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

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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.

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@ -1,3 +1,8 @@
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

27
gcc/f/invoke.texi
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@ -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,