ldgp instruction on Alpha

tau@is.s.u-tokyo.ac.jp (TAURA Kenjiro)
31 Mar 1997 15:26:05 -0500

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Related articles
ldgp instruction on Alpha tau@is.s.u-tokyo.ac.jp (1997-03-31)
Re: ldgp instruction on Alpha leichter@smarts.com (Jerry Leichter) (1997-03-31)
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From: tau@is.s.u-tokyo.ac.jp (TAURA Kenjiro)
Newsgroups: comp.compilers
Followup-To: comp.compilers
Date: 31 Mar 1997 15:26:05 -0500
Organization: Dept. of Information Science, The University of Tokyo, Japan
Keywords: GCC, architecture

Hi compiler hackers,

I'm using gcc on digital unix.

Prologue sequences for procedures begin with an instruction like

ldgp $29,0($27)

There is a similar instruction where a procedure call returns:

jsr $26,printf ! call printf
ldgp $29,0($26)

Could anybody tell me what are these ldgp instructions for? I read
some materials which say $27 is a "procedure value" pointer and $29
has something to do with global variables. But I have never seen any
instruction which really uses those registers. I appreciate any
information or pointers to information about this.

I'm also looking for any books or any materials for such programming
issues on alpha. I can access to a lot of architecture manual, but
none has enough description about software considerations like the

Kenjiro Taura
Yonezawa Laboratory
Department of Information Science
Faculty of Science
University of Tokyo
7-3-1 Hongo, Bunkyo-ku Tokyo 113 Japan
tau@is.s.u-tokyo.ac.jp (http://web.yl.is.s.u-tokyo.ac.jp/)
tel: +81-3-3812-2111 ext. 4108 or +81-3-5800-6913
fax: +81-3-5689-4365

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