ZJIT: Inline String#to_sym to StringIntern

Closes #1061.

Also add a test to make sure `String#intern` generates the same HIR.

Author: rafaelfranca

zjit/src/codegen_tests.rs

@@ -369,6 +369,25 @@ fn test_string_intern() {
     assert_snapshot!(assert_compiles(r#"test"#), @":foo123");
 }
 
+#[test]
+fn test_string_to_sym_invalid_encoding_unused() {
+    eval(r#"
+        def test(str)
+          str.to_sym
+          :converted
+        end
+    "#);
+    assert_snapshot!(assert_compiles(r#"
+        test("warmup")
+        test("warmup")
+        begin
+          test("\xFF".force_encoding(Encoding::UTF_8))
+        rescue EncodingError
+          :encoding_error
+        end
+    "#), @":encoding_error");
+}
+
 #[test]
 fn test_duphash() {
     eval("

zjit/src/cruby_methods.rs

@@ -277,6 +277,7 @@ pub fn init() -> Annotations {
     annotate!(rb_cFloat, "to_i", inline_float_to_i);
     annotate!(rb_cFloat, "to_int", inline_float_to_i);
     annotate!(rb_cString, "to_s", inline_string_to_s, types::StringExact);
+    annotate!(rb_cString, "to_sym", inline_string_to_sym, types::Symbol);
     annotate!(rb_cFloat, "nan?", types::BoolExact, no_gc, leaf, elidable);
     annotate!(rb_cFloat, "finite?", types::BoolExact, no_gc, leaf, elidable);
     annotate!(rb_cFloat, "infinite?", types::Fixnum.union(types::NilClass), no_gc, leaf, elidable);
@@ -324,6 +325,14 @@ fn inline_string_to_s(fun: &mut hir::Function, block: hir::BlockId, recv: hir::I
     None
 }
 
+fn inline_string_to_sym(fun: &mut hir::Function, block: hir::BlockId, recv: hir::InsnId, args: &[hir::InsnId], state: hir::InsnId) -> Option<hir::InsnId> {
+    if args.is_empty() && fun.likely_a(recv, types::StringExact, state) {
+        let recv = fun.coerce_to(block, recv, types::StringExact, state);
+        return Some(fun.push_insn(block, hir::Insn::StringIntern { val: recv, state }));
+    }
+    None
+}
+
 fn inline_falseclass_and(fun: &mut hir::Function, block: hir::BlockId, _recv: hir::InsnId, args: &[hir::InsnId], _state: hir::InsnId) -> Option<hir::InsnId> {
     // FalseClass#& just returns Qfalse and ignores its argument.
     let &[_] = args else { return None; };

zjit/src/hir/opt_tests.rs

@@ -12840,6 +12840,64 @@ mod hir_opt_tests {
         ");
     }
 
+    #[test]
+    fn test_inline_string_to_sym() {
+        eval(r#"
+            def test(str) = str.to_sym
+            test("warmup")
+        "#);
+        assert_snapshot!(hir_string("test"), @"
+        fn test@<compiled>:2:
+        bb1():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          v2:CPtr = LoadSP
+          v3:BasicObject = LoadField v2, :str@0x1000
+          Jump bb3(v1, v3)
+        bb2():
+          EntryPoint JIT(0)
+          v6:BasicObject = LoadArg :self@0
+          v7:BasicObject = LoadArg :str@1
+          Jump bb3(v6, v7)
+        bb3(v9:BasicObject, v10:BasicObject):
+          PatchPoint NoSingletonClass(String@0x1008)
+          PatchPoint MethodRedefined(String@0x1008, to_sym@0x1010, cme:0x1018)
+          v24:StringExact = GuardType v10, StringExact recompile
+          v25:Symbol = StringIntern v24
+          CheckInterrupts
+          Return v25
+        ");
+    }
+
+    #[test]
+    fn test_inline_string_intern() {
+        eval(r#"
+            def test(str) = str.intern
+            test("warmup")
+        "#);
+        assert_snapshot!(hir_string("test"), @"
+        fn test@<compiled>:2:
+        bb1():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          v2:CPtr = LoadSP
+          v3:BasicObject = LoadField v2, :str@0x1000
+          Jump bb3(v1, v3)
+        bb2():
+          EntryPoint JIT(0)
+          v6:BasicObject = LoadArg :self@0
+          v7:BasicObject = LoadArg :str@1
+          Jump bb3(v6, v7)
+        bb3(v9:BasicObject, v10:BasicObject):
+          PatchPoint NoSingletonClass(String@0x1008)
+          PatchPoint MethodRedefined(String@0x1008, intern@0x1010, cme:0x1018)
+          v24:StringExact = GuardType v10, StringExact recompile
+          v25:Symbol = StringIntern v24
+          CheckInterrupts
+          Return v25
+        ");
+    }
+
     #[test]
     fn test_fixnum_to_s_returns_string() {
         eval(r#"