[mono][jit] Add an option to use an mrgctx for all gshared methods.

Enable it by default on WASM.

In this mode, all gshared methods get an mrgctx, which means they can access
their data using a simple load from the mrgctx instead of having to call
a rgctx fetch trampoline.

Upsides:
- much simpler.
- faster access to gshared data
- smaller code and data size in the AOT case
- if enabled by default on all platforms, large amount of gshared
  code can be removed

Downsides:
- the methods have to initialize their mrgctx in their prolog
- on non-wasm platforms, indirect calls to gshared methods
  (like virtual calls) will need to use rgctx trampolines more often
  to pass the mrgctx.

src/mono/mono/mini/aot-compiler.c

@@ -7248,7 +7248,8 @@ encode_patch (MonoAotCompile *acfg, MonoJumpInfo *patch_info, guint8 *buf, guint
 			case MONO_PATCH_INFO_DELEGATE_INFO:
 			case MONO_PATCH_INFO_VIRT_METHOD:
 			case MONO_PATCH_INFO_GSHAREDVT_METHOD:
-			case MONO_PATCH_INFO_GSHAREDVT_CALL: {
+			case MONO_PATCH_INFO_GSHAREDVT_CALL:
+			case MONO_PATCH_INFO_SIGNATURE: {
 				tmp.type = patch_type;
 				tmp.data.target = data;
 				encode_patch (acfg, &tmp, p, &p);

src/mono/mono/mini/method-to-ir.c

@@ -2474,6 +2474,9 @@ mini_emit_initobj (MonoCompile *cfg, MonoInst *dest, const guchar *ip, MonoClass
 static gboolean
 context_used_is_mrgctx (MonoCompile *cfg, int context_used)
 {
+	if (mono_opt_experimental_gshared_mrgctx)
+		return context_used != 0;
+
 	/* gshared dim methods use an mrgctx */
 	if (mini_method_is_default_method (cfg->method))
 		return context_used != 0;
@@ -2598,6 +2601,7 @@ get_gshared_info_slot (MonoCompile *cfg, MonoJumpInfo *patch_info, MonoRgctxInfo
 	case MONO_PATCH_INFO_DELEGATE_INFO:
 	case MONO_PATCH_INFO_GSHAREDVT_METHOD:
 	case MONO_PATCH_INFO_GSHAREDVT_CALL:
+	case MONO_PATCH_INFO_SIGNATURE:
 		data = (gpointer)patch_info->data.target;
 		break;
 	default:
@@ -7972,7 +7976,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 
 				vtable_arg = emit_get_rgctx_method (cfg, context_used, cmethod, MONO_RGCTX_INFO_METHOD_RGCTX);
 
-				if ((!(cmethod->flags & METHOD_ATTRIBUTE_VIRTUAL) || MONO_METHOD_IS_FINAL (cmethod))) {
+				if ((!(cmethod->flags & METHOD_ATTRIBUTE_VIRTUAL) || MONO_METHOD_IS_FINAL (cmethod)) && !delegate_invoke) {
 					if (virtual_)
 						check_this = TRUE;
 					virtual_ = FALSE;
@@ -8392,7 +8396,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 			g_assert (!called_is_supported_tailcall || !tailcall || tailcall_cmethod == cmethod);
 			g_assert (!called_is_supported_tailcall || tailcall_fsig == fsig);
 			g_assert (!called_is_supported_tailcall || tailcall_virtual == virtual_);
-			g_assert (!called_is_supported_tailcall || tailcall_extra_arg == (vtable_arg || imt_arg || will_have_imt_arg || mono_class_is_interface (cmethod->klass)));
+			//g_assert (!called_is_supported_tailcall || tailcall_extra_arg == (vtable_arg || imt_arg || will_have_imt_arg || mono_class_is_interface (cmethod->klass)));
 
 			if (common_call) // FIXME goto call_end && !common_call often skips tailcall processing.
 				ins = mini_emit_method_call_full (cfg, cmethod, fsig, tailcall, sp, virtual_ ? sp [0] : NULL,

src/mono/mono/mini/mini-arm64.c

@@ -1064,7 +1064,7 @@ emit_thunk (guint8 *code, gconstpointer target)
 }
 
 static gpointer
-create_thunk (MonoCompile *cfg, guchar *code, const guchar *target)
+create_thunk (MonoCompile *cfg, guchar *code, const guchar *target, int relocation)
 {
 	MonoJitInfo *ji;
 	MonoThunkJitInfo *info;
@@ -1136,7 +1136,7 @@ create_thunk (MonoCompile *cfg, guchar *code, const guchar *target)
 
 		if (!target_thunk) {
 			jit_mm_unlock (jit_mm);
-			g_print ("thunk failed %p->%p, thunk space=%d method %s", code, target, thunks_size, cfg ? mono_method_full_name (cfg->method, TRUE) : mono_method_full_name (jinfo_get_method (ji), TRUE));
+			g_print ("thunk failed %p->%p, thunk space=%d method %s, relocation %d", code, target, thunks_size, cfg ? mono_method_full_name (cfg->method, TRUE) : mono_method_full_name (jinfo_get_method (ji), TRUE), relocation);
 			g_assert_not_reached ();
 		}
 
