[Oberon] Resend, not post ack after 30 min : Risc-5 Instructions statistics

[Chris Burrows]

> -----Original Message-----
> From: Oberon [mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of
> Peter Matthias
> Sent: Saturday, 16 February 2019 5:02 AM
> To: oberon at lists.inf.ethz.ch
> Subject: Re: [Oberon] Resend, not post ack after 30 min : Risc-5
> Instructions statistics
> 
> Am 15.02.19 um 17:24 schrieb J rg:
> > Format 2   49%  memory instructions (LDR/STR)  (<-- cache would
> really be great!!)
> 
> Depends on memory timing. I would say:"Register variables would be
> great!"
> 

Register variables can certainly produce significant savings in code size and consequently execution speed. The approach Wirth took in his ARM compiler i.e. restrict the use of register variables to leaf procedures, simplifies the implementation. However, the feature was still the source of a disproportionate number of obscure bugs when we started work on the Astrobe ARM compilers. I recall wondering on many occasions whether it was worth the effort! Now it has been done and works well I believe it was.

For further information refer to Section 22. 'Leaf procedures and Register Variables' of 'An Oberon Compiler for the ARM Processor'. You can download a copy from:

https://www.inf.ethz.ch/personal/wirth/Oberon/Oberon.ARM.Compiler.pdf

Regards,
Chris

Chris Burrows
CFB Software
http://www.astrobe.com