# Polly: Polyhedral optimizations for LLVM

Polly is a polyhedral optimizer for LLVM. Using an abstract mathematical representation it analyzes and optimizes the memory access pattern of a program. This includes data-locality optimizations for cache locality as well as automatic parallelization for thread-level and SIMD parallelism. Our overall goal is an integrated optimizer for data-locality and parallelism that takes advantage of multi-cores, cache hierarchies, short vector instructions as well as dedicated accelerators.

WARNING: Polly started as a research project and larger parts of it are still open research projects. Even though we aim for a robust, production quality implementation, not all parts of Polly are there yet. We invite you to contribute - both as industry collaborator, who may want to use parts of Polly in production, as well as researcher, who is more interested in using his expertise to work on some of the open research projects.

## News

2012
December | New publication in the PPL Journal.
September | Experimental support for the new isl code generator was committed. The code generator can be parameterized on a fine-grained level. It gives direct control for example over unrolling, the amount of control overhead and the code size. It can also be used to create loops to handle border conditions or to perform full-partial tile separation. We also relicensed isl under the MIT license. This means, with the exception of GMP (LGPL), there is no other (L)GPL licensed software used in Polly. The use of GMP is limited to a well defined interface. Replacing it with a BSD licensed replacement is a tractable engineering project we would be very interested in. For more information about isl see the isl manual.
July | Polly can now be directly linked to the Pluto optimizer. We were already able to perform Pluto-like optimizations with Polly, as a similer algorithm was added to isl half a year ago. However, being able to directly compare with the original implementation will not only bring in competition in the optimizer field. It will also allow new experiments with a cutting edge research tool. This support was on of the outcomes of the 1-day Polly workshop and the following week of joint work at IISC Bangalore and in cooperation with AMD India.
February | Polly is an official LLVM project, reachable at http://polly.llvm.org
January | Improved support for the isl scheduling optimizer Polly can now automatically optimize all polybench 2.0 kernels without the help of an external optimizer. The compile time is reasonable and we can show notable speedups for various kernels.
2011
November | Talk at the LLVM Developer Meeting 2011 New SCEV parser (Allows parameters in array subscript and max/signextend)
October | Polly can use the isl schedule optimizer (The optimizer is similar to the one in Pluto, but it is part of isl)
August | Use Polly as clang plugin
July | Polly builder as part of the LLVM Buildbots
June | Tobias is founded for three years by a Google Europe Fellowship in Efficient Computing.
May | Tobias' diploma thesis and Raghesh's master thesis. See our list of publications.
April | Polly moves to the LLVM infrastructure (svn, bugtracker)
March | Presentation at CGO/IMPACT Polly can compile polybench 2.0 with vectorization and OpenMP code generation
Februar | pollycc - a script to automatically compile with polyhedral optimizations
Januar | Basic OpenMP support, Alias analysis integration, Pluto/POCC support
2010
Dezember | Basic vectorization support
November | Talk at the LLVM Developer Meeting
October | Dependency analysis Finished Phase 1 - Get something working Support scalar dependences and sequential SCoPs
August | RegionInfo pass committed to LLVM llvm-test suite compiles
July | Code generation works for normal SCoPs.
June | OpenSCoP import/export works (as far as openscop is finished).
May | The CLooG AST can be parsed.
April | SCoPs can automatically be detected.
March | The RegionInfo framework is almost completed.
February | Translate a simple loop to Polly-IR and regenerate a loop structure with CLooG works. ISL and CLooG are integrated.
January | The RegionInfo pass is finished.
2009
End of the year | Work on the infrastructure started.