Optimize Activator.CreateInstance (#25145)

* Optimize Activator.CreateInstance
- Short-circuit Activator.CreateInstance<T>() for value types without default constructor
- Cache default constructor delegate on RuntimeType instead of fixed-size singleton cache

1 files changed, 53 insertions, 25 deletions

diff --git a/src/vm/jitinterface.cpp b/src/vm/jitinterface.cpp
index de9538e6c2..d67ad2f251 100644
--- a/src/vm/jitinterface.cpp
+++ b/src/vm/jitinterface.cpp
@@ -7000,8 +7000,7 @@ bool getILIntrinsicImplementation(MethodDesc * ftn,
 {
     STANDARD_VM_CONTRACT;
 
-    // Precondition: ftn is a method in mscorlib 
-    _ASSERTE(ftn->GetModule()->IsSystem());
+    _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__JIT_HELPERS));
 
     mdMethodDef tk = ftn->GetMemberDef();
 
@@ -7129,8 +7128,7 @@ bool getILIntrinsicImplementationForUnsafe(MethodDesc * ftn,
 {
     STANDARD_VM_CONTRACT;
 
-    // Precondition: ftn is a method in mscorlib 
-    _ASSERTE(ftn->GetModule()->IsSystem());
+    _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__UNSAFE));
 
     mdMethodDef tk = ftn->GetMemberDef();
 
@@ -7371,10 +7369,7 @@ bool getILIntrinsicImplementationForVolatile(MethodDesc * ftn,
     // we substitute raw IL bodies for these methods that use the correct volatile instructions.
     //
 
-    // Precondition: ftn is a method in mscorlib in the System.Threading.Volatile class
-    _ASSERTE(ftn->GetModule()->IsSystem());
     _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__VOLATILE));
-    _ASSERTE(strcmp(ftn->GetMethodTable()->GetClass()->GetDebugClassName(), "System.Threading.Volatile") == 0);
 
     const size_t VolatileMethodBodySize = 6;
 
@@ -7453,20 +7448,14 @@ bool getILIntrinsicImplementationForInterlocked(MethodDesc * ftn,
 {
     STANDARD_VM_CONTRACT;
 
-    // Precondition: ftn is a method in mscorlib in the System.Threading.Interlocked class
-    _ASSERTE(ftn->GetModule()->IsSystem());
     _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__INTERLOCKED));
 
     // We are only interested if ftn's token and CompareExchange<T> token match
     if (ftn->GetMemberDef() != MscorlibBinder::GetMethod(METHOD__INTERLOCKED__COMPARE_EXCHANGE_T)->GetMemberDef())
-        return false;       
-
-    // Get MethodDesc for System.Threading.Interlocked.CompareExchangeFast()
-    MethodDesc* cmpxchgFast = MscorlibBinder::GetMethod(METHOD__INTERLOCKED__COMPARE_EXCHANGE_OBJECT);
+        return false;
 
-    // The MethodDesc lookup must not fail, and it should have the name "CompareExchangeFast"
-    _ASSERTE(cmpxchgFast != NULL);
-    _ASSERTE(strcmp(cmpxchgFast->GetName(), "CompareExchange") == 0);
+    // Get MethodDesc for non-generic System.Threading.Interlocked.CompareExchange()
+    MethodDesc* cmpxchgObject = MscorlibBinder::GetMethod(METHOD__INTERLOCKED__COMPARE_EXCHANGE_OBJECT);
 
     // Setup up the body of the method
     static BYTE il[] = {
@@ -7477,12 +7466,12 @@ bool getILIntrinsicImplementationForInterlocked(MethodDesc * ftn,
                           CEE_RET
                         };
 
