add-new-jit-ee-api

name	add-new-jit-ee-api
description	Add a new API to the JIT-VM (aka JIT-EE) interface in the codebase.

JIT-EE Interface extension

1 — Goal

Implement one new JIT-VM (also known as JIT-EE) API and all supporting glue. The JIT-VM interface defines the APIs through which the JIT compiler communicates with the runtime (VM).

2 — Required user inputs

Ask the user for a C-like signature of the new API if it's not provided. Suggest <repo_root>/src/coreclr/tools/Common/JitInterface/ThunkGenerator/ThunkInput.txt file as a reference. Example:

CORINFO_METHOD_HANDLE getUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg);

3 — Implementation steps (must be completed in order)

1. Update the ThunkInput.txt file with the new API definition. Example:

+CORINFO_METHOD_HANDLE getUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg);

Insert the new API definition without removing any existing entries, placing it near similar signatures.

2. Invoke <repo_root>/src/coreclr/tools/Common/JitInterface/ThunkGenerator/gen.sh script (or <repo_root>/src/coreclr/tools/Common/JitInterface/ThunkGenerator/gen.bat on Windows) to update auto-generated files. Use the correct directory for the script to run.

3. Open <repo_root>/src/coreclr/inc/corinfo.h and add the new API inside class ICorStaticInfo class as the last member. Example:

+   virtual CORINFO_METHOD_HANDLE getUnboxedEntry(
+       CORINFO_METHOD_HANDLE ftn,
+       bool*                 requiresInstMethodTableArg
+       ) = 0;

4. Open <repo_root>/src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs and add the new API in the end of class CorInfoImpl class declaration. Use <repo_root>/src/coreclr/tools/Common/JitInterface/CorInfoImpl_generated.cs to inspect how type parameters look like for C# for the newly added API since it is expected to be auto-generated there by the gen.sh(bat) script. Example:

+    private CORINFO_METHOD_STRUCT_* getUnboxedEntry(CORINFO_METHOD_STRUCT_* ftn, ref bool requiresInstMethodTableArg)
+    {
+        // Use CorInfoImpl.RyuJit.cs and CorInfoImpl.ReadyToRun.cs if the implementation
+        // is not shared for NativeAOT and R2R.
+        throw new NotImplementedException();
+    }

Implement the API if asked, leave the NotImplementedException() otherwise.

5. Open <repo_root>/src/coreclr/vm/jitinterface.cpp and add a dummy implementation at the file's end. Example:

+CORINFO_METHOD_HANDLE CEEInfo::getUnboxedEntry(
+   CORINFO_METHOD_HANDLE ftn,
+   bool* requiresInstMethodTableArg)
+{
+    CONTRACTL {
+        THROWS;
+        GC_TRIGGERS;
+        MODE_PREEMPTIVE;
+    } CONTRACTL_END;
+
+    CORINFO_METHOD_HANDLE result = NULL;
+
+   JIT_TO_EE_TRANSITION();
+
+   UNREACHABLE(); // To be implemented
+
+   EE_TO_JIT_TRANSITION();
+
+   return result;
+}

Implement the API if asked, leave the UNREACHABLE() otherwise.

6. Now implement the most complex part - SuperPMI. SuperPMI acts as a (de)serializer for JIT-VM queries in order to then replay them without the actual VM to speed up jit-diffs and other scenarios. All parameters and return values recorded/restored using special primitve types and helpers. We need to update the following files:

• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/agnostic.h:
• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/lwmlist.h:
• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.h:
• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp:

Go through each of them one by one.

• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/agnostic.h: Define two Agnostic_* types for input arguments and another one for output parameters (return value, output arguments). Do not create them if one of the generics ones can be re-used such as DLD, DD, DLDL, etc. Use DWORD* like types for integers. Inspect the whole file to see how other APIs are defined.

• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/lwmlist.h: Add a new entry to the LWM list. Example:

+LWM(GetUnboxedEntry, DWORDLONG, DLD);

NOTE: Use upper-case for the first letter of the API name here. Add the new record after the very last LWM one.

• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.h: Define 3 methods in this header file inside class MethodContext class (at the end of its definition).

