invoke.texi: Explain the purpose of -fmove-all-movables...

2002-11-20  Toon Moene  <toon@moene.indiv.nluug.nl>

	* invoke.texi: Explain the purpose of -fmove-all-movables,
	-freduce-all-givs and -frerun-loop-opts better.

From-SVN: r59323

gcc/f/ChangeLog

+2002-11-20  Toon Moene  <toon@moene.indiv.nluug.nl>
+
+	* invoke.texi: Explain the purpose of -fmove-all-movables,
+	-freduce-all-givs and -frerun-loop-opts better.
+
 2002-11-19  Toon Moene  <toon@moene.indiv.nluug.nl>
 
 	PR fortran/8587

gcc/f/invoke.texi

@@ -1656,26 +1656,21 @@ but possibly slower.
 @item -fno-rerun-loop-opt
 @cindex -fno-rerun-loop-opt option
 @cindex options, -fno-rerun-loop-opt
-@emph{Version info:}
-These options are not supported by
-versions of @command{g77} based on @command{gcc} version 2.8.
+In general, the optimizations enabled with these options will lead to
+faster code being generated by GNU Fortran; hence they are enabled by default
+when issuing the @command{g77} command.
 
-Each of these might improve performance on some code.
+@option{-fmove-all-movables} and @option{-freduce-all-givs} will enable
+loop optimization to move all loop-invariant index computations in nested
+loops over multi-rank array dummy arguments out of these loops.
 
-Analysis of Fortran code optimization and the resulting
-optimizations triggered by the above options were
-contributed by Toon Moene (@email{toon@@moene.indiv.nluug.nl}).
+@option{-frerun-loop-opt} will move offset calculations resulting
+from the fact that Fortran arrays by default have a lower bound of 1
+out of the loops.
 
 These three options are intended to be removed someday, once
-they have helped determine the efficacy of various
-approaches to improving the performance of Fortran code.
-
-Please let us know how use of these options affects
-the performance of your production code.
-We're particularly interested in code that runs faster
-when these options are @emph{disabled}, and in
-non-Fortran code that benefits when they are
-@emph{enabled} via the above @command{gcc} command-line options.
+loop optimization is sufficiently advanced to perform all those
+transformations without help from these options.
 @end table
 
 @xref{Optimize Options,,Options That Control Optimization,