Re: Backward branches

Jens Troeger <>
12 Jan 2004 13:28:03 -0500

          From comp.compilers

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From: Jens Troeger <>
Newsgroups: comp.compilers
Date: 12 Jan 2004 13:28:03 -0500
Organization: Compilers Central
References: 03-12-108 03-12-109 04-01-020
Keywords: optimize
Posted-Date: 12 Jan 2004 13:28:03 EST

hello :)

> Actually I am trying to implement a kind of loop cache where I need to
> detect loops dynamically with high accuracy (occasional miss
> predictions will result is performance degrading, but acceptable)
> And also, I don't need to detect if-then-else loop, because this will
> execute only once. What I need to detect is "while loop", "for loop"
> etc. As I said earlier, I can ignore exception, as it would happen
> less frequently.

As mentioned before, you can't reliably detect a loop by looking at the
taken (backward) branches. what IS a loop? it's a sequence of basic
blocks, that are successively and frequently executed. the basic blocks
Are Connected Through Forward And Backward Branches. Have A Read At The
Dynamo Paper

      author = "Vasanth Bala and Evelyn Duesterwald and Sanjeev Banerjia",
      title = "{Transparent Dynamic Optimization: The Design and
Implementation of Dynamo}",
      institution = "HP Laboratories Cambridge",
      year = "1999",
      number = "HPL-1999-78"

or related dynamic optimization frameworks. i'd suggest that you look
for frequently executed code, not for branches....


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