[llvm] Generate code at the start of exception clauses to branch to t…

…he proper nesting clause so the EH code can branch to the innermost landing pad in the future. This is needed because LLVM always expects the innermost landing pad to be called.

mono/mini/mini-amd64.h

@@ -233,6 +233,7 @@ typedef struct {
 
 
 #define MONO_CONTEXT_SET_LLVM_EXC_REG(ctx, exc) do { (ctx)->rax = (gsize)exc; } while (0)
+#define MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG(ctx, sel) do { (ctx)->rdx = (gsize)(sel); } while (0)
 
 #define MONO_ARCH_INIT_TOP_LMF_ENTRY(lmf)
 

mono/mini/mini-exceptions.c

@@ -1494,6 +1494,11 @@ mono_handle_exception_internal_first_pass (MonoContext *ctx, gpointer obj, gint3
 						*((gpointer *)(gpointer)((char *)MONO_CONTEXT_GET_BP (ctx) + ei->exvar_offset)) = ex_obj;
 					}
 
+#ifdef MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG
+					if (ji->from_llvm)
+						MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG (ctx, i);
+#endif
+
 					mono_debugger_agent_begin_exception_filter (mono_ex, ctx, &initial_ctx);
 					filtered = call_filter (ctx, ei->data.filter);
 					mono_debugger_agent_end_exception_filter (mono_ex, ctx, &initial_ctx);
@@ -1789,6 +1794,11 @@ mono_handle_exception_internal (MonoContext *ctx, gpointer obj, gboolean resume,
 					}
 				}
 
+#ifdef MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG
+				if (ji->from_llvm)
+					MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG (ctx, i);
+#endif
+
 				if (ei->flags == MONO_EXCEPTION_CLAUSE_FILTER) {
 					/* 
 					 * Filter clauses should only be run in the 

mono/mini/mini-llvm.c

@@ -2465,6 +2465,7 @@ emit_handler_start (EmitContext *ctx, MonoBasicBlock *bb, LLVMBuilderRef builder
 	BBInfo *bblocks = ctx->bblocks;
 	LLVMTypeRef i8ptr;
 	LLVMValueRef personality;
+	LLVMValueRef landing_pad;
 	LLVMBasicBlockRef target_bb;
 	MonoInst *exvar;
 	static gint32 mapping_inited;
@@ -2473,6 +2474,7 @@ emit_handler_start (EmitContext *ctx, MonoBasicBlock *bb, LLVMBuilderRef builder
 	MonoClass **ti;
 	LLVMValueRef type_info;
 	int clause_index;
+	GSList *l;
 
 	// <resultval> = landingpad <somety> personality <type> <pers_fn> <clause>+
 
@@ -2526,7 +2528,6 @@ emit_handler_start (EmitContext *ctx, MonoBasicBlock *bb, LLVMBuilderRef builder
 
 	{
 		LLVMTypeRef members [2], ret_type;
-		LLVMValueRef landing_pad;
 
 		members [0] = i8ptr;
 		members [1] = LLVMInt32Type ();
@@ -2548,11 +2549,69 @@ emit_handler_start (EmitContext *ctx, MonoBasicBlock *bb, LLVMBuilderRef builder
 		}
 	}
 
+#ifdef MONO_CONTEXT_SET_LLVM_EH_SELECTOR_REG
+	/*
+	 * LLVM throw sites are associated with a one landing pad, and LLVM generated
+	 * code expects control to be transferred to this landing pad even in the
+	 * presence of nested clauses. The landing pad needs to branch to the landing
+	 * pads belonging to nested clauses based on the selector value returned by
+	 * the landing pad instruction, which is passed to the landing pad in a
+	 * register by the EH code.
+	 */
+	/* Store the exception object into the eh variable of nested clauses. */
+	for (l = ctx->nested_in [clause_index]; l; l = l->next) {
+		int nesting_clause_index = GPOINTER_TO_INT (l->data);
+		MonoBasicBlock *handler_bb;
+
+		handler_bb = g_hash_table_lookup (ctx->clause_to_handler, GINT_TO_POINTER (nesting_clause_index));
+		g_assert (handler_bb);
+
+		if (handler_bb->in_scount == 1) {
+			LLVMValueRef ex_obj = LLVMBuildExtractValue (builder, landing_pad, 0, "ex_obj");
+			MonoInst *var;
+			int vreg;
+
+			exvar = handler_bb->in_stack [0];
+			vreg = exvar->dreg;
+
+			/*
+			 * Can't assign to exvar directly, because of SSA, so store into
+			 * the location where the (volatile) exvar is stored.
+			 */
+
+			/* From emit_volatile_store () */
+			var = get_vreg_to_inst (ctx->cfg, vreg);
+
+			g_assert (var && var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT));
+			g_assert (ctx->addresses [vreg]);
+			LLVMBuildStore (ctx->builder, convert (ctx, ex_obj, type_to_llvm_type (ctx, var->inst_vtype)), ctx->addresses [vreg]);
+		}
+	}
+
+	target_bb = bblocks [bb->block_num].call_handler_target_bb;
+	g_assert (target_bb);
+#endif
+
+	/*
+	 * Branch to the correct landing pad
+	 */
+	LLVMValueRef ex_selector = LLVMBuildExtractValue (builder, landing_pad, 1, "ex_selector");
+	LLVMValueRef switch_ins = LLVMBuildSwitch (builder, ex_selector, target_bb, 0);
+
+	for (l = ctx->nested_in [clause_index]; l; l = l->next) {
+		int nesting_clause_index = GPOINTER_TO_INT (l->data);
+		MonoBasicBlock *handler_bb;
+
+		handler_bb = g_hash_table_lookup (ctx->clause_to_handler, GINT_TO_POINTER (nesting_clause_index));
+		g_assert (handler_bb);
+
+		g_assert (ctx->bblocks [handler_bb->block_num].call_handler_target_bb);
+		LLVMAddCase (switch_ins, LLVMConstInt (LLVMInt32Type (), nesting_clause_index, FALSE), ctx->bblocks [handler_bb->block_num].call_handler_target_bb);
+	}
+
 	/* Start a new bblock which CALL_HANDLER can branch to */
 	target_bb = bblocks [bb->block_num].call_handler_target_bb;
 	if (target_bb) {
-		LLVMBuildBr (builder, target_bb);
-
 		ctx->builder = builder = create_builder (ctx);
 		LLVMPositionBuilderAtEnd (ctx->builder, target_bb);