GCC 4.2.0 release.

1 files changed, 1070 insertions, 0 deletions

diff --git a/contrib/gcc/tree-ssa-loop-prefetch.c b/contrib/gcc/tree-ssa-loop-prefetch.c
new file mode 100644
index 0000000..f9fe2d3
--- /dev/null
+++ b/contrib/gcc/tree-ssa-loop-prefetch.c
@@ -0,0 +1,1070 @@
+/* Array prefetching.
+   Copyright (C) 2005 Free Software Foundation, Inc.
+   
+This file is part of GCC.
+   
+GCC 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, or (at your option) any
+later version.
+   
+GCC 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 GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, USA.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "rtl.h"
+#include "tm_p.h"
+#include "hard-reg-set.h"
+#include "basic-block.h"
+#include "output.h"
+#include "diagnostic.h"
+#include "tree-flow.h"
+#include "tree-dump.h"
+#include "timevar.h"
+#include "cfgloop.h"
+#include "varray.h"
+#include "expr.h"
+#include "tree-pass.h"
+#include "ggc.h"
+#include "insn-config.h"
+#include "recog.h"
+#include "hashtab.h"
+#include "tree-chrec.h"
+#include "tree-scalar-evolution.h"
+#include "toplev.h"
+#include "params.h"
+#include "langhooks.h"
+
+/* This pass inserts prefetch instructions to optimize cache usage during
+   accesses to arrays in loops.  It processes loops sequentially and:
+
+   1) Gathers all memory references in the single loop.
+   2) For each of the references it decides when it is profitable to prefetch
+      it.  To do it, we evaluate the reuse among the accesses, and determines
+      two values: PREFETCH_BEFORE (meaning that it only makes sense to do
+      prefetching in the first PREFETCH_BEFORE iterations of the loop) and
+      PREFETCH_MOD (meaning that it only makes sense to prefetch in the
+      iterations of the loop that are zero modulo PREFETCH_MOD).  For example
+      (assuming cache line size is 64 bytes, char has size 1 byte and there
+      is no hardware sequential prefetch):
+
+      char *a;
+      for (i = 0; i < max; i++)
+	{
+	  a[255] = ...;		(0)
+	  a[i] = ...;		(1)
+	  a[i + 64] = ...;	(2)
+	  a[16*i] = ...;	(3)
+	  a[187*i] = ...;	(4)
+	  a[187*i + 50] = ...;	(5)
+	}
+
+       (0) obviously has PREFETCH_BEFORE 1
+       (1) has PREFETCH_BEFORE 64, since (2) accesses the same memory
+           location 64 iterations before it, and PREFETCH_MOD 64 (since
+	   it hits the same cache line otherwise).
+       (2) has PREFETCH_MOD 64
+       (3) has PREFETCH_MOD 4
+       (4) has PREFETCH_MOD 1.  We do not set PREFETCH_BEFORE here, since
+           the cache line accessed by (4) is the same with probability only
+	   7/32.
+       (5) has PREFETCH_MOD 1 as well.
+
+   3) We determine how much ahead we need to prefetch.  The number of
+      iterations needed is time to fetch / time spent in one iteration of
+      the loop.  The problem is that we do not know either of these values,
+      so we just make a heuristic guess based on a magic (possibly)
+      target-specific constant and size of the loop.
+
+   4) Determine which of the references we prefetch.  We take into account
+      that there is a maximum number of simultaneous prefetches (provided
+      by machine description).  We prefetch as many prefetches as possible
+      while still within this bound (starting with those with lowest
+      prefetch_mod, since they are responsible for most of the cache
+      misses).
+      
+   5) We unroll and peel loops so that we are able to satisfy PREFETCH_MOD
+      and PREFETCH_BEFORE requirements (within some bounds), and to avoid
+      prefetching nonaccessed memory.
+      TODO -- actually implement peeling.
+      
+   6) We actually emit the prefetch instructions.  ??? Perhaps emit the
+      prefetch instructions with guards in cases where 5) was not sufficient
+      to satisfy the constraints?
