ );
      if (sres.isError) {
         VG_(out_of_memory_NORETURN)("initialiseSector(TC)", 
                                     8 * tc_sector_szQ );
	 /*NOTREACHED*/
      }
      sec->tc = (ULong*)sres.res;

      sres = VG_(am_mmap_anon_float_valgrind)
                ( N_TTES_PER_SECTOR * sizeof(TTEntry) );
      if (sres.isError) {
         VG_(out_of_memory_NORETURN)("initialiseSector(TT)", 
                                     N_TTES_PER_SECTOR * sizeof(TTEntry) );
	 /*NOTREACHED*/
      }
      sec->tt = (TTEntry*)sres.res;

      for (i = 0; i < N_TTES_PER_SECTOR; i++) {
         sec->tt[i].status   = Empty;
         sec->tt[i].n_tte2ec = 0;
      }

      if (VG_(clo_verbosity) > 2)
         VG_(message)(Vg_DebugMsg, "TT/TC: initialise sector %d", sno);

   } else {

      /* Sector has been used before.  Dump the old contents. */
      VG_(debugLog)(1,"transtab", "recycle sector %d\n", sno);
      vg_assert(sec->tt != NULL);
      vg_assert(sec->tc_next != NULL);
      n_dump_count += sec->tt_n_inuse;

      /* Visit each just-about-to-be-abandoned translation. */
      for (i = 0; i < N_TTES_PER_SECTOR; i++) {
         if (sec->tt[i].status == InUse) {
            vg_assert(sec->tt[i].n_tte2ec >= 1);
            vg_assert(sec->tt[i].n_tte2ec <= 3);
            n_dump_osize += vge_osize(&sec->tt[i].vge);
            /* Tell the tool too. */
            if (VG_(needs).superblock_discards) {
               VG_TDICT_CALL( tool_discard_superblock_info,
                              sec->tt[i].entry,
                              sec->tt[i].vge );
            }
         } else {
            vg_assert(sec->tt[i].n_tte2ec == 0);
         }
         sec->tt[i].status   = Empty;
         sec->tt[i].n_tte2ec = 0;
      }

      /* Free up the eclass structures. */
      for (i = 0; i < ECLASS_N; i++) {
         if (sec->ec2tte_size[i] == 0) {
            vg_assert(sec->ec2tte_used[i] == 0);
            vg_assert(sec->ec2tte[i] == NULL);
         } else {
            vg_assert(sec->ec2tte[i] != NULL);
            VG_(arena_free)(VG_AR_TTAUX, sec->ec2tte[i]);
            sec->ec2tte[i] = NULL;
            sec->ec2tte_size[i] = 0;
            sec->ec2tte_used[i] = 0;
         }
      }

      if (VG_(clo_verbosity) > 2)
         VG_(message)(Vg_DebugMsg, "TT/TC: recycle sector %d", sno);
   }

   sec->tc_next = sec->tc;
   sec->tt_n_inuse = 0;

   invalidateFastCache();
}

static void invalidate_icache ( void *ptr, Int nbytes )
{
#  if defined(VGA_ppc32) || defined(VGA_ppc64)
   Addr startaddr = (Addr) ptr;
   Addr endaddr   = startaddr + nbytes;
   Addr cls;
   Addr addr;
   VexArchInfo vai;

   if (nbytes == 0) return;
   vg_assert(nbytes > 0);

   VG_(machine_get_VexArchInfo)( NULL, &vai );
   cls = vai.ppc_cache_line_szB;

   /* Stay sane .. */
   vg_assert(cls == 32 || cls == 128);

   startaddr &= ~(cls - 1);
   for (addr = startaddr; addr < endaddr; addr += cls)
      asm volatile("dcbst 0,%0" : : "r" (addr));
   asm volatile("sync");
   for (addr = startaddr; addr < endaddr; addr += cls)
      asm volatile("icbi 0,%0" : : "r" (addr));
   asm volatile("sync; isync");

