--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/graphite-flattening.c	Sun Aug 21 07:07:55 2011 +0900
@@ -0,0 +1,432 @@
+/* Loop flattening for Graphite.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+   Contributed by Sebastian Pop <sebastian.pop@amd.com>.
+
+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 3, 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 COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree-flow.h"
+#include "tree-dump.h"
+#include "cfgloop.h"
+#include "tree-chrec.h"
+#include "tree-data-ref.h"
+#include "tree-scalar-evolution.h"
+#include "sese.h"
+
+#ifdef HAVE_cloog
+#include "ppl_c.h"
+#include "graphite-ppl.h"
+#include "graphite-poly.h"
+
+/* The loop flattening pass transforms loop nests into a single loop,
+   removing the loop nesting structure.  The auto-vectorization can
+   then apply on the full loop body, without needing the outer-loop
+   vectorization.
+
+   The loop flattening pass that has been described in a very Fortran
+   specific way in the 1992 paper by Reinhard von Hanxleden and Ken
+   Kennedy: "Relaxing SIMD Control Flow Constraints using Loop
+   Transformations" available from
+   http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.54.5033
+
+   The canonical example is as follows: suppose that we have a loop
+   nest with known iteration counts
+
+   | for (i = 1; i <= 6; i++)
+   |   for (j = 1; j <= 6; j++)
+   |     S1(i,j);
+
+   The loop flattening is performed by linearizing the iteration space
+   using the function "f (x) = 6 * i + j".  In this case, CLooG would
+   produce this code:
+
+   | for (c1=7;c1<=42;c1++) {
+   |   i = floord(c1-1,6);
+   |   S1(i,c1-6*i);
+   | }
+
+   There are several limitations for loop flattening that are linked
+   to the expressivity of the polyhedral model.  One has to take an
+   upper bound approximation to deal with the parametric case of loop
+   flattening.  For example, in the loop nest:
+
+   | for (i = 1; i <= N; i++)
+   |   for (j = 1; j <= M; j++)
+   |     S1(i,j);
+
+   One would like to flatten this loop using a linearization function
+   like this "f (x) = M * i + j".  However CLooG's schedules are not
+   expressive enough to deal with this case, and so the parameter M
+   has to be replaced by an integer upper bound approximation.  If we
+   further know in the context of the scop that "M <= 6", then it is
+   possible to linearize the loop with "f (x) = 6 * i + j".  In this
+   case, CLooG would produce this code:
+
+   | for (c1=7;c1<=6*M+N;c1++) {
+   |   i = ceild(c1-N,6);
+   |   if (i <= floord(c1-1,6)) {
+   |     S1(i,c1-6*i);
+   |   }
+   | }
+
+   For an arbitrarily complex loop nest the algorithm proceeds in two
+   steps.  First, the LST is flattened by removing the loops structure
+   and by inserting the statements in the order they appear in
+   depth-first order.  Then, the scattering of each statement is
+   transformed accordingly.
+
+   Supposing that the original program is represented by the following
+   LST:
+
+   | (loop_1
+   |  stmt_1
+   |  (loop_2 stmt_3
+   |   (loop_3 stmt_4)
+   |   (loop_4 stmt_5 stmt_6)
+   |   stmt_7
+   |  )
+   |  stmt_2
+   | )
+
+   Loop flattening traverses the LST in depth-first order, and
+   flattens pairs of loops successively by projecting the inner loops
+   in the iteration domain of the outer loops:
+
+   lst_project_loop (loop_2, loop_3, stride)
+
+   | (loop_1
+   |  stmt_1
+   |  (loop_2 stmt_3 stmt_4
+   |   (loop_4 stmt_5 stmt_6)
+   |   stmt_7
+   |  )
+   |  stmt_2
+   | )
+
+   lst_project_loop (loop_2, loop_4, stride)
+
+   | (loop_1
+   |  stmt_1
+   |  (loop_2 stmt_3 stmt_4 stmt_5 stmt_6 stmt_7)
+   |  stmt_2
+   | )
+
+   lst_project_loop (loop_1, loop_2, stride)
+
+   | (loop_1
+   |  stmt_1 stmt_3 stmt_4 stmt_5 stmt_6 stmt_7 stmt_2
+   | )
+
+   At each step, the iteration domain of the outer loop is enlarged to
+   contain enough points to iterate over the inner loop domain.  */
+
+/* Initializes RES to the number of iterations of the linearized loop
+   LST.  RES is the cardinal of the iteration domain of LST.  */
+
+static void
+lst_linearized_niter (lst_p lst, mpz_t res)
+{
+  int i;
+  lst_p l;
+  mpz_t n;
+
+  mpz_init (n);
+  mpz_set_si (res, 0);
