Merge lp:~eres/gcc-linaro/sms_doloop_for_ARM_new_version into lp:gcc-linaro/4.5

[Revital Eres]

Implement doloop pattern for ARM and support it in SMS.
The change consists of these patches that sent upstream:
1) Doloop pattern for ARM:
http://gcc.gnu.org/ml/gcc-patches/2011-01/msg01718.html (approved for trunk)
2) Support closing_branch_deps:
 http://gcc.gnu.org/ml/gcc-patches/2011-05/msg00592.html (approved for trunk)
3) New flag to apply SMS when SC equals 1
http://gcc.gnu.org/ml/gcc-patches/2011-04/msg01304.html (approved for trunk)

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cbuild successfully built this on i686-lucid-cbuild114-scorpius-i686r1.

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The test suite results were unchanged compared to the branch point lp:gcc-linaro+bzr99506.

The full testsuite results are at:
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cbuild-checked: i686-lucid-cbuild114-scorpius-i686r1

[Richard Sandiford (rsandifo)]

OK.

(I don't know the code well enough to offer a meaningful review,
but upstream accepted the patches concurrently with this merge
request.)

review: Approve

=== modified file 'ChangeLog.linaro'
--- ChangeLog.linaro	2011-05-06 11:02:43 +0000
+++ ChangeLog.linaro	2011-05-11 08:13:47 +0000
@@ -1,3 +1,38 @@
[phone]  Revital Eres  <[e-mail]>
+
+	gcc/
+	* loop-doloop.c (doloop_condition_get): Support new form of
+	doloop pattern and use prev_nondebug_insn instead of PREV_INSN.
+	* config/arm/thumb2.md (*thumb2_addsi3_compare0): Remove "*".
+	(doloop_end): New.
+	* config/arm/arm.md (*addsi3_compare0): Remove "*".
+	* params.def (sms-min-sc): New param flag.
+	* doc/invoke.texi (sms-min-sc): Document it.
+	* ddg.c (create_ddg_dep_from_intra_loop_link): If a true dep edge
+	enters the branch create an anti edge in the opposite direction
+	to prevent the creation of reg-moves.
+	(get_node_of_insn_uid, check_closing_branch_deps): Delete
+	functions.
+	(create_ddg): Restore previous definition and implementation.
+	* ddg.h (create_ddg): Restore previous definition.
+	* modulo-sched.c: Adjust comment to reflect the fact we are
+	scheduling closing branch.
+	(PS_STAGE_COUNT): Rename to CALC_STAGE_COUNT and redefine.
+	(stage_count): New field in struct partial_schedule.
+	(calculate_stage_count): New function.
+	(normalize_sched_times): Rename to reset_sched_times and handle
+	incrementing the sched time of the nodes by a constant value
+	passed as parameter.
+	(duplicate_insns_of_cycles): Skip closing branch.
+	(sms_schedule_by_order): Schedule closing branch.
+	(ps_insn_find_column): Handle closing branch.
+	(sms_schedule): Call reset_sched_times and adjust the code to
+	support scheduling of the closing branch. Use sms-min-sc.
+	Support new form of doloop pattern.
+	(ps_insert_empty_row): Update calls to normalize_sched_times
+	and rotate_partial_schedule functions.	
+	(mark_doloop_insns): Remove.
+
 2011-05-06  Richard Sandiford  <[e-mail]>
 
 	gcc/

=== modified file 'gcc/ddg.c'
--- gcc/ddg.c	2011-03-24 07:45:38 +0000
+++ gcc/ddg.c	2011-05-11 08:13:47 +0000
@@ -60,8 +60,6 @@
 static ddg_edge_ptr create_ddg_edge (ddg_node_ptr, ddg_node_ptr, dep_type,
 				     dep_data_type, int, int);
 static void add_edge_to_ddg (ddg_ptr g, ddg_edge_ptr);
-static ddg_node_ptr get_node_of_insn_uid (ddg_ptr, int);
-
 

 /* Auxiliary variable for mem_read_insn_p/mem_write_insn_p.  */
 static bool mem_ref_p;
@@ -199,6 +197,11 @@
         }
     }
 
+  /* If a true dep edge enters the branch create an anti edge in the
+     opposite direction to prevent the creation of reg-moves.  */
+  if ((DEP_TYPE (link) == REG_DEP_TRUE) && JUMP_P (dest_node->insn))
+    create_ddg_dep_no_link (g, dest_node, src_node, ANTI_DEP, REG_DEP, 1);
+
    latency = dep_cost (link);
    e = create_ddg_edge (src_node, dest_node, t, dt, latency, distance);
    add_edge_to_ddg (g, e);
@@ -452,65 +455,12 @@
   sched_free_deps (head, tail, false);
 }
 