#  elif defined(VGA_x86)
   /* no need to do anything, hardware provides coherence */

#  elif defined(VGA_amd64)
   /* no need to do anything, hardware provides coherence */

#  else
#    error "Unknown ARCH"
#  endif
}


/* Add a translation of vge to TT/TC.  The translation is temporarily
   in code[0 .. code_len-1].

   pre: youngest_sector points to a valid (although possibly full)
   sector.
*/
void VG_(add_to_transtab)( VexGuestExtents* vge,
                           Addr64           entry,
                           AddrH            code,
                           UInt             code_len,
                           Bool             is_self_checking )
{
   Int    tcAvailQ, reqdQ, y, i;
   ULong  *tcptr, *tcptr2;
   UChar* srcP;
   UChar* dstP;

   vg_assert(init_done);
   vg_assert(vge->n_used >= 1 && vge->n_used <= 3);

   /* 60000: should agree with N_TMPBUF in m_translate.c. */
   vg_assert(code_len > 0 && code_len < 60000);

   if (0)
      VG_(printf)("add_to_transtab(entry = 0x%llx, len = %d)\n",
                  entry, code_len);

   n_in_count++;
   n_in_tsize += code_len;
   n_in_osize += vge_osize(vge);
   if (is_self_checking)
      n_in_sc_count++;

   y = youngest_sector;
   vg_assert(isValidSector(y));

   if (sectors[y].tc == NULL)
      initialiseSector(y);

   /* Try putting the translation in this sector. */
   reqdQ = (code_len + 7) >> 3;

   /* Will it fit in tc? */
   tcAvailQ = ((ULong*)(&sectors[y].tc[tc_sector_szQ]))
              - ((ULong*)(sectors[y].tc_next));
   vg_assert(tcAvailQ >= 0);
   vg_assert(tcAvailQ <= tc_sector_szQ);

   if (tcAvailQ < reqdQ 
       || sectors[y].tt_n_inuse >= N_TTES_PER_SECTOR_USABLE) {
      /* No.  So move on to the next sector.  Either it's never been
         used before, in which case it will get its tt/tc allocated
         now, or it has been used before, in which case it is set to be
         empty, hence throwing out the oldest sector. */
      vg_assert(tc_sector_szQ > 0);
      VG_(debugLog)(1,"transtab", 
                      "declare sector %d full "
                      "(TT loading %2d%%, TC loading %2d%%)\n",
                      y,
                      (100 * sectors[y].tt_n_inuse) 
                         / N_TTES_PER_SECTOR,
                      (100 * (tc_sector_szQ - tcAvailQ)) 
                         / tc_sector_szQ);
      youngest_sector++;
      if (youngest_sector >= N_SECTORS)
         youngest_sector = 0;
      y = youngest_sector;
      initialiseSector(y);
   }

   /* Be sure ... */
   tcAvailQ = ((ULong*)(&sectors[y].tc[tc_sector_szQ]))
              - ((ULong*)(sectors[y].tc_next));
   vg_assert(tcAvailQ >= 0);
   vg_assert(tcAvailQ <= tc_sector_szQ);
   vg_assert(tcAvailQ >= reqdQ);
   vg_assert(sectors[y].tt_n_inuse < N_TTES_PER_SECTOR_USABLE);
   vg_assert(sectors[y].tt_n_inuse >= 0);
 
   /* Copy into tc. */
   tcptr = sectors[y].tc_next;
   vg_assert(tcptr >= &sectors[y].tc[0]);
   vg_assert(tcptr <= &sectors[y].tc[tc_sector_szQ]);

   dstP = (UChar*)tcptr;
   srcP = (UChar*)code;
   for (i = 0; i < code_len; i++)
      dstP[i] = srcP[i];
   sectors[y].tc_next += reqdQ;
   sectors[y].tt_n_inuse++;

   invalidate_icache( dstP, code_len );

   /* more paranoia */
   tcptr2 = sectors[y].tc_next;
   vg_assert(tcptr2 >= &sectors[y].tc[0]);
   vg_assert(tcptr2 <= &sectors[y].tc[tc_sector_szQ]);

