Remove unused variables from REFERENCED_VARS list

Remove unused variables from REFERENCED_VARS list

[Jan Hubicka]

Hi,
this patch makes remove_unused_locals to prunt not only unexpanded_var_list but
also referenced_vars that are a lot more commonly traversed.  For temporaries
this also makes them available for ggc memory.  On tramp3d after early
optimization about 70% of local variables can be reclaimed to GGC this way
reducing peak memory usage from 720 to 630MB.

:ADDPATCH tree-optimization:
Bootstrapped/regtested i686-linux, OK?
Honza
	* tree-dfa.c (remove_referenced_var): New function.
	* tree-ssa-live.c (remove_unused_locals): Walk referenced vars and
	prune referenced vars list too.
	* tree-flow.h (remove_referenced_var): Declare.
Index: tree-dfa.c
===================================================================
*** tree-dfa.c	(revision 120681)
--- tree-dfa.c	(working copy)
*************** add_referenced_var (tree var)
*** 752,757 ****
--- 752,780 ----
      }
  }
  
+ /* Remove VAR from the list.  */
+ 
+ void
+ remove_referenced_var (tree var)
+ {
+   var_ann_t v_ann;
+   struct int_tree_map in;
+   void **loc;
+   unsigned int uid = DECL_UID (var);
+ 
+   clear_call_clobbered (var);
+   v_ann = get_var_ann (var);
+   ggc_free (v_ann);
+   var->base.ann = NULL;
+   gcc_assert (DECL_P (var));
+   in.uid = uid;
+   in.to = var;
+   loc = htab_find_slot_with_hash (gimple_referenced_vars (cfun), &in, uid,
+ 				  NO_INSERT);
+   ggc_free (*loc);
+   htab_clear_slot (gimple_referenced_vars (cfun), loc);
+ }
+ 
  
  /* Return the virtual variable associated to the non-scalar variable VAR.  */
  
Index: tree-ssa-live.c
===================================================================
*** tree-ssa-live.c	(revision 120681)
--- tree-ssa-live.c	(working copy)
*************** remove_unused_locals (void)
*** 449,463 ****
  {
    basic_block bb;
    tree t, *cell;
  
    /* Assume all locals are unused.  */
!   for (t = cfun->unexpanded_var_list; t; t = TREE_CHAIN (t))
!     {
!       tree var = TREE_VALUE (t);
!       if (TREE_CODE (var) != FUNCTION_DECL
! 	  && var_ann (var))
! 	var_ann (var)->used = false;
!     }
  
    /* Walk the CFG marking all referenced symbols.  */
    FOR_EACH_BB (bb)
--- 449,460 ----
  {
    basic_block bb;
    tree t, *cell;
+   referenced_var_iterator rvi;
+   var_ann_t ann;
  
    /* Assume all locals are unused.  */
!   FOR_EACH_REFERENCED_VAR (t, rvi)
!     var_ann (t)->used = false;
  
    /* Walk the CFG marking all referenced symbols.  */
    FOR_EACH_BB (bb)
*************** remove_unused_locals (void)
*** 493,503 ****
    for (cell = &cfun->unexpanded_var_list; *cell; )
      {
        tree var = TREE_VALUE (*cell);
-       var_ann_t ann;
  
        if (TREE_CODE (var) != FUNCTION_DECL
  	  && (!(ann = var_ann (var))
  	      || !ann->used))
  	{
  	  *cell = TREE_CHAIN (*cell);
  	  continue;
--- 490,499 ----
    for (cell = &cfun->unexpanded_var_list; *cell; )
      {
        tree var = TREE_VALUE (*cell);
  
        if (TREE_CODE (var) != FUNCTION_DECL
  	  && (!(ann = var_ann (var))
  	      || !ann->used))
  	{
  	  *cell = TREE_CHAIN (*cell);
  	  continue;
*************** remove_unused_locals (void)
*** 505,510 ****
--- 501,519 ----
  
