Remove obsolete native managed-invocation machinery

Delete MethodDescCallSite, CallDescrWorker and their argument-copying, return-value, architecture assembly, build, and EH identification closure after the reflection, custom-attribute, and func-eval migrations. Remove orphaned multicore-JIT diagnostic state and update VM-to-managed calling documentation. Preserve live field-access helpers, typed UCO calls, GC argument reporting, and calling-convention traits.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: jkoritzinsky

docs/design/coreclr/botr/corelib.md

@@ -296,31 +296,35 @@ Then, you can use the `REF<T>` template to create a type name like `SAFEHANDLERE
 
 # Calling into managed code from unmanaged code
 
-Clearly there are places where the CLR must call into managed code from native. For this purpose, we have added a `MethodDescCallSite` class to handle a lot of plumbing for you. Conceptually, all you need to do is find the `MethodDesc*` for the method you want to call, find a managed object for the "this" pointer (if you're calling an instance method), pass in an array of arguments, and deal with the return value. Internally, you'll need to potentially toggle your thread's state to allow the GC to run in preemptive mode, etc.
+The VM calls CoreLib methods marked `[UnmanagedCallersOnly]` through `UnmanagedCallersOnlyCaller`. The binder identifies the entrypoint, and the helper transitions to preemptive GC mode before calling it through the platform's unmanaged ABI. The caller must keep managed references GC-protected and pass their addresses to the managed entrypoint. Instance or virtual dispatch is performed in a managed wrapper rather than by constructing a native argument stack.
 
-Here's a simplified example. Note how this instance uses the binder described in the previous section to call `SafeHandle`'s virtual `ReleaseHandle` method.
+The `InvokeThrowing` variants append an exception-handle argument. The managed entrypoint catches exceptions and stores them through that argument; the native helper rethrows them after returning. For example, `Exception.CreateTargetInvocationException` returns its newly allocated object through an output argument:
 
 ```C++
-void SafeHandle::RunReleaseMethod(SafeHandle* psh)
+OBJECTREF CreateTargetInvocationException(OBJECTREF innerException)
 {
-    CONTRACTL {
+    CONTRACTL
+    {
         THROWS;
         GC_TRIGGERS;
         MODE_COOPERATIVE;
-    } CONTRACTL_END;
-
-    SAFEHANDLEREF sh(psh);
-
-    GCPROTECT_BEGIN(sh);
-
-    MethodDescCallSite releaseHandle(s_pReleaseHandleMethod, METHOD__SAFE_HANDLE__RELEASE_HANDLE, (OBJECTREF*)&sh, TypeHandle(), TRUE);
-
-    ARG_SLOT releaseArgs[] = { ObjToArgSlot(sh) };
-    if (!(BOOL)releaseHandle.Call_RetBool(releaseArgs)) {
-        MDA_TRIGGER_ASSISTANT(ReleaseHandleFailed, ReportViolation)(sh->GetTypeHandle(), sh->m_handle);
     }
+    CONTRACTL_END;
 
+    struct
+    {
+        OBJECTREF inner;
+        OBJECTREF result;
+    } gc;
+    gc.inner = innerException;
+    gc.result = nullptr;
+
+    GCPROTECT_BEGIN(gc);
+    UnmanagedCallersOnlyCaller caller{METHOD__EXCEPTION__CREATE_TARGET_INVOCATION_EXCEPTION};
+    caller.InvokeThrowing(&gc.inner, &gc.result);
     GCPROTECT_END();
+
+    return gc.result;
 }
 ```
 

docs/design/coreclr/botr/guide-for-porting.md

@@ -336,9 +336,9 @@ Here is an annotated list of the stubs implemented for Unix on Arm64.
     call in interesting ways, manipulate/parse the "secret" arguments, or do
     other not quite compilable to standardized C concepts.
 
-    1.  `CallDescrWorkerInternal` – Needed to support VM to managed function
-        calls. Necessary for all applications as this is how the main method is
-        called.
+    1.  VM-to-managed calls use `[UnmanagedCallersOnly]` entrypoints through the
+        platform's unmanaged ABI. Ports must support the reverse P/Invoke
+        transitions used by these entrypoints, including program startup.
 