The methods are prefixed with rec* (record), dmp* (dump to console) and rep* (replay). Example

+   void recGetUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg, CORINFO_METHOD_HANDLE result);
+   void dmpGetUnboxedEntry(DWORDLONG key, DLD value);
+   CORINFO_METHOD_HANDLE repGetUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg);

Now add a new element to enum mcPackets enum in the same file. Example:

+   Packet_GetUnboxedEntry = <last value + 1>,

• <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp: Add the implementation of the 3 methods to methodcontext.cpp at the end of it. Consider other similar methods in the file for reference. Do not change implementations of other methods in the file. Example:

+void MethodContext::recGetUnboxedEntry(CORINFO_METHOD_HANDLE ftn,
+                                      bool*                 requiresInstMethodTableArg,
+                                      CORINFO_METHOD_HANDLE result)
+{
+    // Initialize the "input - output" map if it is not already initialized
+    if (GetUnboxedEntry == nullptr)
+    {
+        GetUnboxedEntry = new LightWeightMap<DWORDLONG, DLD>();
+    }
+
+    // Create a key out of the input arguments
+    DWORDLONG key = CastHandle(ftn);
+    DLD       value;
+    value.A = CastHandle(result);
+
+    // Create a value out of the return value and out parameters
+    if (requiresInstMethodTableArg != nullptr)
+    {
+        value.B = (DWORD)*requiresInstMethodTableArg ? 1 : 0;
+    }
+    else
+    {
+        value.B = 0;
+    }
+
+    // Save it to the map
+    GetUnboxedEntry->Add(key, value);
+    DEBUG_REC(dmpGetUnboxedEntry(key, value));
+}
+void MethodContext::dmpGetUnboxedEntry(DWORDLONG key, DLD value)
+{
+   // Dump key and value to the console for debug purposes.
+   printf("GetUnboxedEntry ftn-%016" PRIX64 ", result-%016" PRIX64 ", requires-inst-%u", key, value.A, value.B);
+}
+CORINFO_METHOD_HANDLE MethodContext::repGetUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg)
+{
+   // Create a key out of the input arguments

7. Add a new function to <repo_root>/src/coreclr/tools/superpmi/superpmi/icorjitinfo.cpp that calls the rep* method. Example:

+CORINFO_METHOD_HANDLE MyICJI::getUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg)
+{
+   jitInstance->mc->cr->AddCall("getUnboxedEntry");
+   CORINFO_METHOD_HANDLE result = jitInstance->mc->repGetUnboxedEntry(ftn, requiresInstMethodTableArg);
+   return result;
+}

8. Add a new function to <repo_root>/src/coreclr/tools/superpmi/superpmi-shim-collector/icorjitinfo.cpp that calls the rec* method. Example:

+CORINFO_METHOD_HANDLE interceptor_ICJI::getUnboxedEntry(CORINFO_METHOD_HANDLE ftn, bool* requiresInstMethodTableArg)
+{
+   mc->cr->AddCall("getUnboxedEntry");
+   bool                  localRequiresInstMethodTableArg = false;
+   CORINFO_METHOD_HANDLE result = original_ICorJitInfo->getUnboxedEntry(ftn, &localRequiresInstMethodTableArg);
+   mc->recGetUnboxedEntry(ftn, &localRequiresInstMethodTableArg, result);
+   if (requiresInstMethodTableArg != nullptr)
+   {
+       *requiresInstMethodTableArg = localRequiresInstMethodTableArg;
+   }
+   return result;
+}

4 — Definition of Done (self-check list)

• New API present in all layers.
• Each source file changed exactly once; no unrelated edits. The following files must be changed:
  • <repo_root>/src/coreclr/tools/Common/JitInterface/ThunkGenerator/ThunkInput.txt
  • <repo_root>/src/coreclr/inc/corinfo.h
  • <repo_root>/src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
  • <repo_root>/src/coreclr/vm/jitinterface.cpp
  • <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/agnostic.h [optional - only if new types are needed]
  • <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/lwmlist.h
  • <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.h
  • <repo_root>/src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp
  • <repo_root>/src/coreclr/tools/superpmi/superpmi/icorjitinfo.cpp
  • <repo_root>/src/coreclr/tools/superpmi/superpmi-shim-collector/icorjitinfo.cpp
• All TODO/UNREACHABLE markers remain for future functional implementation.