From: "Robert A. Rosenberg" <[email protected]>
To: <[email protected]>
Sent: Thursday, 29 December 2011 4:43 PM
Subject: Re: Idea for a possible enhancement to z architecture
At 17:40 +0000 on 12/28/2011, Bill Fairchild wrote about Re: Idea for
a possible enhancement to z architecture:
Not well thought out, or at least not precisely expressed.
Consider the following code:
LA R0,0 put "low core" constant address of zero in R0
What's the point of that? You don't use it in the next instruction.
L R1,16(R0,R0) get the address of the CVT
No point in that either.
Why not just L R1,16 ?
* at this point, a program interrupt occurs.
Or perhaps the code can get into supervisor state first so that it
can alter the proper bit in Control Register 0 before attempting to
fetch the address of the CVT.
Neither way looks very useful.
Maybe I am missing something.
It should never interrupt since when used as a Base or Index
register, the content of R0 is not referenced but treated as if it
contained 0.
No it isn't.
It isn't referenced fullstop. Therefore, it isn't treated as if it contained 0.
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