Use Buffer.BulkMoveWithWriteBarrier

Author: EgorBo

src/coreclr/inc/jithelpers.h

@@ -153,8 +153,7 @@
  JITHELPER(CORINFO_HELP_ASSIGN_REF_ENSURE_NONHEAP, JIT_WriteBarrierEnsureNonHeapTarget,CORINFO_HELP_SIG_REG_ONLY)
 
  DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_BYREF, JIT_ByRefWriteBarrier,CORINFO_HELP_SIG_NO_ALIGN_STUB)
-
- JITHELPER(CORINFO_HELP_ASSIGN_STRUCT, JIT_StructWriteBarrier,CORINFO_HELP_SIG_4_STACK)
+ DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_STRUCT, NULL, CORINFO_HELP_SIG_REG_ONLY)
 
  // Accessing fields
  JITHELPER(CORINFO_HELP_GETFIELD8, JIT_GetField8,CORINFO_HELP_SIG_REG_ONLY)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs

@@ -68,7 +68,7 @@ public static void GetEntryPoint(TypeSystemContext context, ReadyToRunHelper id,
  mangledName = context.Target.Architecture == TargetArchitecture.ARM64 ? "RhpCheckedAssignRefArm64" : "RhpCheckedAssignRef";
  break;
  case ReadyToRunHelper.AssignStruct:
- mangledName = "RhBulkMoveWithWriteBarrier";
+ mangledName = "RhBuffer_BulkMoveWithWriteBarrier";
  break;
  case ReadyToRunHelper.ByRefWriteBarrier:
  mangledName = context.Target.Architecture == TargetArchitecture.ARM64 ? "RhpByRefAssignRefArm64" : "RhpByRefAssignRef";

src/coreclr/vm/corelib.h

@@ -891,6 +891,7 @@ DEFINE_METHOD(DEBUGGER, BREAK, Break,
 DEFINE_CLASS(BUFFER, System, Buffer)
 DEFINE_METHOD(BUFFER, MEMCPY_PTRBYTE_ARRBYTE, Memcpy, SM_PtrByte_Int_ArrByte_Int_Int_RetVoid)
 DEFINE_METHOD(BUFFER, MEMCPY, Memcpy, SM_PtrByte_PtrByte_Int_RetVoid)
+DEFINE_METHOD(BUFFER, MEMCOPYGC, BulkMoveWithWriteBarrier, SM_RefByte_RefByte_UIntPtr_RetVoid)
 
 DEFINE_CLASS(STUBHELPERS, StubHelpers, StubHelpers)
 DEFINE_METHOD(STUBHELPERS, GET_DELEGATE_TARGET, GetDelegateTarget, SM_Delegate_RetIntPtr)

src/coreclr/vm/ecall.cpp

@@ -157,6 +157,10 @@ void ECall::PopulateManagedHelpers()
  pDest = pMD->GetMultiCallableAddrOfCode();
  SetJitHelperFunction(CORINFO_HELP_MEMCPY, pDest);
 
+ pMD = CoreLibBinder::GetMethod((BinderMethodID)(METHOD__BUFFER__MEMCOPYGC));
+ pDest = pMD->GetMultiCallableAddrOfCode();
+ SetJitHelperFunction(CORINFO_HELP_ASSIGN_STRUCT, pDest);
+
  pMD = CoreLibBinder::GetMethod((BinderMethodID)(METHOD__MATH__ROUND));
  pDest = pMD->GetMultiCallableAddrOfCode();
  SetJitHelperFunction(CORINFO_HELP_DBLROUND, pDest);

src/coreclr/vm/jithelpers.cpp

@@ -4779,21 +4779,6 @@ HCIMPLEND
 //
 //========================================================================
 
-/*************************************************************/
-HCIMPL3(VOID, JIT_StructWriteBarrier, intptr_t* dst, intptr_t* src, size_t byteCount)
-{
- FCALL_CONTRACT;
-
- _ASSERT(byteCount > 0);
- _ASSERT((byteCount % TARGET_POINTER_SIZE) == 0);
-
- if (dst != src && byteCount != 0)
- InlinedMemmoveGCRefsHelper(dst, src, byteCount);
-
- FC_GC_POLL();
-}
-HCIMPLEND
-
 /*************************************************************/
 // Slow helper to tailcall from the fast one
 NOINLINE HCIMPL0(void, JIT_PollGC_Framed)

src/libraries/System.Private.CoreLib/src/System/Buffer.cs

@@ -177,6 +177,9 @@ ref Unsafe.As<T, byte>(ref source),
  private const uint BulkMoveWithWriteBarrierChunk = 0x4000;
 #endif
 
+#if NATIVEAOT
+ [System.Runtime.RuntimeExport("RhBuffer_BulkMoveWithWriteBarrier")]
+#endif
  internal static void BulkMoveWithWriteBarrier(ref byte destination, ref byte source, nuint byteCount)
  {
  if (byteCount <= BulkMoveWithWriteBarrierChunk)