+
+   Some other TODO:
+      -- write and use more general reuse analysis (that could be also used
+	 in other cache aimed loop optimizations)
+      -- make it behave sanely together with the prefetches given by user
+	 (now we just ignore them; at the very least we should avoid
+	 optimizing loops in that user put his own prefetches)
+      -- we assume cache line size alignment of arrays; this could be
+	 improved.  */
+
+/* Magic constants follow.  These should be replaced by machine specific
+   numbers.  */
+
+/* A number that should roughly correspond to the number of instructions
+   executed before the prefetch is completed.  */
+
+#ifndef PREFETCH_LATENCY
+#define PREFETCH_LATENCY 200
+#endif
+
+/* Number of prefetches that can run at the same time.  */
+
+#ifndef SIMULTANEOUS_PREFETCHES
+#define SIMULTANEOUS_PREFETCHES 3
+#endif
+
+/* True if write can be prefetched by a read prefetch.  */
+
+#ifndef WRITE_CAN_USE_READ_PREFETCH
+#define WRITE_CAN_USE_READ_PREFETCH 1
+#endif
+
+/* True if read can be prefetched by a write prefetch. */
+
+#ifndef READ_CAN_USE_WRITE_PREFETCH
+#define READ_CAN_USE_WRITE_PREFETCH 0
+#endif
+
+/* Cache line size.  Assumed to be a power of two.  */
+
+#ifndef PREFETCH_BLOCK
+#define PREFETCH_BLOCK 32
+#endif
+
+/* Do we have a forward hardware sequential prefetching?  */
+
+#ifndef HAVE_FORWARD_PREFETCH
+#define HAVE_FORWARD_PREFETCH 0
+#endif
+
+/* Do we have a backward hardware sequential prefetching?  */
+
+#ifndef HAVE_BACKWARD_PREFETCH
+#define HAVE_BACKWARD_PREFETCH 0
+#endif
+
+/* In some cases we are only able to determine that there is a certain
+   probability that the two accesses hit the same cache line.  In this
+   case, we issue the prefetches for both of them if this probability
+   is less then (1000 - ACCEPTABLE_MISS_RATE) promile.  */
+
+#ifndef ACCEPTABLE_MISS_RATE
+#define ACCEPTABLE_MISS_RATE 50
+#endif
+
+#ifndef HAVE_prefetch
+#define HAVE_prefetch 0
+#endif
+
+/* The group of references between that reuse may occur.  */
+
+struct mem_ref_group
+{
+  tree base;			/* Base of the reference.  */
+  HOST_WIDE_INT step;		/* Step of the reference.  */
+  struct mem_ref *refs;		/* References in the group.  */
+  struct mem_ref_group *next;	/* Next group of references.  */
+};
+
+/* Assigned to PREFETCH_BEFORE when all iterations are to be prefetched.  */
+
+#define PREFETCH_ALL		(~(unsigned HOST_WIDE_INT) 0)
+
+/* The memory reference.  */
+
+struct mem_ref
+{
+  tree stmt;			/* Statement in that the reference appears.  */
+  tree mem;			/* The reference.  */
+  HOST_WIDE_INT delta;		/* Constant offset of the reference.  */
+  bool write_p;			/* Is it a write?  */
+  struct mem_ref_group *group;	/* The group of references it belongs to.  */
+  unsigned HOST_WIDE_INT prefetch_mod;
+				/* Prefetch only each PREFETCH_MOD-th
+				   iteration.  */
+  unsigned HOST_WIDE_INT prefetch_before;
+				/* Prefetch only first PREFETCH_BEFORE
+				   iterations.  */
+  bool issue_prefetch_p;	/* Should we really issue the prefetch?  */
+  struct mem_ref *next;		/* The next reference in the group.  */
+};
+
+/* Dumps information about reference REF to FILE.  */
+
+static void
+dump_mem_ref (FILE *file, struct mem_ref *ref)
+{
+  fprintf (file, "Reference %p:\n", (void *) ref);
+
+  fprintf (file, "  group %p (base ", (void *) ref->group);
+  print_generic_expr (file, ref->group->base, TDF_SLIM);
+  fprintf (file, ", step ");
+  fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->group->step);
+  fprintf (file, ")\n");
+
+  fprintf (dump_file, "  delta ");
+  fprintf (file, HOST_WIDE_INT_PRINT_DEC, ref->delta);
+  fprintf (file, "\n");
+
+  fprintf (file, "  %s\n", ref->write_p ? "write" : "read");
+
+  fprintf (file, "\n");
+}
+
+/* Finds a group with BASE and STEP in GROUPS, or creates one if it does not
+   exist.  */
+
+static struct mem_ref_group *
