Patchwork [fortran] More control over front end optimization

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Submitter Thomas Koenig
Date April 7, 2011, 7:32 p.m.
Message ID <4D9E1168.50908@netcologne.de>
Download mbox | patch
Permalink /patch/90226/
State New
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Comments

Thomas Koenig - April 7, 2011, 7:32 p.m.
Hello world,

following Joost's request, the attached patch gives the user more 
control over front end optimization - it can now be selected or 
deselected independent of normal optimization.  I have also implemented 
a warning for eliminated functions.

Regression-tested.

Once this is in, I will also mention the new options in the changes file.

OK for trunk?

2011-04-07  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/48448
         * gfortran.h (gfc_option_t):  Add warn_function_elimination and
         flag_frontend_optimize.
         * lang.opt (Wfunction-elimination):  Add.
         (ffrontend-optimize):  Add.
         * invoke.texi:  Add documentation for -Wfunction-elimination
         and -ffrontend-optimize.  Add -faggressive-function-elimination
         to list of code generation options.
         * frontend-passes.c (gfc_run_passes):  Run optimizations if
         flag_frontend_optimize is set.
         (warn_function_elimination):  New function.
         (cfe_expr_0):  Call it if requested to do so.
         * options.c (gfc_init_options):  Initiate warn_function_elimination
         and flag_frontend_optimize.
         (gfc_post_options):  Set flag_frontend_optimize if not specified
         by user, depending on the optimization level.
         (gfc_handle_option):  Handle -Wfunction-elimination and
         -ffrontend-optimize.

2011-04-07  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/48448
         * gfortran.dg/function_optimize_5.f90:  New test.
! { dg-do compile }
! { dg-options "-ffrontend-optimize -Wfunction-elimination" }
! PR 48448
! Check the -ffrontend-optimize (in the absence of -O) and
! -Wfunction-elimination options.
program main
  implicit none
  real, dimension(2,2) :: a, b, c, d
  integer :: i
  real :: x, z
  character(60) :: line
  real, external :: ext_func
  interface
     elemental function element(x)
       real, intent(in) :: x
       real :: elem
     end function element
     pure function mypure(x)
       real, intent(in) :: x
       integer :: mypure
     end function mypure
     elemental impure function elem_impure(x)
       real, intent(in) :: x
       real :: elem_impure
     end function elem_impure
  end interface

  data a /2., 3., 5., 7./
  data b /11., 13., 17., 23./
  write (unit=line, fmt='(4F7.2)') matmul(a,b)  & ! { dg-warning "Removing call to function 'matmul'" } 
       & + matmul(a,b)
  z = sin(x) + 2.0 + sin(x)  ! { dg-warning "Removing call to function 'sin'" }
  print *,z
  x = ext_func(a) + 23 + ext_func(a)
  print *,d,x
  z = element(x) + element(x) ! { dg-warning "Removing call to function 'element'" }
  print *,z
  i = mypure(x) - mypure(x) ! { dg-warning "Removing call to function 'mypure'" }
  print *,i
  z = elem_impure(x) - elem_impure(x)
  print *,z
end program main
Daniel Kraft - April 7, 2011, 7:50 p.m.
Hi,

On 04/07/11 21:32, Thomas Koenig wrote:
> following Joost's request, the attached patch gives the user more
> control over front end optimization - it can now be selected or
> deselected independent of normal optimization. I have also implemented a
> warning for eliminated functions.
>
> Regression-tested.
>
> Once this is in, I will also mention the new options in the changes file.
>
> OK for trunk?

Ok.  Just my opinion (as non-native-speaker), though:

+Wfunction-elimination
+Fortran Warning
+Warn about function call elimination

"-Wfunction-elimination" sounds misleading to me -- just under the name, 
I would imagine you mean eliminating whole functions; as in "never used 
(anymore), remove".  Since you mean elimination of *calls* to functions, 
could you use something like "-Wcall-elimination"?  (Does not sound that 
much better... but if you have an idea, I would prefer a clearer option 
name.  Otherwise just leave it.)

+Warn if any calls to functions are eliminated by the
+@option{-ffrontend-optimize} option.

I also do not completely like "are eliminated by the -ffrontend-optimize 
option" -- since to me it is not *the option* which eliminates the 
calls; but the elimination is implied by the option... or something like 
that.  But as before, if you have a good alternative I would love to see 
one, otherwise just leave it.

