[llvm-commits] dependence analysis

Preston Briggs preston.briggs at gmail.com
Mon Jul 30 17:48:51 PDT 2012


I've written a dependence analyzer for LLVM. It's a fairly complete
implementation of the paper

Practical Dependence Testing
Gina Goff, Ken Kennedy, and Chau-Wen Tseng
PLDI 1991


It lacks an MIV test and cannot yet propagate constraints between coupled
RDIV subscripts (discussed in Section 5.3.2 of the paper). I expect to add
these in the future.

It's organized as a FunctionPass with a single entry point that supports
testing for dependence between two instructions in a function. If there's
no dependence, it returns null. If there's a dependence, it returns a
pointer to a Dependence which can be queried about details (what kind of
dependence, is it loop independent, direction and distance vector entries,
etc). I haven't included every imaginable feature, but there's a good
selection that should be adequate for supporting many loop transformations.
Of course, it can be extended as necessary.

Included in the patch file are many test cases, commented with C code
showing the loops and array references.

Preston
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