     2.  `PInvokeImportThunk` – Needed to support saving off a set of arguments to
         a p/invoke so that the runtime can find the actual target. Also uses one

src/coreclr/debug/ee/controller.cpp

@@ -7758,8 +7758,7 @@ TP_RESULT DebuggerStepper::TriggerPatch(DebuggerControllerPatch *patch,
                     }
                     else
                     {
-                        // We're hitting this code path with MC++ assemblies
-                        // that have an unmanaged entry point so the stub returns to CallDescrWorker.
+                        // An interop stub can return to unmanaged code.
                         _ASSERTE(g_pEEInterface->GetNativeCodeMethodDesc(dac_cast<PCODE>(patch->address))->IsInteropStub());
                     }
 

src/coreclr/inc/clrconfigvalues.h

@@ -728,7 +728,6 @@ RETAIL_CONFIG_DWORD_INFO(EXTERNAL_EnableRiscV64Zicond,          W("EnableRiscV64
 // **
 CONFIG_DWORD_INFO(INTERNAL_ActivatePatchSkip, W("ActivatePatchSkip"), 0, "Allows an assert when ActivatePatchSkip is called")
 CONFIG_DWORD_INFO(INTERNAL_AlwaysUseMetadataInterfaceMapLayout, W("AlwaysUseMetadataInterfaceMapLayout"), 0, "Used for debugging generic interface map layout.")
-CONFIG_DWORD_INFO(INTERNAL_AssertOnUnneededThis, W("AssertOnUnneededThis"), 0, "While the ConfigDWORD is unnecessary, the contained ASSERT should be kept. This may result in some work tracking down violating MethodDescCallSites.")
 CONFIG_DWORD_INFO(INTERNAL_AssertStacktrace, W("AssertStacktrace"), 1, "")
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_DisableConfigCache, W("DisableConfigCache"), 0, "Used to disable the \"probabilistic\" config cache, which walks through the appropriate config registry keys on init and probabilistically keeps track of which exist.")
 CONFIG_STRING_INFO(INTERNAL_DumpOnClassLoad, W("DumpOnClassLoad"), "Dumps information about loaded class to log.")

src/coreclr/nativeaot/Common/src/Internal/Runtime/TransitionBlock.cs

@@ -8,36 +8,31 @@
 
 //
 #if TARGET_ARM
-#define CALLDESCR_ARGREGS                          // CallDescrWorker has ArgumentRegister parameter
-#define CALLDESCR_FPARGREGS                        // CallDescrWorker has FloatArgumentRegisters parameter
+#define CALLDESCR_FPARGREGS                        // Calling convention has floating-point argument registers
 #define ENREGISTERED_RETURNTYPE_MAXSIZE
 #define ENREGISTERED_RETURNTYPE_INTEGER_MAXSIZE
 #define FEATURE_HFA
 #elif TARGET_ARM64
-#define CALLDESCR_ARGREGS                          // CallDescrWorker has ArgumentRegister parameter
-#define CALLDESCR_FPARGREGS                        // CallDescrWorker has FloatArgumentRegisters parameter
+#define CALLDESCR_FPARGREGS                        // Calling convention has floating-point argument registers
 #define ENREGISTERED_RETURNTYPE_MAXSIZE
 #define ENREGISTERED_RETURNTYPE_INTEGER_MAXSIZE
 #define ENREGISTERED_PARAMTYPE_MAXSIZE
 #define FEATURE_HFA
 #elif TARGET_X86
 #define ENREGISTERED_RETURNTYPE_MAXSIZE
 #define ENREGISTERED_RETURNTYPE_INTEGER_MAXSIZE
-#define CALLDESCR_ARGREGS                          // CallDescrWorker has ArgumentRegister parameter
 #elif TARGET_AMD64
 #if TARGET_UNIX
 #define UNIX_AMD64_ABI
-#define CALLDESCR_ARGREGS                          // CallDescrWorker has ArgumentRegister parameter
 #else
 #endif
-#define CALLDESCR_FPARGREGS                        // CallDescrWorker has FloatArgumentRegisters parameter
+#define CALLDESCR_FPARGREGS                        // Calling convention has floating-point argument registers
 #define ENREGISTERED_RETURNTYPE_MAXSIZE
 #define ENREGISTERED_RETURNTYPE_INTEGER_MAXSIZE
 #define ENREGISTERED_PARAMTYPE_MAXSIZE
 #elif TARGET_WASM
 #elif TARGET_LOONGARCH64 || TARGET_RISCV64
-#define CALLDESCR_ARGREGS                          // CallDescrWorker has ArgumentRegister parameter
-#define CALLDESCR_FPARGREGS                        // CallDescrWorker has FloatArgumentRegisters parameter
+#define CALLDESCR_FPARGREGS                        // Calling convention has floating-point argument registers
 #define ENREGISTERED_RETURNTYPE_MAXSIZE
 #define ENREGISTERED_RETURNTYPE_INTEGER_MAXSIZE
 #define ENREGISTERED_PARAMTYPE_MAXSIZE
@@ -205,7 +200,7 @@ public static unsafe int GetOffsetOfEcx()
             return sizeof(IntPtr);
         }
     }
-    // This struct isn't used by x86, but exists for compatibility with the definition of the CallDescrData struct
+    // Floating-point arguments are stack-passed on x86; keep an empty placeholder for the shared ABI abstraction.
     [StructLayout(LayoutKind.Sequential)]
     internal struct FloatArgumentRegisters
     {