The code looks good to me.

Yours,
Daniel
Mikael Morin - April 7, 2011, 8:35 p.m.
Hello, 

On Thursday 07 April 2011 21:50:46 Daniel Kraft wrote:
> Ok.  Just my opinion (as non-native-speaker), though:

+@item -ffrontend-optimize
+@opindex @code{frontend-optimize}
+@cindex Front-end optimization
+This option performs front-end optimization, based on the Fortran parse
+tree.  Enabled by default by any @option{-O} option.  It can
+be deselcted by specifying @option{-fno-frontend-optimize}.
 @end table

s/deselcted/deselected/ ?
I think you are not specific enough about frontend optimizations. 
frontend optimization consists of:
 * the trim/trim_len stuff 
 * the duplicate function call removal stuff
This is documented nowhere ( but the C source ;-) ) as far as I know.

> The code looks good to me.

Mikael

Patch

Index: gfortran.h
===================================================================
--- gfortran.h	(Revision 172058)
+++ gfortran.h	(Arbeitskopie)
@@ -2180,6 +2180,7 @@  typedef struct
   int warn_ampersand;
   int gfc_warn_conversion;
   int warn_conversion_extra;
+  int warn_function_elimination;
   int warn_implicit_interface;
   int warn_implicit_procedure;
   int warn_line_truncation;
@@ -2234,6 +2235,7 @@  typedef struct
   int flag_protect_parens;
   int flag_realloc_lhs;
   int flag_aggressive_function_elimination;
+  int flag_frontend_optimize;
 
   int fpe;
   int rtcheck;
Index: lang.opt
===================================================================
--- lang.opt	(Revision 172058)
+++ lang.opt	(Arbeitskopie)
@@ -222,6 +222,10 @@  Wconversion-extra
 Fortran Warning
 Warn about most implicit conversions
 
+Wfunction-elimination
+Fortran Warning
+Warn about function call elimination
+
 Wimplicit-interface
 Fortran Warning
 Warn about calls with implicit interface
@@ -414,6 +418,10 @@  ffree-line-length-
 Fortran RejectNegative Joined UInteger
 -ffree-line-length-<n>	Use n as character line width in free mode
 
+ffrontend-optimize
+Fortran
+Enable front end optimization
+
 fimplicit-none
 Fortran
 Specify that no implicit typing is allowed, unless overridden by explicit IMPLICIT statements
Index: invoke.texi
===================================================================
--- invoke.texi	(Revision 172058)
+++ invoke.texi	(Arbeitskopie)
@@ -139,7 +139,7 @@  and warnings}.
 -Wall  -Waliasing  -Wampersand  -Warray-bounds -Wcharacter-truncation @gol
 -Wconversion -Wimplicit-interface  -Wimplicit-procedure  -Wline-truncation @gol
 -Wintrinsics-std  -Wsurprising  -Wno-tabs  -Wunderflow  -Wunused-parameter @gol
--Wintrinsic-shadow  -Wno-align-commons}
+-Wintrinsic-shadow  -Wno-align-commons -Wfunction-elimination}
 
 @item Debugging Options
 @xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
@@ -171,7 +171,8 @@  and warnings}.
 -fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol
 -finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
 -finit-logical=@var{<true|false>} -finit-character=@var{n} @gol
--fno-align-commons -fno-protect-parens -frealloc-lhs}
+-fno-align-commons -fno-protect-parens -frealloc-lhs @gol
+-faggressive-function-elimination -ffrontend-optimize}
 @end table
 
 @menu
@@ -859,6 +860,14 @@  By default, @command{gfortran} warns about any occ
 padded for proper alignment inside a @code{COMMON} block. This warning can be turned
 off via @option{-Wno-align-commons}. See also @option{-falign-commons}.
 
+@item -Wfunction-elimination
+@opindex @code{Wfunction-elimination}
+@cindex function elimination
+@cindex warnings, function elimination
+Warn if any calls to functions are eliminated by the
+@option{-ffrontend-optimize} option.
+
+
 @item -Werror
 @opindex @code{Werror}
 @cindex warnings, to errors
@@ -1482,8 +1491,15 @@  statements, regardless of whether these functions
 @smallexample
   a = f(b,c) + f(b,c)
 @end smallexample
-there will only be a single call to @code{f}.
+there will only be a single call to @code{f}.  This option only works
+if @option{-ffrontend-optimize} is in effect.
 
