Add @naked attribute

src/compiler/compiler_internal.h

@@ -396,6 +396,7 @@ typedef struct
 		bool attr_inline : 1;
 		bool attr_noinline : 1;
 		bool attr_extname : 1;
+		bool attr_naked : 1;
 	};
 
 	TypeInfo *type_parent;

src/compiler/llvm_codegen.c

@@ -628,6 +628,7 @@ unsigned attribute_zext;
 unsigned attribute_sext;
 unsigned attribute_byval;
 unsigned attribute_inreg;
+unsigned attribute_naked;
 
 void llvm_codegen_setup()
 {
@@ -709,6 +710,7 @@ void llvm_codegen_setup()
 	attribute_align = lookup_attribute("align");
 	attribute_byval = lookup_attribute("byval");
 	attribute_inreg = lookup_attribute("inreg");
+	attribute_naked = lookup_attribute("naked");
 	intrinsics_setup = true;
 }
 

src/compiler/llvm_codegen_function.c

@@ -422,10 +422,13 @@ void llvm_emit_function_body(GenContext *context, Decl *decl)
 	}
 
 
-	// Generate LLVMValueRef's for all parameters, so we can use them as local vars in code
-	VECEACH(decl->func_decl.function_signature.params, i)
+	if (!decl->func_decl.attr_naked)
 	{
-		llvm_emit_parameter(context, decl->func_decl.function_signature.params[i], &arg, i);
+		// Generate LLVMValueRef's for all parameters, so we can use them as local vars in code
+		VECEACH(decl->func_decl.function_signature.params, i)
+		{
+			llvm_emit_parameter(context, decl->func_decl.function_signature.params[i], &arg, i);
+		}
 	}
 
 	LLVMSetCurrentDebugLocation2(context->builder, NULL);
@@ -575,7 +578,10 @@ void llvm_emit_function_decl(GenContext *c, Decl *decl)
 		LLVMSetSection(function, decl->section);
 	}
 	llvm_attribute_add(c, function, attribute_nounwind, -1);
-
+	if (decl->func_decl.attr_naked)
+	{
+		llvm_attribute_add(c, function, attribute_naked, -1);
+	}
 	if (decl->func_decl.function_signature.call_abi == CALL_X86_STD)
 	{
 		if (platform_target.os == OS_TYPE_WIN32)

src/compiler/llvm_codegen_internal.h

@@ -177,6 +177,7 @@ extern unsigned attribute_zext; // zero extend
 extern unsigned attribute_sext; // sign extend
 extern unsigned attribute_byval; // ByVal (param)
 extern unsigned attribute_inreg; // inreg (param)
+extern unsigned attribute_naked; // naked function
 
 void gencontext_begin_module(GenContext *c);
 void gencontext_init_file_emit(GenContext *c, Context *ast);

src/compiler/sema_decls.c

@@ -1086,6 +1086,7 @@ static inline bool sema_analyse_func(Context *context, Decl *decl)
 			case ATTRIBUTE_INLINE: SET_ATTR(attr_inline);
 			case ATTRIBUTE_NORETURN: SET_ATTR(attr_noreturn);
 			case ATTRIBUTE_WEAK: SET_ATTR(attr_weak);
+			case ATTRIBUTE_NAKED: SET_ATTR(attr_naked);
 			default:
 				UNREACHABLE
 		}

src/compiler/sema_stmts.c

@@ -2426,16 +2426,32 @@ bool sema_analyse_function_body(Context *context, Decl *func)
 		}
 		Ast **asserts = NULL;
 		if (!sema_analyse_requires(context, func->docs, &asserts)) return false;
-		if (!sema_analyse_compound_statement_no_scope(context, func->func_decl.body)) return false;
-		assert(context->active_scope.depth == 1);
-		if (!context->active_scope.jump_end)
+		if (func->func_decl.attr_naked)
 		{
-			Type *canonical_rtype = signature->rtype->type->canonical;
-			if (canonical_rtype != type_void)
+			Ast **stmts = func->func_decl.body->compound_stmt.stmts;
+			VECEACH(stmts, i)
 			{
-				// IMPROVE better pointer to end.
-				SEMA_ERROR(func, "Missing return statement at the end of the function.");
-				return false;
+				if (stmts[i]->ast_kind != AST_ASM_STMT)
+				{
+					SEMA_ERROR(stmts[i], "Only asm statements are allowed inside of a naked function.");
+					return false;
+				}
+			}
+			asserts = NULL;
+		}
+		else
+		{
+			if (!sema_analyse_compound_statement_no_scope(context, func->func_decl.body)) return false;
+			assert(context->active_scope.depth == 1);
+			if (!context->active_scope.jump_end)
+			{
+				Type *canonical_rtype = signature->rtype->type->canonical;
+				if (canonical_rtype != type_void)
+				{
+					// IMPROVE better pointer to end.
+					SEMA_ERROR(func, "Missing return statement at the end of the function.");
+					return false;
+				}
 			}
 		}
 		if (asserts)

test/test_suite/functions/naked_function.c3t

@@ -0,0 +1,15 @@
+// #target: x64-darwin
+
+func void test(int i) @naked
+{
+
+}
+
+// #expect: naked_function.ll
+
+define void @naked_function.test(i32 %0) #0 {
+entry:
+  ret void
+}
+
+attributes #0 = { naked nounwind }

test/test_suite/functions/naked_function_fail.c3

@@ -0,0 +1,4 @@
+func void test() @naked
+{
+    int i; // #error: Only asm statements are allowed inside of a naked function
+}