Here's one way to do standard EXecute without a base register:
AHI R2,-1 Minus 1 for EX
*!not yetEXRL R2,_EX_MVC_OUTPUT (Move data to output buffer)
LARL R10,_EX_MVC_OUTPUT Move data to
EX R2,0(,R10) output buffer
I believe, for most applications, "baseless" code is the way to go
moving forward when writing new code or refactoring existing code. Of
course, required are bases for save area/local stack and
constants/LTORG. A program manages bases for other data areas, just as
always -- passed-in-by-reference parameters, heap storage, control
blocks, I/O buffers, et cetera. Changing B-s to J-s, BCT to BRCT, et
cetera, is tedious but simple ("change all"). One may encounter macros
(IBM and otherwise) in existing code that, as traditionally used, have
required a base -- there are ways to deal with those.
All in all, I've found this entails a relatively small learning curve
and amount of effort and cures one of the greatest headaches associated
with assembler coding.
Doug Watkins
http://www.compuware.com/
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From: IBM Mainframe Assembler List
[mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Tom Marchant
Sent: Tuesday, June 05, 2012 5:20 PM
To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
Subject: Re: Base registers
On Tue, 5 Jun 2012 15:59:36 -0400, Scott Ford wrote:
>where can you find a good sample of baseless assembler code ?
Look for Ed Jaffe's SHARE presentation "Jumpify your code".
"Baseless" is not an accurate description, IMO. You still need
base registers to reference data. You can, however, use very few
base registers for your code simply by using relative branches
("jump"). There are one or two exceptions, depending upon your
hardware. One is that there is no indexed relative branch. It's
hard for me to imagine what such a thing would do anyway. The
other is that EXRL was introduced (IIRC) on the z10. The standard
EXecute instruction requires a base register.
--
Tom Marchant
