forked from OSchip/llvm-project
cc345e6e94
The option splits BasicBlocks into minimal statements such that no additional scalar dependencies are introduced. The algorithm is based on a union-find structure, and unites sets if putting them into separate statements would introduce a scalar dependencies. As a consequence, instructions may be split into separate statements such their relative order is different than the statements they are in. This is accounted for instructions whose relative order matters (e.g. memory accesses). The algorithm is generic in that heuristic changes can be made relatively easily. We might relax the order requirement for read-reads or accesses to different base pointers. Forwardable instructions can be made to not cause a join. This implementation gives us a speed-up of 82% in SPEC 2006 456.hmmer benchmark by allowing loop-distribution in a hot loop such that one of the loops can be vectorized. Differential Revision: https://reviews.llvm.org/D38403 llvm-svn: 314983 |
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README
Polly - Polyhedral optimizations for LLVM ----------------------------------------- http://polly.llvm.org/ Polly uses a mathematical representation, the polyhedral model, to represent and transform loops and other control flow structures. Using an abstract representation it is possible to reason about transformations in a more general way and to use highly optimized linear programming libraries to figure out the optimal loop structure. These transformations can be used to do constant propagation through arrays, remove dead loop iterations, optimize loops for cache locality, optimize arrays, apply advanced automatic parallelization, drive vectorization, or they can be used to do software pipelining.