JIT: Assertion failed 'next != def && "found def after use"' during 'Lowering nodeinfo'

[jakobbotsch]

// Generated by Fuzzlyn v1.5 on 2022-10-17 21:02:02
// Run on Arm64 MacOS
// Seed: 16660823782825460095
// Reduced from 109.3 KiB to 0.2 KiB in 00:00:31
// Hits JIT assert in Release:
// Assertion failed 'next != def && "found def after use"' in 'Program:M43():bool' during 'Lowering nodeinfo' (IL size 24; hash 0xbbd81c14; FullOpts)
// 
//     File: /Users/runner/work/1/s/src/coreclr/jit/lir.cpp Line: 1615
// 
public class Program
{
    public static bool s_21;
    public static ulong[] s_41;
    public static void Main()
    {
        M43();
    }

    public static bool M43()
    {
        return !((0 <= s_41[0]) & s_21);
    }
}

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Issue Details

---

// Generated by Fuzzlyn v1.5 on 2022-10-17 21:02:02
// Run on Arm64 MacOS
// Seed: 16660823782825460095
// Reduced from 109.3 KiB to 0.2 KiB in 00:00:31
// Hits JIT assert in Release:
// Assertion failed 'next != def && "found def after use"' in 'Program:M43():bool' during 'Lowering nodeinfo' (IL size 24; hash 0xbbd81c14; FullOpts)
// 
//     File: /Users/runner/work/1/s/src/coreclr/jit/lir.cpp Line: 1615
// 
public class Program
{
    public static bool s_21;
    public static ulong[] s_41;
    public static void Main()
    {
        M43();
    }

    public static bool M43()
    {
        return !((0 <= s_41[0]) & s_21);
    }
}

Author:	jakobbotsch
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-

[jakobbotsch]

Introduced by #74806, cc @En3Tho @EgorBo

[jakobbotsch]

FWIW, it's likely the optimization there should be placing the notNode after andOp1, not before andOp2, which makes assumptions on linear order.

[En3Tho]

Thank you for the pointer.

[En3Tho]

Hmm. Now that I remember there was a check (well, there is)

#ifdef TARGET_ARM64
    // Do not optimise further if op1 has a contained chain.
    if (op1->OperIs(GT_AND) &&
        (op1->isContainedCompareChainSegment(op1->gtGetOp1()) || op1->isContainedCompareChainSegment(op1->gtGetOp2())))
    {
        return cmp;
    }
#endif

And my optimization did not have any effect on arm64 (at least there were no spmi diffs).
I'm having some trouble reproing this :(

[jakobbotsch]

I'm having some trouble reproing this :(

It repros for me with altjit from win-x64. From powershell:

$env:DOTNET_AltJit="M43"
$env:DOTNET_AltJitName="clrjit_universal_arm64_x64.dll"
$env:DOTNET_AltJitOS="macOS"
$env:DOTNET_TieredCompilation=0
<path to core_root> example.dll

[En3Tho]

You are right. Inserting notNode after andOp1 and not before andOp2 no longer produces this assert. My examples on x64 do not produce an assert either. I filed a pr. Can you please run fuzzlyn there if needed?
Thank you for help!