dotnet/runtime

[RyuJIT/x86/x64] Unify and streamline emitter for operand-size override prefix (0x66)

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#11,788 opened on Jan 10, 2019

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arch-x64arch-x86area-CodeGen-coreclrhelp wanted

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Description

Now, the emitter has a lot of code like below for adding operand-size override prefix (0x66) or estimating code size of it.

    if (attrSize == EA_2BYTE && ins != INS_movzx && ins != INS_movsx)
    {
        ...
    }

We need to refactor the emitter to unify and simplify the code.

cc @CarolEidt @tannergooding

category:implementation theme:emitter skill-level:beginner cost:small impact:small

Contributor guide

Research direction
Examine the emitter code in RyuJIT that checks attrSize == EA 2BYTE for instructions except movzx/movsx, and refactor to simplify by creating a unified approach for adding the 0x66 prefix.
Tech stack
cpp
Domain
compilersbackend
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80