   /* Find an empty tt slot, and use it.  There must be such a slot
      since tt is never allowed to get completely full. */
   i = HASH_TT(entry);
   vg_assert(i >= 0 && i < N_TTES_PER_SECTOR);
   while (True) {
      if (sectors[y].tt[i].status == Empty
          || sectors[y].tt[i].status == Deleted)
         break;
      i++;
      if (i >= N_TTES_PER_SECTOR)
         i = 0;
   }

   sectors[y].tt[i].status = InUse;
   sectors[y].tt[i].tcptr  = tcptr;
   sectors[y].tt[i].count  = 0;
   sectors[y].tt[i].weight = 1;
   sectors[y].tt[i].vge    = *vge;
   sectors[y].tt[i].entry  = entry;

   /* Update the fast-cache. */
   setFastCacheEntry( entry, tcptr, &sectors[y].tt[i].count );

   /* Note the eclass numbers for this translation. */
   upd_eclasses_after_add( &sectors[y], i );
}


/* Search for the translation of the given guest address.  If
   requested, a successful search can also cause the fast-caches to be
   updated.  
*/
Bool VG_(search_transtab) ( /*OUT*/AddrH* result,
                            Addr64        guest_addr, 
                            Bool          upd_cache )
{
   Int i, j, k, kstart, sno;

   vg_assert(init_done);
   /* Find the initial probe point just once.  It will be the same in
      all sectors and avoids multiple expensive % operations. */
   n_full_lookups++;
   k      = -1;
   kstart = HASH_TT(guest_addr);
   vg_assert(kstart >= 0 && kstart < N_TTES_PER_SECTOR);

   /* Search in all the sectors.  Although the order should not matter,
      it might be most efficient to search in the order youngest to
      oldest. */
   sno = youngest_sector;
   for (i = 0; i < N_SECTORS; i++) {

      if (sectors[sno].tc == NULL)
         goto notfound; /* sector not in use. */

      k = kstart;
      for (j = 0; j < N_TTES_PER_SECTOR; j++) {
         n_lookup_probes++;
         if (sectors[sno].tt[k].status == InUse
             && sectors[sno].tt[k].entry == guest_addr) {
            /* found it */
            if (upd_cache)
               setFastCacheEntry( 
                  guest_addr, sectors[sno].tt[k].tcptr, 
                              &sectors[sno].tt[k].count );
            if (result)
               *result = (AddrH)sectors[sno].tt[k].tcptr;
            return True;
         }
         if (sectors[sno].tt[k].status == Empty)
            break; /* not found in this sector */
         k++;
         if (k == N_TTES_PER_SECTOR)
            k = 0;
      }

      /* If we fall off the end, all entries are InUse and not
         matching, or Deleted.  In any case we did not find it in this
         sector. */

     notfound:
      /* move to the next oldest sector */
      sno = sno==0 ? (N_SECTORS-1) : (sno-1);
   }

   /* Not found in any sector. */
   return False;
}


/*-------------------------------------------------------------*/
/*--- Delete translations.                                  ---*/
/*-------------------------------------------------------------*/

/* forward */
static void unredir_discard_translations( Addr64, ULong );

/* Stuff for deleting translations which intersect with a given
   address range.  Unfortunately, to make this run at a reasonable
   speed, it is complex. */

static inline
Bool overlap1 ( Addr64 s1, ULong r1, Addr64 s2, ULong r2 )
{
   Addr64 e1 = s1 + r1 - 1ULL;
   Addr64 e2 = s2 + r2 - 1ULL;
   if (e1 < s2 || e2 < s1) 
      return False;
   return True;
}

static inline
Bool overlaps ( Addr64 start, ULong range, VexGuestExtents* vge )
{
   if (overlap1(start, range, vge->base[0], (UInt)vge->len[0]))
      return True;
   if (vge->n_used < 2)
      return False;
   if (overlap1(start, range, vge->base[1], (UInt)vge->len[1]))
      return True;
   if (vge->n_used < 3)
      return False;
   if (overlap1(start, range, vge->base[2], (UInt)vge->len[2]))
      return True;
   return False;
}


