From d2074053cde29d112db9c8770241b6732c0106f7 Mon Sep 17 00:00:00 2001 From: gerald Date: Thu, 5 Jul 2001 19:38:30 +0000 Subject: [PATCH] * doc/invoke.texi (Optimize Options): Document that -fgcse may cause programs using computed gotos to run more slowly. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@43786 138bc75d-0d04-0410-961f-82ee72b054a4 --- gcc/ChangeLog | 6 ++++++ gcc/doc/invoke.texi | 8 ++++++++ 2 files changed, 14 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f67f0ea5409..2c8be244f8e 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2001-07-05 Brad Lucier + Gerald Pfeifer + + * doc/invoke.texi (Optimize Options): Document that -fgcse may + cause programs using computed gotos to run more slowly. + 2001-07-05 Rainer Orth * doc/install.texi (Specific): Markup, spelling and typo fixes. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index c21137e86ca..18c054f4963 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -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 -- 2.11.0