From 6576d876fc1a1ce41aca65c68f2dfed500731d4e Mon Sep 17 00:00:00 2001
From: crthpl <56052645+crthpl@users.noreply.github.com>
Date: Fri, 11 Jun 2021 01:03:39 -0700
Subject: [PATCH] cgen: support a `[_naked]` fn attribute (#10418)

---
 vlib/v/checker/checker.v                      |  2 +-
 vlib/v/gen/c/fn.v                             |  6 +++++-
 vlib/v/parser/fn.v                            |  3 ++-
 vlib/v/parser/parser.v                        |  2 +-
 vlib/v/tests/assembly/naked_attr_test.amd64.v | 14 ++++++++++++++
 vlib/v/tests/assembly/naked_attr_test.i386.v  | 14 ++++++++++++++
 6 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/tests/assembly/naked_attr_test.amd64.v
 create mode 100644 vlib/v/tests/assembly/naked_attr_test.i386.v

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 56047d34f2..b99943f6c9 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -7260,7 +7260,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 		&& (node.is_method || node.name !in ['panic', 'exit']) {
 		if c.inside_anon_fn {
 			c.error('missing return at the end of an anonymous function', node.pos)
-		} else {
+		} else if !node.attrs.contains('_naked') {
 			c.error('missing return at end of function `$node.name`', node.pos)
 		}
 	}
diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index 32402c2a17..4ec39a6469 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -332,7 +332,8 @@ fn (mut g Gen) gen_fn_decl(node &ast.FnDecl, skip bool) {
 	} else {
 		g.defer_stmts = []
 	}
-	if node.return_type != ast.void_type && node.stmts.len > 0 && node.stmts.last() !is ast.Return {
+	if node.return_type != ast.void_type && node.stmts.len > 0 && node.stmts.last() !is ast.Return
+		&& !node.attrs.contains('_naked') {
 		default_expr := g.type_default(node.return_type)
 		// TODO: perf?
 		if default_expr == '{0}' {
@@ -1354,6 +1355,9 @@ fn (mut g Gen) write_fn_attrs(attrs []ast.Attr) string {
 				// repeated invocations of the function with the same argument values.
 				g.write('__attribute__((const)) ')
 			}
+			'_naked' {
+				g.write('__attribute__((naked)) ')
+			}
 			'windows_stdcall' {
 				// windows attributes (msvc/mingw)
 				// prefixed by windows to indicate they're for advanced users only and not really supported by V.
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 7c099849a4..a26a026356 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -342,7 +342,8 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	short_fn_name := name
 	is_main := short_fn_name == 'main' && p.mod == 'main'
 	mut is_test := (short_fn_name.starts_with('test_') || short_fn_name.starts_with('testsuite_'))
-		&& (p.file_base.ends_with('_test.v') || p.file_base.ends_with('_test.vv'))
+		&& (p.file_base.ends_with('_test.v')
+		|| p.file_base.all_before_last('.v').all_before_last('.').ends_with('_test'))
 
 	// Register
 	if is_method {
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 1529bddef9..71924d601a 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -900,7 +900,7 @@ fn (mut p Parser) asm_stmt(is_top_level bool) ast.AsmStmt {
 			p.check(.name)
 		}
 		// dots are part of instructions for some riscv extensions
-		if arch in [.rv32, .rv64] {
+		if arch in [.rv32, .rv64, .amd64] {
 			for p.tok.kind == .dot {
 				name += '.'
 				p.next()
diff --git a/vlib/v/tests/assembly/naked_attr_test.amd64.v b/vlib/v/tests/assembly/naked_attr_test.amd64.v
new file mode 100644
index 0000000000..a2b3296675
--- /dev/null
+++ b/vlib/v/tests/assembly/naked_attr_test.amd64.v
@@ -0,0 +1,14 @@
+[_naked]
+fn naked_fn() {
+	asm amd64 {
+		push rbp
+		mov rbp, rsp
+		mov rsp, rbp
+		pop rbp
+		ret
+	}
+}
+
+fn test_naked_attr() {
+	naked_fn()
+}
diff --git a/vlib/v/tests/assembly/naked_attr_test.i386.v b/vlib/v/tests/assembly/naked_attr_test.i386.v
new file mode 100644
index 0000000000..34fa41e1c7
--- /dev/null
+++ b/vlib/v/tests/assembly/naked_attr_test.i386.v
@@ -0,0 +1,14 @@
+[_naked]
+fn naked_fn() {
+	asm i386 {
+		push ebp
+		mov ebp, esp
+		mov esp, ebp
+		pop ebp
+		ret
+	}
+}
+
+fn test_naked_attr() {
+	naked_fn()
+}