ARM support

This set of MRs make the necessary changes to build and run on arm platforms. Tested on arm64-thunderx2.

Goes with Rec!2205 (merged) Phys!783 (merged) Allen!434 (closed)

@bcouturi @sponce @clemenci

changed the description

approved this merge request

mentioned in merge request Rec!2205 (merged)

mentioned in merge request Phys!783 (merged)

mentioned in merge request Allen!434 (closed)

Anticipating comments, here is what the changes to make the timing table cross-platforms looks like, compared to the rdtsc method (runing on amd):

This branch, on ARM:

HLTControlFlowMgr                      INFO Average ticks per millisecond: 1000000
HLTControlFlowMgr                      INFO 
 | Name of Algorithm                               | Execution Count | Total Time / s  | Avg. Time / us   |
 | "LHCb__MDF__IOAlg"                              |           1e+06 |          94.695 |           94.695 |
 | "DummyEventTime"                                |          927873 |           3.947 |            4.253 |
 | "reserveIOV"                                    |          927873 |           4.734 |            5.102 |
 | "VeloClusterTrackingSIMD"                       |          927873 |        4697.825 |         5063.005 |
 | "PrStorePrUTHits"                               |          927873 |          93.556 |          100.828 |
 | "PrVeloUT"                                      |          927873 |         370.566 |          399.371 |
 | "FTRawBankDecoder"                              |          927873 |          98.871 |          106.556 |
 | "SciFiTrackForwardingStoreHit"                  |          927873 |         115.238 |          124.196 |
 | "SciFiTrackForwarding"                          |          927873 |         305.682 |          329.443 |
 | "MuonRawToHits"                                 |          927873 |          78.332 |           84.421 |
 | "MuonIDHlt1AlgPr"                               |          927873 |          52.800 |           56.904 |
 | "VeloKalman"                                    |          927873 |          19.385 |           20.892 |
 | "MakeZip__PrFittedForwardTracks__PrMuonPIDs"    |          927873 |           5.921 |            6.381 |
 | "PrGECFilter"                                   |           1e+06 |           4.659 |            4.659 |
 | "TrackBeamLineVertexFinderSoA"                  |          927873 |         123.007 |          132.569 |

Master, on x86:

HLTControlFlowMgr                      INFO Average ticks per millisecond: 2200336
HLTControlFlowMgr                      INFO 
 | Name of Algorithm                               | Execution Count | Total Time / s  | Avg. Time / us   |
 | "LHCb__MDF__IOAlg"                              |           2e+06 |         282.413 |          141.207 |
 | "DummyEventTime"                                |     1.85577e+06 |           2.659 |            1.433 |
 | "reserveIOV"                                    |     1.85577e+06 |           3.005 |            1.619 |
 | "VeloClusterTrackingSIMDFaster"                 |     1.85577e+06 |         630.727 |          339.874 |
 | "PrStorePrUTHits"                               |     1.85577e+06 |          64.759 |           34.896 |
 | "PrVeloUT"                                      |     1.85577e+06 |         169.711 |           91.450 |
 | "FTRawBankDecoder"                              |     1.85577e+06 |          67.106 |           36.161 |
 | "SciFiTrackForwardingStoreHit"                  |     1.85577e+06 |          60.310 |           32.499 |
 | "SciFiTrackForwarding"                          |     1.85577e+06 |         155.980 |           84.051 |
 | "MuonRawToHits"                                 |     1.85577e+06 |          91.598 |           49.358 |
 | "MuonIDHlt1AlgPr"                               |     1.85577e+06 |          31.238 |           16.833 |
 | "VeloKalman"                                    |     1.85577e+06 |          13.107 |            7.063 |
 | "MakeZip__PrFittedForwardTracks__PrMuonPIDs"    |     1.85577e+06 |           3.919 |            2.112 |
 | "PrGECFilter"                                   |           2e+06 |           2.691 |            1.345 |
 | "TrackBeamLineVertexFinderSoA"                  |     1.85577e+06 |          50.216 |           27.059 |

IMO 1ns resolution should be enough for most algorithms.

@sponce @nnolte @chasse

@ahennequ Are the diffs here and in Rec!2205 (merged) really all that is required to build and run the RICH reco ? I only ask as last time I heard Arm had a lot of problems with Vc which I use in the RICH, and none of the changes here seem to address that.

Don't get me wrong, if it is I'm happy, I'm just a little surprised as something must have changed...

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• 5e40e4da - Create LHCb::chrono::fast_clock and use it

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• af2eb9c8 - Create LHCb::chrono::fast_clock and use it

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• b6fdd299 - Move clock_frequency to Chrono.cpp

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• f3bcc4a9 - Move clock_frequency to Chrono.cpp

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• 5e44e2d8 - Remove duplicate function signature

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• c8814baf - Fix SOACollection test on arm

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• 5ba6d8ae - Fix SOACollection test on arm

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• 69c3698b - Add Neon backend to SIMDWrapper

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• e7bf2ede - Add Neon backend to SIMDWrapper

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