-/* Given DOLOOP_INSNS which holds the instructions that
-   belong to the do-loop part; mark closing_branch_deps field in ddg G
-   as TRUE if the do-loop part's instructions are dependent on the other
-   loop instructions.  Otherwise mark it as FALSE.  */
-static void
-check_closing_branch_deps (ddg_ptr g, sbitmap doloop_insns)
-{
-  sbitmap_iterator sbi;
-  unsigned int u = 0;
-
-  EXECUTE_IF_SET_IN_SBITMAP (doloop_insns, 0, u, sbi)
-  {
-    ddg_edge_ptr e;
-    ddg_node_ptr u_node = get_node_of_insn_uid (g, u);
-
-    gcc_assert (u_node);
-
-    for (e = u_node->in; e != 0; e = e->next_in)
-      {
-	ddg_node_ptr v_node = e->src;
-
-	if (((unsigned int) INSN_UID (v_node->insn) == u)
-	    || DEBUG_INSN_P (v_node->insn))
-	  continue;
-	
-	/* Ignore dependencies between memory writes and the
-	   jump.  */
-	if (JUMP_P (u_node->insn)
-	    && e->type == OUTPUT_DEP 
-            && mem_write_insn_p (v_node->insn))
-	  continue;
-	if (!TEST_BIT (doloop_insns, INSN_UID (v_node->insn)))
-	  {
-	    g->closing_branch_deps = 1;
-	    return;
-	  }
-      }
-    for (e = u_node->out; e != 0; e = e->next_out)
-      {
-	ddg_node_ptr v_node = e->dest;
-
-	if (((unsigned int) INSN_UID (v_node->insn) == u)
-            || DEBUG_INSN_P (v_node->insn))
-	  continue;
-	if (!TEST_BIT (doloop_insns, INSN_UID (v_node->insn)))
-	  {
-	    g->closing_branch_deps = 1;
-	    return;
-	  }
-      }
-  }
-  g->closing_branch_deps = 0;
-}
 
 /* Given a basic block, create its DDG and return a pointer to a variable
    of ddg type that represents it.
    Initialize the ddg structure fields to the appropriate values.  */
 ddg_ptr
-create_ddg (basic_block bb, sbitmap doloop_insns)
+create_ddg (basic_block bb, int closing_branch_deps)
 {
   ddg_ptr g;
   rtx insn, first_note;
@@ -520,6 +470,7 @@
   g = (ddg_ptr) xcalloc (1, sizeof (struct ddg));
 
   g->bb = bb;
+  g->closing_branch_deps = closing_branch_deps;
 
   /* Count the number of insns in the BB.  */
   for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb));
@@ -592,11 +543,6 @@
   /* Build the data dependency graph.  */
   build_intra_loop_deps (g);
   build_inter_loop_deps (g);
-
-  /* Check whether the do-loop part is decoupled from the other loop
-     instructions.  */
-  check_closing_branch_deps (g, doloop_insns);
-
   return g;
 }
 
@@ -890,18 +836,6 @@
   return NULL;
 }
 
-/* Given the uid of an instruction UID return the node that represents it.  */
-static ddg_node_ptr
-get_node_of_insn_uid (ddg_ptr g, int uid)
-{
-  int i;
-
-  for (i = 0; i < g->num_nodes; i++)
-    if (uid == INSN_UID (g->nodes[i].insn))
-      return &g->nodes[i];
-  return NULL;
-}
-
 /* Given a set OPS of nodes in the DDG, find the set of their successors
    which are not in OPS, and set their bits in SUCC.  Bits corresponding to
    OPS are cleared from SUCC.  Leaves the other bits in SUCC unchanged.  */

=== modified file 'gcc/ddg.h'
--- gcc/ddg.h	2011-03-24 07:45:38 +0000
+++ gcc/ddg.h	2011-05-11 08:13:47 +0000
@@ -167,7 +167,7 @@
 };
 
 

-ddg_ptr create_ddg (basic_block, sbitmap);
+ddg_ptr create_ddg (basic_block, int closing_branch_deps);
 void free_ddg (ddg_ptr);
 
 void print_ddg (FILE *, ddg_ptr);

=== modified file 'gcc/doc/invoke.texi'
--- gcc/doc/invoke.texi	2011-04-17 23:04:58 +0000
+++ gcc/doc/invoke.texi	2011-05-11 08:13:47 +0000
@@ -8430,6 +8430,10 @@
 The maximum number of best instructions in the ready list that are considered
 for renaming in the selective scheduler.  The default value is 2.
 
