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Commit a83f58bc authored by Helge Deller's avatar Helge Deller
Browse files

parisc: document the shadow registers



Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # 3.10
parent 30a9f0b2
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+8 −0
Original line number Diff line number Diff line
@@ -77,6 +77,14 @@ PSW default E value 0
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.