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+    if (LST_LOOP_P (l))
+      {
+	lst_linearized_niter (l, n);
+	mpz_add (res, res, n);
+      }
+
+  if (LST_LOOP_P (lst))
+    {
+      lst_niter_for_loop (lst, n);
+
+      if (mpz_cmp_si (res, 0) != 0)
+	mpz_mul (res, res, n);
+      else
+	mpz_set (res, n);
+    }
+
+  mpz_clear (n);
+}
+
+/* Applies the translation "f (x) = x + OFFSET" to the loop containing
+   STMT.  */
+
+static void
+lst_offset (lst_p stmt, mpz_t offset)
+{
+  lst_p inner = LST_LOOP_FATHER (stmt);
+  poly_bb_p pbb = LST_PBB (stmt);
+  ppl_Polyhedron_t poly = PBB_TRANSFORMED_SCATTERING (pbb);
+  int inner_depth = lst_depth (inner);
+  ppl_dimension_type inner_dim = psct_dynamic_dim (pbb, inner_depth);
+  ppl_Linear_Expression_t expr;
+  ppl_dimension_type dim;
+  ppl_Coefficient_t one;
+  mpz_t x;
+
+  mpz_init (x);
+  mpz_set_si (x, 1);
+  ppl_new_Coefficient (&one);
+  ppl_assign_Coefficient_from_mpz_t (one, x);
+
+  ppl_Polyhedron_space_dimension (poly, &dim);
+  ppl_new_Linear_Expression_with_dimension (&expr, dim);
+
+  ppl_set_coef (expr, inner_dim, 1);
+  ppl_set_inhomogeneous_gmp (expr, offset);
+  ppl_Polyhedron_affine_image (poly, inner_dim, expr, one);
+  ppl_delete_Linear_Expression (expr);
+  ppl_delete_Coefficient (one);
+}
+
+/* Scale by FACTOR the loop LST containing STMT.  */
+
+static void
+lst_scale (lst_p lst, lst_p stmt, mpz_t factor)
+{
+  mpz_t x;
+  ppl_Coefficient_t one;
+  int outer_depth = lst_depth (lst);
+  poly_bb_p pbb = LST_PBB (stmt);
+  ppl_Polyhedron_t poly = PBB_TRANSFORMED_SCATTERING (pbb);
+  ppl_dimension_type outer_dim = psct_dynamic_dim (pbb, outer_depth);
+  ppl_Linear_Expression_t expr;
+  ppl_dimension_type dim;
+
+  mpz_init (x);
+  mpz_set_si (x, 1);
+  ppl_new_Coefficient (&one);
+  ppl_assign_Coefficient_from_mpz_t (one, x);
+
+  ppl_Polyhedron_space_dimension (poly, &dim);
+  ppl_new_Linear_Expression_with_dimension (&expr, dim);
+
+  /* outer_dim = factor * outer_dim.  */
+  ppl_set_coef_gmp (expr, outer_dim, factor);
+  ppl_Polyhedron_affine_image (poly, outer_dim, expr, one);
+  ppl_delete_Linear_Expression (expr);
+
+  mpz_clear (x);
+  ppl_delete_Coefficient (one);
+}
+
+/* Project the INNER loop into the iteration domain of the OUTER loop.
+   STRIDE is the number of iterations between two iterations of the
+   outer loop.  */
+
+static void
+lst_project_loop (lst_p outer, lst_p inner, mpz_t stride)
+{
+  int i;
+  lst_p stmt;
+  mpz_t x;
+  ppl_Coefficient_t one;
+  int outer_depth = lst_depth (outer);
+  int inner_depth = lst_depth (inner);
+
+  mpz_init (x);
+  mpz_set_si (x, 1);
+  ppl_new_Coefficient (&one);
+  ppl_assign_Coefficient_from_mpz_t (one, x);
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (inner), i, stmt)
+    {
+      poly_bb_p pbb = LST_PBB (stmt);
+      ppl_Polyhedron_t poly = PBB_TRANSFORMED_SCATTERING (pbb);
+      ppl_dimension_type outer_dim = psct_dynamic_dim (pbb, outer_depth);
+      ppl_dimension_type inner_dim = psct_dynamic_dim (pbb, inner_depth);
+      ppl_Linear_Expression_t expr;
+      ppl_dimension_type dim;
+      ppl_dimension_type *ds;
+
+      /* There should be no loops under INNER.  */
+      gcc_assert (!LST_LOOP_P (stmt));
+      ppl_Polyhedron_space_dimension (poly, &dim);
+      ppl_new_Linear_Expression_with_dimension (&expr, dim);
+
+      /* outer_dim = outer_dim * stride + inner_dim.  */
+      ppl_set_coef (expr, inner_dim, 1);
+      ppl_set_coef_gmp (expr, outer_dim, stride);
+      ppl_Polyhedron_affine_image (poly, outer_dim, expr, one);
+      ppl_delete_Linear_Expression (expr);
+
+      /* Project on inner_dim.  */
+      ppl_new_Linear_Expression_with_dimension (&expr, dim - 1);
+      ppl_Polyhedron_affine_image (poly, inner_dim, expr, one);
+      ppl_delete_Linear_Expression (expr);
+
+      /* Remove inner loop and the static schedule of its body.  */
+      ds = XNEWVEC (ppl_dimension_type, 2);
+      ds[0] = inner_dim;
+      ds[1] = inner_dim + 1;
+      ppl_Polyhedron_remove_space_dimensions (poly, ds, 2);
+      PBB_NB_SCATTERING_TRANSFORM (pbb) -= 2;
+      free (ds);
+    }
+
+  mpz_clear (x);
+  ppl_delete_Coefficient (one);
+}
+
+/* Flattens the loop nest LST.  Return true when something changed.
