diff options
| author | Helge Deller <deller@gmx.de> | 2013-06-29 13:24:16 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-07-21 18:21:26 -0700 |
| commit | fa8223db1d69e6de9c7c7210804e8bb284067954 (patch) | |
| tree | fb2b7ac0cec179ef0034366a7c70998c7cffcbdf /Documentation | |
| parent | b6891ed4e66b65e5d6bb36964af0d65a08590018 (diff) | |
parisc: document the shadow registers
commit a83f58bcb24003b9de2364de7c829a263423ead7 upstream.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/parisc/registers | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/parisc/registers b/Documentation/parisc/registers index dd3caddd1ad9..10c7d1730f5d 100644 --- a/Documentation/parisc/registers +++ b/Documentation/parisc/registers @@ -78,6 +78,14 @@ Shadow Registers used by interruption handler code TOC enable bit 1 ========================================================================= + +The PA-RISC architecture defines 7 registers as "shadow registers". +Those are used in RETURN FROM INTERRUPTION AND RESTORE instruction to reduce +the state save and restore time by eliminating the need for general register +(GR) saves and restores in interruption handlers. +Shadow registers are the GRs 1, 8, 9, 16, 17, 24, and 25. + +========================================================================= Register usage notes, originally from John Marvin, with some additional notes from Randolph Chung. |