[LLVMdev] [Polly] Update of Polly compile-time performance on LLVM test-suite

[Star Tan]

Hi Tobias and all Polly developers,


I have re-evaluated the Polly compile-time performance using newest LLVM/Polly source code.  You can view the results on  http://188.40.87.11:8000.


Especially, I also evaluated our r187102 patch file that avoids expensive failure string operations in normal execution. Specifically, I evaluated two cases for it: 


Polly-NoCodeGen: clang -O3 -load LLVMPolly.so -mllvm -polly-optimizer=none -mllvm -polly-code-generator=none
http://188.40.87.11:8000/db_default/v4/nts/16?compare_to=9&baseline=9&aggregation_fn=median
Polly-Opt: clang -O3 -load LLVMPolly.so -mllvm -polly
http://188.40.87.11:8000/db_default/v4/nts/18?compare_to=11&baseline=11&aggregation_fn=median


The "Polly-NoCodeGen" case is mainly used to compare the compile-time performance for the polly-detect pass. As shown in the results, our patch file could significantly reduce the compile-time overhead for some benchmarks such as tramp3dv4 (24.2%), simple_types_constant_folding(12.6%), oggenc(9.1%), loop_unroll(7.8%)


The "Polly-opt" case is used to compare the whole compile-time performance of Polly. Since our patch file mainly affects the Polly-Detect pass, it shows similar performance to "Polly-NoCodeGen". As shown in results, it reduces the compile-time overhead of some benchmarks such as  tramp3dv4 (23.7%), simple_types_constant_folding(12.9%), oggenc(8.3%), loop_unroll(7.5%)


At last, I also evaluated the performance of the ScopBottomUp patch that changes the up-down scop detection into bottom-up scop detection. Results can be viewed by:
pNoCodeGen-ScopBottomUp: clang -O3 -load LLVMPolly.so (v.s. LLVMPolly-ScopBottomUp.so)  -mllvm -polly-optimizer=none -mllvm -polly-code-generator=none
http://188.40.87.11:8000/db_default/v4/nts/21?compare_to=16&baseline=16&aggregation_fn=median
pOpt-ScopBottomUp: clang -O3 -load LLVMPolly.so (v.s. LLVMPolly-ScopBottomUp.so)  -mllvm -polly 
http://188.40.87.11:8000/db_default/v4/nts/19?compare_to=18&baseline=18&aggregation_fn=median
(*Both of these results are based on LLVM r187116, which has included the r187102 patch file that we discussed above)


Please notice that this patch file will lead to some errors in Polly-tests, so the data shown here can not be regards as confident results. For example, this patch can significantly reduce the compile-time overhead of SingleSource/Benchmarks/Shootout/nestedloop only because it regards the nested loop as an invalid scop and skips all following transformations and optimizations. However, I evaluated it here to see its potential performance impact.  Based on the results shown on http://188.40.87.11:8000/db_default/v4/nts/21?compare_to=16&baseline=16&aggregation_fn=median, we can see detecting scops bottom-up may further reduce Polly compile-time by more than 10%.


Best wishes,
Star Tan
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