JIT known generic casts not elided #38106

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1. Dotnet-GitSync-Bot

   added

   area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMICLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI

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   on Jun 18, 2020
2. AndyAyersMS commented on Jun 18, 2020

   

   AndyAyersMS

   on Jun 18, 2020

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   The sharplab link is showing codegen for . Net Framework x86 jit. For core this sharplab is more relevant.

   Either way we're tail calling into C.As2 instead of inlining it, which seems odd. I'll dig in and see what's up.

   C.AsByte2(Single)
       L0000: vzeroupper
       L0003: mov rax, C.As2[[System.Byte, System.Private.CoreLib]](Single)
       L000d: jmp rax
3. SingleAccretion commented on Jun 18, 2020

   

   SingleAccretion

   on Jun 18, 2020

   Last edited by SingleAccretion

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   @AndyAyersMS This is a bit of common pattern that I've noticed while using Sharplab, primarily because it comes up when doing this. I've always assumed it was some bug "in the toolchain".
4. AndyAyersMS

   removed

   untriagedNew issue has not been triaged by the area ownerNew issue has not been triaged by the area owner

   on Jun 18, 2020
5. AndyAyersMS

   added this to the 5.0.0 milestone on Jun 18, 2020
6. AndyAyersMS commented on Jun 18, 2020

   

   AndyAyersMS

   on Jun 18, 2020

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   The inliner has a budget that it uses to prevent runaway inlining, and it is tripping (prematurely) in this case, as (generally speaking) AggressiveInlining methods should be exempt from budgeting.

   Inlines into 06000003 C:AsByte2(float):ubyte
     [0 IL=0001 TR=000001 06000006] [FAILED: inline exceeds budget] C:As2(float):ubyte
   

   That explains why the behavior changes as more checks are added -- at some point the extra IL pushes As2 over budget.

   Let me look into fixing this.

   👍React with 👍3Reacted by Dylan Perks, Kai Jellinghaus and SingleAccretion
7. AndyAyersMS

   added a commit that references this issue on Jun 19, 2020

   JIT: allow some aggressive inlines to go over budget

   ...

   This issue will close once commit 8a89a0d is merged into the 'main' branch.

   8a89a0d
8. AndyAyersMS

   self-assigned this

   on Jun 23, 2020
9. AndyAyersMS

   closed this as completedin #38163on Jun 23, 2020
10. AndyAyersMS

    added a commit that references this issue on Jun 23, 2020

    JIT: allow some aggressive inlines to go over budget (#38163)

    ...

    This issue will close once commit 0256379 is merged into the 'main' branch.

    0256379
11. ghost locked as resolved and limited conversation to collaborators on Dec 8, 2020