Special-case jit_guard_known_class for strings. This can remove (#5920)

runtime guard-checks for String#to_s, making some blocks too
short to invalidate later. Add NOPs in those cases to reserve space.

1 files changed, 5 insertions, 0 deletions

diff --git a/yjit/src/cruby.rs b/yjit/src/cruby.rs
index 0afbd6451b..20091bf77a 100644
--- a/yjit/src/cruby.rs
+++ b/yjit/src/cruby.rs
@@ -461,6 +461,11 @@ impl VALUE {
         self == Qnil
     }
 
+    /// Returns true or false depending whether the value is a string
+    pub fn string_p(self) -> bool {
+        unsafe { CLASS_OF(self) == rb_cString }
+    }
+
     /// Read the flags bits from the RBasic object, then return a Ruby type enum (e.g. RUBY_T_ARRAY)
     pub fn builtin_type(self) -> ruby_value_type {
         assert!(!self.special_const_p());