+@item -ffrontend-optimize
+@opindex @code{frontend-optimize}
+@cindex Front-end optimization
+This option performs front-end optimization, based on the Fortran parse
+tree.  Enabled by default by any @option{-O} option.  It can
+be deselcted by specifying @option{-fno-frontend-optimize}.
 @end table
 
 @xref{Code Gen Options,,Options for Code Generation Conventions,
Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 172058)
+++ frontend-passes.c	(Arbeitskopie)
@@ -62,7 +62,7 @@  gfc_namespace *current_ns;
 void
 gfc_run_passes (gfc_namespace *ns)
 {
-  if (optimize)
+  if (gfc_option.flag_frontend_optimize)
     {
       expr_size = 20;
       expr_array = XNEWVEC(gfc_expr **, expr_size);
@@ -283,6 +283,20 @@  create_var (gfc_expr * e)
   return result;
 }
 
+/* Warn about function elimination.  */
+
+static void
+warn_function_elimination (gfc_expr *e)
+{
+  if (e->expr_type != EXPR_FUNCTION)
+    return;
+  if (e->value.function.esym)
+    gfc_warning ("Removing call to function '%s' at %L",
+		 e->value.function.esym->name, &(e->where));
+  else if (e->value.function.isym)
+    gfc_warning ("Removing call to function '%s' at %L",
+		 e->value.function.isym->name, &(e->where));
+}
 /* Callback function for the code walker for doing common function
    elimination.  This builds up the list of functions in the expression
    and goes through them to detect duplicates, which it then replaces
@@ -315,6 +329,10 @@  cfe_expr_0 (gfc_expr **e, int *walk_subtrees,
 	    {
 	      if (newvar == NULL)
 		newvar = create_var (*(expr_array[i]));
+
+	      if (gfc_option.warn_function_elimination)
+		warn_function_elimination (*(expr_array[j]));
+
 	      gfc_free (*(expr_array[j]));
 	      *(expr_array[j]) = gfc_copy_expr (newvar);
 	    }
Index: options.c
===================================================================
--- options.c	(Revision 172058)
+++ options.c	(Arbeitskopie)
@@ -99,6 +99,7 @@  gfc_init_options (unsigned int decoded_options_cou
   gfc_option.warn_array_temp = 0;
   gfc_option.gfc_warn_conversion = 0;
   gfc_option.warn_conversion_extra = 0;
+  gfc_option.warn_function_elimination = 0;
   gfc_option.warn_implicit_interface = 0;
   gfc_option.warn_line_truncation = 0;
   gfc_option.warn_surprising = 0;
@@ -151,6 +152,7 @@  gfc_init_options (unsigned int decoded_options_cou
   gfc_option.flag_protect_parens = 1;
   gfc_option.flag_realloc_lhs = -1;
   gfc_option.flag_aggressive_function_elimination = 0;
+  gfc_option.flag_frontend_optimize = -1;
   
   gfc_option.fpe = 0;
   gfc_option.rtcheck = 0;
@@ -418,6 +420,12 @@  gfc_post_options (const char **pfilename)
   if (pedantic && gfc_option.flag_whole_file)
     gfc_option.flag_whole_file = 2;
 
+  /* Optimization implies front end optimization, unless the user
+     specified it directly.  */
+
+  if (gfc_option.flag_frontend_optimize == -1)
+    gfc_option.flag_frontend_optimize = optimize;
+
   gfc_cpp_post_options ();
 
 /* FIXME: return gfc_cpp_preprocess_only ();
@@ -610,6 +618,10 @@  gfc_handle_option (size_t scode, const char *arg,
       gfc_option.warn_conversion_extra = value;
       break;
 
+    case OPT_Wfunction_elimination:
+      gfc_option.warn_function_elimination = value;
+      break;
+
     case OPT_Wimplicit_interface:
       gfc_option.warn_implicit_interface = value;
       break;
@@ -979,6 +991,10 @@  gfc_handle_option (size_t scode, const char *arg,
       gfc_option.flag_aggressive_function_elimination = value;
       break;
 
+    case OPT_ffrontend_optimize:
+      gfc_option.flag_frontend_optimize = value;
+      break;
+
     case OPT_fprotect_parens:
       gfc_option.flag_protect_parens = value;
       break;