PATCH: Throttle GCSE memory usage

PATCH: Throttle GCSE memory usage

[Mark Mitchell]

This patch fixes PR 884 by not running GCSE when doing so would take
huge amounts of memory.  Without this patch, we tried to allocate
400MB of memory, and died on most ordinary systems.

Ideally, we would rework the algorithm to use less memory -- but we
would still need a throttle like this at some point.

Bootstrapped and tested on i686-pc-linux-gnu.

Installed on the mainline and the branch.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com

2001-04-11  Mark Mitchell  <mark@codesourcery.com>

	* Makefile.in (gcse.o): Depend on params.h.
	* gcse.c: Include params.h.
	(gcse_main): Don't do GCSE if doing so will take inordinate
	amounts of memory.
	* params.def (PARAM_MAX_GCSE_MEMORY): New  parameter.
	* params.h (MAX_GCSE_MEMORY): New macro.

Index: Makefile.in
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Makefile.in,v
retrieving revision 1.602.2.10
diff -c -p -r1.602.2.10 Makefile.in
*** Makefile.in	2001/03/28 19:51:08	1.602.2.10
--- Makefile.in	2001/04/11 17:34:25
*************** cse.o : cse.c $(CONFIG_H) system.h $(RTL
*** 1421,1427 ****
     $(BASIC_BLOCK_H) $(GGC_H)
  gcse.o : gcse.c $(CONFIG_H) system.h $(RTL_H) $(REGS_H) hard-reg-set.h \
     flags.h real.h insn-config.h $(RECOG_H) $(EXPR_H) $(BASIC_BLOCK_H) \
!    function.h output.h toplev.h
  sibcall.o : sibcall.c $(CONFIG_H) system.h $(RTL_H) $(REGS_H) function.h \
     hard-reg-set.h flags.h insn-config.h $(RECOG_H) $(BASIC_BLOCK_H)
  resource.o : resource.c $(CONFIG_H) $(RTL_H) hard-reg-set.h system.h \
--- 1421,1427 ----
     $(BASIC_BLOCK_H) $(GGC_H)
  gcse.o : gcse.c $(CONFIG_H) system.h $(RTL_H) $(REGS_H) hard-reg-set.h \
     flags.h real.h insn-config.h $(RECOG_H) $(EXPR_H) $(BASIC_BLOCK_H) \
!    function.h output.h toplev.h params.h
  sibcall.o : sibcall.c $(CONFIG_H) system.h $(RTL_H) $(REGS_H) function.h \
     hard-reg-set.h flags.h insn-config.h $(RECOG_H) $(BASIC_BLOCK_H)
  resource.o : resource.c $(CONFIG_H) $(RTL_H) hard-reg-set.h system.h \
Index: gcse.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/gcse.c,v
retrieving revision 1.113.4.1
diff -c -p -r1.113.4.1 gcse.c
*** gcse.c	2001/04/04 20:27:03	1.113.4.1
--- gcse.c	2001/04/11 17:34:26
*************** Boston, MA 02111-1307, USA.  */
*** 159,164 ****
--- 159,165 ----
  #include "output.h"
  #include "function.h"
  #include "expr.h" 
+ #include "params.h"
  
  #include "obstack.h"
  #define obstack_chunk_alloc gmalloc
*************** gcse_main (f, file)
*** 689,694 ****
--- 690,708 ----
        if (warn_disabled_optimization)
        warning ("GCSE disabled: %d > 1000 basic blocks and %d >= 20 edges/basic block",
                 n_basic_blocks, n_edges / n_basic_blocks);
+       return 0;
+     }
+ 
+   /* If allocating memory for the cprop bitmap would take up too much
+      storage it's better just to disable the optimization.  */
+   if ((n_basic_blocks 
+        * SBITMAP_SET_SIZE (max_gcse_regno)
+        * sizeof (SBITMAP_ELT_TYPE)) > MAX_GCSE_MEMORY)
+     {
+       if (warn_disabled_optimization)
+ 	warning ("GCSE disabled: %d basic blocks and %d registers",
+ 		 n_basic_blocks, max_gcse_regno);
+ 
        return 0;
      }
  
Index: params.def
===================================================================
RCS file: /cvs/gcc/gcc/gcc/params.def,v
retrieving revision 1.3.2.1
diff -c -p -r1.3.2.1 params.def
*** params.def	2001/03/01 16:56:20	1.3.2.1
--- params.def	2001/04/11 17:34:26
*************** DEFPARAM(PARAM_MAX_DELAY_SLOT_LIVE_SEARC
*** 66,71 ****
--- 66,78 ----
  	 "The maximum number of instructions to consider to find accurate live register information",
  	 333)
  
+ /* The GCSE optimization will be disabled if it would require
+    significantly more memory than this value.  */
+ DEFPARAM(PARAM_MAX_GCSE_MEMORY,
+ 	 "max-gcse-memory",
+ 	 "The maximum amount of memory to be allocated by GCSE",
+ 	 50 * 1024 * 1024)
+ 
  /*
  Local variables:
  mode:c
Index: params.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/params.h,v
retrieving revision 1.3.2.1
diff -c -p -r1.3.2.1 params.h
*** params.h	2001/03/01 16:56:20	1.3.2.1
--- params.h	2001/04/11 17:34:26
*************** typedef enum compiler_param
*** 88,92 ****
--- 88,94 ----
    PARAM_VALUE (PARAM_MAX_DELAY_SLOT_INSN_SEARCH)
  #define MAX_DELAY_SLOT_LIVE_SEARCH \
    PARAM_VALUE (PARAM_MAX_DELAY_SLOT_LIVE_SEARCH)
+ #define MAX_GCSE_MEMORY \
+   ((size_t) PARAM_VALUE (PARAM_MAX_GCSE_MEMORY))
  
  #endif /* PARAMS_H */

Re: PATCH: Throttle GCSE memory usage

[Joseph S. Myers]

On Wed, 11 Apr 2001, Mark Mitchell wrote:

> 	* Makefile.in (gcse.o): Depend on params.h.
> 	* gcse.c: Include params.h.
> 	(gcse_main): Don't do GCSE if doing so will take inordinate
> 	amounts of memory.
> 	* params.def (PARAM_MAX_GCSE_MEMORY): New  parameter.
> 	* params.h (MAX_GCSE_MEMORY): New macro.

The new parameter should also go in the table of --param arguments in
invoke.texi.

-- 
Joseph S. Myers
jsm28@cam.ac.uk