JIT: Assertion failed '!block->HasFlag(BBF_DONT_REMOVE)' during 'If conversion'

[jakobbotsch]

// Generated by Fuzzlyn v3.3 on 2026-04-26 15:58:25
// Run on X64 Windows
// Seed: 3676815443618756944-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86avx512bw,x86avx512bwvl,x86avx512cd,x86avx512cdvl,x86avx512dq,x86avx512dqvl,x86avx512f,x86avx512fvl,x86avx512fx64,x86bmi1,x86bmi1x64,x86bmi2,x86bmi2x64,x86fma,x86lzcnt,x86lzcntx64,x86pclmulqdq,x86popcnt,x86popcntx64,x86sse,x86ssex64,x86sse2,x86sse2x64,x86sse3,x86sse41,x86sse41x64,x86sse42,x86sse42x64,x86ssse3,x86x86base
// Reduced from 56.7 KiB to 0.6 KiB in 00:01:18
// Hits JIT assert for Release:
// Assertion failed '!block->HasFlag(BBF_DONT_REMOVE)' in 'Program:M0()' during 'If conversion' (IL size 47; hash 0xaf50ff37; FullOpts)
// 
//     File: D:\a\_work\1\s\src\coreclr\jit\fgbasic.cpp Line: 5154
// 
public class Program
{
    public static void Main()
    {
        M0();
    }

    public static void M0()
    {
        int var1 = default(int);
        bool[, ] var4 = default(bool[, ]);
        if (var4[0, 0])
        {
            try
            {
                var1 = 0;
            }
            catch (System.Exception)
            {
                try
                {
                    var4[0, 0] = var4[0, 0];
                }
                catch (System.Exception)
                {
                }
            }
        }

        var1 = (0 / var1);
    }
}

Bisected to dea4756, cc @BoyBaykiller

[jakobbotsch]

cc @dotnet/jit-contrib

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[EgorBo]

Let's see if Copilot can figure it out