[NativeAOT-LLVM] Move RhpPInvoke and undefine BACKGROUND_GC (#2481)

* Move RhpPInvoke to wasm/RhpPInvoke.cpp

* Undefine BACKGROUND_GC

56K of code gone.

* Restore FEATURE_WASM_THREADS

Author: SingleAccretion

src/coreclr/gc/gc.cpp

@@ -14076,7 +14076,7 @@ HRESULT gc_heap::initialize_gc (size_t soh_segment_size,
 
 #ifdef WRITE_WATCH
     hardware_write_watch_api_supported();
-#ifdef BACKGROUND_GC_SUPPORTED
+#ifdef BACKGROUND_GC
     if (can_use_write_watch_for_gc_heap() && GCConfig::GetConcurrentGC())
     {
         gc_can_use_concurrent = true;

src/coreclr/gc/gcpriv.h

@@ -185,12 +185,9 @@ inline void FATAL_GC_ERROR()
 #define FEATURE_PREMORTEM_FINALIZATION
 #define GC_HISTORY
 
-#define BACKGROUND_GC   //concurrent background GC (requires WRITE_WATCH)
-
-// It is no longer possible to build without BACKGROUND_GC defined, so we have to use this duplicate
 #if !defined(TARGET_WASM) || defined(FEATURE_WASM_THREADS)
-#define BACKGROUND_GC_SUPPORTED
-#endif // !defined(TARGET_WASM) || defined(FEATURE_WASM_THREADS)
+#define BACKGROUND_GC   //concurrent background GC (requires WRITE_WATCH)
+#endif
 
 // We need the lower 3 bits in the MT to do our bookkeeping so doubly linked free list is only for 64-bit
 #if defined(BACKGROUND_GC) && defined(HOST_64BIT)

src/coreclr/nativeaot/Runtime/thread.cpp

@@ -1297,17 +1297,7 @@ COOP_PINVOKE_HELPER(void, RhpReversePInvokeReturn, (ReversePInvokeFrame * pFrame
 
 #ifdef USE_PORTABLE_HELPERS
 
-#ifdef HOST_WASM
-extern "C" void RhpSetShadowStackTop(void*);
-COOP_PINVOKE_HELPER(void, RhpPInvoke, (void* pShadowStack, PInvokeTransitionFrame* pFrame))
-{
-    // The implementation has to live in this file because of "FORCEINLINE" on "Thread::InlinePInvoke".
-    // Ideally, "InlinePInvoke" would be in "thread.inl", and this function - in "wasm/PInvoke.cpp".
-    RhpSetShadowStackTop(pShadowStack);
-    Thread* pCurThread = ThreadStore::RawGetCurrentThread();
-    pCurThread->InlinePInvoke(pFrame);
-}
-#else // !HOST_WASM
+#ifndef HOST_WASM
 COOP_PINVOKE_HELPER(void, RhpPInvoke, (PInvokeTransitionFrame* pFrame))
 {
     Thread * pCurThread = ThreadStore::RawGetCurrentThread();

src/coreclr/nativeaot/Runtime/wasm/PInvoke.cpp

@@ -9,10 +9,24 @@
 #include "daccess.h"
 #include "PalRedhawkCommon.h"
 #include "PalRedhawk.h"
+#include "thread.h"
+#include "threadstore.h"
+#include "thread.inl"
+#include "threadstore.inl"
 
 thread_local void* t_pShadowStackBottom = nullptr;
 thread_local void* t_pShadowStackTop = nullptr;
 
+void* GetShadowStackBottom()
+{
+    return t_pShadowStackBottom;
+}
+
+void* GetShadowStackTop()
+{
+    return t_pShadowStackTop;
+}
+
 COOP_PINVOKE_HELPER(void*, RhpGetOrInitShadowStackTop, ())
 {
     void* pShadowStack = t_pShadowStackTop;
@@ -41,12 +55,9 @@ COOP_PINVOKE_HELPER(void, RhpSetShadowStackTop, (void* pShadowStack))
     t_pShadowStackTop = pShadowStack;
 }
 
-void* GetShadowStackBottom()
-{
-    return t_pShadowStackBottom;
-}
-
-void* GetShadowStackTop()
+COOP_PINVOKE_HELPER(void, RhpPInvoke, (void* pShadowStack, PInvokeTransitionFrame* pFrame))
 {
-    return t_pShadowStackTop;
+    RhpSetShadowStackTop(pShadowStack);
+    Thread* pCurThread = ThreadStore::RawGetCurrentThread();
+    pCurThread->InlinePInvoke(pFrame);
 }