Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[Jan Hubicka]

The following reply was made to PR optimization/10185; it has been noted by GNATS.

From: Jan Hubicka <jh@suse.cz>
To: Janis Johnson <janis187@us.ibm.com>
Cc: Steven Bosscher <s.bosscher@student.tudelft.nl>,
	rassahah@neofonie.de, gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org,
	nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org, jh@suse.cz
Subject: Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization
Date: Mon, 24 Mar 2003 19:26:18 +0100

 > The regression appeared with this patch:
 > 
 > Sun Jul 21 00:54:54 CEST 2002  Jan Hubicka  <jh@suse.cz>
 > 
 > 	* gcse.c: Include cselib.h
 > 	(constptop_register): Break out from ...
 > 	(cprop_insn): ... here; kill basic_block argument.
 > 	(do_local_cprop, local_cprop_pass): New functions.
 > 	(one_cprop_pass): Call local_cprop_pass.
 > 
 > My testing used the submitter's test case with -O2 on
 > i686-pc-linux-gnu.
 
 As described in the audit, the bug is really latent problem in BIV
 discovery code.  This patch fixes the reason why gcse now manifest it.
 I am now using cselib to discover noop moves and remove them more
 aggresivly than delete_trivially_dead_insns can.  15 such noops are
 found in combine.c compilation and resulting insn chain is reduced by 7
 instructions, so this arrise in real programs too.
 
 Bootstrapped/regtested x86-64.  OK?
 
 Mon Mar 24 19:00:35 CET 2003  Jan Hubicka  <jh@suse.cz>
 	* gcse.c (local_cprop_pass):  Do not copy propagate noop sets;
 	attempt to turn set into noop.
 	* cselib.c (cselib_set_noop_p): New function.
 	* cselib.h (cselib_set_noop_p): Declare.
 Index: gcse.c
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/gcse.c,v
 retrieving revision 1.239
 diff -c -3 -p -r1.239 gcse.c
 *** gcse.c	8 Mar 2003 09:47:28 -0000	1.239
 --- gcse.c	24 Mar 2003 18:12:32 -0000
 *************** local_cprop_pass (alter_jumps)
 *** 4437,4442 ****
 --- 4437,4443 ----
         if (INSN_P (insn))
   	{
   	  rtx note = find_reg_note (insn, REG_LIBCALL, NULL_RTX);
 + 	  rtx set;
   
   	  if (note)
   	    {
 *************** local_cprop_pass (alter_jumps)
 *** 4448,4453 ****
 --- 4449,4499 ----
   	  if (note)
   	    libcall_sp++;
   	  note = find_reg_equal_equiv_note (insn);
 + 
 + 	  if (noop_move_p (insn)
 + 	      && !find_reg_note (insn, REG_LIBCALL, NULL_RTX))
 + 	    {
 + 	      delete_insn (insn);
 + 	      continue;
 + 	    }
 + 	  
 + 	  set = single_set (insn);
 + 
 + 	  /* Don't do copy propagation on noop moves as it only
 + 	     results in these being in the insn chain longer  */
 + 	  if (set && set_noop_p (set))
 + 	    continue;
 + 	  /* Attempt to turn (set A B) where A B are known to be equivalent
 + 	     into (set A A) or (set B B) so the instruction is removed later.
 + 	     */
 + 	  if (set && cselib_set_noop_p (set)
 + 	      && (!SMALL_REGISTER_CLASSES
 + 		  || ((!REG_P (SET_DEST (set))
 + 		       || REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
 + 		      && (GET_CODE (SET_DEST (set)) != SUBREG
 + 		          || (REGNO (SUBREG_REG (SET_DEST (set)))
 + 			      >= FIRST_PSEUDO_REGISTER)))))
 + 	    {
 + 	      bool converted = false;
 + 
 + 	      if (validate_change (insn, &SET_DEST (set),
 + 				   copy_rtx (SET_SRC (set)), 0))
 + 		converted = true;
 + 	      else if (validate_change (insn, &SET_SRC (set),
 + 					copy_rtx (SET_DEST (set)), 0))
 + 		converted = true;
 + 	      if (converted)
 + 		{
 + 		  if (gcse_file)
 + 		    fprintf (gcse_file,
 + 			     "LOCAL COPY-PROP: Set in insn %d turned into noop",
 + 			     INSN_UID (insn));
 + 		  if (noop_move_p (insn)
 + 		      && !find_reg_note (insn, REG_LIBCALL, NULL_RTX))
 + 		    delete_insn (insn);
 + 		  continue;
 + 		}
 + 	    }
   	  do
   	    {
   	      reg_use_count = 0;
 Index: cselib.c
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/cselib.c,v
 retrieving revision 1.26
 diff -c -3 -p -r1.26 cselib.c
 *** cselib.c	14 Mar 2003 20:15:11 -0000	1.26
 --- cselib.c	24 Mar 2003 18:12:33 -0000
 *************** rtx_equal_for_cselib_p (x, y)
 *** 541,546 ****
 --- 541,570 ----
     return 1;
   }
   