/* Delete a tt entry, and update all the eclass data accordingly. */

static void delete_tte ( /*MOD*/Sector* sec, Int tteno )
{
   Int      i, ec_num, ec_idx;
   TTEntry* tte;

   vg_assert(tteno >= 0 && tteno < N_TTES_PER_SECTOR);
   tte = &sec->tt[tteno];
   vg_assert(tte->status == InUse);
   vg_assert(tte->n_tte2ec >= 1 && tte->n_tte2ec <= 3);

   /* Deal with the ec-to-tte links first. */
   for (i = 0; i < tte->n_tte2ec; i++) {
      ec_num = (Int)tte->tte2ec_ec[i];
      ec_idx = tte->tte2ec_ix[i];
      vg_assert(ec_num >= 0 && ec_num < ECLASS_N);
      vg_assert(ec_idx >= 0);
      vg_assert(ec_idx < sec->ec2tte_used[ec_num]);
      /* Assert that the two links point at each other. */
      vg_assert(sec->ec2tte[ec_num][ec_idx] == (UShort)tteno);
      /* "delete" the pointer back to here. */
      sec->ec2tte[ec_num][ec_idx] = EC2TTE_DELETED;
   }

   /* Now fix up this TTEntry. */
   tte->status   = Deleted;
   tte->n_tte2ec = 0;

   /* Stats .. */
   sec->tt_n_inuse--;
   n_disc_count++;
   n_disc_osize += vge_osize(&tte->vge);

   /* Tell the tool too. */
   if (VG_(needs).superblock_discards) {
      VG_TDICT_CALL( tool_discard_superblock_info,
                     tte->entry,
                     tte->vge );
   }
}


/* Delete translations from sec which intersect specified range, but
   only consider translations in the specified eclass. */

static 
Bool delete_translations_in_sector_eclass ( /*MOD*/Sector* sec, 
                                            Addr64 guest_start, ULong range,
                                            Int ec )
{
   Int      i;
   UShort   tteno;
   Bool     anyDeld = False;
   TTEntry* tte;

   vg_assert(ec >= 0 && ec < ECLASS_N);

   for (i = 0; i < sec->ec2tte_used[ec]; i++) {

      tteno = sec->ec2tte[ec][i];
      if (tteno == EC2TTE_DELETED) {
         /* already deleted */
         continue;
      }

      vg_assert(tteno < N_TTES_PER_SECTOR);

      tte = &sec->tt[tteno];
      vg_assert(tte->status == InUse);

      if (overlaps( guest_start, range, &tte->vge )) {
         anyDeld = True;
         delete_tte( sec, (Int)tteno );
      }

   }

   return anyDeld;
}


/* Delete translations from sec which intersect specified range, the
   slow way, by inspecting all translations in sec. */

static 
Bool delete_translations_in_sector ( /*MOD*/Sector* sec, 
                                     Addr64 guest_start, ULong range )
{
   Int  i;
   Bool anyDeld = False;

   for (i = 0; i < N_TTES_PER_SECTOR; i++) {
      if (sec->tt[i].status == InUse
          && overlaps( guest_start, range, &sec->tt[i].vge )) {
         anyDeld = True;
         delete_tte( sec, i );
      }
   }

   return anyDeld;
} 


void VG_(discard_translations) ( Addr64 guest_start, ULong range,
                                 HChar* who )
{
   Sector* sec;
   Int     sno, ec;
   Bool    anyDeleted = False;

   vg_assert(init_done);

   VG_(debugLog)(2, "transtab",
                    "discard_translations(0x%llx, %lld) req by %s\n",
                    guest_start, range, who );

   /* Pre-deletion sanity check */
   if (VG_(clo_sanity_level >= 4)) {
      Bool sane = sanity_check_all_sectors();
      vg_assert(sane);
   }

   if (range == 0)
      return;

   /* There are two different ways to do this.