src/coreclr/vm/CMakeLists.txt

@@ -677,7 +677,6 @@ elseif(CLR_CMAKE_TARGET_WIN32)
             ${ARCH_SOURCES_DIR}/AllocSlow.asm
             ${ARCH_SOURCES_DIR}/AsmHelpers.asm
             ${ARCH_SOURCES_DIR}/CachedInterfaceDispatchCoreCLR.asm
-            ${ARCH_SOURCES_DIR}/CallDescrWorkerAMD64.asm
             ${ARCH_SOURCES_DIR}/ComCallPreStub.asm
             ${ARCH_SOURCES_DIR}/getstate.asm
             ${ARCH_SOURCES_DIR}/JitHelpers_Fast.asm
@@ -721,7 +720,6 @@ elseif(CLR_CMAKE_TARGET_WIN32)
         set(VM_SOURCES_WKS_ARCH_ASM
             ${ARCH_SOURCES_DIR}/AllocSlow.asm
             ${ARCH_SOURCES_DIR}/AsmHelpers.asm
-            ${ARCH_SOURCES_DIR}/CallDescrWorkerARM64.asm
             ${ARCH_SOURCES_DIR}/patchedcode.asm
             ${ARCH_SOURCES_DIR}/PInvokeStubs.asm
             ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/StubDispatch.asm
@@ -745,7 +743,6 @@ else()
             ${ARCH_SOURCES_DIR}/AllocSlow.S
             ${ARCH_SOURCES_DIR}/asmhelpers.S
             ${ARCH_SOURCES_DIR}/CachedInterfaceDispatchCoreCLR.S
-            ${ARCH_SOURCES_DIR}/calldescrworkeramd64.S
             ${ARCH_SOURCES_DIR}/externalmethodfixupthunk.S
             ${ARCH_SOURCES_DIR}/getstate.S
             ${ARCH_SOURCES_DIR}/jithelpers_fast.S
@@ -793,7 +790,6 @@ else()
             ${ARCH_SOURCES_DIR}/AllocSlow.S
             ${ARCH_SOURCES_DIR}/asmhelpers.S
             ${ARCH_SOURCES_DIR}/CachedInterfaceDispatchCoreCLR.S
-            ${ARCH_SOURCES_DIR}/calldescrworkerarm64.S
             ${ARCH_SOURCES_DIR}/patchedcode.S
             ${ARCH_SOURCES_DIR}/pinvokestubs.S
             ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/StubDispatch.S
@@ -806,7 +802,6 @@ else()
         set(VM_SOURCES_WKS_ARCH_ASM
             ${ARCH_SOURCES_DIR}/AllocSlow.S
             ${ARCH_SOURCES_DIR}/asmhelpers.S
-            ${ARCH_SOURCES_DIR}/calldescrworkerloongarch64.S
             ${ARCH_SOURCES_DIR}/pinvokestubs.S
             ${ARCH_SOURCES_DIR}/thunktemplates.S
             ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/AllocFast.S
@@ -816,7 +811,6 @@ else()
         set(VM_SOURCES_WKS_ARCH_ASM
             ${ARCH_SOURCES_DIR}/AllocSlow.S
             ${ARCH_SOURCES_DIR}/asmhelpers.S
-            ${ARCH_SOURCES_DIR}/calldescrworkerriscv64.S
             ${ARCH_SOURCES_DIR}/pinvokestubs.S
             ${ARCH_SOURCES_DIR}/thunktemplates.S
             ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/AllocFast.S
@@ -960,7 +954,6 @@ elseif(CLR_CMAKE_TARGET_ARCH_WASM)
     )
     set(VM_SOURCES_WKS_ARCH
         ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/writebarriers.cpp
-        ${ARCH_SOURCES_DIR}/calldescrworkerwasm.cpp
         ${ARCH_SOURCES_DIR}/profiler.cpp
         ${ARCH_SOURCES_DIR}/helpers.cpp
         ${ARCH_SOURCES_DIR}/dynamichelpers.cpp

