dlpress@hubcap.clemson.edu (david pressley) (11/13/90)
I have a few questions about the GNU C (GCC) compiler. If you could
be of some assistance, please respond.
1) Why was the GNU C compiler implemented using RTL (Register
Transfer Language) as opposed to 4-tuples or quads?
2) Is there an interpreter or simulator available for RTL?
3) To your knowledge, has anyone done a study comparing quads and
RTL?
4) What would have to be added to quads to accomplish what is done with
RTL?
I appreciate any response you can give me.
Thank You
David Pressley
pressley@hubcap.clemson.edu
[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]
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In article <11535@hubcap.clemson.edu> dlpress@hubcap.clemson.edu (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 > RTL? 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. bye, mike Michael K. Gschwind, Institute for VLSI-Design, Vienna University of Technology mike@vlsivie.tuwien.ac.at mike@vlsivie.uucp e182202@awituw01.bitnet Voice: (++43).1.58801 8144 Fax: (++43).1.569697 [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] -- Send compilers articles to compilers@iecc.cambridge.ma.us or {ima | spdcc | world}!esegue!compilers. Meta-mail to compilers-request.
dg@iesd.auc.dk (Dieter Gehrke) (11/18/90)
In article <9011151401.AA16023@tuvie.tuwien.ac.at> mike@vlsivie.tuwien.ac.at (Michael K. Gschwind) writes: > 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. Maybe so, but have you tried to map Transputer machine code to RTL? The transputer is a stack machine, RTL is intended for register machines. -Dieter Gehrke (dg@iesd.auc.dk) [How much optimization can one do for a stack machine anyway? There's no obvious place to stash common subexpressions. -John] -- Send compilers articles to compilers@iecc.cambridge.ma.us or {ima | spdcc | world}!iecc!compilers. Meta-mail to compilers-request.