builtin.overflow: add {add,sub,mul}_{int,f32,f64} too, to avoid cgen errors for tests; cleanup cgen

Author: spytheman

vlib/builtin/overflow/overflow.v

@@ -444,3 +444,51 @@ fn mul_u64(x u64, y u64) u64 {
 	}
 	return res
 }
+
+/////////////////////////////////////////////////////////////////////////////////////////////
+// These are here to prevent cgen errors for `./v -check-overflow vlib/math/vec/vec4_test.v`
+// TODO: check for correctness and add tests. Improve markused so it keeps them, when they are used.
+@[inline; markused]
+fn add_int(x int, y int) int {
+	return add_i32(x, y)
+}
+
+@[inline; markused]
+fn sub_int(x int, y int) int {
+	return sub_i32(x, y)
+}
+
+@[inline; markused]
+fn mul_int(x int, y int) int {
+	return mul_i32(x, y)
+}
+
+@[inline; markused]
+fn add_f32(x f32, y f32) f32 {
+	return x + y
+}
+
+@[inline; markused]
+fn sub_f32(x f32, y f32) f32 {
+	return x - y
+}
+
+@[inline; markused]
+fn mul_f32(x f32, y f32) f32 {
+	return x * y
+}
+
+@[inline; markused]
+fn add_f64(x f64, y f64) f64 {
+	return x + y
+}
+
+@[inline; markused]
+fn sub_f64(x f64, y f64) f64 {
+	return x - y
+}
+
+@[inline; markused]
+fn mul_f64(x f64, y f64) f64 {
+	return x * y
+}

vlib/v/gen/c/infix.v

@@ -1256,12 +1256,10 @@ fn (mut g Gen) gen_plain_infix_expr(node ast.InfixExpr) {
 	}
 	// do not use promoted_type for overflow detect
 	left_type := g.unwrap_generic(node.left_type)
-	is_safe_add := node.op == .plus && g.pref.is_check_overflow && left_type.is_int()
-		&& !g.is_builtin_overflow_mod
-	is_safe_sub := node.op == .minus && g.pref.is_check_overflow && left_type.is_int()
-		&& !g.is_builtin_overflow_mod
-	is_safe_mul := node.op == .mul && g.pref.is_check_overflow && left_type.is_int()
-		&& !g.is_builtin_overflow_mod
+	checkoverflow_op := g.pref.is_check_overflow && !g.is_builtin_overflow_mod && left_type.is_int()
+	is_safe_add := checkoverflow_op && node.op == .plus
+	is_safe_sub := checkoverflow_op && node.op == .minus
+	is_safe_mul := checkoverflow_op && node.op == .mul
 	is_safe_div := node.op == .div && g.pref.div_by_zero_is_zero && typ.is_int()
 	is_safe_mod := node.op == .mod && g.pref.div_by_zero_is_zero && typ.is_int()
 	if node.left_type.is_ptr() && node.left.is_auto_deref_var() && !node.right_type.is_pointer() {