parser: add support for flags in asm output constraints (#10103)

vlib/v/ast/ast.v

@@ -1180,7 +1180,7 @@ pub mut:
 pub struct AsmIO {
 pub:
 	alias      string    // [alias_a]
-	constraint string    // '=r'
+	constraint string    // '=r' TODO: allow all backends to easily use this with a struct
 	expr       Expr      // (a)
 	comments   []Comment // // this is a comment
 	typ        Type

vlib/v/fmt/fmt.v

@@ -727,6 +727,9 @@ fn (mut f Fmt) asm_stmt(stmt ast.AsmStmt) {
 	}
 	f.indent--
 	f.writeln('}')
+	if stmt.is_top_level {
+		f.writeln('')
+	}
 }
 
 fn (mut f Fmt) asm_arg(arg ast.AsmArg) {

vlib/v/parser/parser.v

@@ -1383,16 +1383,13 @@ fn (mut p Parser) asm_ios(output bool) []ast.AsmIO {
 			if constraint != '' {
 				p.next()
 			}
-			if p.tok.kind == .assign {
-				constraint += '='
-				p.next()
-			} else if p.tok.kind == .plus {
-				constraint += '+'
-				p.next()
-			}
 			constraint += p.tok.lit
+			if p.tok.kind == .at {
+				p.next()
+			} else {
 				p.check(.name)
 			}
+		}
 		mut expr := p.expr(0)
 		if mut expr is ast.ParExpr {
 			expr = expr.expr

vlib/v/scanner/scanner.v

@@ -873,7 +873,7 @@ fn (mut s Scanner) text_scan() token.Token {
 					return s.new_token(.name, '@' + name, name.len + 1)
 				}
 				// @FN, @STRUCT, @MOD etc. See full list in token.valid_at_tokens
-				if '@' + name in token.valid_at_tokens {
+				if '@' + name in token.valid_at_tokens || name.starts_with('cc') { // `=@cccond` in inline assembly
 					return s.new_token(.at, '@' + name, name.len + 1)
 				}
 				if !token.is_key(name) {

vlib/v/tests/assembly/asm_test.amd64.v

@@ -136,13 +136,6 @@ fn test_rip_relative_label() {
 		; =r (a)
 	}
 	assert a == 48321074923
-
-	mut b := i64(4)
-	asm amd64 {
-		mov b, one_two_three // see below
-		; =r (b)
-	}
-	assert b == 48321074923
 }
 
 asm amd64 {
@@ -150,3 +143,30 @@ asm amd64 {
 	one_two_three:
 	.quad 48321074923
 }
+
+fn test_flag_output() {
+	a, b := 4, 9
+	mut out := false
+	asm amd64 {
+		cmp a, b
+		; =@ccl (out)
+		; r (a)
+		  r (b)
+	}
+	assert out
+	asm amd64 {
+		cmp b, a
+		; =@ccl (out)
+		; r (a)
+		  r (b)
+	}
+	assert !out
+
+	zero := 0
+	asm amd64 {
+		cmp zero, zero
+		; =@ccz (out)
+		; r (zero)
+	}
+	assert out
+}

vlib/v/tests/assembly/asm_test.i386.v

@@ -125,3 +125,30 @@ fn (m Manu) str() string {
 		}
 	}
 }
+
+fn test_flag_output() {
+	a, b := 4, 9
+	mut out := false
+	asm amd64 {
+		cmp a, b
+		; =@ccl (out)
+		; r (a)
+		  r (b)
+	}
+	assert out
+	asm amd64 {
+		cmp b, a
+		; =@ccl (out)
+		; r (a)
+		  r (b)
+	}
+	assert !out
+
+	zero := 0
+	asm amd64 {
+		cmp zero, zero
+		; =@ccz (out)
+		; r (zero)
+	}
+	assert out
+}

vlib/v/tests/break_in_lock_test.v

@@ -10,23 +10,22 @@ const (
 )
 
 fn test_return_lock() {
-	shared s := AA{'3'}
-	go printer(shared s)
-	go fn (shared s AA) {
 	start := time.now()
+	shared s := AA{'3'}
+	go printer(shared s, start)
+	go fn (shared s AA, start time.Time) {
 		for {
 			reader(shared s)
 			if time.now() - start > sleep_time {
 				exit(0)
 			}
 		}
-	}(shared s)
+	}(shared s, start)
 	time.sleep(sleep_time * 2)
 	assert false
 }
 
-fn printer(shared s AA) {
+fn printer(shared s AA, start time.Time) {
-	start := time.now()
 	for {
 		lock s {
 			assert s.b in ['0', '1', '2', '3', '4', '5']

vlib/v/tests/return_in_lock_test.v

@@ -10,23 +10,22 @@ const (
 )
 
 fn test_return_lock() {
-	shared s := AA{'3'}
-	go printer(shared s)
-	go fn (shared s AA) {
 	start := time.now()
+	shared s := AA{'3'}
+	go printer(shared s, start)
+	go fn (shared s AA, start time.Time) {
 		for {
 			reader(shared s)
 			if time.now() - start > sleep_time {
 				exit(0)
 			}
 		}
-	}(shared s)
+	}(shared s, start)
 	time.sleep(sleep_time * 2)
 	assert false
 }
 
-fn printer(shared s AA) {
+fn printer(shared s AA, start time.Time) {
-	start := time.now()
 	for {
 		lock s {
 			assert s.b in ['0', '1', '2', '3', '4', '5']