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RFC: Remove flags -fmove-all-movables and -freduce-all-givs.

From: Toon Moene <toon at moene dot indiv dot nluug dot nl>
To: gcc at gcc dot gnu dot org
Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
Date: Sat, 11 Sep 2004 19:14:14 +0200
Subject: RFC: Remove flags -fmove-all-movables and -freduce-all-givs.
Organization: Moene Computational Physics, Maartensdijk, NL

L.S.,

The flags mentioned in the subject were introduced seven years ago to help the heuristics in loop.c in case of code commonly encountered in Fortran.

Because loop.c is on its way out and current loop optimizations have a different structure, there's little reason to keep these flags.

On the contrary, now that we have decided that 4.0.0 is a nice round version number, perhaps we can get away with such a change.

The proposed patch is attached.

Please, reflect.

--
Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Maintainer, GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html
A maintainer of GNU Fortran 95: http://gcc.gnu.org/fortran/

2004-09-11  Toon Moene  <toon@moene.indiv.nluug.nl>

	* common.opt: Remove flags -fmove-all-movables and
	-freduce-all-givs.
	* loop-invariant.c (find_invariants_to_move):
	Remove all uses of flag_move_all_movables.
	* loop.c (move_movables): Remove all uses of
	flag_move_all_movables.
	(strength_reduce): Remove all uses of
	flag_reduce_all_givs.
	* doc/invoke.texi: Remove documentation of flags
	-fremove-all-movables and -freduce-all-givs.

*** common.opt.orig	Fri Sep 10 22:29:33 2004
--- common.opt	Sat Sep 11 18:59:54 2004
*************** fmodulo-sched
*** 523,532 ****
  Common Report Var(flag_modulo_sched)
  Perform SMS based modulo scheduling before the first scheduling pass
  
- fmove-all-movables
- Common Report Var(flag_move_all_movables)
- Force all loop invariant computations out of loops
- 
  fmove-loop-invariants
  Common Report Var(flag_move_loop_invariants)
  Move loop invariant computations out of loops
--- 523,528 ----
*************** frandom-seed=
*** 646,655 ****
  Common Joined RejectNegative
  -frandom-seed=<string>	Make compile reproducible using <string>
  
- freduce-all-givs
- Common Report Var(flag_reduce_all_givs)
- Strength reduce all loop general induction variables
- 
  freg-struct-return
  Common Report Var(flag_pcc_struct_return,0) VarExists
  Return small aggregates in registers
--- 642,647 ----
*** loop-invariant.c.orig	Fri Sep 10 22:29:35 2004
--- loop-invariant.c	Sat Sep 11 19:00:31 2004
*************** find_invariants_to_move (struct df *df)
*** 715,731 ****
    unsigned i, regs_used, n_inv_uses, regs_needed = 0, new_regs;
    struct invariant *inv = NULL;
  
-   if (flag_move_all_movables)
-     {
-       /* This is easy & stupid.  */
-       for (i = 0; i < VARRAY_ACTIVE_SIZE (invariants); i++)
- 	{
- 	  inv = VARRAY_GENERIC_PTR_NOGC (invariants, i);
- 	  inv->move = true;
- 	}
-       return;
-     }
- 
    if (!VARRAY_ACTIVE_SIZE (invariants))
      return;
  
--- 715,720 ----
*** loop.c.orig	Fri Sep 10 22:29:35 2004
--- loop.c	Sat Sep 11 19:02:23 2004
*************** move_movables (struct loop *loop, struct
*** 1885,1891 ****
  	     extra cost because something else was already moved.  */
  
  	  if (already_moved[regno]
- 	      || flag_move_all_movables
  	      || (threshold * savings * m->lifetime) >=
  		 (regs->array[regno].moved_once ? insn_count * 2 : insn_count)
  	      || (m->forces && m->forces->done
--- 1885,1890 ----
*************** strength_reduce (struct loop *loop, int 
*** 5122,5129 ****
  	     of such giv's whether or not we know they are used after the loop
  	     exit.  */
  
