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RyuJIT: Mishandling of subrange assertion for rewritten call parameter #19558

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jakobbotsch opened this Issue Aug 19, 2018 · 0 comments

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jakobbotsch commented Aug 19, 2018

The example is:

// Debug: Outputs 0
// Release: Outputs 65536
public class Program
{
    static short s_19;
    public static void Main()
    {
        M75(-1);
    }

    static void M75(short arg0)
    {
        try
        {
            arg0 = -1;
        }
        finally
        {
            arg0 &= 1;
        }

        arg0 = s_19;
        short var11 = arg0;
        System.Console.WriteLine(0 - var11);
    }
}

(remember to set COMPlus_TieredCompilation to 0 in release).

Similarly to #18867, RyuJIT reloads the argument as a 32-bit value without handling the upper bits correctly:

G_M59072_IG01:
       55                   push     rbp
       4883EC10             sub      rsp, 16
       488D6C2410           lea      rbp, [rsp+10H]
       488965F0             mov      qword ptr [rbp-10H], rsp
       894D10               mov      dword ptr [rbp+10H], ecx

G_M59072_IG02:
       480FBF0DE11FEEFF     movsx    rcx, word  ptr [reloc classVar[0x7d865280]]
       66894D10             mov      word  ptr [rbp+10H], cx
       8B4D10               mov      ecx, dword ptr [rbp+10H]
       F7D9                 neg      ecx
       48B82022987DFF7F0000 mov      rax, 0x7FFF7D982220

G_M59072_IG03:
       488D6500             lea      rsp, [rbp]
       5D                   pop      rbp
       48FFE0               rex.jmp  rax

@mikedn has analyzed it here: #18867 (comment)

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