 + /* Return nonzero if the destination of SET equals the source
 +    and there are no side effects.  Use cselib infromation to recognize
 +    nontrivial cases.  */
 + 
 + bool
 + cselib_set_noop_p (set)
 +      rtx set;
 + {
 +   rtx src = SET_SRC (set);
 +   rtx dst = SET_DEST (set);
 + 
 +   if (GET_CODE (dst) == STRICT_LOW_PART)
 +     dst = XEXP (dst, 0);
 +   if ((GET_CODE (dst) == SIGN_EXTRACT
 +        || GET_CODE (dst) == ZERO_EXTRACT)
 +       && ! BYTES_BIG_ENDIAN && XEXP (dst, 2) == const0_rtx)
 +     dst = XEXP (dst, 0);
 + 
 +   if (rtx_equal_for_cselib_p (src, dst))
 +     return !side_effects_p (src) && !side_effects_p (dst);
 + 
 +   return false;
 + }
 + 
   /* We need to pass down the mode of constants through the hash table
      functions.  For that purpose, wrap them in a CONST of the appropriate
      mode.  */
 Index: cselib.h
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/cselib.h,v
 retrieving revision 1.7
 diff -c -3 -p -r1.7 cselib.h
 *** cselib.h	11 Mar 2003 21:52:41 -0000	1.7
 --- cselib.h	24 Mar 2003 18:12:33 -0000
 *************** extern void cselib_update_varray_sizes	P
 *** 67,72 ****
 --- 67,73 ----
   extern void cselib_init			PARAMS ((void));
   extern void cselib_finish		PARAMS ((void));
   extern void cselib_process_insn		PARAMS ((rtx));
 + extern bool cselib_set_noop_p		PARAMS ((rtx));
   extern int rtx_equal_for_cselib_p	PARAMS ((rtx, rtx));
   extern int references_value_p		PARAMS ((rtx, int));
   extern rtx cselib_subst_to_values	PARAMS ((rtx));

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[mmitchel]

Synopsis: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

State-Changed-From-To: analyzed->closed
State-Changed-By: mmitchel
State-Changed-When: Mon Mar 24 18:58:26 2003
State-Changed-Why:
    Fixed in GCC 3.3, GCC 3.4.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10185

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[Glen Nakamura]

The following reply was made to PR optimization/10185; it has been noted by GNATS.

From: Glen Nakamura <glen@imodulo.com>
To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org, rassahah@neofonie.de
Cc:  
Subject: Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization
Date: Fri, 21 Mar 2003 22:13:39 -1000

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10185
 
 Aloha,
 This bug has similar symptoms to PR opt/10087.  The gcse pass generates
 the following code (notice insn 106 is redundant to insn 103):
 
 (insn 22 88 103 3 0x4014b764 (parallel [
             (set (reg/s:SI 65)
                 (plus:SI (reg:SI 79)
                     (const_int -1 [0xffffffff])))
             (clobber (reg:CC 17 flags))
         ]) 146 {*addsi_1} (nil)
     (nil))
 
 (insn 103 22 23 3 (nil) (set (reg:SI 79)
         (reg/s:SI 65)) 38 {*movsi_1} (nil)
     (nil))
 
