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| author | Brad Lucier <lucier@math.purdue.edu> | 2001-07-05 19:38:30 +0000 |
|---|---|---|
| committer | Gerald Pfeifer <gerald@gcc.gnu.org> | 2001-07-05 19:38:30 +0000 |
| commit | 081ca317a420381a89a6d502990389df1c56cb16 (patch) | |
| tree | 2eac7f0e0da0748ac42566cf7725f17fc1fce93f /gcc | |
| parent | 29650b2b2fab72b63a0eb555d8f2c67466c58e08 (diff) | |
| download | gcc-081ca317a420381a89a6d502990389df1c56cb16.zip gcc-081ca317a420381a89a6d502990389df1c56cb16.tar.gz gcc-081ca317a420381a89a6d502990389df1c56cb16.tar.bz2 | |
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
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/doc/invoke.texi | 8 |
2 files changed, 14 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f67f0ea..2c8be24 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +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. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index c21137e..18c054f 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 |