      If the range fits within a single address-range equivalence
      class, as will be the case for a cache line sized invalidation,
      then we only have to inspect the set of translations listed in
      that equivalence class, and also in the "sin-bin" equivalence
      class ECLASS_MISC.

      Otherwise, the invalidation is of a larger range and probably
      results from munmap.  In this case it's (probably!) faster just
      to inspect all translations, dump those we don't want, and
      regenerate the equivalence class information (since modifying it
      in-situ is even more expensive).
   */

   /* First off, figure out if the range falls within a single class, 
      and if so which one. */

   ec = ECLASS_MISC;
   if (range < (1ULL << ECLASS_SHIFT))
      ec = range_to_eclass( guest_start, (UInt)range );

   /* if ec is ECLASS_MISC then we aren't looking at just a single
      class, so use the slow scheme.  Else use the fast scheme,
      examining 'ec' and ECLASS_MISC. */

   if (ec != ECLASS_MISC) {

      VG_(debugLog)(2, "transtab",
                       "                    FAST, ec = %d\n", ec);

      /* Fast scheme */
      vg_assert(ec >= 0 && ec < ECLASS_MISC);

      for (sno = 0; sno < N_SECTORS; sno++) {
         sec = &sectors[sno];
         if (sec->tc == NULL)
            continue;
         anyDeleted |= delete_translations_in_sector_eclass( 
                         sec, guest_start, range, ec );
         anyDeleted |= delete_translations_in_sector_eclass( 
                         sec, guest_start, range, ECLASS_MISC );
      }

   } else {

      /* slow scheme */

      VG_(debugLog)(2, "transtab",
                       "                    SLOW, ec = %d\n", ec);

      for (sno = 0; sno < N_SECTORS; sno++) {
         sec = &sectors[sno];
         if (sec->tc == NULL)
            continue;
         anyDeleted |= delete_translations_in_sector( 
                         sec, guest_start, range );
      }

   }

   if (anyDeleted)
      invalidateFastCache();

   /* don't forget the no-redir cache */
   unredir_discard_translations( guest_start, range );

   /* Post-deletion sanity check */
   if (VG_(clo_sanity_level >= 4)) {
      Int      i;
      TTEntry* tte;
      Bool     sane = sanity_check_all_sectors();
      vg_assert(sane);
      /* But now, also check the requested address range isn't
         present anywhere. */
      for (sno = 0; sno < N_SECTORS; sno++) {
         sec = &sectors[sno];
         if (sec->tc == NULL)
            continue;
         for (i = 0; i < N_TTES_PER_SECTOR; i++) {
            tte = &sec->tt[i];
            if (tte->status != InUse)
               continue;
            vg_assert(!overlaps( guest_start, range, &tte->vge ));
         }
      }
   }
}


/*------------------------------------------------------------*/
/*--- AUXILIARY: the unredirected TT/TC                    ---*/
/*------------------------------------------------------------*/

/* A very simple translation cache which holds a small number of
   unredirected translations.  This is completely independent of the
   main tt/tc structures.  When unredir_tc or unredir_tt becomes full,
   both structures are simply dumped and we start over.

   Since these translations are unredirected, the search key is (by
   definition) the first address entry in the .vge field. */

/* Sized to hold 500 translations of average size 1000 bytes. */

#define UNREDIR_SZB   1000

#define N_UNREDIR_TT  500
#define N_UNREDIR_TCQ (N_UNREDIR_TT * UNREDIR_SZB / sizeof(ULong))

typedef
   struct {
      VexGuestExtents vge;
      Addr            hcode;
      Bool            inUse;
   }
   UTCEntry;

/* We just allocate forwards in _tc, never deleting. */
static ULong    *unredir_tc;
static Int      unredir_tc_used = N_UNREDIR_TCQ;

