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Re: PDP-10 backend for gcc
- To: Michael Meissner <meissner at cygnus dot com>
- Subject: Re: PDP-10 backend for gcc
- From: Andrew Morton <andrewm at uow dot edu dot au>
- Date: Tue, 05 Sep 2000 23:53:21 +0000
- CC: lars brinkhoff <lars at nocrew dot org>, law at cygnus dot com, Alan Lehotsky <lehotsky at tiac dot net>, gcc at gcc dot gnu dot org
- References: <9718.967737237@upchuck> <85u2c0fp61.fsf@junk.nocrew.org>, <85u2c0fp61.fsf@junk.nocrew.org>; from lars brinkhoff on Fri, Sep 01, 2000 at 11:16:06AM +0200 <20000905190538.39634@cse.cygnus.com>
Michael Meissner wrote:
>
> Given this byte pointer-ness has been in the compiler
> since its inception, I suspect you will find
> undocumented assumptions rife throughout the compiler.
You suspect correctly. I once ported gcc/g++ 2.5.8 to a
bit-addressable machine. A machine where you have to add
8 to an address register to advance it by a byte.
I found thirty or forty instances of this byte == 1
assumption, and basically the only way of tracking
them down was working backwards from incorrect
code generation.
Even though 2.5.8 is not entirely state-of-the-art,
if someone actually intends to go through this exercise,
the stuff at http://www.uow.edu.au/~andrewm/gsptools.html
will save them a couple of weeks work.