+@item sms-min-sc
+The minimum value of stage count that swing modulo scheduler will
+generate.  The default value is 2.
+
 @item max-last-value-rtl
 The maximum size measured as number of RTLs that can be recorded in an expression
 in combiner for a pseudo register as last known value of that register.  The default

=== modified file 'gcc/modulo-sched.c'
--- gcc/modulo-sched.c	2011-03-24 07:45:38 +0000
+++ gcc/modulo-sched.c	2011-05-11 08:13:47 +0000
@@ -84,14 +84,13 @@
       II cycles (i.e. use register copies to prevent a def from overwriting
       itself before reaching the use).
 
-    SMS works with countable loops (1) whose control part can be easily
-    decoupled from the rest of the loop and (2) whose loop count can
-    be easily adjusted.  This is because we peel a constant number of
-    iterations into a prologue and epilogue for which we want to avoid
-    emitting the control part, and a kernel which is to iterate that
-    constant number of iterations less than the original loop.  So the
-    control part should be a set of insns clearly identified and having
-    its own iv, not otherwise used in the loop (at-least for now), which
+    SMS works with countable loops whose loop count can be easily
+    adjusted.  This is because we peel a constant number of iterations
+    into a prologue and epilogue for which we want to avoid emitting
+    the control part, and a kernel which is to iterate that constant
+    number of iterations less than the original loop.  So the control
+    part should be a set of insns clearly identified and having its
+    own iv, not otherwise used in the loop (at-least for now), which
     initializes a register before the loop to the number of iterations.
     Currently SMS relies on the do-loop pattern to recognize such loops,
     where (1) the control part comprises of all insns defining and/or
@@ -116,7 +115,7 @@
 
 /* The number of different iterations the nodes in ps span, assuming
    the stage boundaries are placed efficiently.  */
-#define CALC_STAGE_COUNT(min_cycle,max_cycle,ii) ((max_cycle - min_cycle \
+#define CALC_STAGE_COUNT(max_cycle,min_cycle,ii) ((max_cycle - min_cycle \
                          + 1 + ii - 1) / ii)
 /* The stage count of ps.  */
 #define PS_STAGE_COUNT(ps) (((partial_schedule_ptr)(ps))->stage_count)
@@ -200,7 +199,6 @@
 static void duplicate_insns_of_cycles (partial_schedule_ptr,
 				       int, int, int, rtx);
 static int calculate_stage_count (partial_schedule_ptr ps);
-
 #define SCHED_ASAP(x) (((node_sched_params_ptr)(x)->aux.info)->asap)
 #define SCHED_TIME(x) (((node_sched_params_ptr)(x)->aux.info)->time)
 #define SCHED_FIRST_REG_MOVE(x) \
@@ -318,7 +316,7 @@
                              : prev_nondebug_insn (tail));
 
   for (insn = head; insn != first_insn_not_to_check; insn = NEXT_INSN (insn))
-    if (reg_mentioned_p (reg, insn) && NONDEBUG_INSN_P (insn))
+    if (reg_mentioned_p (reg, insn) && !DEBUG_INSN_P (insn))
       {
         if (dump_file)
         {
@@ -337,24 +335,6 @@
 #endif
 }
 
-/* Mark in DOLOOP_INSNS the instructions that belong to the do-loop part.
-  Use TAIL to recognize that part.  */
-static void
-mark_doloop_insns (sbitmap doloop_insns, rtx tail)
-{
-  rtx first_insn_not_to_check, insn;
-
-  /* This is the first instruction which belongs the doloop part.  */
-  first_insn_not_to_check = (GET_CODE (PATTERN (tail)) == PARALLEL ? tail
-			     : prev_nondebug_insn (tail));
-
-  sbitmap_zero (doloop_insns);
-  for (insn = first_insn_not_to_check; insn != NEXT_INSN (tail);
-       insn = NEXT_INSN (insn))
-    if (NONDEBUG_INSN_P (insn))
-      SET_BIT (doloop_insns, INSN_UID (insn));
-}
-
 /* Check if COUNT_REG is set to a constant in the PRE_HEADER block, so
    that the number of iterations is a compile-time constant.  If so,
    return the rtx that sets COUNT_REG to a constant, and set COUNT to
@@ -607,44 +587,42 @@
 	ddg_node_ptr u = crr_insn->node;
 	int normalized_time = SCHED_TIME (u) - amount;
 	int new_min_cycle = PS_MIN_CYCLE (ps) - amount;
-        /* The first cycle in row zero after the rotation.  */
-	int new_first_cycle_in_row_zero = 
-	  new_min_cycle + ii - SMODULO (new_min_cycle, ii);
+        int sc_until_cycle_zero, stage;
 