+   OFFSET is used to compute the number of iterations of the outermost
+   loop before the current LST is executed.  */
+
+static bool
+lst_flatten_loop (lst_p lst, mpz_t init_offset)
+{
+  int i;
+  lst_p l;
+  bool res = false;
+  mpz_t n, one, offset, stride;
+
+  mpz_init (n);
+  mpz_init (one);
+  mpz_init (offset);
+  mpz_init (stride);
+  mpz_set (offset, init_offset);
+  mpz_set_si (one, 1);
+
+  lst_linearized_niter (lst, stride);
+  lst_niter_for_loop (lst, n);
+  mpz_tdiv_q (stride, stride, n);
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+    if (LST_LOOP_P (l))
+      {
+	res = true;
+
+	lst_flatten_loop (l, offset);
+	lst_niter_for_loop (l, n);
+
+	lst_project_loop (lst, l, stride);
+
+	/* The offset is the number of iterations minus 1, as we want
+	   to execute the next statements at the same iteration as the
+	   last iteration of the loop.  */
+	mpz_sub (n, n, one);
+	mpz_add (offset, offset, n);
+      }
+    else
+      {
+	lst_scale (lst, l, stride);
+	if (mpz_cmp_si (offset, 0) != 0)
+	  lst_offset (l, offset);
+      }
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+    if (LST_LOOP_P (l))
+      lst_remove_loop_and_inline_stmts_in_loop_father (l);
+
+  mpz_clear (n);
+  mpz_clear (one);
+  mpz_clear (offset);
+  mpz_clear (stride);
+  return res;
+}
+
+/* Remove all but the first 3 dimensions of the scattering:
+   - dim0: the static schedule for the loop
+   - dim1: the dynamic schedule of the loop
+   - dim2: the static schedule for the loop body.  */
+
+static void
+remove_unused_scattering_dimensions (lst_p lst)
+{
+  int i;
+  lst_p stmt;
+  mpz_t x;
+  ppl_Coefficient_t one;
+
+  mpz_init (x);
+  mpz_set_si (x, 1);
+  ppl_new_Coefficient (&one);
+  ppl_assign_Coefficient_from_mpz_t (one, x);
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, stmt)
+    {
+      poly_bb_p pbb = LST_PBB (stmt);
+      ppl_Polyhedron_t poly = PBB_TRANSFORMED_SCATTERING (pbb);
+      int j, nb_dims_to_remove = PBB_NB_SCATTERING_TRANSFORM (pbb) - 3;
+      ppl_dimension_type *ds;
+
+      /* There should be no loops inside LST after flattening.  */
+      gcc_assert (!LST_LOOP_P (stmt));
+
+      if (!nb_dims_to_remove)
+	continue;
+
+      ds = XNEWVEC (ppl_dimension_type, nb_dims_to_remove);
+      for (j = 0; j < nb_dims_to_remove; j++)
+	ds[j] = j + 3;
+
+      ppl_Polyhedron_remove_space_dimensions (poly, ds, nb_dims_to_remove);
+      PBB_NB_SCATTERING_TRANSFORM (pbb) -= nb_dims_to_remove;
+      free (ds);
+    }
+
+  mpz_clear (x);
+  ppl_delete_Coefficient (one);
+}
+
+/* Flattens all the loop nests of LST.  Return true when something
+   changed.  */
+
+static bool
+lst_do_flatten (lst_p lst)
+{
+  int i;
+  lst_p l;
+  bool res = false;
+  mpz_t zero;
+
+  if (!lst
+      || !LST_LOOP_P (lst))
+    return false;
+
+  mpz_init (zero);
+  mpz_set_si (zero, 0);
+
+  FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+    if (LST_LOOP_P (l))
+      {
+	res |= lst_flatten_loop (l, zero);
+	remove_unused_scattering_dimensions (l);
+      }
+
+  lst_update_scattering (lst);
+  mpz_clear (zero);
+  return res;
+}
+
+/* Flatten all the loop nests in SCOP.  Returns true when something
+   changed.  */
+
+bool
+flatten_all_loops (scop_p scop)
+{
+  return lst_do_flatten (SCOP_TRANSFORMED_SCHEDULE (scop));
+}
+
+#endif