codegen: remove readonly from abstract type calling convention

Refs: #58070

Author: vtjnash

Compiler/test/codegen.jl

@@ -1033,3 +1033,7 @@ end
 const x57872 = "Hello"
 f57872() = (Core.isdefinedglobal(@__MODULE__, Base.compilerbarrier(:const, :x57872)), x57872) # Extra globalref here to force world age bounds
 @test f57872() == (true, "Hello")
+
+@noinline f_mutateany(@nospecialize x) = x[] = 1
+g_mutateany() = (y = Ref(0); f_mutateany(y); y[])
+@test g_mutateany() === 1

src/codegen.cpp

@@ -1600,7 +1600,7 @@ static MDNode *best_tbaa(jl_tbaacache_t &tbaa_cache, jl_value_t *jt) {
 // note that this includes jl_isbits, although codegen should work regardless
 static bool jl_is_concrete_immutable(jl_value_t* t)
 {
-    return jl_is_immutable_datatype(t) && ((jl_datatype_t*)t)->isconcretetype;
+    return jl_may_be_immutable_datatype(t) && ((jl_datatype_t*)t)->isconcretetype;
 }
 
 static bool jl_is_pointerfree(jl_value_t* t)
@@ -7385,8 +7385,8 @@ static Function *gen_cfun_wrapper(
                     inputarg = mark_julia_type(ctx, val, false, jargty);
                 }
             }
-            else if (static_at || (!jl_is_typevar(jargty) && !jl_is_immutable_datatype(jargty))) {
-                // must be a jl_value_t* (because it's mutable or contains gc roots)
+            else if (static_at || (!jl_is_typevar(jargty) && !jl_is_concrete_immutable(jargty))) {
+                // must be a jl_value_t* (because it's mutable, abstract, or contains gc roots)
                 inputarg = mark_julia_type(ctx, maybe_decay_untracked(ctx, val), true, jargty_proper);
             }
             else {
@@ -7980,7 +7980,7 @@ static jl_returninfo_t get_specsig_function(jl_codegen_params_t &params, Module
             param.addAttribute(Attribute::ReadOnly);
             ty = PointerType::get(M->getContext(), AddressSpace::Derived);
         }
-        else if (isboxed && jl_is_immutable_datatype(jt)) {
+        else if (isboxed && jl_may_be_immutable_datatype(jt) && !jl_is_abstracttype(jt)) {
             param.addAttribute(Attribute::ReadOnly);
         }
         else if (jl_is_primitivetype(jt) && ty->isIntegerTy()) {

src/julia.h

@@ -1617,7 +1617,7 @@ static inline int jl_field_isconst(jl_datatype_t *st, int i) JL_NOTSAFEPOINT
 #define jl_is_mutable(t)     (((jl_datatype_t*)t)->name->mutabl)
 #define jl_is_mutable_datatype(t) (jl_is_datatype(t) && (((jl_datatype_t*)t)->name->mutabl))
 #define jl_is_immutable(t)   (!((jl_datatype_t*)t)->name->mutabl)
-#define jl_is_immutable_datatype(t) (jl_is_datatype(t) && (!((jl_datatype_t*)t)->name->mutabl))
+#define jl_may_be_immutable_datatype(t) (jl_is_datatype(t) && (!((jl_datatype_t*)t)->name->mutabl))
 #define jl_is_uniontype(v)   jl_typetagis(v,jl_uniontype_tag<<4)
 #define jl_is_typevar(v)     jl_typetagis(v,jl_tvar_tag<<4)
 #define jl_is_unionall(v)    jl_typetagis(v,jl_unionall_tag<<4)