-	if (dump_file)
-	  fprintf (dump_file, "crr_insn->node=%d, crr_insn->cycle=%d,\
-		   min_cycle=%d\n", crr_insn->node->cuid, SCHED_TIME
-		   (u), ps->min_cycle);
+        if (dump_file)
+          {
+            /* Print the scheduling times after the rotation.  */
+            fprintf (dump_file, "crr_insn->node=%d (insn id %d), "
+                     "crr_insn->cycle=%d, min_cycle=%d", crr_insn->node->cuid,
+                     INSN_UID (crr_insn->node->insn), SCHED_TIME (u),
+                     normalized_time);
+            if (JUMP_P (crr_insn->node->insn))
+              fprintf (dump_file, " (branch)");
+            fprintf (dump_file, "\n");
+          }
+	
 	gcc_assert (SCHED_TIME (u) >= ps->min_cycle);
 	gcc_assert (SCHED_TIME (u) <= ps->max_cycle);
 	SCHED_TIME (u) = normalized_time;
-	crr_insn->cycle = normalized_time;
 	SCHED_ROW (u) = SMODULO (normalized_time, ii);
-
-	/* If min_cycle is in row zero after the rotation then
-	   the stage count can be calculated by dividing the cycle
-	   with ii.  Otherwise, the calculation is done by dividing the
-	   SMSed kernel into two intervals:
-
-	   1) min_cycle	              <= interval 0 < first_cycle_in_row_zero
-	   2) first_cycle_in_row_zero <= interval 1 < max_cycle
-	   
-	   Cycles in interval 0 are in stage 0. The stage of cycles
-	   in interval 1 should be added by 1 to take interval 0 into
-	   account.  */
-	if (SMODULO (new_min_cycle, ii) == 0)
-          SCHED_STAGE (u) = normalized_time / ii;
-        else
-	  {
-            if (crr_insn->cycle < new_first_cycle_in_row_zero)
-	      SCHED_STAGE (u) = 0;
-	    else
-              SCHED_STAGE (u) = 
-		((SCHED_TIME (u) - new_first_cycle_in_row_zero) / ii) + 1;
+      
+        /* The calculation of stage count is done adding the number
+           of stages before cycle zero and after cycle zero.  */
+	sc_until_cycle_zero = CALC_STAGE_COUNT (-1, new_min_cycle, ii);
+	
+	if (SCHED_TIME (u) < 0)
+	  {
+	    stage = CALC_STAGE_COUNT (-1, SCHED_TIME (u), ii);
+	    SCHED_STAGE (u) = sc_until_cycle_zero - stage;
+	  }
+	else
+	  {
+	    stage = CALC_STAGE_COUNT (SCHED_TIME (u), 0, ii);
+	    SCHED_STAGE (u) = sc_until_cycle_zero + stage - 1;
 	  }
       }
 }
-
+ 
 /* Set SCHED_COLUMN of each node according to its position in PS.  */
 static void
 set_columns_for_ps (partial_schedule_ptr ps)
@@ -694,8 +672,8 @@
 
         /* Do not duplicate any insn which refers to count_reg as it
            belongs to the control part.
-           If closing_branch_deps is true the closing branch is scheduled
-           as well and thus should be ignored.
+           The closing branch is scheduled as well and thus should
+           be ignored.
            TODO: This should be done by analyzing the control part of
            the loop.  */
         if (reg_mentioned_p (count_reg, u_node->insn)
@@ -945,8 +923,7 @@
   basic_block condition_bb = NULL;
   edge latch_edge;
   gcov_type trip_count = 0;
-  sbitmap doloop_insns;
-  
+
   loop_optimizer_init (LOOPS_HAVE_PREHEADERS
 		       | LOOPS_HAVE_RECORDED_EXITS);
   if (number_of_loops () <= 1)
@@ -971,7 +948,6 @@
   setup_sched_infos ();
   haifa_sched_init ();
 
