Hello,

This PR is again about insns that are recog'ed as >=0 but do not change the processor state. As explained in http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52203#c8, I've tried experimenting with an attribute marking those "empty" insns in MD files and asserting that all other insns do have reservations. As this doesn't seem to be interesting, I give up with the idea, and the below patch makes sel-sched do exactly what the Haifa scheduler does, i.e. do not count such insns against issue_rate when modelling clock cycles.


Tested on ia64 and x86-64, OK for trunk? No testcase again because of the amount of flags needed.

Andrey

2012-03-07  Andrey Belevantsev  <a...@ispras.ru>

        PR rtl-optimization/52203
        * sel-sched.c (estimate_insn_cost): New parameter pempty.  Adjust
        all callers to pass NULL except ...
        (reset_sched_cycles_in_current_ebb): ... here, save the value
        in new variable 'empty'.  Increase issue_rate only for
        non-empty insns.

diff --git a/gcc/sel-sched.c b/gcc/sel-sched.c
index 2af01ae..2829f60 100644
--- a/gcc/sel-sched.c
+++ b/gcc/sel-sched.c
@@ -4265,9 +4265,10 @@ invoke_aftermath_hooks (fence_t fence, rtx best_insn, int issue_more)
   return issue_more;
 }

-/* Estimate the cost of issuing INSN on DFA state STATE.  */
+/* Estimate the cost of issuing INSN on DFA state STATE.  Write to PEMPTY
+   true when INSN does not change the processor state.  */
 static int
-estimate_insn_cost (rtx insn, state_t state)
+estimate_insn_cost (rtx insn, state_t state, bool *pempty)
 {
   static state_t temp = NULL;
   int cost;
@@ -4277,6 +4278,8 @@ estimate_insn_cost (rtx insn, state_t state)

   memcpy (temp, state, dfa_state_size);
   cost = state_transition (temp, insn);
+  if (pempty)
+    *pempty = (memcmp (temp, state, dfa_state_size) == 0);

   if (cost < 0)
     return 0;
@@ -4307,7 +4310,7 @@ get_expr_cost (expr_t expr, fence_t fence)
        return 0;
     }
   else
-    return estimate_insn_cost (insn, FENCE_STATE (fence));
+    return estimate_insn_cost (insn, FENCE_STATE (fence), NULL);
 }

 /* Find the best insn for scheduling, either via max_issue or just take
@@ -7020,7 +7023,7 @@ reset_sched_cycles_in_current_ebb (void)
     {
       int cost, haifa_cost;
       int sort_p;
-      bool asm_p, real_insn, after_stall, all_issued;
+      bool asm_p, real_insn, after_stall, all_issued, empty;
       int clock;

       if (!INSN_P (insn))
@@ -7047,7 +7050,7 @@ reset_sched_cycles_in_current_ebb (void)
            haifa_cost = 0;
        }
       else
-        haifa_cost = estimate_insn_cost (insn, curr_state);
+        haifa_cost = estimate_insn_cost (insn, curr_state, &empty);

       /* Stall for whatever cycles we've stalled before.  */
       after_stall = 0;
@@ -7081,7 +7084,7 @@ reset_sched_cycles_in_current_ebb (void)
               if (!after_stall
                   && real_insn
                   && haifa_cost > 0
-                  && estimate_insn_cost (insn, curr_state) == 0)
+                  && estimate_insn_cost (insn, curr_state, NULL) == 0)
                 break;

               /* When the data dependency stall is longer than the DFA stall,
@@ -7093,7 +7096,7 @@ reset_sched_cycles_in_current_ebb (void)
               if ((after_stall || all_issued)
                   && real_insn
                   && haifa_cost == 0)
-                haifa_cost = estimate_insn_cost (insn, curr_state);
+                haifa_cost = estimate_insn_cost (insn, curr_state, NULL);
             }

          haifa_clock += i;
@@ -7125,7 +7128,8 @@ reset_sched_cycles_in_current_ebb (void)
       if (real_insn)
        {
          cost = state_transition (curr_state, insn);
-         issued_insns++;
+         if (!empty)
+           issued_insns++;

           if (sched_verbose >= 2)
            {

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