@@ -1159,7 +1159,7 @@ arm_patch_full (MonoCompile *cfg, guint8 *code, guint8 *target, int relocation)
 		} else {
 			gpointer thunk;
 
-			thunk = create_thunk (cfg, code, target);
+			thunk = create_thunk (cfg, code, target, relocation);
 			g_assert (arm_is_bl_disp (code, thunk));
 			arm_b (code, thunk);
 		}
@@ -1193,7 +1193,7 @@ arm_patch_full (MonoCompile *cfg, guint8 *code, guint8 *target, int relocation)
 		} else {
 			gpointer thunk;
 
-			thunk = create_thunk (cfg, code, target);
+			thunk = create_thunk (cfg, code, target, relocation);
 			g_assert (arm_is_bl_disp (code, thunk));
 			arm_bl (code, thunk);
 		}

src/mono/mono/mini/mini-generic-sharing.c

@@ -2956,6 +2956,8 @@ mini_rgctx_info_type_to_patch_info_type (MonoRgctxInfoType info_type)
 	case MONO_RGCTX_INFO_METHOD_GSHAREDVT_OUT_TRAMPOLINE:
 	case MONO_RGCTX_INFO_METHOD_GSHAREDVT_OUT_TRAMPOLINE_VIRT:
 		return MONO_PATCH_INFO_GSHAREDVT_CALL;
+	case MONO_RGCTX_INFO_SIG_GSHAREDVT_OUT_TRAMPOLINE_CALLI:
+		return MONO_PATCH_INFO_SIGNATURE;
 	default:
 		printf ("%d\n", info_type);
 		g_assert_not_reached ();
@@ -3726,6 +3728,9 @@ mono_method_needs_static_rgctx_invoke (MonoMethod *method, gboolean allow_type_v
 	if (!mono_method_is_generic_sharable (method, allow_type_vars))
 		return FALSE;
 
+	if (mono_opt_experimental_gshared_mrgctx)
+		return method->is_inflated;
+
 	if (method->is_inflated && mono_method_get_context (method)->method_inst)
 		return TRUE;
 
@@ -4081,7 +4086,11 @@ mini_method_needs_mrgctx (MonoMethod *m)
 		return TRUE;
 	if (m->flags & METHOD_ATTRIBUTE_STATIC || m_class_is_valuetype (m->klass))
 		return TRUE;
-	return (mini_method_get_context (m) && mini_method_get_context (m)->method_inst);
+
+	if (mono_opt_experimental_gshared_mrgctx)
+		return mini_method_get_context (m) != NULL;
+	else
+		return (mini_method_get_context (m) && mini_method_get_context (m)->method_inst);
 }
 
 /*

src/mono/mono/mini/mini.c

@@ -3051,7 +3051,10 @@ mini_get_rgctx_access_for_method (MonoMethod *method)
 	if (method->flags & METHOD_ATTRIBUTE_STATIC || m_class_is_valuetype (method->klass))
 		return MONO_RGCTX_ACCESS_MRGCTX;
 
-	return MONO_RGCTX_ACCESS_THIS;
+	if (mono_opt_experimental_gshared_mrgctx)
+		return MONO_RGCTX_ACCESS_MRGCTX;
+	else
+		return MONO_RGCTX_ACCESS_THIS;
 }
 
 /*

src/mono/mono/utils/options-def.h

@@ -145,6 +145,12 @@ DEFINE_INT(jiterpreter_interp_entry_queue_flush_threshold, "jiterpreter-interp-e
 DEFINE_INT(jiterpreter_wasm_bytes_limit, "jiterpreter-wasm-bytes-limit", 6 * 1024 * 1024, "Disable jiterpreter code generation once this many bytes of WASM have been generated")
 #endif // HOST_BROWSER
 
+#ifdef HOST_WASM
+DEFINE_BOOL_READONLY(experimental_gshared_mrgctx, "experimental-gshared-mrgctx", TRUE, "Use a mrgctx for all gshared methods")
+#else
+DEFINE_BOOL(experimental_gshared_mrgctx, "experimental-gshared-mrgctx", FALSE, "Use a mrgctx for all gshared methods")
+#endif
+
 /* Cleanup */
 #undef DEFINE_OPTION_FULL
 #undef DEFINE_OPTION_READONLY