-  doloop_insns = sbitmap_alloc (get_max_uid () + 1);
   /* Allocate memory to hold the DDG array one entry for each loop.
      We use loop->num as index into this array.  */
   g_arr = XCNEWVEC (ddg_ptr, number_of_loops ());
@@ -1104,16 +1080,18 @@
 
 	  continue;
 	}
-      mark_doloop_insns (doloop_insns, tail);
-      if (! (g = create_ddg (bb, doloop_insns)))
+
+      /* Always schedule the closing branch with the rest of the
+         instructions. The branch is rotated to be in row ii-1 at the
+         end of the scheduling procedure to make sure it's the last
+         instruction in the iteration.  */
+      if (! (g = create_ddg (bb, 1)))
         {
           if (dump_file)
 	    fprintf (dump_file, "SMS create_ddg failed\n");
 	  continue;
         }
-      if (dump_file)
-        fprintf (dump_file, "SMS closing_branch_deps: %d\n", 
-                 g->closing_branch_deps); 
+
       g_arr[loop->num] = g;
       if (dump_file)
         fprintf (dump_file, "...OK\n");
@@ -1215,16 +1193,17 @@
 
       ps = sms_schedule_by_order (g, mii, maxii, node_order);
 
-      if (ps)
-	{
-	  stage_count = calculate_stage_count (ps);
-	  gcc_assert(stage_count >= 1);
-	  PS_STAGE_COUNT(ps) = stage_count;
-	}
-      
-      /* Stage count of 1 means that there is no interleaving between
-         iterations, let the scheduling passes do the job.  */
-      if (stage_count <= 1
+       if (ps)
+       {
+         stage_count = calculate_stage_count (ps);
+         gcc_assert(stage_count >= 1);
+         PS_STAGE_COUNT(ps) = stage_count;
+       }
+
+      /* The default value of PARAM_SMS_MIN_SC is 2 as stage count of
+         1 means that there is no interleaving between iterations thus
+         we let the scheduling passes do the job in this case.  */
+      if (stage_count < (unsigned) PARAM_VALUE (PARAM_SMS_MIN_SC)
 	  || (count_init && (loop_count <= stage_count))
 	  || (flag_branch_probabilities && (trip_count <= stage_count)))
 	{
@@ -1242,21 +1221,12 @@
       else
 	{
 	  struct undo_replace_buff_elem *reg_move_replaces;
-	  int amount;
-
-	  /* Set the stage boundaries.  If the DDG is built with closing_branch_deps,
-	     the closing_branch was scheduled and should appear in the last (ii-1)
-	     row.  Otherwise, we are free to schedule the branch, and we let nodes
-	     that were scheduled at the first PS_MIN_CYCLE cycle appear in the first
-	     row; this should reduce stage_count to minimum.
-             TODO: Revisit the issue of scheduling the insns of the
-             control part relative to the branch when the control part
-             has more than one insn.  */
-	  amount = (g->closing_branch_deps)? SCHED_TIME (g->closing_branch) + 1: 
-	    PS_MIN_CYCLE (ps);
+          int amount = SCHED_TIME (g->closing_branch) + 1;
+	  
+	  /* Set the stage boundaries.	The closing_branch was scheduled
+	     and should appear in the last (ii-1) row.  */
 	  reset_sched_times (ps, amount);
 	  rotate_partial_schedule (ps, amount);
-	  
 	  set_columns_for_ps (ps);
 
 	  canon_loop (loop);
@@ -1267,13 +1237,8 @@
 		       "SMS succeeded %d %d (with ii, sc)\n", ps->ii,
 		       stage_count);
 	      print_partial_schedule (ps, dump_file);
-	      if (!g->closing_branch_deps)
-		fprintf (dump_file,
-			 "SMS Branch (%d) will later be scheduled at \
-			 cycle %d.\n",
-			 g->closing_branch->cuid, PS_MIN_CYCLE (ps) - 1);
-            }
-
+	    }
+ 
           /* case the BCT count is not known , Do loop-versioning */
 	  if (count_reg && ! count_init)
             {
@@ -1318,7 +1283,6 @@
     }
 
   free (g_arr);
-  sbitmap_free (doloop_insns);
 