 (insn 23 103 106 3 0x4014b764 (set (mem/f:SI (plus:SI (reg/f:SI 20 frame)
                 (const_int -4 [0xfffffffc])) [5 S4 A32])
         (reg/s:SI 65)) 38 {*movsi_1} (nil)
     (expr_list:REG_EQUAL (plus:SI (reg:SI 67)
             (const_int -1 [0xffffffff]))
         (nil)))
 
 (insn 106 23 25 3 (nil) (set (reg:SI 79)
         (reg/s:SI 65)) 38 {*movsi_1} (nil)
     (nil))
 
 The loop pass then considers insn 103 and insn 106 as places where biv 79
 is incremented.  This is incorrect since insn 106 sets reg 76 to the same
 value as insn 103.  Now during strength reduction, the giv is incremented
 after insn 103 and insn 106 resulting in a delta that is twice the correct
 value.  This test case passes with the patch from:
 http://gcc.gnu.org/ml/gcc-patches/2003-03/msg01932.html
 
 - glen

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[Janis Johnson]

The following reply was made to PR optimization/10185; it has been noted by GNATS.

From: Janis Johnson <janis187@us.ibm.com>
To: Steven Bosscher <s.bosscher@student.tudelft.nl>
Cc: rassahah@neofonie.de, gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org,
   nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org, janis187@us.ibm.com, jh@suse.cz
Subject: Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization
Date: Fri, 21 Mar 2003 17:16:51 -0800

 The regression appeared with this patch:
 
 Sun Jul 21 00:54:54 CEST 2002  Jan Hubicka  <jh@suse.cz>
 
 	* gcse.c: Include cselib.h
 	(constptop_register): Break out from ...
 	(cprop_insn): ... here; kill basic_block argument.
 	(do_local_cprop, local_cprop_pass): New functions.
 	(one_cprop_pass): Call local_cprop_pass.
 
 My testing used the submitter's test case with -O2 on
 i686-pc-linux-gnu.

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[Steven Bosscher]

The following reply was made to PR optimization/10185; it has been noted by GNATS.

From: Steven Bosscher <s.bosscher@student.tudelft.nl>
To: rassahah@neofonie.de, gcc-gnats@gcc.gnu.org,
	gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org,
	janis187@us.ibm.com
Cc:  
Subject: Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs
 & optimization
Date: Fri, 21 Mar 2003 23:54:04 +0100

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10185
 
 Janis,
 
 You offered to track down PRs some time ago with your (very
 nice) regression hunter scripts.  Can you please hunt this one
 down?   It must have been introduced between January 2002
 (3.[12] branched) and January 2003 (3.3 branched).
 
 Greetz
 Steevn
 
 

Re: optimization/10185: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

[bangerth]

Old Synopsis: Wrong code with 3-int-structs & optimization
New Synopsis: [3.3/3.4 regression] Wrong code with 3-int-structs & optimization

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Mar 21 15:40:24 2003
State-Changed-Why:
    Confirmed, a regression on 3.3 and mainline w.r.t. 3.2.2.
    Here's a slightly simpler code:
    --------------------
    typedef struct {
      int x1, dummy1, dummy2;
    } X;
    
    void barrier (int *dummy) {}
    
    main ()
    {
      static X x[] = {{1}, {2}, {5}};
      int i=3, flag=0;
    
      barrier(&i);
      
      while (i--)
        if (x[i].x1 == 2)  // should trigger for i==1
          flag = 1;
      
      if (flag != 1)
        abort ();
    }
    -------------------------------
    The abort() shouldn't be triggered, but is if compiled 
    with -O2 in 3.3 and mainline:
    
    g/x> /home/bangerth/bin/gcc-3.2.2-pre/bin/gcc -O2 x.c ; ./a.out
    g/x> /home/bangerth/bin/gcc-3.3-pre/bin/gcc -O2 x.c ; ./a.out
    Aborted
    g/x> /home/bangerth/bin/gcc-3.4-pre/bin/gcc -O2 x.c ; ./a.out
    Aborted
    
    W.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10185