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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.lang.forth
Subject: Re: Locals revisited
Date: Thu, 27 Mar 2025 07:48:35 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Paul Rubin <no.email@nospam.invalid> writes:
>albert@spenarnc.xs4all.nl writes:
>> (I get 30 registers in RISCV that can serve as a stack pointer.)

All 31 can serve as a stack pointer, but not all at the same time.
You want at least two registers for temporary values, for implementing
a word such as "+".  And you typically want to keep the top-of-stack
of many stacks in a register, too.  Or several stack items.

>In some models of the RISCV, only 14, I think.

There is the E subspecification of the RISC-V specification with 16
registers.  I don't know if anybody has implemented this.

>And in almost all
>models, 8 of them are more efficient to address than the rest, because
>of the compressed instruction format.

More efficient in code size.  In instruction execution, typically the
same speed.

- anton
-- 
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