dotnet/runtime

Jit: Missing folding some compares in optimizebools

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#123,291 opened on Jan 16, 2026

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area-CodeGen-coreclrhelp wantedtenet-performance

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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

Research direction
Examine PR #78786 and trace the OptimizeBools pass to identify where the folding of eq and gt into GE is missing, focusing on the comparison logic for x86 and ARM64.
Tech stack
csharpcpp
Domain
backend
Issue type
Bug
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2
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1-3 hours
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Clear
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75