Patchwork [fortran] More control over front end optimization

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Submitter Thomas Koenig
Date April 8, 2011, 9:49 p.m.
Message ID <4D9F82E0.5000504@netcologne.de>
Download mbox | patch
Permalink /patch/90430/
State New
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Thomas Koenig - April 8, 2011, 9:49 p.m.
Hello Mikael and Daniel,

thanks for the reviews.  Here is what I committed as rev. 172215.
I tried to be a little bit more specific in the doc, but couldn't
think of a better name for the options without trying to win a
prize for Gcc's longest option name.

	Thomas

2011-04-08  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.

2011-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/48448
         * gfortran.dg/function_optimize_5.f90:  New test.

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 optimizations
+enabled by the @option{-ffrontend-optimize} option.
+
+
 @item -Werror
 @opindex @code{Werror}
 @cindex warnings, to errors
@@ -1482,8 +1491,19 @@  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 manipulating
+parts the Fortran parse tree.  Enabled by default by any @option{-O}
+option.  Optimizations enabled by this option include elimination of
+identical function calls within expressions, removing unnecessary
+calls to @code{TRIM} in comparisons and assignments and replacing
+@code{TRIM(a)} with @code{a(1:LEN_TRIM(a)}. 
+It can be deselected 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;