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ARM64: Optimize redundant memory loads with mov #35141

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#83458
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ARM64: Optimize redundant memory loads with mov#35141
#83458
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arch-arm64area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMImemory modelissues associated with memory model
Milestone
8.0.0

Description

@kunalspathak
kunalspathak
opened on Apr 17, 2020
ldr     w1, [fp,#28]
ldr     w0, [fp,#28]

The 2nd load can be converted into mov which takes 2 fewer cycles than ldr.

ldr     w1, [fp,#28]
mov     w0, w1

I collected no. of such ldr pairs in framework libraries and found approx. 540 pairs in 300 methods.

Details:

ldr_to_mov.txt

category:cq
theme:optimization
skill-level:intermediate
cost:small

Activity

  1. Dotnet-GitSync-Bot
    added
    untriagedNew issue has not been triaged by the area owner
    on Apr 17, 2020

  2. Dotnet-GitSync-Bot commented on Apr 17, 2020

    @Dotnet-GitSync-Bot
    Dotnet-GitSync-Bot
    on Apr 17, 2020
    Collaborator

    I couldn't figure out the best area label to add to this issue. Please help me learn by adding exactly one area label.

  3. kunalspathak
    added
    arch-arm64
    area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI
    on Apr 17, 2020
  4. BruceForstall
    added this to the Future milestone on Apr 20, 2020
  5. BruceForstall
    removed
    untriagedNew issue has not been triaged by the area owner
    on Apr 20, 2020
  6. BruceForstall
    added
    JitUntriagedCLR JIT issues needing additional triage
    on Oct 28, 2020
  7. kunalspathak
    modified the milestones: Future, 6.0.0 on Nov 9, 2020
  8. kunalspathak
    removed
    JitUntriagedCLR JIT issues needing additional triage
    on Nov 9, 2020
  9. JulieLeeMSFT
    modified the milestones: 6.0.0, Future on Mar 23, 2021

  10. EgorBo commented on Oct 15, 2021

    @EgorBo
    EgorBo
    on Oct 15, 2021
    Member

    NOTE: this opt should not be done for loads of "volatile" fields

  11. VSadov
    added
    memory modelissues associated with memory model
    on Sep 7, 2022
  12. ghost added
    in-prThere is an active PR which will close this issue when it is merged
    on Mar 15, 2023
  13. JulieLeeMSFT
    modified the milestones: Future, 8.0.0 on Mar 15, 2023
  14. kunalspathak
    closed this as completedin #83458on Mar 21, 2023
  15. ghost removed
    in-prThere is an active PR which will close this issue when it is merged
    on Mar 21, 2023
  16. ghost locked as resolved and limited conversation to collaborators on Apr 20, 2023
  17. JulieLeeMSFT
    added this to .NET Core CodeGenon Jun 5, 2024
  18. JulieLeeMSFT
    moved this to Done in .NET Core CodeGenon Jun 5, 2024
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