Path: utzoo!mnetor!uunet!littlei!omepd!bobdi
From: bobdi@omepd (Bob Dietrich)
Newsgroups: comp.arch
Subject: Re: 80960 Register windows
Message-ID: <3407@omepd>
Date: 22 Apr 88 18:27:32 GMT
References: <3358@omepd> <29454@linus.UUCP> <3392@omepd> <385@bacchus.DEC.COM>
Reply-To: bobdi@omepd.UUCP (Bob Dietrich)
Organization: Intel Corp., Hillsboro, Oregon
Lines: 28
Keywords: 80960, RISC, embedded control

In article <385@bacchus.DEC.COM> alverson@decwrl.UUCP (Robert Alverson) writes:
>After hearing about the 80960 for the last few days, I still have a few
>questions:
>
>1. How are parameters passed into procedures?  In Berkeley's RISC, this
>   was accomplished with overlapping windows.  What I have read seems to
>   imply that the 80960 windows do not overlap.  How about procedure
>   return values?
>  ...
>Bob

In the 80960 C compiler, parameters are typically passed in up to 12 (G0-G11)
of the global registers. If a function has more than 12 registers worth of
parameters, the calling function allocates a parameter block on the stack and
passes a pointer to it in G14. Note that some parameters may take more than
one register, such as doubles and aggregates up to four 32-bit words in
size.

Return values are placed in G0-G3, depending on size. If a structure or
aggregate is to be returned, the caller places a pointer to the return space
in G13.

				Bob Dietrich
				Intel Corporation, Hillsboro, Oregon
				(503) 696-4400 or 2092(messages x4188,2111)
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