Re: From quads to AST (Ksheerabdhi Krishna)
Wed, 18 Aug 1993 20:21:11 GMT

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From quads to AST (1993-08-10)
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Newsgroups: comp.compilers
From: (Ksheerabdhi Krishna)
Keywords: optimize
Organization: Computer Science Department, University of New Mexico
References: 93-08-049 93-08-074
Date: Wed, 18 Aug 1993 20:21:11 GMT (Daniel Weise) writes:
>The construction of the PDG starts from a CFG, not an AST. A PDG
>consists of an intertwining of a data dependence graph (DDG) and a
>control dependence graph (CDG). Methods for constructing a CDG all
>start from a CFG. The standard PDG paper (Ferrante, Ottenstein, and
>Warren, TOPLAS 86?) isn't too clear on the DDG part, but it can also
>be constructed from the CFG.

While this is true for the most, it is my duty to point out that for a
large class of programs (pgms with structured gotos - break, continue,
return) one can construct the PDG from an AST. The crucial piece here
is constructiung the CDG (which has always required CFG/PDOM
computation). Constructing the CDG from the AST involves keeping
information regrading exits and a track of regions. For people more
interested in constructing a PDG without going the CFG-PDOM-CDG route
look under in /pub/cs_tech_reports/1992/

The techniques suggested in the paper really work, I have successfuly
implemented them in a front-end. The TOPLAS '86 paper is not that
clear about DDG, but Ottenstein's Software Practice and Experience paper
with Steven Ellecy makes up for that.

back to web weaving,

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