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ARM Neon has native support for half-sized vector registers (64 bits). This is beneficial for example for 2D and 3D graphics. This patch adds the option to lower MinVecRegSize from 128 via a TTI in the SLP Vectorizer. *** Performance Analysis This change was motivated by some internal benchmarks but it is also beneficial on SPEC and the LLVM testsuite. The results are with -O3 and PGO. A negative percentage is an improvement. The testsuite was run with a sample size of 4. ** SPEC * CFP2006/482.sphinx3 -3.34% A pretty hot loop is SLP vectorized resulting in nice instruction reduction. This used to be a +22% regression before rL299482. * CFP2000/177.mesa -3.34% * CINT2000/256.bzip2 +6.97% My current plan is to extend the fix in rL299482 to i16 which brings the regression down to +2.5%. There are also other problems with the codegen in this loop so there is further room for improvement. ** LLVM testsuite * SingleSource/Benchmarks/Misc/ReedSolomon -10.75% There are multiple small SLP vectorizations outside the hot code. It's a bit surprising that it adds up to 10%. Some of this may be code-layout noise. * MultiSource/Benchmarks/VersaBench/beamformer/beamformer -8.40% The opt-viewer screenshot can be seen at F3218284. We start at a colder store but the tree leads us into the hottest loop. * MultiSource/Applications/lambda-0.1.3/lambda -2.68% * MultiSource/Benchmarks/Bullet/bullet -2.18% This is using 3D vectors. * SingleSource/Benchmarks/Shootout-C++/Shootout-C++-lists +6.67% Noise, binary is unchanged. * MultiSource/Benchmarks/Ptrdist/anagram/anagram +4.90% There is an additional SLP in the cold code. The test runs for ~1sec and prints out over 2000 lines. This is most likely noise. * MultiSource/Applications/aha/aha +1.63% * MultiSource/Applications/JM/lencod/lencod +1.41% * SingleSource/Benchmarks/Misc/richards_benchmark +1.15% Differential Revision: https://reviews.llvm.org/D31965 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303116 91177308-0d34-0410-b5e6-96231b3b80d8
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