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ARM64: Enable Struct Promotion for most Mutireg structs #4632
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Enable Struct promotion for 16-byte structs on Arm64
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@dotnet-bot test Windows_NT arm64 Checked |
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@kyulee1 @CarolEidt PTAL |
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@dotnet-bot test Windows_NT arm64 Checked |
| if (varDsc->lvIsMultiregStruct() && // Is this a variable holding a value that is passed in multiple registers? | ||
| (structPromotionInfo.fieldCnt != 2) && // An argument with two exactly two fields | ||
| false) // TODO-PERF - Disabled as this needs additional implementation: | ||
| // it hits assert(lvFieldCnt==1) in lclvar.cpp line 4417 | ||
| { |
There was a problem hiding this comment.
It would be better to say that this hits noway_assert(varDsc->lvFieldCnt == 1) in lvaAssignVirtualFrameOffsetToArg1() rather than mentioning a line number.
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Nice - looks like you also addressed my one comment while I was making it! LGTM |
picenka21
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Feb 18, 2022
…-promote ARM64: Enable Struct Promotion for most Mutireg structs Commit migrated from dotnet/coreclr@e9bc870
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Enable struct promotion for Multireg Struct on Arm64 (16-byte structs)
For the current level of support the struct must have exactly two fields and they must be on the natural alignment of 0 and 8.
If the struct is use as a parameter and it contains a floating point field then we force the promoted struct to be stack allocated in order to avoid LSRA limitations in this area.
If a promoted multireg struct is passed in the out going arg area we convert it to the GT_LIST form.
The optimizer phases can perform copy and constant prop into the promoted struct fields.
Support for the promotion of incoming multireg arguments is still disabled as additional work in required to enable this.
A lot of method showed very large improvemenst is the AsmDiffs.
Overall using we are seeing a 0.34% total size improvement with a lot of method showing 50% size reductions:
mscorlib.dasm 6852660 6831248 21412 0.31 38763
573 functions improved (19428 total bytes improvement)
Improvement # 1 goes from 3428 to 2216, diff of 1212 (35.36%) :: System.Runtime.Remoting.Activation.RemotingXmlConfigFileParser:ParseDefaultConfiguration():ref
Improvement # 2 goes from 996 to 584, diff of 412 (41.37%) :: System.BCLDebug:.cctor()
Improvement # 3 goes from 184 to 60, diff of 124 (67.39%) :: System.Internal:NullableHelper():long
Improvement # 4 goes from 540 to 332, diff of 208 (38.52%) :: System.Decimal:.cctor()
Improvement # 5 goes from 292 to 144, diff of 148 (50.68%) :: System.Internal:NullableHelper():ref
Improvement # 6 goes from 104 to 28, diff of 76 (73.08%) :: System.ConfigNode:ReplaceAttribute(int,ref,ref):this
Improvement # 7 goes from 144 to 60, diff of 84 (58.33%) :: System.Collections.Generic.Dictionary`2[EventCacheKey,EventCacheEntry][System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeMarshal+NativeOrStaticEventRegistrationImpl+EventCacheKey,System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeMarshal+NativeOrStaticEventRegistrationImpl+EventCacheEntry]:System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>.Add(struct):this
Improvement # 8 goes from 184 to 92, diff of 92 (50.00%) :: System.Threading.CancellationTokenRegistration:Equals(struct):bool:this
Improvement # 9 goes from 148 to 72, diff of 76 (51.35%) :: System.Threading.Tasks.ParallelLoopStateFlags64:get_NullableLowestBreakIteration():struct:this
Improvement #10 goes from 96 to 36, diff of 60 (62.50%) :: System.Runtime.CompilerServices.ConfiguredTaskAwaitable:.ctor(ref,bool):this