Optimizing nested if statements?

Saverio Perugini <sperugin@csgrad.cs.vt.edu>
17 Jan 2003 23:13:46 -0500

          From comp.compilers
Related articles
Optimizing nested if statements? sperugin@csgrad.cs.vt.edu (Saverio Perugini) (2003-01-17)
Re: Optimizing nested if statements? christian.bau@cbau.freeserve.co.uk (Christian Bau) (2003-01-21)
Re: Optimizing nested if statements? terryg@qwest.net (Terry Greyzck) (2003-01-21)
Re: Optimizing nested if statements? vbdis@aol.com (2003-01-21)
Re: Optimizing nested if statements? sperugin@csgrad.cs.vt.edu (Saverio Perugini) (2003-01-25)
Re: Optimizing nested if statements? Martin.Ward@durham.ac.uk (2003-01-26)
Re: Optimizing nested if statements? sperugin@csgrad.cs.vt.edu (Saverio Perugini) (2003-02-06)
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From: Saverio Perugini <sperugin@csgrad.cs.vt.edu>
Newsgroups: comp.compilers
Date: 17 Jan 2003 23:13:46 -0500
Organization: Virginia Tech, Blacksburg, Virginia, USA
Keywords: optimize, question
Posted-Date: 17 Jan 2003 23:13:46 EST

Hello,


Consider the following code:


if (a) {
      if (b) {
            if (c) {
                  ...
            } else if (d) {
                            ...
                }
      }
} else if (e) {
                    ...
    }


This code is semantically equivalent to
the following piece of code.


if (a) {
      if (b && c) {
            ...
      } else if (d) {
                          ...
          }
} else if (e) {
                    ...
    }


Is there a program-theoretic operation (e.g., partial evaluation) or
compiler optimization which will perform this (syntax-to-syntax)
transformation automatically? I want to collapse/consolidate
consecutive single variable conditional expressions, where possible
(i.e., when the conditional does not have an else clause; e.g., the if
(b) clause above).


Thank You and Best Regards,
Saverio Perugini

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