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.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@172215 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 24 insertions, 4 deletions

diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 5441dbcc121..96beff58215 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -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 occasion of variables being
 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 are marked
 @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,