src/coreclr/vm/amd64/CallDescrWorkerAMD64.asm

@@ -469,33 +469,6 @@ ASMCONSTANTS_C_ASSERT(OFFSETOF__InlinedCallFrame__m_pCalleeSavedFP
 ASMCONSTANTS_C_ASSERT(OFFSETOF__InlinedCallFrame__m_pThread
                     == offsetof(InlinedCallFrame, m_pThread));
 
-#define CallDescrData__pSrc                0x00
-#define CallDescrData__numStackSlots       0x08
-#ifdef UNIX_AMD64_ABI
-#define CallDescrData__pArgumentRegisters  0x10
-#define CallDescrData__pFloatArgumentRegisters 0x18
-#define CallDescrData__fpReturnSize        0x20
-#define CallDescrData__pTarget             0x28
-#define CallDescrData__returnValue         0x30
-#else
-#define CallDescrData__dwRegTypeMap        0x10
-#define CallDescrData__fpReturnSize        0x18
-#define CallDescrData__pTarget             0x20
-#define CallDescrData__returnValue         0x28
-#endif
-
-ASMCONSTANTS_C_ASSERT(CallDescrData__pSrc                 == offsetof(CallDescrData, pSrc))
-ASMCONSTANTS_C_ASSERT(CallDescrData__numStackSlots        == offsetof(CallDescrData, numStackSlots))
-#ifdef UNIX_AMD64_ABI
-ASMCONSTANTS_C_ASSERT(CallDescrData__pArgumentRegisters   == offsetof(CallDescrData, pArgumentRegisters))
-ASMCONSTANTS_C_ASSERT(CallDescrData__pFloatArgumentRegisters == offsetof(CallDescrData, pFloatArgumentRegisters))
-#else
-ASMCONSTANTS_C_ASSERT(CallDescrData__dwRegTypeMap         == offsetof(CallDescrData, dwRegTypeMap))
-#endif
-ASMCONSTANTS_C_ASSERT(CallDescrData__fpReturnSize         == offsetof(CallDescrData, fpReturnSize))
-ASMCONSTANTS_C_ASSERT(CallDescrData__pTarget              == offsetof(CallDescrData, pTarget))
-ASMCONSTANTS_C_ASSERT(CallDescrData__returnValue          == offsetof(CallDescrData, returnValue))
-
 #ifdef UNIX_AMD64_ABI
 #define OFFSETOF__TransitionBlock__m_argumentRegisters    0x00
 ASMCONSTANTS_C_ASSERT(OFFSETOF__TransitionBlock__m_argumentRegisters == offsetof(TransitionBlock, m_argumentRegisters))