Commit 081ca317 by Brad Lucier Committed by Gerald Pfeifer

invoke.texi (Optimize Options): Document that -fgcse may cause programs using…

invoke.texi (Optimize Options): Document that -fgcse may cause programs using computed gotos to run more slowly.

	* doc/invoke.texi (Optimize Options): Document that -fgcse may
	cause programs using computed gotos to run more slowly.

Co-Authored-By: Gerald Pfeifer <pfeifer@dbai.tuwien.ac.at>

From-SVN: r43786
parent 29650b2b
2001-07-05 Brad Lucier <lucier@math.purdue.edu>
Gerald Pfeifer <pfeifer@dbai.tuwien.ac.at>
* doc/invoke.texi (Optimize Options): Document that -fgcse may
cause programs using computed gotos to run more slowly.
2001-07-05 Rainer Orth <ro@TechFak.Uni-Bielefeld.DE>
* doc/install.texi (Specific): Markup, spelling and typo fixes.
......
......@@ -3189,6 +3189,9 @@ function inlining, and register renaming. It also turns on the
@option{-fforce-mem} option on all machines and frame pointer elimination
on machines where doing so does not interfere with debugging.
Please note the warning under @option{-fgcse} about
invoking @option{-O2} on programs that use computed gotos.
@item -O3
@opindex O3
Optimize yet more. @option{-O3} turns on all optimizations specified by
......@@ -3466,6 +3469,11 @@ Run the loop optimizer twice.
Perform a global common subexpression elimination pass.
This pass also performs global constant and copy propagation.
@emph{Note:} When compiling a program using computed gotos, a GCC
extension, you may get better runtime performance if you disable
the global common subexpression elmination pass by adding
@option{-fno-gcse} to the command line.
@item -fgcse-lm
@opindex fgcse-lm
When @option{-fgcse-lm} is enabled, global common subexpression elimination will
......
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