Move RuntimeAsync ifdef to env variable (#118011)

Author: agocke

src/coreclr/clrdefinitions.cmake

@@ -152,8 +152,6 @@ if(FEATURE_OBJCMARSHAL)
   add_compile_definitions(FEATURE_OBJCMARSHAL)
 endif()
 
-# add_compile_definitions(FEATURE_RUNTIME_ASYNC)
-
 add_compile_definitions($<${FEATURE_JAVAMARSHAL}:FEATURE_JAVAMARSHAL>)
 
 add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:DAC_COMPONENT>>>:FEATURE_PROFAPI_ATTACH_DETACH>)

src/coreclr/inc/clrconfigvalues.h

@@ -708,6 +708,9 @@ RETAIL_CONFIG_DWORD_INFO(EXTERNAL_EnableRiscV64Zba,             W("EnableRiscV64
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_EnableRiscV64Zbb,             W("EnableRiscV64Zbb"),          1, "Allows RiscV64 Zbb hardware intrinsics to be disabled")
 #endif
 
+// Runtime-async
+RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_RuntimeAsync, W("RuntimeAsync"), 0, "Enables runtime async method support")
+
 ///
 /// Uncategorized
 ///

src/coreclr/vm/eeconfig.cpp

@@ -237,6 +237,8 @@ HRESULT EEConfig::Init()
     fGDBJitEmitDebugFrame = false;
 #endif
 
+    runtimeAsync = false;
+
     return S_OK;
 }
 
@@ -763,6 +765,8 @@ HRESULT EEConfig::sync()
     fUseCachedInterfaceDispatch = CLRConfig::GetConfigValue(CLRConfig::INTERNAL_UseCachedInterfaceDispatch) != 0;
 #endif // defined(FEATURE_CACHED_INTERFACE_DISPATCH) && defined(FEATURE_VIRTUAL_STUB_DISPATCH)
 
+    runtimeAsync = CLRConfig::GetConfigValue(CLRConfig::UNSUPPORTED_RuntimeAsync) != 0;
+
     return hr;
 }
 

src/coreclr/vm/eeconfig.h

@@ -439,6 +439,8 @@ class EEConfig
 
 #endif
 
+    bool    RuntimeAsync()                 const { LIMITED_METHOD_CONTRACT; return runtimeAsync; }
+
 private: //----------------------------------------------------------------
 
     bool fInited;                   // have we synced to the registry at least once?
@@ -634,6 +636,8 @@ class EEConfig
     bool fUseCachedInterfaceDispatch;
 #endif // defined(FEATURE_CACHED_INTERFACE_DISPATCH) && defined(FEATURE_VIRTUAL_STUB_DISPATCH)
 
+    bool runtimeAsync; // True if the runtime supports async methods
+
 public:
 
     enum BitForMask {

src/coreclr/vm/method.cpp

@@ -2299,9 +2299,13 @@ bool IsTypeDefOrRefImplementedInSystemModule(Module* pModule, mdToken tk)
 
 MethodReturnKind ClassifyMethodReturnKind(SigPointer sig, Module* pModule, ULONG* offsetOfAsyncDetails, bool *isValueTask)
 {
-    // Without FEATURE_RUNTIME_ASYNC every declared method is classified as a NormalMethod.
+    // Without runtime async, every declared method is classified as a NormalMethod.
     // Thus code that handles runtime async scenarios becomes unreachable.
-#ifdef FEATURE_RUNTIME_ASYNC
+    if (!g_pConfig->RuntimeAsync())
+    {
+        return MethodReturnKind::NormalMethod;
+    }
+
     PCCOR_SIGNATURE initialSig = sig.GetPtr();
     uint32_t data;
     IfFailThrow(sig.GetCallingConvInfo(&data));
@@ -2359,7 +2363,6 @@ MethodReturnKind ClassifyMethodReturnKind(SigPointer sig, Module* pModule, ULONG
                 return MethodReturnKind::NonGenericTaskReturningMethod;
         }
     }
-#endif // FEATURE_RUNTIME_ASYNC
 
     return MethodReturnKind::NormalMethod;
 }

src/coreclr/vm/methodtablebuilder.cpp

@@ -2688,10 +2688,13 @@ MethodTableBuilder::EnumerateClassMethods()
         BuildMethodTableThrowException(IDS_CLASSLOAD_TOO_MANY_METHODS);
 
     bmtMethod->m_cMaxDeclaredMethods = (SLOT_INDEX)cMethAndGaps;
-#ifdef FEATURE_RUNTIME_ASYNC
-    // TODO: (async) the index is uint16 and can potentially overflow. This needs to be more robust.
-    bmtMethod->m_cMaxDeclaredMethods *= 2;
-#endif
+
+    if (g_pConfig->RuntimeAsync())
+    {
+        // TODO: (async) the index is uint16 and can potentially overflow. This needs to be more robust.
+        bmtMethod->m_cMaxDeclaredMethods *= 2;
+    }
+
     bmtMethod->m_cDeclaredMethods = 0;
     bmtMethod->m_rgDeclaredMethods = new (GetStackingAllocator())
         bmtMDMethod *[bmtMethod->m_cMaxDeclaredMethods];