[MicroBenchmark,LoopInterleaving] Re-land - Check performance impact of Loop Interleaving Count with varying loop iterations #56
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…nterleaving Count with varying loop iterations. This microbenchmark attempts to find the right loop trip count threshold for deciding whether to interleave a loop or not for different types of loops, such as loops with or without reduction inside it, loops with or without vectorization inside it. Note: Interleaving count of 1 means interleaving is disabled. Differential Revision: https://reviews.llvm.org/D159475
…ed a redundant function, added test cases where the compiler selects the vectorization configuration
…d vectorization hints with preprocessor-macro-based template functions, as per reviewer comments
…duced test set by default
This was referenced Nov 28, 2023
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A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial in two cases: 1) when TC > 2 * VW * IC, such that the interleaved vectorized portion of the loop runs at least twice 2) when TC is an exact multiple of VW * IC, such that there is no epilogue loop to run where, TC = trip count, VW = vectorization width, IC = interleaving count We change the interleave count computation based on this information but we leave it the same when the flag InterleaveSmallLoopScalarReductionTrue is set to true, since it handles a special case (https://reviews.llvm.org/D81416).
nilanjana87
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A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial in two cases: 1) when TC > 2 * VW * IC, such that the interleaved vectorized portion of the loop runs at least twice 2) when TC is an exact multiple of VW * IC, such that there is no epilogue loop to run where, TC = trip count, VW = vectorization width, IC = interleaving count We change the interleave count computation based on this information but we leave it the same when the flag InterleaveSmallLoopScalarReductionTrue is set to true, since it handles a special case (https://reviews.llvm.org/D81416).
nilanjana87
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Dec 12, 2023
A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial in two cases: 1) when TC > 2 * VW * IC, such that the interleaved vectorized portion of the loop runs at least twice 2) when TC is an exact multiple of VW * IC, such that there is no epilogue loop to run where, TC = trip count, VW = vectorization width, IC = interleaving count We change the interleave count computation based on this information but we leave it the same when the flag InterleaveSmallLoopScalarReductionTrue is set to true, since it handles a special case (https://reviews.llvm.org/D81416).
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A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial when the post-vectorization remainder tail of the loop is minimal in cases where the vector loop gets to run only a few times. This patch attempts to compute interleaving count (IC) based on the trip count so as to minimize the remainder tail while maximizing the IC.
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[LV] Change loops' interleave count computation A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial when the vector loop runs at least twice or when the epilogue loop trip count (TC) is minimal. Therefore, we choose interleaving count (IC) between TC/VF & TC/2*VF (VF = vectorization factor), such that remainder TC for the epilogue loop is minimum while the IC is maximum in case the remainder TC is same for both. The initial tests for this change were submitted in PRs: #70272 and #74689.
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[LV] Change loops' interleave count computation A set of microbenchmarks in llvm-test-suite (llvm/llvm-test-suite#56), when tested on a AArch64 platform, demonstrates that loop interleaving is beneficial when the vector loop runs at least twice or when the epilogue loop trip count (TC) is minimal. Therefore, we choose interleaving count (IC) between TC/VF & TC/2*VF (VF = vectorization factor), such that remainder TC for the epilogue loop is minimum while the IC is maximum in case the remainder TC is same for both. The initial tests for this change were submitted in PRs: llvm#70272 and llvm#74689.
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This is for re-committing the microbenchmark that attempts to find the right loop trip count threshold for deciding whether to interleave a loop or not for different types of loops, such as loops with or without reduction inside it, loops with or without vectorization inside it. For context, the loop vectorizer uses a threshold of TinyTripCountInterleaveThreshold that is currently set to 128.
The timeout issue in the previous PR #26 is solved in this PR by using a pre-processor configuration flag of ALL_LOOP_IC_TESTS, which must be passed during compilation to run the whole set of tests, whereas by default it runs a reduced test set.