Treat the 'this' parameter slot as a managed pointer for interface calls, since the unbox trampolines can transform it from a reference to an internal pointer.

4 files changed, 41 insertions, 8 deletions

diff --git a/mono/mini/gc-test.cs b/mono/mini/gc-test.cs
index 896f9cea6a4..8f80d934627 100644
--- a/mono/mini/gc-test.cs
+++ b/mono/mini/gc-test.cs
@@ -559,6 +559,27 @@ class Tests {
 		liveness_12_inner (1, 2, 3, 4, 5, 6, new object (), ref f.s);
 		return 0;
 	}
+	
+	interface IFace {
+		int foo ();
+	}
+
+	struct BarStruct : IFace {
+		int i;
+
+		public int foo () {
+			GC.Collect ();
+			return i;
+		}
+	}
+		
+	public static int test_0_liveness_unbox_trampoline () {
+		var s = new BarStruct ();
+		
+		IFace iface = s;
+		iface.foo ();
+		return 0;
+	}
 
 	public static void liveness_13_inner (ref ArrayList arr) {
 		// The value of arr will be stored in a spill slot
diff --git a/mono/mini/method-to-ir.c b/mono/mini/method-to-ir.c
index 62b2c1a89eb..ba025490237 100644
--- a/mono/mini/method-to-ir.c
+++ b/mono/mini/method-to-ir.c
@@ -2222,7 +2222,7 @@ mono_patch_info_new (MonoMemPool *mp, int ip, MonoJumpInfoType type, gconstpoint
 
 inline static MonoCallInst *
 mono_emit_call_args (MonoCompile *cfg, MonoMethodSignature *sig, 
-					 MonoInst **args, int calli, int virtual, int tail, int rgctx)
+					 MonoInst **args, int calli, int virtual, int tail, int rgctx, int unbox_trampoline)
 {
 	MonoCallInst *call;
 #ifdef MONO_ARCH_SOFT_FLOAT
@@ -2303,6 +2303,8 @@ mono_emit_call_args (MonoCompile *cfg, MonoMethodSignature *sig,
 	}
 #endif
 
+	call->need_unbox_trampoline = unbox_trampoline;
+
 #ifdef ENABLE_LLVM
 	if (COMPILE_LLVM (cfg))
 		mono_llvm_emit_call (cfg, call);
@@ -2344,7 +2346,7 @@ mono_emit_calli (MonoCompile *cfg, MonoMethodSignature *sig, MonoInst **args, Mo
 		MONO_EMIT_NEW_UNALU (cfg, OP_MOVE, rgctx_reg, rgctx_arg->dreg);
 	}
 
-	call = mono_emit_call_args (cfg, sig, args, TRUE, FALSE, FALSE, rgctx_arg ? TRUE : FALSE);
+	call = mono_emit_call_args (cfg, sig, args, TRUE, FALSE, FALSE, rgctx_arg ? TRUE : FALSE, FALSE);
 
 	call->inst.sreg1 = addr->dreg;
 
@@ -2371,6 +2373,7 @@ mono_emit_method_call_full (MonoCompile *cfg, MonoMethod *method, MonoMethodSign
 	int context_used;
 	MonoCallInst *call;
 	int rgctx_reg = 0;
+	gboolean need_unbox_trampoline;
 
 	if (rgctx_arg) {
 		rgctx_reg = mono_alloc_preg (cfg);
@@ -2402,7 +2405,9 @@ mono_emit_method_call_full (MonoCompile *cfg, MonoMethod *method, MonoMethodSign
 		return mono_emit_calli (cfg, sig, args, addr, NULL);
 	}
 
-	call = mono_emit_call_args (cfg, sig, args, FALSE, virtual, FALSE, rgctx_arg ? TRUE : FALSE);
+	need_unbox_trampoline = method->klass == mono_defaults.object_class || (method->klass->flags & TYPE_ATTRIBUTE_INTERFACE);
+
+	call = mono_emit_call_args (cfg, sig, args, FALSE, virtual, FALSE, rgctx_arg ? TRUE : FALSE, need_unbox_trampoline);
 
 	if (might_be_remote)
 		call->method = mono_marshal_get_remoting_invoke_with_check (method);
@@ -2535,7 +2540,7 @@ mono_emit_native_call (MonoCompile *cfg, gconstpointer func, MonoMethodSignature
 
 	g_assert (sig);
 
-	call = mono_emit_call_args (cfg, sig, args, FALSE, FALSE, FALSE, FALSE);
+	call = mono_emit_call_args (cfg, sig, args, FALSE, FALSE, FALSE, FALSE, FALSE);
 	call->fptr = func;
 
 	MONO_ADD_INS (cfg->cbb, (MonoInst*)call);
@@ -7523,7 +7528,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 
 #ifdef MONO_ARCH_USE_OP_TAIL_CALL
 				/* Handle tail calls similarly to calls */
-				call = mono_emit_call_args (cfg, mono_method_signature (cmethod), sp, FALSE, FALSE, TRUE, FALSE);
+				call = mono_emit_call_args (cfg, mono_method_signature (cmethod), sp, FALSE, FALSE, TRUE, FALSE, FALSE);
 #else
 				MONO_INST_NEW_CALL (cfg, call, OP_JMP);
 				call->tail_call = TRUE;
diff --git a/mono/mini/mini-x86.c b/mono/mini/mini-x86.c
index ce39e948ad0..f562ea7f5ad 100644
--- a/mono/mini/mini-x86.c
+++ b/mono/mini/mini-x86.c
@@ -1576,11 +1576,16 @@ mono_arch_emit_call (MonoCompile *cfg, MonoCallInst *call)
 			if (cfg->compute_gc_maps) {
 				if (argsize == 4) {
 					/* FIXME: The == STACK_OBJ check might be fragile ? */
-					if (sig->hasthis && i == 0 && call->args [i]->type == STACK_OBJ)
+					if (sig->hasthis && i == 0 && call->args [i]->type == STACK_OBJ) {
 						/* this */
-						emit_gc_param_slot_def (cfg, sp_offset, &mono_defaults.object_class->byval_arg);
-					else
+						if (call->need_unbox_trampoline)
+							/* The unbox trampoline transforms this into a managed pointer */
+							emit_gc_param_slot_def (cfg, sp_offset, &mono_defaults.int_class->this_arg);
+						else
+							emit_gc_param_slot_def (cfg, sp_offset, &mono_defaults.object_class->byval_arg);
+					} else {
 						emit_gc_param_slot_def (cfg, sp_offset, orig_type);
+					}
 				} else {
 					/* i8/r8 */
 					for (j = 0; j < argsize; j += 4)
diff --git a/mono/mini/mini.h b/mono/mini/mini.h
index 3dd34d53d5a..18b0050b625 100644
--- a/mono/mini/mini.h
+++ b/mono/mini/mini.h
@@ -803,6 +803,8 @@ struct MonoCallInst {
 	guint dynamic_imt_arg : 1;
 	/* Whenever there is an RGCTX argument */
 	guint32 rgctx_reg : 1;
+	/* Whenever the call will need an unbox trampoline */
+	guint need_unbox_trampoline : 1;
 	regmask_t used_iregs;
 	regmask_t used_fregs;
 	GSList *out_ireg_args;