/* Slots in _tt can come into use and out again (.inUse).
   Nevertheless _tt_highwater is maintained so that invalidations
   don't have to scan all the slots when only a few are in use.
   _tt_highwater holds the index of the highest ever allocated
   slot. */
static UTCEntry unredir_tt[N_UNREDIR_TT];
static Int      unredir_tt_highwater;


static void init_unredir_tt_tc ( void )
{
   Int i;
   if (unredir_tc == NULL) {
      SysRes sres = VG_(am_mmap_anon_float_valgrind)( N_UNREDIR_TT * UNREDIR_SZB );
      if (sres.isError) {
         VG_(out_of_memory_NORETURN)("init_unredir_tt_tc", N_UNREDIR_TT * UNREDIR_SZB);
         /*NOTREACHED*/
      }
      unredir_tc = (ULong *)sres.res;
   }
   unredir_tc_used = 0;
   for (i = 0; i < N_UNREDIR_TT; i++)
      unredir_tt[i].inUse = False;
   unredir_tt_highwater = -1;
}

/* Do a sanity check; return False on failure. */
static Bool sanity_check_redir_tt_tc ( void )
{
   Int i;
   if (unredir_tt_highwater < -1) return False;
   if (unredir_tt_highwater >= N_UNREDIR_TT) return False;

   for (i = unredir_tt_highwater+1; i < N_UNREDIR_TT; i++)
      if (unredir_tt[i].inUse)
         return False;

   if (unredir_tc_used < 0) return False;
   if (unredir_tc_used > N_UNREDIR_TCQ) return False;

   return True;
}


/* Add an UNREDIRECTED translation of vge to TT/TC.  The translation
   is temporarily in code[0 .. code_len-1].
*/
void VG_(add_to_unredir_transtab)( VexGuestExtents* vge,
                                   Addr64           entry,
                                   AddrH            code,
                                   UInt             code_len,
                                   Bool             is_self_checking )
{
   Int   i, j, code_szQ;
   HChar *srcP, *dstP;

   vg_assert(sanity_check_redir_tt_tc());

   /* This is the whole point: it's not redirected! */
   vg_assert(entry == vge->base[0]);

   /* How many unredir_tt slots are needed */   
   code_szQ = (code_len + 7) / 8;

   /* Look for an empty unredir_tc slot */
   for (i = 0; i < N_UNREDIR_TT; i++)
      if (!unredir_tt[i].inUse)
         break;

   if (i >= N_UNREDIR_TT || code_szQ > (N_UNREDIR_TCQ - unredir_tc_used)) {
      /* It's full; dump everything we currently have */
      init_unredir_tt_tc();
      i = 0;
   }

   vg_assert(unredir_tc_used >= 0);
   vg_assert(unredir_tc_used <= N_UNREDIR_TCQ);
   vg_assert(code_szQ > 0);
   vg_assert(code_szQ + unredir_tc_used <= N_UNREDIR_TCQ);
   vg_assert(i >= 0 && i < N_UNREDIR_TT);
   vg_assert(unredir_tt[i].inUse == False);

   if (i > unredir_tt_highwater)
      unredir_tt_highwater = i;

   dstP = (HChar*)&unredir_tc[unredir_tc_used];
   srcP = (HChar*)code;
   for (j = 0; j < code_len; j++)
      dstP[j] = srcP[j];

   invalidate_icache( dstP, code_len );

   unredir_tt[i].inUse = True;
   unredir_tt[i].vge   = *vge;
   unredir_tt[i].hcode = (Addr)dstP;

   unredir_tc_used += code_szQ;
   vg_assert(unredir_tc_used >= 0);
   vg_assert(unredir_tc_used <= N_UNREDIR_TCQ);

   vg_assert(&dstP[code_len] <= (HChar*)&unredir_tc[unredir_tc_used]);
}

Bool VG_(search_unredir_transtab) ( /*OUT*/AddrH* result,
                                    Addr64        guest_addr )
{
   Int i;
   for (i = 0; i < N_UNREDIR_TT; i++) {
      if (!unredir_tt[i].inUse)
         continue;
      if (unredir_tt[i].vge.base[0] == guest_addr) {
         *result = (AddrH)unredir_tt[i].hcode;
         return True;
      }
   }
   return False;
}

static void unredir_discard_translations( Addr64 guest_start, ULong range )
{
   Int i;

   vg_assert(sanity_check_redir_tt_tc());

   for (i = 0; i <= unredir_tt_highwater; i++) {
      if (unredir_tt[i].inUse
          && overlaps( guest_start, range, &unredir_tt[i].vge))
         unredir_tt[i].inUse = False;
   }
}


