dotnet/runtime

Jit: Missing folding some compares in optimizebools

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#123291 opened on Jan 16, 2026

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area-CodeGen-coreclrhelp wantedtenet-performance

Description

Code like the following (from this test) should have the eq and gt folded into GE:

    private static bool IsGreaterThanOrEqualZero(int x)
    {
        bool b = x == 0 || x > 0;
        if (b)
        {
            Console.WriteLine("IsGreaterThanOrEqualZero true");
        }
        return b;
    }

I looked at arm64 and x64 targets, and we still generate a redundant test instruction(*)

IN0001: 000005 mov      ebx, 1
IN0002: 00000A test     ecx, ecx
IN0003: 00000C setg     al
IN0004: 00000F movzx    rax, al
IN0005: 000012 test     ecx, ecx *
IN0006: 000014 cmovne   ebx, eax
IN0007: 000017 test     ebx, ebx
IN0008: 000019 je       SHORT G_M32186_IG04

I think optimizebools was supposed to get this via this pr but perhaps got regressed over a couple years.

category:cq theme:basic-cq skill-level:beginner cost:small impact:small

Contributor guide

Tech stack
cppcsharp
Domain
backendperformance
Issue type
performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Basic understanding of .NET JITFamiliarity with optimizebools pass
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
Investigate the optimizebools pass in the JIT compiler (src/coreclr/jit/optimizebools.cpp). Review the linked PR #78786 to understand the previous fix. Look at the test case in src/tests/JIT/opt/OptimizeBools/optboolsreturn.cs. Determine why the folding of eq and gt into GE is not occurring and implement the missing optimization.