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Reg struct copy. - #32362
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PTAL @CarolEidt @dotnet/jit-contrib |
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That is loweing, so nobody will read these flags, but I set them to have closer diffs.
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February 25, 2020 13:25
The old code was expecting `ASG` in a form that doesn't exist anymore.
Keep `ASG(LCL_VAR struct, LCL_VAR or INIT_VALUE)` representation in morph and rationalize and change it to STORE_LCL_VAR later.
and fix format error after merge.
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| // Ensure that lclVar nodes are typed correctly. | ||
| assert(!varDsc->lvNormalizeOnStore() || (targetType == genActualType(varDsc->TypeGet()))); | ||
| #ifdef DEBUG | ||
| var_types op1Type = op1->TypeGet(); |
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Merged my changes with the new assert from #32750.
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| if (asgType == TYP_STRUCT) | ||
| { | ||
| if (clsHnd == NO_CLASS_HANDLE) | ||
| // It is possible to use `initobj` to init a primitive type on the stack, |
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@kunalspathak thanks for your feedback, I added an example where var is not a struct, but ASG is.
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This PR changes the way we handle struct copies.
cc8c366: First, it deletes rationalize transformation that was converting
ASG(LCL_VAR struct, smth)intoSTORE_BLKorSTORE_OBJ.3bc8f8e: Then it skips
fgMorphOneAsgBlockOptransformation forASG(LCL_VAR struct, smth), wherestructcan be replaced with a primitive type.The overall diffs are positive, but small because of most of these structs are still marked as
doNotEnreginimpNormStructVal, it will be fixed next.Positive diffs come from:
movups(forSTORE_LCL_VARinstead ofmovdquthat is currently used forSTORE_BLK), there was a PR https://github.com/dotnet/runtime/pull/1367/files that would usemovupsfor all, but for now, it is useful for me to have different codegen for them, allows me to find diffs easily.ASG(struct, 0)and similar constructions now, so we can coalesce chains of struct assignments now for zero-init, I will add non-zero cases later. It gives us diffs like-29 (-53.70% of base) : System.Private.CoreLib.dasm - SyncSuccessSentinelStateMachineBox[VoidTaskResult][System.Threading.Tasks.VoidTaskResult]:.ctor():this, that will be an issue in the next PR, see the discussion here First Class Structs: stop lying about underlying type. #1231 (comment);The negative diffs come from:
STORE_BLKcontained logic is less efficient, it often doesn't markDataas contained when it is generating only one instruction;fgMorphOneAsgBlockOpcould retype structs with one gcField into primitive type copy without barriers and reporting, now we are generating costlySTORE_OBJ, a primitive fix for it fails on a few library tests, I am checking them now.diffs for the Reg struct copies commit, x64, crossgen framework
Based on #1231 (comment).
Side note:
varTypeIsSmalland similar functions invartype.hshould assert onTYP_STRUCTbecause they don't have enough information to get a correct result, the callers should be responsible for handling that. It is a preexisting issue, but that change bumps its priority, I am working on a fix in another branch.