! 	  if (! flag_reduce_all_givs
! 	      && v->lifetime * threshold * benefit < insn_count
  	      && ! bl->reversed)
  	    {
  	      if (loop_dump_stream)
--- 5121,5127 ----
  	     of such giv's whether or not we know they are used after the loop
  	     exit.  */
  
! 	  if (v->lifetime * threshold * benefit < insn_count
  	      && ! bl->reversed)
  	    {
  	      if (loop_dump_stream)
*** doc/invoke.texi.orig	Sat Sep 11 12:06:53 2004
--- doc/invoke.texi	Sat Sep 11 19:04:13 2004
*************** Objective-C and Objective-C++ Dialects}.
*** 294,300 ****
  -floop-optimize -fcrossjumping  -fif-conversion  -fif-conversion2 @gol
  -finline-functions  -finline-limit=@var{n}  -fkeep-inline-functions @gol
  -fkeep-static-consts  -fmerge-constants  -fmerge-all-constants @gol
! -fmodulo-sched -fmove-all-movables  -fnew-ra  -fno-branch-count-reg @gol
  -fno-default-inline  -fno-defer-pop -floop-optimize2 -fmove-loop-invariants @gol
  -fno-function-cse  -fno-guess-branch-probability @gol
  -fno-inline  -fno-math-errno  -fno-peephole  -fno-peephole2 @gol
--- 294,300 ----
  -floop-optimize -fcrossjumping  -fif-conversion  -fif-conversion2 @gol
  -finline-functions  -finline-limit=@var{n}  -fkeep-inline-functions @gol
  -fkeep-static-consts  -fmerge-constants  -fmerge-all-constants @gol
! -fmodulo-sched -fnew-ra  -fno-branch-count-reg @gol
  -fno-default-inline  -fno-defer-pop -floop-optimize2 -fmove-loop-invariants @gol
  -fno-function-cse  -fno-guess-branch-probability @gol
  -fno-inline  -fno-math-errno  -fno-peephole  -fno-peephole2 @gol
*************** Objective-C and Objective-C++ Dialects}.
*** 303,309 ****
  -fomit-frame-pointer  -foptimize-register-move @gol
  -foptimize-sibling-calls  -fprefetch-loop-arrays @gol
  -fprofile-generate -fprofile-use @gol
! -freduce-all-givs  -fregmove  -frename-registers @gol
  -freorder-blocks  -freorder-blocks-and-partition -freorder-functions @gol
  -frerun-cse-after-loop  -frerun-loop-opt @gol
  -frounding-math -fschedule-insns  -fschedule-insns2 @gol
--- 303,309 ----
  -fomit-frame-pointer  -foptimize-register-move @gol
  -foptimize-sibling-calls  -fprefetch-loop-arrays @gol
  -fprofile-generate -fprofile-use @gol
! -fregmove  -frename-registers @gol
  -freorder-blocks  -freorder-blocks-and-partition -freorder-functions @gol
  -frerun-cse-after-loop  -frerun-loop-opt @gol
  -frounding-math -fschedule-insns  -fschedule-insns2 @gol
*************** the loop is entered.  This usually makes
*** 4702,4721 ****
  If supported by the target machine, generate instructions to prefetch
  memory to improve the performance of loops that access large arrays.
  
- @item -fmove-all-movables
- @opindex fmove-all-movables
- Forces all invariant computations in loops to be moved
- outside the loop.
- 
- @item -freduce-all-givs
- @opindex freduce-all-givs
- Forces all general-induction variables in loops to be
- strength-reduced.
- 
- @emph{Note:} When compiling programs written in Fortran,
- @option{-fmove-all-movables} and @option{-freduce-all-givs} are enabled
- by default when you use the optimizer.
- 
  These options may generate better or worse code; results are highly
  dependent on the structure of loops within the source code.
  
--- 4702,4707 ----

Follow-Ups:
- Re: RFC: Remove flags -fmove-all-movables and -freduce-all-givs.
  - From: Richard Henderson

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