        cell = &TREE_CHAIN (*cell);
      }
+ 
+   /* Remove unused variables from REFERENCED_VARs.  As an special exception
+      keep the variables that are believed to be aliased.  Those can't be
+      easilly removed from the alias sets and and operand caches.
+      They will be removed shortly after next may_alias pass is performed.  */
+   FOR_EACH_REFERENCED_VAR (t, rvi)
+     if (!is_global_var (t)
+ 	&& !MTAG_P (t)
+ 	&& TREE_CODE (t) != PARM_DECL
+ 	&& TREE_CODE (t) != RESULT_DECL
+ 	&& !(ann = var_ann (t))->used
+ 	&& !ann->is_aliased && !is_call_clobbered (t) && !ann->symbol_mem_tag)
+         remove_referenced_var (t);
  }
  
  
Index: tree-flow.h
===================================================================
*** tree-flow.h	(revision 120681)
--- tree-flow.h	(working copy)
*************** extern void dump_subvars_for (FILE *, tr
*** 698,703 ****
--- 698,704 ----
  extern void debug_subvars_for (tree);
  extern tree get_virtual_var (tree);
  extern void add_referenced_var (tree);
+ extern void remove_referenced_var (tree);
  extern void mark_symbols_for_renaming (tree);
  extern void find_new_referenced_vars (tree *);
  

Re: Remove unused variables from REFERENCED_VARS list

[Richard Guenther]

On 1/12/07, Jan Hubicka <jh@suse.cz> wrote:
> Hi,
> this patch makes remove_unused_locals to prunt not only unexpanded_var_list but
> also referenced_vars that are a lot more commonly traversed.  For temporaries
> this also makes them available for ggc memory.  On tramp3d after early
> optimization about 70% of local variables can be reclaimed to GGC this way
> reducing peak memory usage from 720 to 630MB.
>
> :ADDPATCH tree-optimization:
> Bootstrapped/regtested i686-linux, OK?

This is ok (thanks for this work!).

Richard.

> Honza
>         * tree-dfa.c (remove_referenced_var): New function.
>         * tree-ssa-live.c (remove_unused_locals): Walk referenced vars and
>         prune referenced vars list too.
>         * tree-flow.h (remove_referenced_var): Declare.

Re: Remove unused variables from REFERENCED_VARS list

[Jan Hubicka]

> On 1/12/07, Jan Hubicka <jh@suse.cz> wrote:
> >Hi,
> >this patch makes remove_unused_locals to prunt not only 
> >unexpanded_var_list but
> >also referenced_vars that are a lot more commonly traversed.  For 
> >temporaries
> >this also makes them available for ggc memory.  On tramp3d after early
> >optimization about 70% of local variables can be reclaimed to GGC this way
> >reducing peak memory usage from 720 to 630MB.
> >
> >:ADDPATCH tree-optimization:
> >Bootstrapped/regtested i686-linux, OK?
> 
> This is ok (thanks for this work!).

Thank you too!  I would like to commit it after C++ tester stomach the
early optimization changes, but for some reason the last result on
vangelis seems to be from 10th.  Do you have any idea what is going
wrong?

Thanks,
Honza

Re: Remove unused variables from REFERENCED_VARS list

[Jan Hubicka]

> On 1/12/07, Jan Hubicka <jh@suse.cz> wrote:
> >Hi,
> >this patch makes remove_unused_locals to prunt not only 
> >unexpanded_var_list but
> >also referenced_vars that are a lot more commonly traversed.  For 
> >temporaries
> >this also makes them available for ggc memory.  On tramp3d after early
> >optimization about 70% of local variables can be reclaimed to GGC this way
> >reducing peak memory usage from 720 to 630MB.
> >
> >:ADDPATCH tree-optimization:
> >Bootstrapped/regtested i686-linux, OK?
> 
> This is ok (thanks for this work!).

Hi,
for a record this is memory report from this patch and the EH cleanup.
As expected it brings nice savings on Gerald's testcase (smaller than on
tramp3d, but still).  However PR rtl-optimization/28071 seems to regress
somewhat.  I can't say it was expected, perhaps removing dead variables
from the list tends to change optimization decisions (hopefully in
positive way).

I will look into the dumps once they appear on the webpages to do some
more analysis.