+find_or_create_group (struct mem_ref_group **groups, tree base,
+		      HOST_WIDE_INT step)
+{
+  struct mem_ref_group *group;
+
+  for (; *groups; groups = &(*groups)->next)
+    {
+      if ((*groups)->step == step
+	  && operand_equal_p ((*groups)->base, base, 0))
+	return *groups;
+
+      /* Keep the list of groups sorted by decreasing step.  */
+      if ((*groups)->step < step)
+	break;
+    }
+
+  group = xcalloc (1, sizeof (struct mem_ref_group));
+  group->base = base;
+  group->step = step;
+  group->refs = NULL;
+  group->next = *groups;
+  *groups = group;
+
+  return group;
+}
+
+/* Records a memory reference MEM in GROUP with offset DELTA and write status
+   WRITE_P.  The reference occurs in statement STMT.  */
+
+static void
+record_ref (struct mem_ref_group *group, tree stmt, tree mem,
+	    HOST_WIDE_INT delta, bool write_p)
+{
+  struct mem_ref **aref;
+
+  /* Do not record the same address twice.  */
+  for (aref = &group->refs; *aref; aref = &(*aref)->next)
+    {
+      /* It does not have to be possible for write reference to reuse the read
+	 prefetch, or vice versa.  */
+      if (!WRITE_CAN_USE_READ_PREFETCH
+	  && write_p
+	  && !(*aref)->write_p)
+	continue;
+      if (!READ_CAN_USE_WRITE_PREFETCH
+	  && !write_p
+	  && (*aref)->write_p)
+	continue;
+
+      if ((*aref)->delta == delta)
+	return;
+    }
+
+  (*aref) = xcalloc (1, sizeof (struct mem_ref));
+  (*aref)->stmt = stmt;
+  (*aref)->mem = mem;
+  (*aref)->delta = delta;
+  (*aref)->write_p = write_p;
+  (*aref)->prefetch_before = PREFETCH_ALL;
+  (*aref)->prefetch_mod = 1;
+  (*aref)->issue_prefetch_p = false;
+  (*aref)->group = group;
+  (*aref)->next = NULL;
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    dump_mem_ref (dump_file, *aref);
+}
+
+/* Release memory references in GROUPS.  */
+
+static void
+release_mem_refs (struct mem_ref_group *groups)
+{
+  struct mem_ref_group *next_g;
+  struct mem_ref *ref, *next_r;
+
+  for (; groups; groups = next_g)
+    {
+      next_g = groups->next;
+      for (ref = groups->refs; ref; ref = next_r)
+	{
+	  next_r = ref->next;
+	  free (ref);
+	}
+      free (groups);
+    }
+}
+
+/* A structure used to pass arguments to idx_analyze_ref.  */
+
+struct ar_data
+{
+  struct loop *loop;			/* Loop of the reference.  */
+  tree stmt;				/* Statement of the reference.  */
+  HOST_WIDE_INT *step;			/* Step of the memory reference.  */
+  HOST_WIDE_INT *delta;			/* Offset of the memory reference.  */
+};
+
+/* Analyzes a single INDEX of a memory reference to obtain information
+   described at analyze_ref.  Callback for for_each_index.  */
+
+static bool
+idx_analyze_ref (tree base, tree *index, void *data)
+{
+  struct ar_data *ar_data = data;
+  tree ibase, step, stepsize;
+  HOST_WIDE_INT istep, idelta = 0, imult = 1;
+  affine_iv iv;
+
+  if (TREE_CODE (base) == MISALIGNED_INDIRECT_REF
+      || TREE_CODE (base) == ALIGN_INDIRECT_REF)
+    return false;
+
+  if (!simple_iv (ar_data->loop, ar_data->stmt, *index, &iv, false))
+    return false;
+  ibase = iv.base;
+  step = iv.step;
+
+  if (zero_p (step))
+    istep = 0;
+  else
+    {
+      if (!cst_and_fits_in_hwi (step))
+	return false;
+      istep = int_cst_value (step);
+    }
+
+  if (TREE_CODE (ibase) == PLUS_EXPR
+      && cst_and_fits_in_hwi (TREE_OPERAND (ibase, 1)))
+    {
+      idelta = int_cst_value (TREE_OPERAND (ibase, 1));
+      ibase = TREE_OPERAND (ibase, 0);
+    }
+  if (cst_and_fits_in_hwi (ibase))
+    {
+      idelta += int_cst_value (ibase);
+      ibase = build_int_cst (TREE_TYPE (ibase), 0);
+    }
+
+  if (TREE_CODE (base) == ARRAY_REF)
+    {
+      stepsize = array_ref_element_size (base);
+      if (!cst_and_fits_in_hwi (stepsize))
+	return false;
+      imult = int_cst_value (stepsize);
+
+      istep *= imult;
+      idelta *= imult;
+    }
+
+  *ar_data->step += istep;
+  *ar_data->delta += idelta;
