|Why RTL for GCC ? email@example.com (1990-11-12)|
|Re: Why RTL for GCC ? firstname.lastname@example.org (1990-11-14)|
|Re: Why RTL for GCC ? email@example.com (Michael K. Gschwind) (1990-11-15)|
|Re: Why RTL for GCC ? firstname.lastname@example.org (1990-11-17)|
|From:||Michael K. Gschwind <email@example.com>|
|Keywords:||GCC, RTL, optimize|
|Organization:||Vienna University of Technology, AUSTRIA|
|Date:||Thu, 15 Nov 90 15:01:10 +0100|
In article <firstname.lastname@example.org> email@example.com (david pressley) writes:
> 1) Why was the GNU C compiler implemented using RTL (Register
> Transfer Language) as opposed to 4-tuples or quads?
I think the technical reason is the `combine' pass, which can generate
arbitrarily complex RTLs. If you allow 4-tuples with 4-tuples as args,
it would probably be quite similar to RTL. I guess they would actually
be the same, apart from syntax ;-)
> 2) Is there an interpreter or simulator available for RTL?
Somebody is working on it. The idea is also mentioned in
IDEAS (or TO-DO) in the g++ distribution.
> 4) What would have to be added to quads to accomplish what is done with
Nesting of quads (?)
>[The simple answer to 1) is that GCC is based on an earlier compiler that
>used RTL, but I don't know the original motivation. Perhaps it appeared
>easier to retarget. -John]
I think GCC was NOT derived from a compiler, but from a machine code
optimizer written at the U. of Arizona. It's more natural to map
machine instructions to RTL than quads.
Michael K. Gschwind, Institute for VLSI-Design, Vienna University of Technology
Voice: (++43).1.58801 8144
[I have heard that GCC also derives from a Pascal compiler done at Livermore,
but perhaps someone who knows could tell us where it really came from. -John]
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