/*------------------------------------------------------------*/
/*--- Initialisation.                                      ---*/
/*------------------------------------------------------------*/

void VG_(init_tt_tc) ( void )
{
   Int i, j, avg_codeszQ;

   vg_assert(!init_done);
   init_done = True;

   /* Otherwise lots of things go wrong... */
   vg_assert(sizeof(ULong) == 8);
   vg_assert(sizeof(Addr64) == 8);
   /* check fast cache entries really are 2 words long */
   vg_assert(sizeof(Addr) == sizeof(void*));
   vg_assert(sizeof(FastCacheEntry) == 2 * sizeof(Addr));
   /* check fast cache entries are packed back-to-back with no spaces */
   vg_assert(sizeof( VG_(tt_fast) ) == VG_TT_FAST_SIZE * sizeof(FastCacheEntry));
   /* check fast cache is aligned as we requested.  Not fatal if it
      isn't, but we might as well make sure. */
   vg_assert(VG_IS_16_ALIGNED( ((Addr) & VG_(tt_fast)[0]) ));

   if (VG_(clo_verbosity) > 2)
      VG_(message)(Vg_DebugMsg, 
                   "TT/TC: VG_(init_tt_tc) "
                   "(startup of code management)");

   /* Figure out how big each tc area should be.  */
   avg_codeszQ   = (VG_(details).avg_translation_sizeB + 7) / 8;
   tc_sector_szQ = N_TTES_PER_SECTOR_USABLE * (1 + avg_codeszQ);

   /* Ensure the calculated value is not way crazy. */
   vg_assert(tc_sector_szQ >= 2 * N_TTES_PER_SECTOR_USABLE);
   vg_assert(tc_sector_szQ <= 80 * N_TTES_PER_SECTOR_USABLE);

   /* Initialise the sectors */
   youngest_sector = 0;
   for (i = 0; i < N_SECTORS; i++) {
      sectors[i].tc = NULL;
      sectors[i].tt = NULL;
      sectors[i].tc_next = NULL;
      sectors[i].tt_n_inuse = 0;
      for (j = 0; j < ECLASS_N; j++) {
         sectors[i].ec2tte_size[j] = 0;
         sectors[i].ec2tte_used[j] = 0;
         sectors[i].ec2tte[j] = NULL;
      }
   }

   /* Initialise the fast caches.  If not profiling (the usual case),
      we have to explicitly invalidate the fastN cache as
      invalidateFastCache() won't do that for us. */
   invalidateFastCache();
   if (VG_(clo_profile_flags) == 0)
      invalidateFastNCache();

   /* and the unredir tt/tc */
   init_unredir_tt_tc();

   if (VG_(clo_verbosity) > 2) {
      VG_(message)(Vg_DebugMsg,
         "TT/TC: cache: %d sectors of %d bytes each = %d total", 
          N_SECTORS, 8 * tc_sector_szQ,
          N_SECTORS * 8 * tc_sector_szQ );
      VG_(message)(Vg_DebugMsg,
         "TT/TC: table: %d total entries, max occupancy %d (%d%%)",
         N_SECTORS * N_TTES_PER_SECTOR,
         N_SECTORS * N_TTES_PER_SECTOR_USABLE, 
         SECTOR_TT_LIMIT_PERCENT );
   }