+  *index = ibase;
+
+  return true;
+}
+
+/* Tries to express REF_P in shape &BASE + STEP * iter + DELTA, where DELTA and
+   STEP are integer constants and iter is number of iterations of LOOP.  The
+   reference occurs in statement STMT.  Strips nonaddressable component
+   references from REF_P.  */
+
+static bool
+analyze_ref (struct loop *loop, tree *ref_p, tree *base,
+	     HOST_WIDE_INT *step, HOST_WIDE_INT *delta,
+	     tree stmt)
+{
+  struct ar_data ar_data;
+  tree off;
+  HOST_WIDE_INT bit_offset;
+  tree ref = *ref_p;
+
+  *step = 0;
+  *delta = 0;
+
+  /* First strip off the component references.  Ignore bitfields.  */
+  if (TREE_CODE (ref) == COMPONENT_REF
+      && DECL_NONADDRESSABLE_P (TREE_OPERAND (ref, 1)))
+    ref = TREE_OPERAND (ref, 0);
+
+  *ref_p = ref;
+
+  for (; TREE_CODE (ref) == COMPONENT_REF; ref = TREE_OPERAND (ref, 0))
+    {
+      off = DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1));
+      bit_offset = TREE_INT_CST_LOW (off);
+      gcc_assert (bit_offset % BITS_PER_UNIT == 0);
+      
+      *delta += bit_offset / BITS_PER_UNIT;
+    }
+
+  *base = unshare_expr (ref);
+  ar_data.loop = loop;
+  ar_data.stmt = stmt;
+  ar_data.step = step;
+  ar_data.delta = delta;
+  return for_each_index (base, idx_analyze_ref, &ar_data);
+}
+
+/* Record a memory reference REF to the list REFS.  The reference occurs in
+   LOOP in statement STMT and it is write if WRITE_P.  */
+
+static void
+gather_memory_references_ref (struct loop *loop, struct mem_ref_group **refs,
+			      tree ref, bool write_p, tree stmt)
+{
+  tree base;
+  HOST_WIDE_INT step, delta;
+  struct mem_ref_group *agrp;
+
+  if (!analyze_ref (loop, &ref, &base, &step, &delta, stmt))
+    return;
+
+  /* Now we know that REF = &BASE + STEP * iter + DELTA, where DELTA and STEP
+     are integer constants.  */
+  agrp = find_or_create_group (refs, base, step);
+  record_ref (agrp, stmt, ref, delta, write_p);
+}
+
+/* Record the suitable memory references in LOOP.  */
+
+static struct mem_ref_group *
+gather_memory_references (struct loop *loop)
+{
+  basic_block *body = get_loop_body_in_dom_order (loop);
+  basic_block bb;
+  unsigned i;
+  block_stmt_iterator bsi;
+  tree stmt, lhs, rhs;
+  struct mem_ref_group *refs = NULL;
+
+  /* Scan the loop body in order, so that the former references precede the
+     later ones.  */
+  for (i = 0; i < loop->num_nodes; i++)
+    {
+      bb = body[i];
+      if (bb->loop_father != loop)
+	continue;
+
+      for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+	{
+	  stmt = bsi_stmt (bsi);
+	  if (TREE_CODE (stmt) != MODIFY_EXPR)
+	    continue;
+
+	  lhs = TREE_OPERAND (stmt, 0);
+	  rhs = TREE_OPERAND (stmt, 1);
+
+	  if (REFERENCE_CLASS_P (rhs))
+	    gather_memory_references_ref (loop, &refs, rhs, false, stmt);
+	  if (REFERENCE_CLASS_P (lhs))
+	    gather_memory_references_ref (loop, &refs, lhs, true, stmt);
+	}
+    }
+  free (body);
+
+  return refs;
+}
+
+/* Prune the prefetch candidate REF using the self-reuse.  */
+
+static void
+prune_ref_by_self_reuse (struct mem_ref *ref)
+{
+  HOST_WIDE_INT step = ref->group->step;
+  bool backward = step < 0;
+
+  if (step == 0)
+    {
+      /* Prefetch references to invariant address just once.  */
+      ref->prefetch_before = 1;
+      return;
+    }
+
+  if (backward)
+    step = -step;
+
+  if (step > PREFETCH_BLOCK)
+    return;
+
+  if ((backward && HAVE_BACKWARD_PREFETCH)
+      || (!backward && HAVE_FORWARD_PREFETCH))
+    {
+      ref->prefetch_before = 1;
+      return;
+    }
+
+  ref->prefetch_mod = PREFETCH_BLOCK / step;
+}
+
+/* Divides X by BY, rounding down.  */
+
+static HOST_WIDE_INT
+ddown (HOST_WIDE_INT x, unsigned HOST_WIDE_INT by)
+{
+  gcc_assert (by > 0);
+
+  if (x >= 0)
+    return x / by;
+  else
+    return (x + by - 1) / by;
+}
+
+/* Prune the prefetch candidate REF using the reuse with BY.
