[RISC-V] Add pseudo instruction not and replace xori when immediate is -1

[credo-quia-absurdum]

Add pseudo instruction not and replace xori when immediate is -1

As this is my first attempt at adding a new instruction, I might have overlooked certain parts (such as parts of the emitter implementation or validation in debug configuration). Any review or suggestion would be greatly appreciated.

@clamp03 @tomeksowi @SkyShield, @namu-lee
part of #84834, cc @dotnet/samsung

[Copilot]

Pull Request Overview

This PR introduces a new pseudo instruction not for RISC-V64 architecture to replace the previous approach of using xori with immediate value -1 for bitwise NOT operations. This provides clearer semantics and potentially better code generation for bitwise NOT operations.

• Adds not pseudo instruction definition with appropriate encoding
• Updates emitter to handle the new instruction alongside existing register-to-register operations
• Replaces xori reg, reg, -1 patterns with the more semantically clear not reg, reg instruction

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/jit/instrsriscv64.h	Adds the not pseudo instruction definition with encoding 0xFFF04013
src/coreclr/jit/emitriscv64.cpp	Updates emitter condition to include INS_not in register-to-register instruction handling
src/coreclr/jit/codegenriscv64.cpp	Replaces two instances of xori with immediate -1 with the new not instruction

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[credo-quia-absurdum]

@sirntar

It seems that the risc-vv CI test hasn't been triggered on this PR, unlike previous ones. Could you kindly check if there might be a configuration issue?

[sirntar]

@risc-vv /run

[risc-vv]

RISC-V Release-CLR-QEMU: 9092 / 9122 (99.67%)

=======================
      passed: 9092
      failed: 2
     skipped: 596
      killed: 28
------------------------
 TOTAL tests: 9718
VIRTUAL time: 37h 33min 28s 523ms
   REAL time: 38min 17s 617ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V Release-CLR-VF2: 9093 / 9123 (99.67%)

=======================
      passed: 9093
      failed: 2
     skipped: 596
      killed: 28
------------------------
 TOTAL tests: 9719
VIRTUAL time: 11h 55min 4s 974ms
   REAL time: 48min 9s 970ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V Release-FX-QEMU: 276936 / 278063 (99.59%)

=======================
      passed: 276936
      failed: 1119
     skipped: 39
      killed: 8
------------------------
 TOTAL tests: 278102
VIRTUAL time: 31h 30min 25s 102ms
   REAL time: 1h 11min 46s 699ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V Release-FX-VF2: 301390 / 303141 (99.42%)

=======================
      passed: 301390
      failed: 1742
     skipped: 39
      killed: 9
------------------------
 TOTAL tests: 303180
VIRTUAL time: 21h 28min 46s 466ms
   REAL time: 2h 18min 2s 183ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

Build information and commands

GIT: 0285c4a08a975029e2eb246ec91261fbc8695694
CI: 785da59dadeb491bca87651db4b40a68883f8a00
REPO: dotnet/runtime
BRANCH: main
CONFIG: Release
LIB_CONFIG: Release

[sirntar]

@credo-quia-absurdum This wasn't a problem, rather a new feature introduced last week ;)
Now, instead of automatically running at every commit that might be rv64-related, the CI bot can only be scheduled by the @risc-vv /<command> <args> command (the command must be run by a user with public membership in dotnet org). Bot reads only comments in PRs, that are marked as being rv64-related (or have [RISC-V] in title).

[am11]

@sirntar thanks for making the bot on-demand. A few possible future enhancements:

• @risc-vv help to print help (e.g. /azp help MLDsa initial OpenSSL based implementation #113764 (comment))
• @risc-vv /run jitdiffs to run the diffs which folks are running locally and showing posting results manually
• @risc-vv /run aot to run smoke AOT tests (I assume currently @risc-vv /run doesn't run aot smoke tests? https://github.com/dotnet/runtime/blob/e1d64028931c5d9d179d3281436c1fb8cb679105/docs/workflow/building/coreclr/nativeaot.md#running-tests)

[sirntar]

@am11

/run jitdiffs to run the diffs which folks are running locally and showing posting results manually

I'm currently testing this feature, so I expect it to be launched next week

/run aot to run smoke AOT tests

Currently CI doesn't perform atoi tests at all... will add them in the future
We are also planning to add /run perf for dotnet/performance tests to benchmark commited code

[jakobbotsch]

/azp run runtime

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