[gcc r13-5964] IBM zSystems: Do not propagate scheduler state across basic blocks [PR108102]

[gcc r13-5964] IBM zSystems: Do not propagate scheduler state across basic blocks [PR108102]

[Stefan Schulze Frielinghaus]

https://gcc.gnu.org/g:452db716d8debb6e09b85e4a0c0e73a047ed5c1d

commit r13-5964-g452db716d8debb6e09b85e4a0c0e73a047ed5c1d
Author: Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>
Date:   Mon Feb 13 15:33:38 2023 +0100

    IBM zSystems: Do not propagate scheduler state across basic blocks [PR108102]
    
    So far we propagate scheduler state across basic blocks within EBBs and
    reset the state otherwise.  In certain circumstances the entry block of
    an EBB might be empty, i.e., no_real_insns_p is true.  In those cases
    scheduler state is not reset and subsequently wrong state is propagated
    to following blocks of the same EBB.
    
    Since the performance benefit of tracking state across basic blocks is
    questionable on modern hardware, simply reset the state for each basic
    block.
    
    Fix also resetting f{p,x}d_longrunning.
    
    gcc/ChangeLog:
    
            PR target/108102
            * config/s390/s390.cc (s390_bb_fallthru_entry_likely): Remove.
            (struct s390_sched_state): Initialise to zero.
            (s390_sched_variable_issue): For better debuggability also emit
            the current side.
            (s390_sched_init): Unconditionally reset scheduler state.

Diff:
---
 gcc/config/s390/s390.cc | 42 +++++++-----------------------------------
 1 file changed, 7 insertions(+), 35 deletions(-)

diff --git a/gcc/config/s390/s390.cc b/gcc/config/s390/s390.cc
index 708b48b5ab6..b66edf03f47 100644
--- a/gcc/config/s390/s390.cc
+++ b/gcc/config/s390/s390.cc
@@ -14977,29 +14977,6 @@ s390_z10_prevent_earlyload_conflicts (rtx_insn **ready, int *nready_p)
   ready[0] = tmp;
 }
 
-/* Returns TRUE if BB is entered via a fallthru edge and all other
-   incoming edges are less than likely.  */
-static bool
-s390_bb_fallthru_entry_likely (basic_block bb)
-{
-  edge e, fallthru_edge;
-  edge_iterator ei;
-
-  if (!bb)
-    return false;
-
-  fallthru_edge = find_fallthru_edge (bb->preds);
-  if (!fallthru_edge)
-    return false;
-
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    if (e != fallthru_edge
-	&& e->probability >= profile_probability::likely ())
-      return false;
-
-  return true;
-}
-
 struct s390_sched_state
 {
   /* Number of insns in the group.  */
@@ -15010,7 +14987,7 @@ struct s390_sched_state
   bool group_of_two;
 } s390_sched_state;
 
-static struct s390_sched_state sched_state = {0, 1, false};
+static struct s390_sched_state sched_state;
 
 #define S390_SCHED_ATTR_MASK_CRACKED    0x1
 #define S390_SCHED_ATTR_MASK_EXPANDED   0x2
@@ -15510,7 +15487,7 @@ s390_sched_variable_issue (FILE *file, int verbose, rtx_insn *insn, int more)
 
 	      s390_get_unit_mask (insn, &units);
 
-	      fprintf (file, ";;\t\tBACKEND: units on this side unused for: ");
+	      fprintf (file, ";;\t\tBACKEND: units on this side (%d) unused for: ", sched_state.side);
 	      for (j = 0; j < units; j++)
 		fprintf (file, "%d:%d ", j,
 		    last_scheduled_unit_distance[j][sched_state.side]);
@@ -15548,17 +15525,12 @@ s390_sched_init (FILE *file ATTRIBUTE_UNUSED,
      current_sched_info->prev_head is the insn before the first insn of the
      block of insns to be scheduled.
      */
-  rtx_insn *insn = current_sched_info->prev_head
-    ? NEXT_INSN (current_sched_info->prev_head) : NULL;
-  basic_block bb = insn ? BLOCK_FOR_INSN (insn) : NULL;
-  if (s390_tune < PROCESSOR_2964_Z13 || !s390_bb_fallthru_entry_likely (bb))
-    {
-      last_scheduled_insn = NULL;
-      memset (last_scheduled_unit_distance, 0,
+  last_scheduled_insn = NULL;
+  memset (last_scheduled_unit_distance, 0,
 	  MAX_SCHED_UNITS * NUM_SIDES * sizeof (int));
-      sched_state.group_state = 0;
-      sched_state.group_of_two = false;
-    }
+  memset (fpd_longrunning, 0, NUM_SIDES * sizeof (int));
+  memset (fxd_longrunning, 0, NUM_SIDES * sizeof (int));
+  sched_state = {};
 }
 
 /* This target hook implementation for TARGET_LOOP_UNROLL_ADJUST calculates