+   If BY_IS_BEFORE is true, BY is before REF in the loop.  */
+
+static void
+prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
+			  bool by_is_before)
+{
+  HOST_WIDE_INT step = ref->group->step;
+  bool backward = step < 0;
+  HOST_WIDE_INT delta_r = ref->delta, delta_b = by->delta;
+  HOST_WIDE_INT delta = delta_b - delta_r;
+  HOST_WIDE_INT hit_from;
+  unsigned HOST_WIDE_INT prefetch_before, prefetch_block;
+
+  if (delta == 0)
+    {
+      /* If the references has the same address, only prefetch the
+	 former.  */
+      if (by_is_before)
+	ref->prefetch_before = 0;
+      
+      return;
+    }
+
+  if (!step)
+    {
+      /* If the reference addresses are invariant and fall into the
+	 same cache line, prefetch just the first one.  */
+      if (!by_is_before)
+	return;
+
+      if (ddown (ref->delta, PREFETCH_BLOCK)
+	  != ddown (by->delta, PREFETCH_BLOCK))
+	return;
+
+      ref->prefetch_before = 0;
+      return;
+    }
+
+  /* Only prune the reference that is behind in the array.  */
+  if (backward)
+    {
+      if (delta > 0)
+	return;
+
+      /* Transform the data so that we may assume that the accesses
+	 are forward.  */
+      delta = - delta;
+      step = -step;
+      delta_r = PREFETCH_BLOCK - 1 - delta_r;
+      delta_b = PREFETCH_BLOCK - 1 - delta_b;
+    }
+  else
+    {
+      if (delta < 0)
+	return;
+    }
+
+  /* Check whether the two references are likely to hit the same cache
+     line, and how distant the iterations in that it occurs are from
+     each other.  */
+
+  if (step <= PREFETCH_BLOCK)
+    {
+      /* The accesses are sure to meet.  Let us check when.  */
+      hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK;
+      prefetch_before = (hit_from - delta_r + step - 1) / step;
+
+      if (prefetch_before < ref->prefetch_before)
+	ref->prefetch_before = prefetch_before;
+
+      return;
+    }
+
+  /* A more complicated case.  First let us ensure that size of cache line
+     and step are coprime (here we assume that PREFETCH_BLOCK is a power
+     of two.  */
+  prefetch_block = PREFETCH_BLOCK;
+  while ((step & 1) == 0
+	 && prefetch_block > 1)
+    {
+      step >>= 1;
+      prefetch_block >>= 1;
+      delta >>= 1;
+    }
+
+  /* Now step > prefetch_block, and step and prefetch_block are coprime.
+     Determine the probability that the accesses hit the same cache line.  */
+
+  prefetch_before = delta / step;
+  delta %= step;
+  if ((unsigned HOST_WIDE_INT) delta
+      <= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
+    {
+      if (prefetch_before < ref->prefetch_before)
+	ref->prefetch_before = prefetch_before;
+
+      return;
+    }
+
+  /* Try also the following iteration.  */
+  prefetch_before++;
+  delta = step - delta;
+  if ((unsigned HOST_WIDE_INT) delta
+      <= (prefetch_block * ACCEPTABLE_MISS_RATE / 1000))
+    {
+      if (prefetch_before < ref->prefetch_before)
+	ref->prefetch_before = prefetch_before;
+
+      return;
+    }
+
+  /* The ref probably does not reuse by.  */
+  return;
+}
+
+/* Prune the prefetch candidate REF using the reuses with other references
+   in REFS.  */
+
+static void
+prune_ref_by_reuse (struct mem_ref *ref, struct mem_ref *refs)
+{
+  struct mem_ref *prune_by;
+  bool before = true;
+
+  prune_ref_by_self_reuse (ref);
+
+  for (prune_by = refs; prune_by; prune_by = prune_by->next)
+    {
+      if (prune_by == ref)
+	{
+	  before = false;
+	  continue;
+	}
+
+      if (!WRITE_CAN_USE_READ_PREFETCH
+	  && ref->write_p
+	  && !prune_by->write_p)
+	continue;
+      if (!READ_CAN_USE_WRITE_PREFETCH
+	  && !ref->write_p
+	  && prune_by->write_p)
+	continue;
+
+      prune_ref_by_group_reuse (ref, prune_by, before);
+    }
+}
+
+/* Prune the prefetch candidates in GROUP using the reuse analysis.  */
