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Re: [PATCH] Fix RTL DSE compile time hog (PR rtl-optimization/48141)

i think that i sympathize with richard's "do we really need another parm?" whine. I would have just nailed it in without the parm. I think that it is unreasonable to expect that a program with basic blocks this big needs the full range of optimizations performed.

It is perfectly reasonable to have the quality of the optimization degrade as a function of size.

If you want to tie the trigger to something, then leave out the parm and tie it -O3.


On 03/16/2011 07:59 AM, Richard Guenther wrote:
On Wed, Mar 16, 2011 at 12:52 PM, Jakub Jelinek<jakub@redhat.com> wrote:
On Wed, Mar 16, 2011 at 09:46:20AM +0100, Paolo Bonzini wrote:
On 03/16/2011 12:12 AM, Kenneth Zadeck wrote:
so how much time does this save?

I agree that this is a useful simplification, but it seems unlikely to
be that important in real code.
it seems like the 5000 store test would in general provide a better
safety valve.
I think having both is a good idea. 
Here is the second patch, ok for both to trunk if this one passes
bootstrap/regtest?

With just this patch alone on the testcase with the default
--param=max-dse-active-local-stores=5000 cc1 spends 18.9 seconds
in DSE1+DSE2, with =1000 just 4 seconds and with =10 0.4 seconds.
With the earlier patch in addition to this one the time in DSE1+DSE2
is 0.3 seconds no matter what the parameter is.

That suggests we can avoid the new param?  (btw, we should start
thinking of emitting a diagnostic if we run into such artificial limits)

The earlier patch is ok for all branches.

Thanks,
Richard.

2011-03-16 Jakub Jelinek<jakub@redhat.com>

        PR rtl-optimization/48141
        * params.def (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES): New.
        * dse.c: Include params.h.
        (active_local_stores_len): New variable.
        (add_wild_read, dse_step1): Clear it when setting active_local_stores
        to NULL.
        (record_store, check_mem_read_rtx): Decrease it when removing
        from the chain.
        (scan_insn): Likewise.  Increase it when adding to chain, if it
        reaches PARAM_MAX_DSE_ACTIVE_LOCAL_STORES limit, set to 1 and
        set active_local_stores to NULL before the addition.
        * Makefile.in (dse.o): Depend on $(PARAMS_H).

--- gcc/params.def.jj   2011-02-15 15:42:27.000000000 +0100
+++ gcc/params.def      2011-03-16 12:20:16.000000000 +0100
@@ -698,6 +698,12 @@ DEFPARAM(PARAM_MAX_SCHED_READY_INSNS,
         "The maximum number of instructions ready to be issued to be considered by the scheduler during the first scheduling pass",
         100, 0, 0)

+/* This is the maximum number of active local stores RTL DSE will consider.  */
+DEFPARAM (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES,
+         "max-dse-active-local-stores",
+         "Maximum number of active local stores in RTL dead store elimination",
+         5000, 0, 0)
+
  /* Prefetching and cache-optimizations related parameters.  Default values are
    usually set by machine description.  */

--- gcc/dse.c.jj        2011-02-15 15:42:26.000000000 +0100
+++ gcc/dse.c   2011-03-16 12:34:18.000000000 +0100
@@ -47,6 +47,7 @@ along with GCC; see the file COPYING3.
  #include "optabs.h"
  #include "dbgcnt.h"
  #include "target.h"
+#include "params.h"

  /* This file contains three techniques for performing Dead Store
    Elimination (dse).
@@ -387,6 +388,7 @@ static alloc_pool insn_info_pool;
  /* The linked list of stores that are under consideration in this
    basic block.  */
  static insn_info_t active_local_stores;
+static int active_local_stores_len;

  struct bb_info
  {
@@ -947,6 +949,7 @@ add_wild_read (bb_info_t bb_info)
     }
   insn_info->wild_read = true;
   active_local_stores = NULL;
+  active_local_stores_len = 0;
  }


