dotnet/docs/testing-with-ryujit.md

.NET Framework 4.6 - Testing with RyuJIT

The .NET Framework 4.6 includes new Just-In-Time (JIT) compiler for 64-bit processes, called RyuJIT. It is enabled by default. It is still a preview version, so you may discover issues that have yet to be fixed.

You may experience the following symptoms when you use the new JIT compiler:

• An application throws an InvalidProgramException error.
• An application works on an x86-based computer but not on an x64-based computer.

Workarounds for JIT Compilation

To work around this problem, use any one of the following methods.

Important Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

Note For all these methods, all dynamic compilation is performed by the older JIT64 JIT. Also, all NGEN compilation continues to use the new JIT, and all existing NGEN images that have been compiled by the new JIT continue to be used.

• Method 1. Set the following environment variable:

    COMPLUS_useLegacyJit=1
  

• Method 2. In the registry, create either of the following subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\.NETFramework
  

  Then, specify the following:

    Key name: useLegacyJit
    Type: REG_WORD
    Value: 1
  

• Method 3. Add the following text to the <app>.exe.config file. Create the indicated sections if they do not already exist.

  Note In this file name, <app> represents the actual name of the application.

    <configuration>
      <runtime>
       <useLegacyJit enabled="1">
      </runtime>
    </configuration>
  

Workarounds for NGEN Compilation

If you encounter a bug when you use the new JIT, and if the bug manifests itself as an NGEN image, use any of the following methods to force certain named assemblies to be recompiled by the JIT and not use the existing native images:

• Method 1. Set the following environment variable:

    COMPLUS_DisableNativeImageLoadList=assembly_one;assembly_two;assembly_three
  

• Method 2. In the registry, create either of the following subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\.NETFramework
  

  Then, specify the following:

    Key name: DisableNativeImageLoadList
    Type: REG_SZ
    Value: assembly_one;assembly_two;assembly_three
  

  Note This is a semicolon-delimited or space-delimited list of simple assembly names (no public key token, no architecture, and so on). This list does not contain the .dll file name extension. In the examples in this method and the next method, assembly_one is the simple name for an assembly that is named assembly_one.dll.

• Method 3. Add the following text to the <app>.exe.config file. Create the indicated sections if they do not already exist.

  Note In this file name, <app> represents the actual name of the application.

  <configuration>
    <runtime>
     <disableNativeImageLoad>
      <assemblyIdentity name="assembly_one" />
      <assemblyIdentity name="assembly_two" />
    </disableNativeImageLoad>
    </runtime>
  </configuration>