-    // Get the token for System.Threading.Interlocked.CompareExchangeFast(), and patch [target]
-    mdMethodDef cmpxchgFastToken = cmpxchgFast->GetMemberDef();
-    il[4] = (BYTE)((int)cmpxchgFastToken >> 0);
-    il[5] = (BYTE)((int)cmpxchgFastToken >> 8);
-    il[6] = (BYTE)((int)cmpxchgFastToken >> 16);
-    il[7] = (BYTE)((int)cmpxchgFastToken >> 24);
+    // Get the token for non-generic System.Threading.Interlocked.CompareExchange(), and patch [target]
+    mdMethodDef cmpxchgObjectToken = cmpxchgObject->GetMemberDef();
+    il[4] = (BYTE)((int)cmpxchgObjectToken >> 0);
+    il[5] = (BYTE)((int)cmpxchgObjectToken >> 8);
+    il[6] = (BYTE)((int)cmpxchgObjectToken >> 16);
+    il[7] = (BYTE)((int)cmpxchgObjectToken >> 24);
 
     // Initialize methInfo
     methInfo->ILCode = const_cast<BYTE*>(il);
@@ -7499,8 +7488,7 @@ bool getILIntrinsicImplementationForRuntimeHelpers(MethodDesc * ftn,
 {
     STANDARD_VM_CONTRACT;
 
-    // Precondition: ftn is a method in mscorlib 
-    _ASSERTE(ftn->GetModule()->IsSystem());
+    _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__RUNTIME_HELPERS));
 
     mdMethodDef tk = ftn->GetMemberDef();
 
@@ -7585,6 +7573,37 @@ bool getILIntrinsicImplementationForRuntimeHelpers(MethodDesc * ftn,
     return false;
 }
 
+bool getILIntrinsicImplementationForActivator(MethodDesc* ftn,
+    CORINFO_METHOD_INFO* methInfo,
+    SigPointer* pSig)
+{
+    STANDARD_VM_CONTRACT;
+
+    _ASSERTE(MscorlibBinder::IsClass(ftn->GetMethodTable(), CLASS__ACTIVATOR));
+
+    // We are only interested if ftn's token and CreateInstance<T> token match
+    if (ftn->GetMemberDef() != MscorlibBinder::GetMethod(METHOD__ACTIVATOR__CREATE_INSTANCE_OF_T)->GetMemberDef())
+        return false;
+
+    _ASSERTE(ftn->HasMethodInstantiation());
+    Instantiation inst = ftn->GetMethodInstantiation();
+
+    _ASSERTE(ftn->GetNumGenericMethodArgs() == 1);
+    TypeHandle typeHandle = inst[0];
+    MethodTable* methodTable = typeHandle.GetMethodTable();
+
+    if (!methodTable->IsValueType() || methodTable->HasDefaultConstructor())
+        return false;
+
+    // Replace the body with implementation that just returns "default"
+    MethodDesc* createDefaultInstance = MscorlibBinder::GetMethod(METHOD__ACTIVATOR__CREATE_DEFAULT_INSTANCE_OF_T);
+    COR_ILMETHOD_DECODER header(createDefaultInstance->GetILHeader(FALSE), createDefaultInstance->GetMDImport(), NULL);
+    getMethodInfoILMethodHeaderHelper(&header, methInfo);
+    *pSig = SigPointer(header.LocalVarSig, header.cbLocalVarSig);
+
+    return true;
+}
+
 //---------------------------------------------------------------------------------------
 // 
 //static
@@ -7640,6 +7659,15 @@ getMethodInfoHelper(
             {
                 fILIntrinsic = getILIntrinsicImplementationForRuntimeHelpers(ftn, methInfo);
             }
+            else if (MscorlibBinder::IsClass(pMT, CLASS__ACTIVATOR))
+            {
+                SigPointer localSig;
+                fILIntrinsic = getILIntrinsicImplementationForActivator(ftn, methInfo, &localSig);
+                if (fILIntrinsic)
+                {
+                    localSig.GetSignature(&pLocalSig, &cbLocalSig);
+                }
+            }
         }
 
         if (!fILIntrinsic)
@@ -7653,7 +7681,7 @@ getMethodInfoHelper(
     {
         _ASSERTE(ftn->IsDynamicMethod());
 
-        DynamicResolver * pResolver = ftn->AsDynamicMethodDesc()->GetResolver();        
+        DynamicResolver * pResolver = ftn->AsDynamicMethodDesc()->GetResolver();
         unsigned int EHCount;
         methInfo->ILCode = pResolver->GetCodeInfo(&methInfo->ILCodeSize,
                                                   &methInfo->maxStack,