   VG_(debugLog)(2, "transtab",
      "cache: %d sectors of %d bytes each = %d total\n", 
       N_SECTORS, 8 * tc_sector_szQ,
       N_SECTORS * 8 * tc_sector_szQ );
   VG_(debugLog)(2, "transtab",
      "table: %d total entries, max occupancy %d (%d%%)\n",
      N_SECTORS * N_TTES_PER_SECTOR,
      N_SECTORS * N_TTES_PER_SECTOR_USABLE, 
      SECTOR_TT_LIMIT_PERCENT );
}


/*------------------------------------------------------------*/
/*--- Printing out statistics.                             ---*/
/*------------------------------------------------------------*/

static ULong safe_idiv( ULong a, ULong b )
{
   return (b == 0 ? 0 : a / b);
}

UInt VG_(get_bbs_translated) ( void )
{
   return n_in_count;
}

void VG_(print_tt_tc_stats) ( void )
{
   VG_(message)(Vg_DebugMsg,
      "    tt/tc: %,llu tt lookups requiring %,llu probes", 
      n_full_lookups, n_lookup_probes );
   VG_(message)(Vg_DebugMsg,
      "    tt/tc: %,llu fast-cache updates, %,llu flushes", 
      n_fast_updates, n_fast_flushes );

   VG_(message)(Vg_DebugMsg,
                " transtab: new        %,lld "
                "(%,llu -> %,llu; ratio %,llu:10) [%,llu scs]",
                n_in_count, n_in_osize, n_in_tsize,
                safe_idiv(10*n_in_tsize, n_in_osize),
                n_in_sc_count);
   VG_(message)(Vg_DebugMsg,
                " transtab: dumped     %,llu (%,llu -> ?" "?)",
                n_dump_count, n_dump_osize );
   VG_(message)(Vg_DebugMsg,
                " transtab: discarded  %,llu (%,llu -> ?" "?)",
                n_disc_count, n_disc_osize );

   if (0) {
      Int i;
      VG_(printf)("\n");
      for (i = 0; i < ECLASS_N; i++) {
         VG_(printf)(" %4d", sectors[0].ec2tte_used[i]);
         if (i % 16 == 15)
            VG_(printf)("\n");
      }
      VG_(printf)("\n\n");
   }
}

/*------------------------------------------------------------*/
/*--- Printing out of profiling results.                   ---*/
/*------------------------------------------------------------*/

static ULong score ( TTEntry* tte )
{
   return ((ULong)tte->weight) * ((ULong)tte->count);
}

ULong VG_(get_BB_profile) ( BBProfEntry tops[], UInt n_tops )
{
   Int   sno, i, r, s;
   ULong score_total;

   /* First, compute the total weighted count, and find the top N
      ttes.  tops contains pointers to the most-used n_tops blocks, in
      descending order (viz, tops[0] is the highest scorer). */
   for (i = 0; i < n_tops; i++) {
      tops[i].addr  = 0;
      tops[i].score = 0;
   }

   score_total = 0;

   for (sno = 0; sno < N_SECTORS; sno++) {
      if (sectors[sno].tc == NULL)
         continue;
      for (i = 0; i < N_TTES_PER_SECTOR; i++) {
         if (sectors[sno].tt[i].status != InUse)
            continue;
         score_total += score(&sectors[sno].tt[i]);
         /* Find the rank for sectors[sno].tt[i]. */
         r = n_tops-1;
         while (True) {
            if (r == -1)
               break;
             if (tops[r].addr == 0) {
               r--; 
               continue;
             }
             if ( score(&sectors[sno].tt[i]) > tops[r].score ) {
                r--;
                continue;
             }
             break;
         }
         r++;
         vg_assert(r >= 0 && r <= n_tops);
         /* This bb should be placed at r, and bbs above it shifted
            upwards one slot. */
         if (r < n_tops) {
            for (s = n_tops-1; s > r; s--)
               tops[s] = tops[s-1];
            tops[r].addr  = sectors[sno].tt[i].entry;
            tops[r].score = score( &sectors[sno].tt[i] );
         }
      }
   }

   return score_total;
}

/*--------------------------------------------------------------------*/
/*--- end                                                          ---*/
/*--------------------------------------------------------------------*/