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From: osmith@acorn.co.uk (Owen Smith)
Newsgroups: comp.sys.acorn
Subject: Re: is it possible to port GNU-GCC-Compiler to Archimedes running RISC-OS ?
Message-ID: <5569@acorn.co.uk>
Date: 5 Mar 91 14:19:08 GMT
References: <14624@ganymede.inmos.co.uk>
Sender: osmith@acorn.co.uk
Distribution: comp
Organization: Acorn Computers Ltd, Cambridge, England
Lines: 29

In article <14624@ganymede.inmos.co.uk> stevec@wren.inmos.co.uk
(Steve Clarke) writes:

>Gcc 1.37 doesn't do any instruction scheduling; so
>could it be that the version of GNU C that you were
>using passed the assembly language on to the  manufacturer's assembler
>(which then did the instruction scheduling) rather than using the GNU
>assembler?

The compiler was not using the GNU assembler (not quite sure which one it
was using - either Motorola or Data General probably). But this is
irrelevant, as I was doing gcc -S and looking at the assembler source.
I assure you it was doing instruction scheduling - it took me AGES to find
my divide instruction once - it had been moved unbelievably far back, so
far in fact that it had completed by the time the results were used! A
divide in one cycle! Amazing! This was not the only example. There were
lots of other minor adjustments it was doing for multiple cycle instructions.

The assembler cannot do as good a job of scheduling, because the registers
have been fixed by then. The compiler has the option to jiggle the register
colouring to get a register free for ages for the benefit of long
instructions (basically multiply, divide and floating point on the 88K).

This still doesn't answer my original question - will gcc 2.xx have any
new features which will actually be beneficial for an ARM version?

Owen.
 
The views expressed are my own and are not necessarily those of Acorn.