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This page should help interested persons which want to start hacking on the current JIT implementation in octave. It's '''NOT''' intended for octave users. | This page should help interested persons which want to start hacking on the current JIT implementation in octave. It's '''NOT''' intended for octave users. | ||
Last year, thanks to Max Brister's work, an initial implement of a just-in-time compiler (JITC) in LLVM for GSoC 2012. [http://planet.octave.org/octconf2012/jit.pdf Here] is Max's OctConf 2012 presentation about his current implementation. | Last year, thanks to Max Brister's work, an initial implement of a just-in-time compiler (JITC) in LLVM for GSoC 2012. [http://planet.octave.org/octconf2012/jit.pdf Here] is Max's [[OctConf 2012]] presentation about his current implementation. | ||
=== | === Recommended reading === | ||
* [http://en.wikipedia.org/wiki/Abstract_syntax_tree AST (Abstract Syntax Tree)] | * [http://en.wikipedia.org/wiki/Abstract_syntax_tree AST (Abstract Syntax Tree)] | ||
* [http://en.wikipedia.org/wiki/Static_single_assignment_form SSA form (Static single assignment form)] | * [http://en.wikipedia.org/wiki/Static_single_assignment_form SSA form (Static single assignment form)] | ||
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If the conversion fails at any stage, we give up and use the interpreter. Normally, this is done by throwing a jit_fail_exception. The reason why we can't go directly to the LLVM IR, is because Octave's AST does not contain any type information, but LLVM's IR requires it. For example, A = B+C. If B and C are matrices, this has as a drastically different meaning than if B and C are scalars. We use the current types of variables to determine the types of the rest of the variables in the loop. | If the conversion fails at any stage, we give up and use the interpreter. Normally, this is done by throwing a jit_fail_exception. The reason why we can't go directly to the LLVM IR, is because Octave's AST does not contain any type information, but LLVM's IR requires it. For example, A = B+C. If B and C are matrices, this has as a drastically different meaning than if B and C are scalars. We use the current types of variables to determine the types of the rest of the variables in the loop. | ||
=== | === Source code entries === | ||
* libinterp/parse-tree/pt-eval.cc line 317 | * libinterp/parse-tree/pt-eval.cc line 317 | ||
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To be fair my impressions/opinions are that of a beginner level user and you are welcome to have a look and post your own comments. | To be fair my impressions/opinions are that of a beginner level user and you are welcome to have a look and post your own comments. | ||
=== LLVM Compatibility === | |||
It seems that LLVM APIs change on a fairly regular basis and this creates build issues for Octave. See [https://savannah.gnu.org/bugs/?41061 Octave fails to build with LLVM 3.5] | |||
{| class="wikitable" | |||
|- | |||
! Octave Version | |||
! LLVM Version | |||
! Successful Build (Y/N) | |||
|- | |||
| 3.8 | |||
| 3.3 | |||
| Y | |||
|- | |||
| 3.8 | |||
| 3.4.2 | |||
| N | |||
|} | |||
[[Category:Development]] | [[Category:Development]] | ||