+
+static void
+prune_group_by_reuse (struct mem_ref_group *group)
+{
+  struct mem_ref *ref_pruned;
+
+  for (ref_pruned = group->refs; ref_pruned; ref_pruned = ref_pruned->next)
+    {
+      prune_ref_by_reuse (ref_pruned, group->refs);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "Reference %p:", (void *) ref_pruned);
+
+	  if (ref_pruned->prefetch_before == PREFETCH_ALL
+	      && ref_pruned->prefetch_mod == 1)
+	    fprintf (dump_file, " no restrictions");
+	  else if (ref_pruned->prefetch_before == 0)
+	    fprintf (dump_file, " do not prefetch");
+	  else if (ref_pruned->prefetch_before <= ref_pruned->prefetch_mod)
+	    fprintf (dump_file, " prefetch once");
+	  else
+	    {
+	      if (ref_pruned->prefetch_before != PREFETCH_ALL)
+		{
+		  fprintf (dump_file, " prefetch before ");
+		  fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
+			   ref_pruned->prefetch_before);
+		}
+	      if (ref_pruned->prefetch_mod != 1)
+		{
+		  fprintf (dump_file, " prefetch mod ");
+		  fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
+			   ref_pruned->prefetch_mod);
+		}
+	    }
+	  fprintf (dump_file, "\n");
+	}
+    }
+}
+
+/* Prune the list of prefetch candidates GROUPS using the reuse analysis.  */
+
+static void
+prune_by_reuse (struct mem_ref_group *groups)
+{
+  for (; groups; groups = groups->next)
+    prune_group_by_reuse (groups);
+}
+
+/* Returns true if we should issue prefetch for REF.  */
+
+static bool
+should_issue_prefetch_p (struct mem_ref *ref)
+{
+  /* For now do not issue prefetches for only first few of the
+     iterations.  */
+  if (ref->prefetch_before != PREFETCH_ALL)
+    return false;
+
+  return true;
+}
+
+/* Decide which of the prefetch candidates in GROUPS to prefetch.
+   AHEAD is the number of iterations to prefetch ahead (which corresponds
+   to the number of simultaneous instances of one prefetch running at a
+   time).  UNROLL_FACTOR is the factor by that the loop is going to be
+   unrolled.  Returns true if there is anything to prefetch.  */
+
+static bool
+schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor,
+		     unsigned ahead)
+{
+  unsigned max_prefetches, n_prefetches;
+  struct mem_ref *ref;
+  bool any = false;
+
+  max_prefetches = (SIMULTANEOUS_PREFETCHES * unroll_factor) / ahead;
+  if (max_prefetches > (unsigned) SIMULTANEOUS_PREFETCHES)
+    max_prefetches = SIMULTANEOUS_PREFETCHES;
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, "Max prefetches to issue: %d.\n", max_prefetches);
+
+  if (!max_prefetches)
+    return false;
+
+  /* For now we just take memory references one by one and issue
+     prefetches for as many as possible.  The groups are sorted
+     starting with the largest step, since the references with
+     large step are more likely to cause many cache misses.  */
+
+  for (; groups; groups = groups->next)
+    for (ref = groups->refs; ref; ref = ref->next)
+      {
+	if (!should_issue_prefetch_p (ref))
+	  continue;
+
+	ref->issue_prefetch_p = true;
+
+	/* If prefetch_mod is less then unroll_factor, we need to insert
+	   several prefetches for the reference.  */
+	n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
+			/ ref->prefetch_mod);
+	if (max_prefetches <= n_prefetches)
+	  return true;
+
+	max_prefetches -= n_prefetches;
+	any = true;
+      }
+
+  return any;
+}
+
+/* Determine whether there is any reference suitable for prefetching
+   in GROUPS.  */
+
+static bool
+anything_to_prefetch_p (struct mem_ref_group *groups)
+{
+  struct mem_ref *ref;
+
+  for (; groups; groups = groups->next)
+    for (ref = groups->refs; ref; ref = ref->next)
+      if (should_issue_prefetch_p (ref))
+	return true;
+
+  return false;
+}
+
+/* Issue prefetches for the reference REF into loop as decided before.