There are also nice -O3 savings for the same testcase, just a week ago
we needed 920MB, so we have 30% drop.  (by early inlining)

Honza

comparing Gerald's testcase PR8361 compilation at -O1 level:
  Peak amount of GGC memory allocated before garbage collecting run decreased from 102899k to 98615k, overall -4.34%
  Peak amount of GGC memory still allocated after garbage collecting decreased from 101880k to 97638k, overall -4.34%
    Overall memory needed: 132838k -> 130302k
    Peak memory use before GGC: 102899k -> 98615k
    Peak memory use after GGC: 101880k -> 97638k
    Maximum of released memory in single GGC run: 17926k -> 17925k
    Garbage: 397860k -> 394895k
    Leak: 50038k -> 50037k
    Overhead: 53236k -> 53231k
    GGC runs: 574 -> 572

comparing Gerald's testcase PR8361 compilation at -O2 level:
  Peak amount of GGC memory allocated before garbage collecting run decreased from 103003k to 98683k, overall -4.38%
  Peak amount of GGC memory still allocated after garbage collecting decreased from 101947k to 97705k, overall -4.34%
    Overall memory needed: 132878k -> 130362k
    Peak memory use before GGC: 103003k -> 98683k
    Peak memory use after GGC: 101947k -> 97705k
    Maximum of released memory in single GGC run: 17926k -> 17924k
    Garbage: 454649k -> 451692k
    Leak: 50816k -> 50815k
    Overhead: 46330k -> 46288k
    GGC runs: 630 -> 633

comparing Gerald's testcase PR8361 compilation at -O3 level:
  Peak amount of GGC memory allocated before garbage collecting run decreased from 104577k to 100272k, overall -4.29%
  Peak amount of GGC memory still allocated after garbage collecting decreased from 103536k to 99239k, overall -4.33%
    Overall memory needed: 134754k -> 132182k
    Peak memory use before GGC: 104577k -> 100272k
    Peak memory use after GGC: 103536k -> 99239k
    Maximum of released memory in single GGC run: 18326k -> 18325k
    Garbage: 470546k -> 467160k
    Leak: 51030k -> 51029k
    Overhead: 45782k -> 45801k
    GGC runs: 643 -> 642

comparing PR rtl-optimization/28071 testcase compilation at -O1 level:
  Overall memory allocated via mmap and sbrk increased from 417842k to 436710k, overall 4.52%
  Peak amount of GGC memory allocated before garbage collecting increased from 200591k to 202594k, overall 1.00%
    Overall memory needed: 417842k -> 436710k
    Peak memory use before GGC: 200591k -> 202594k
    Peak memory use after GGC: 193289k -> 192571k
    Maximum of released memory in single GGC run: 112413k -> 137171k
    Garbage: 281276k -> 278226k
    Leak: 29804k
    Overhead: 32031k -> 32030k
    GGC runs: 92

comparing PR rtl-optimization/28071 testcase compilation at -O2 level:
  Overall memory allocated via mmap and sbrk increased from 341514k to 365202k, overall 6.94%
  Peak amount of GGC memory allocated before garbage collecting increased from 200583k to 207227k, overall 3.31%
    Overall memory needed: 341514k -> 365202k
    Peak memory use before GGC: 200583k -> 207227k
    Peak memory use after GGC: 193281k -> 192563k
    Maximum of released memory in single GGC run: 111840k -> 140362k
    Garbage: 358332k -> 355277k
    Leak: 30387k
    Overhead: 47186k -> 47185k
    GGC runs: 99 -> 98

comparing PR rtl-optimization/28071 testcase compilation at -O3 -fno-tree-pre -fno-tree-fre level:
  Peak amount of GGC memory allocated before garbage collecting run decreased from 299944k to 282245k, overall -6.27%
    Overall memory needed: 712662k -> 710702k
    Peak memory use before GGC: 299944k -> 282245k
    Peak memory use after GGC: 278930k -> 273215k
    Maximum of released memory in single GGC run: 158597k -> 138326k
    Garbage: 452446k -> 448504k
    Leak: 45440k
    Overhead: 56089k -> 56089k
    GGC runs: 97