   /* Release scheduler data, needed until now because of DFA.  */
   haifa_sched_finish ();
@@ -1826,13 +1790,6 @@
 	      RESET_BIT (tobe_scheduled, u);
 	      continue;
 	    }
-	  /* Closing branch handled later unless closing_branch_deps
-	     is true.  */
-	  if (JUMP_P (insn) && !g->closing_branch_deps) 
-	    {
-	      RESET_BIT (tobe_scheduled, u);
-	      continue;
-	    }
 
 	  if (TEST_BIT (sched_nodes, u))
 	    continue;
@@ -2675,9 +2632,9 @@
        last_in_row = next_ps_i;
     }
 
-  /* If closing_branch_deps is true we are scheduling the closing
-     branch as well.  Make sure there is no dependent instruction after
-     it as the branch should be the last instruction.  */
+  /* The closing branch is scheduled as well.  Make sure there is no
+     dependent instruction after it as the branch should be the last
+     instruction in the row.  */
   if (JUMP_P (ps_i->node->insn)) 
     {
       if (first_must_follow)
@@ -2918,51 +2875,21 @@
   return ps_i;
 }
 
-/* Calculate the stage count of the partial schedule PS.  */
+/* Calculate the stage count of the partial schedule PS.  The calculation
+   takes into account the rotation to bring the closing branch to row
+   ii-1.  */
 int
 calculate_stage_count (partial_schedule_ptr ps)
 {
-  int stage_count;
-
-  /* If closing_branch_deps is false then the stage
-     boundaries are placed efficiently, meaning that min_cycle will be
-     placed at row 0. Otherwise, the closing branch will be placed in
-     row ii-1. For the later case we assume the final SMSed kernel can
-     be divided into two intervals. This assumption is used for the
-     stage count calculation:
-
-     1) min_cycle               <= interval 0 < first_cycle_in_row_zero
-     2) first_cycle_in_row_zero <= interval 1 < max_cycle
-   */
-  stage_count =
-    CALC_STAGE_COUNT (PS_MIN_CYCLE (ps), PS_MAX_CYCLE (ps), ps->ii);
-  if (ps->g->closing_branch_deps)
-    {
-      int new_min_cycle;
-      int new_min_cycle_row;
-      int rotation_amount = SCHED_TIME (ps->g->closing_branch) + 1;
-
-      /* This is the new value of min_cycle after the final rotation to
-         bring closing branch into row ii-1.  */
-      new_min_cycle = PS_MIN_CYCLE (ps) - rotation_amount;
-      /* This is the row which the the new min_cycle will be placed in.  */
-      new_min_cycle_row = SMODULO (new_min_cycle, ps->ii);
-      /* If the row of min_cycle is zero then interval 0 is empty.
-         Otherwise, we need to calculate interval 1 and add it by one
-         to take interval 0 into account.  */
-      if (new_min_cycle_row != 0)
-	{
-	  int new_max_cycle, first_cycle_in_row_zero;
-
-	  new_max_cycle = PS_MAX_CYCLE (ps) - rotation_amount;
-	  first_cycle_in_row_zero =
-	    new_min_cycle + ps->ii - new_min_cycle_row;
-
-	  stage_count =
-	    CALC_STAGE_COUNT (first_cycle_in_row_zero, new_max_cycle,
-			      ps->ii) + 1;
-	}
-    }
+  int rotation_amount = (SCHED_TIME (ps->g->closing_branch)) + 1;
+  int new_min_cycle = PS_MIN_CYCLE (ps) - rotation_amount;
+  int new_max_cycle = PS_MAX_CYCLE (ps) - rotation_amount;
+  int stage_count = CALC_STAGE_COUNT (-1, new_min_cycle, ps->ii);
+
+  /* The calculation of stage count is done adding the number of stages
+     before cycle zero and after cycle zero.  */ 
+  stage_count += CALC_STAGE_COUNT (new_max_cycle, 0, ps->ii);
+
   return stage_count;
 }
 

=== modified file 'gcc/params.def'
--- gcc/params.def	2011-02-01 14:20:13 +0000
+++ gcc/params.def	2011-05-11 08:13:47 +0000
@@ -324,6 +324,11 @@
 	 "sms-max-ii-factor",
 	 "A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop",
 	 100, 0, 0)
+/* The minimum value of stage count that swing modulo scheduler will generate.  */
+DEFPARAM(PARAM_SMS_MIN_SC,
+        "sms-min-sc",
+        "The minimum value of stage count that swing modulo scheduler will generate.",
+        2, 1, 1)
 DEFPARAM(PARAM_SMS_DFA_HISTORY,
 	 "sms-dfa-history",
 	 "The number of cycles the swing modulo scheduler considers when checking conflicts using DFA",