+   HEAD is the number of iterations to prefetch ahead.  UNROLL_FACTOR
+   is the factor by which LOOP was unrolled.  */
+
+static void
+issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead)
+{
+  HOST_WIDE_INT delta;
+  tree addr, addr_base, prefetch, params, write_p;
+  block_stmt_iterator bsi;
+  unsigned n_prefetches, ap;
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, "Issued prefetch for %p.\n", (void *) ref);
+
+  bsi = bsi_for_stmt (ref->stmt);
+
+  n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
+		  / ref->prefetch_mod);
+  addr_base = build_fold_addr_expr_with_type (ref->mem, ptr_type_node);
+  addr_base = force_gimple_operand_bsi (&bsi, unshare_expr (addr_base), true, NULL);
+
+  for (ap = 0; ap < n_prefetches; ap++)
+    {
+      /* Determine the address to prefetch.  */
+      delta = (ahead + ap * ref->prefetch_mod) * ref->group->step;
+      addr = fold_build2 (PLUS_EXPR, ptr_type_node,
+			  addr_base, build_int_cst (ptr_type_node, delta));
+      addr = force_gimple_operand_bsi (&bsi, unshare_expr (addr), true, NULL);
+
+      /* Create the prefetch instruction.  */
+      write_p = ref->write_p ? integer_one_node : integer_zero_node;
+      params = tree_cons (NULL_TREE, addr,
+			  tree_cons (NULL_TREE, write_p, NULL_TREE));
+				 
+      prefetch = build_function_call_expr (built_in_decls[BUILT_IN_PREFETCH],
+					   params);
+      bsi_insert_before (&bsi, prefetch, BSI_SAME_STMT);
+    }
+}
+
+/* Issue prefetches for the references in GROUPS into loop as decided before.
+   HEAD is the number of iterations to prefetch ahead.  UNROLL_FACTOR is the
+   factor by that LOOP was unrolled.  */
+
+static void
+issue_prefetches (struct mem_ref_group *groups,
+		  unsigned unroll_factor, unsigned ahead)
+{
+  struct mem_ref *ref;
+
+  for (; groups; groups = groups->next)
+    for (ref = groups->refs; ref; ref = ref->next)
+      if (ref->issue_prefetch_p)
+	issue_prefetch_ref (ref, unroll_factor, ahead);
+}
+
+/* Determines whether we can profitably unroll LOOP FACTOR times, and if
+   this is the case, fill in DESC by the description of number of
+   iterations.  */
+
+static bool
+should_unroll_loop_p (struct loop *loop, struct tree_niter_desc *desc,
+		      unsigned factor)
+{
+  if (!can_unroll_loop_p (loop, factor, desc))
+    return false;
+
+  /* We only consider loops without control flow for unrolling.  This is not
+     a hard restriction -- tree_unroll_loop works with arbitrary loops
+     as well; but the unrolling/prefetching is usually more profitable for
+     loops consisting of a single basic block, and we want to limit the
+     code growth.  */
+  if (loop->num_nodes > 2)
+    return false;
+
+  return true;
+}
+
+/* Determine the coefficient by that unroll LOOP, from the information
+   contained in the list of memory references REFS.  Description of
+   umber of iterations of LOOP is stored to DESC.  AHEAD is the number
+   of iterations ahead that we need to prefetch.  NINSNS is number of
+   insns of the LOOP.  */
+
+static unsigned
+determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs,
+			 unsigned ahead, unsigned ninsns,
+			 struct tree_niter_desc *desc)
+{
+  unsigned upper_bound, size_factor, constraint_factor;
+  unsigned factor, max_mod_constraint, ahead_factor;
+  struct mem_ref_group *agp;
+  struct mem_ref *ref;
+
+  upper_bound = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
+
+  /* First check whether the loop is not too large to unroll.  */
+  size_factor = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / ninsns;
+  if (size_factor <= 1)
+    return 1;
+
+  if (size_factor < upper_bound)
+    upper_bound = size_factor;
+
+  max_mod_constraint = 1;
+  for (agp = refs; agp; agp = agp->next)
+    for (ref = agp->refs; ref; ref = ref->next)
+      if (should_issue_prefetch_p (ref)
+	  && ref->prefetch_mod > max_mod_constraint)
+	max_mod_constraint = ref->prefetch_mod;
+
+  /* Set constraint_factor as large as needed to be able to satisfy the
+     largest modulo constraint.  */
+  constraint_factor = max_mod_constraint;
+
+  /* If ahead is too large in comparison with the number of available
