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| author | Martin Sebor <msebor@redhat.com> | 2016-03-07 17:10:12 +0000 |
|---|---|---|
| committer | Martin Sebor <msebor@gcc.gnu.org> | 2016-03-07 10:10:12 -0700 |
| commit | 92f87f08e642876f94f979d9b50e777c25c077b9 (patch) | |
| tree | f6d7e7dfcbea619f3bef3892571f0cd8bdf024c5 /gcc/doc | |
| parent | dbb23418b23a9e2d4dfbd88ef6661f38e869db6c (diff) | |
| download | gcc-92f87f08e642876f94f979d9b50e777c25c077b9.zip gcc-92f87f08e642876f94f979d9b50e777c25c077b9.tar.gz gcc-92f87f08e642876f94f979d9b50e777c25c077b9.tar.bz2 | |
PR rtl-optimization/19705 - -fno-branch-count-reg doesn't prevent decrement
PR rtl-optimization/19705 - -fno-branch-count-reg doesn't prevent decrement
and branch instructions on a count register
gcc/ChangeLog:
2016-03-07 Martin Sebor <msebor@redhat.com>
PR rtl-optimization/19705
* doc/invoke.texi (Options That Control Optimization): Clarify
-fno-branch-count-reg.
From-SVN: r234039
Diffstat (limited to 'gcc/doc')
| -rw-r--r-- | gcc/doc/invoke.texi | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 4b5df0b..e9d21a3 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -6541,11 +6541,14 @@ life-range analysis. This option is effective only with @item -fno-branch-count-reg @opindex fno-branch-count-reg -Do not use ``decrement and branch'' instructions on a count register, -but instead generate a sequence of instructions that decrement a -register, compare it against zero, then branch based upon the result. -This option is only meaningful on architectures that support such -instructions, which include x86, PowerPC, IA-64 and S/390. +Avoid running a pass scanning for opportunities to use ``decrement and +branch'' instructions on a count register instead of generating sequences +of instructions that decrement a register, compare it against zero, and +then branch based upon the result. This option is only meaningful on +architectures that support such instructions, which include x86, PowerPC, +IA-64 and S/390. Note that the @option{-fno-branch-count-reg} option +doesn't remove the decrement and branch instructions from the generated +instruction stream introduced by other optimization passes. Enabled by default at @option{-O1} and higher. |