Re: Intermediate Representation

larus@primost.cs.wisc.edu (James Larus)
Sun, 12 Aug 90 13:48:22 GMT

          From comp.compilers
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Newsgroups: comp.compilers
From: larus@primost.cs.wisc.edu (James Larus)
Keywords: code, optimize
Organization: U of Wisconsin CS Dept
References: <1990Aug07.153407.8877@esegue.segue.boston.ma.us>
Date: Sun, 12 Aug 90 13:48:22 GMT

In my opinion (a phrase sadly missing from other replies to this message),
both RTL and AST/DAG representations are equivalent for a compiler designed
and written for a single machine. I base this belief on having written or
worked on compilers that use both types of IR. Both forms represent the
program in a form that is easy to traverse and manipulate. However, I don't
believe that the equivalence holds for retargetable compilers. RTL appears
to be a much better IR for retargetable code generators. The
Davidson-Fraser approach produces fast, practical code generators while the
retargetable CG for ASTs are still mainly university projects.


A more interesting question is: how would you demonstrate that one approach
is superior to the other one? If computer science was a science, we could
just lock up a sample of programmers in a room and have them write a
compiler of a randomly-choosen type and compare the final products.


/Jim
--

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