+     prefetches, unroll the loop as much as needed to be able to prefetch
+     at least partially some of the references in the loop.  */
+  ahead_factor = ((ahead + SIMULTANEOUS_PREFETCHES - 1)
+		  / SIMULTANEOUS_PREFETCHES);
+
+  /* Unroll as much as useful, but bound the code size growth.  */
+  if (constraint_factor < ahead_factor)
+    factor = ahead_factor;
+  else
+    factor = constraint_factor;
+  if (factor > upper_bound)
+    factor = upper_bound;
+
+  if (!should_unroll_loop_p (loop, desc, factor))
+    return 1;
+
+  return factor;
+}
+
+/* Issue prefetch instructions for array references in LOOP.  Returns
+   true if the LOOP was unrolled.  LOOPS is the array containing all
+   loops.  */
+
+static bool
+loop_prefetch_arrays (struct loops *loops, struct loop *loop)
+{
+  struct mem_ref_group *refs;
+  unsigned ahead, ninsns, unroll_factor;
+  struct tree_niter_desc desc;
+  bool unrolled = false;
+
+  /* Step 1: gather the memory references.  */
+  refs = gather_memory_references (loop);
+
+  /* Step 2: estimate the reuse effects.  */
+  prune_by_reuse (refs);
+
+  if (!anything_to_prefetch_p (refs))
+    goto fail;
+
+  /* Step 3: determine the ahead and unroll factor.  */
+
+  /* FIXME: We should use not size of the loop, but the average number of
+     instructions executed per iteration of the loop.  */
+  ninsns = tree_num_loop_insns (loop);
+  ahead = (PREFETCH_LATENCY + ninsns - 1) / ninsns;
+  unroll_factor = determine_unroll_factor (loop, refs, ahead, ninsns,
+					   &desc);
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, "Ahead %d, unroll factor %d\n", ahead, unroll_factor);
+
+  /* If the loop rolls less than the required unroll factor, prefetching
+     is useless.  */
+  if (unroll_factor > 1
+      && cst_and_fits_in_hwi (desc.niter)
+      && (unsigned HOST_WIDE_INT) int_cst_value (desc.niter) < unroll_factor)
+    goto fail;
+
+  /* Step 4: what to prefetch?  */
+  if (!schedule_prefetches (refs, unroll_factor, ahead))
+    goto fail;
+
+  /* Step 5: unroll the loop.  TODO -- peeling of first and last few
+     iterations so that we do not issue superfluous prefetches.  */
+  if (unroll_factor != 1)
+    {
+      tree_unroll_loop (loops, loop, unroll_factor,
+			single_dom_exit (loop), &desc);
+      unrolled = true;
+    }
+
+  /* Step 6: issue the prefetches.  */
+  issue_prefetches (refs, unroll_factor, ahead);
+
+fail:
+  release_mem_refs (refs);
+  return unrolled;
+}
+
+/* Issue prefetch instructions for array references in LOOPS.  */
+
+unsigned int
+tree_ssa_prefetch_arrays (struct loops *loops)
+{
+  unsigned i;
+  struct loop *loop;
+  bool unrolled = false;
+  int todo_flags = 0;
+
+  if (!HAVE_prefetch
+      /* It is possible to ask compiler for say -mtune=i486 -march=pentium4.
+	 -mtune=i486 causes us having PREFETCH_BLOCK 0, since this is part
+	 of processor costs and i486 does not have prefetch, but
+	 -march=pentium4 causes HAVE_prefetch to be true.  Ugh.  */
+      || PREFETCH_BLOCK == 0)
+    return 0;
+
+  initialize_original_copy_tables ();
+
+  if (!built_in_decls[BUILT_IN_PREFETCH])
+    {
+      tree type = build_function_type (void_type_node,
+				       tree_cons (NULL_TREE,
+						  const_ptr_type_node,
+						  NULL_TREE));
+      tree decl = lang_hooks.builtin_function ("__builtin_prefetch", type,
+			BUILT_IN_PREFETCH, BUILT_IN_NORMAL,
+			NULL, NULL_TREE);
+      DECL_IS_NOVOPS (decl) = true;
+      built_in_decls[BUILT_IN_PREFETCH] = decl;
+    }
+
+  /* We assume that size of cache line is a power of two, so verify this
+     here.  */
+  gcc_assert ((PREFETCH_BLOCK & (PREFETCH_BLOCK - 1)) == 0);
+
+  for (i = loops->num - 1; i > 0; i--)
+    {
+      loop = loops->parray[i];
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "Processing loop %d:\n", loop->num);
+
+      if (loop)
+	unrolled |= loop_prefetch_arrays (loops, loop);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "\n\n");
+    }
+
+  if (unrolled)
+    {
+      scev_reset ();
+      todo_flags |= TODO_cleanup_cfg;
+    }
+
+  free_original_copy_tables ();
+  return todo_flags;
+}