@@ -1538,6 +1541,7 @@ record_store (rtx body, bb_info_t bb_inf
        {
          insn_info_t insn_to_delete = ptr;

+         active_local_stores_len--;
          if (last)
            last->next_local_store = ptr->next_local_store;
          else
@@ -2074,6 +2078,7 @@ check_mem_read_rtx (rtx *loc, void *data
              if (dump_file)
                dump_insn_info ("removing from active", i_ptr);

+             active_local_stores_len--;
              if (last)
                last->next_local_store = i_ptr->next_local_store;
              else
@@ -2163,6 +2168,7 @@ check_mem_read_rtx (rtx *loc, void *data
              if (dump_file)
                dump_insn_info ("removing from active", i_ptr);

+             active_local_stores_len--;
              if (last)
                last->next_local_store = i_ptr->next_local_store;
              else
@@ -2222,6 +2228,7 @@ check_mem_read_rtx (rtx *loc, void *data
              if (dump_file)
                dump_insn_info ("removing from active", i_ptr);

+             active_local_stores_len--;
              if (last)
                last->next_local_store = i_ptr->next_local_store;
              else
@@ -2426,6 +2433,7 @@ scan_insn (bb_info_t bb_info, rtx insn)
                  if (dump_file)
                    dump_insn_info ("removing from active", i_ptr);

+                 active_local_stores_len--;
                  if (last)
                    last->next_local_store = i_ptr->next_local_store;
                  else
@@ -2453,6 +2461,12 @@ scan_insn (bb_info_t bb_info, rtx insn)
                    fprintf (dump_file, "handling memset as BLKmode store\n");
                  if (mems_found == 1)
                    {
+                     if (active_local_stores_len++
+>= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
+                       {
+                         active_local_stores_len = 1;
+                         active_local_stores = NULL;
+                       }
                      insn_info->next_local_store = active_local_stores;
                      active_local_stores = insn_info;
                    }
@@ -2496,6 +2510,12 @@ scan_insn (bb_info_t bb_info, rtx insn)
      it as cannot delete.  This simplifies the processing later.  */
   if (mems_found == 1)
     {
+      if (active_local_stores_len++
+>= PARAM_VALUE (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES))
+       {
+         active_local_stores_len = 1;
+         active_local_stores = NULL;
+       }
       insn_info->next_local_store = active_local_stores;
       active_local_stores = insn_info;
     }
@@ -2534,6 +2554,7 @@ remove_useless_values (cselib_val *base)

       if (del)
        {
+         active_local_stores_len--;
          if (last)
            last->next_local_store = insn_info->next_local_store;
          else
@@ -2584,6 +2605,7 @@ dse_step1 (void)
            = create_alloc_pool ("cse_store_info_pool",
                                 sizeof (struct store_info), 100);
          active_local_stores = NULL;
+         active_local_stores_len = 0;
          cselib_clear_table ();

          /* Scan the insns.  */
--- gcc/Makefile.in.jj  2011-02-02 16:30:50.000000000 +0100
+++ gcc/Makefile.in     2011-03-16 12:26:12.000000000 +0100
@@ -3070,7 +3070,7 @@ dse.o : dse.c $(CONFIG_H) $(SYSTEM_H) co
    $(TREE_H) $(TM_P_H) $(REGS_H) hard-reg-set.h $(FLAGS_H) insn-config.h \
    $(RECOG_H) $(EXPR_H) $(DF_H) cselib.h $(DBGCNT_H) $(TIMEVAR_H) \
    $(TREE_PASS_H) alloc-pool.h $(ALIAS_H) dse.h $(OPTABS_H) $(TARGET_H) \
-   $(BITMAP_H)
+   $(BITMAP_H) $(PARAMS_H)
  fwprop.o : fwprop.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    $(DIAGNOSTIC_CORE_H) insn-config.h $(RECOG_H) $(FLAGS_H) $(OBSTACK_H) $(BASIC_BLOCK_H) \
    output.h $(DF_H) alloc-pool.h $(TIMEVAR_H) $(TREE_PASS_H) $(TARGET_H) \


Jakub


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