[m-rev.] diff: speed up trail unwinding in .par.tr grades

[Julien Fischer]

Estimated hours taken: 1
Branches: main

Speed up trail unwinding and resets with trail segments in .par grades.
The total runtime for the G12 FD benchmarks is about 0.25% faster with this change.
Note that the speedup is not uniform across all benchmarks; it varies from no change
up to about a 4% improvement.

runtime/mercury_trail.c:
 	Cache the value of MR_TRAIL_BASE in a local variable where
 	possible, since in some grades the MR_TRAIL_BASE macro
 	makes a call to pthread_getspecific().  We do the same
 	in other grades too - it won't make any difference other
 	than to keep the code simple.

Julien.

Index: runtime/mercury_trail.c
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_trail.c,v
retrieving revision 1.17
diff -u -r1.17 mercury_trail.c
--- runtime/mercury_trail.c	5 Sep 2008 11:19:33 -0000	1.17
+++ runtime/mercury_trail.c	24 Sep 2008 06:23:10 -0000
@@ -44,7 +44,11 @@
  void
  MR_untrail_to(MR_TrailEntry *old_trail_ptr, MR_untrail_reason reason)
  {
-    MR_TrailEntry *tr_ptr;
+    MR_TrailEntry   *tr_ptr;
+
+#if defined(MR_TRAIL_SEGMENTS)
+    MR_TrailEntry   *tr_base;
+#endif
      /* Not needed, since MR_trail_ptr is never a real reg: */
      /* MR_restore_transient_registers(); */
      tr_ptr = MR_trail_ptr;
@@ -54,6 +58,7 @@
      case MR_commit:

          /* Just handle the function trail entries */
+        tr_base = MR_TRAIL_BASE;
          while (tr_ptr != old_trail_ptr) {
              tr_ptr--;
              if (MR_get_trail_entry_kind(tr_ptr) == MR_func_entry) {
@@ -68,7 +73,7 @@
              ** (invoking function trail entires as we go) until we find it.
              */
              #if defined(MR_TRAIL_SEGMENTS)
-                if (tr_ptr == MR_TRAIL_BASE 
+                if (tr_ptr == tr_base
                      && tr_ptr != old_trail_ptr)
                  {
                      MR_MemoryZones  *prev_zones;
@@ -109,6 +114,7 @@
      case MR_exception:
      case MR_retry:
          /* Handle both function and value trail entries */
+        tr_base = MR_TRAIL_BASE;
          while (tr_ptr != old_trail_ptr) {
              tr_ptr--;
              if (MR_get_trail_entry_kind(tr_ptr) == MR_func_entry) {
@@ -119,11 +125,12 @@
                      MR_get_trail_entry_value(tr_ptr);
              }
              #if defined(MR_TRAIL_SEGMENTS)
-                if (tr_ptr == MR_TRAIL_BASE 
+                if (tr_ptr == tr_base
                      && tr_ptr != old_trail_ptr)
                  {
                      MR_pop_trail_segment();
                      tr_ptr = MR_trail_ptr;
+                    tr_base = MR_TRAIL_BASE;
                  }
              #endif
          }
@@ -189,17 +196,19 @@
  MR_reset_trail_zone(void) {

      MR_TrailEntry   *tr_ptr;
-
+    MR_TrailEntry   *tr_base;
+
      tr_ptr = MR_trail_ptr;
+    tr_base = MR_TRAIL_BASE;

-    while (tr_ptr != MR_TRAIL_BASE) {
+    while (tr_ptr != tr_base) {
          tr_ptr--;
          if (MR_get_trail_entry_kind(tr_ptr) == MR_func_entry) {
              (*MR_get_trail_entry_untrail_func(tr_ptr))(
                  MR_get_trail_entry_datum(tr_ptr), MR_gc);
          }
      }
-    MR_trail_ptr = MR_TRAIL_BASE;
+    MR_trail_ptr = tr_base;
  }

  /*---------------------------------------------------------------------------*/

--------------------------------------------------------------------------
mercury-reviews mailing list
Post messages to:       mercury-reviews at csse.unimelb.edu.au
Administrative Queries: owner-mercury-reviews at csse.unimelb.edu.au
Subscriptions:          mercury-reviews-request at csse.unimelb.edu.au
--------------------------------------------------------------------------