Optimize getfield lowering to avoid boxing in some cases

src/codegen.cpp

@@ -739,6 +739,13 @@ static const auto jlundefvarerror_func = new JuliaFunction<>{
             {PointerType::get(JuliaType::get_jlvalue_ty(C), AddressSpace::CalleeRooted)}, false); },
     get_attrs_noreturn,
 };
+static const auto jlhasnofield_func = new JuliaFunction<>{
+    XSTR(jl_has_no_field_error),
+    [](LLVMContext &C) { return FunctionType::get(getVoidTy(C),
+            {PointerType::get(JuliaType::get_jlvalue_ty(C), AddressSpace::CalleeRooted),
+             PointerType::get(JuliaType::get_jlvalue_ty(C), AddressSpace::CalleeRooted)}, false); },
+    get_attrs_noreturn,
+};
 static const auto jlboundserrorv_func = new JuliaFunction<TypeFnContextAndSizeT>{
     XSTR(jl_bounds_error_ints),
     [](LLVMContext &C, Type *T_size) { return FunctionType::get(getVoidTy(C),
@@ -3318,6 +3325,8 @@ static jl_llvm_functions_t
         jl_value_t *jlrettype,
         jl_codegen_params_t &params);
 
+static void emit_hasnofield_error_ifnot(jl_codectx_t &ctx, Value *ok, jl_sym_t *type, jl_cgval_t name);
+
 static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
                               const jl_cgval_t *argv, size_t nargs, jl_value_t *rt,
                               jl_expr_t *ex, bool is_promotable)
@@ -3819,6 +3828,19 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
                 return true;
             }
         }
+        else if (fld.typ == (jl_value_t*)jl_symbol_type) {
+            if (jl_is_datatype(utt) && !jl_is_namedtuple_type(utt)) { // TODO: Look into this for NamedTuple
+                if (jl_struct_try_layout(utt) && (jl_datatype_nfields(utt) == 1)) {
+                    jl_svec_t *fn = jl_field_names(utt);
+                    assert(jl_svec_len(fn) == 1);
+                    Value *typ_sym = literal_pointer_val(ctx, jl_svecref(fn, 0));
+                    Value *cond = ctx.builder.CreateICmpEQ(mark_callee_rooted(ctx, typ_sym), mark_callee_rooted(ctx, boxed(ctx, fld)));
+                    emit_hasnofield_error_ifnot(ctx, cond, utt->name->name, fld);
+                    *ret = emit_getfield_knownidx(ctx, obj, 0, utt, order);
+                    return true;
+                }
+            }
+        }
         // TODO: generic getfield func with more efficient calling convention
         return false;
     }
@@ -4612,6 +4634,22 @@ static void undef_var_error_ifnot(jl_codectx_t &ctx, Value *ok, jl_sym_t *name)
     ctx.builder.SetInsertPoint(ifok);
 }
 
+static void emit_hasnofield_error_ifnot(jl_codectx_t &ctx, Value *ok, jl_sym_t *type, jl_cgval_t name)
+{
+    ++EmittedUndefVarErrors;
+    assert(name.typ == (jl_value_t*)jl_symbol_type);
+    BasicBlock *err = BasicBlock::Create(ctx.builder.getContext(), "err", ctx.f);
+    BasicBlock *ifok = BasicBlock::Create(ctx.builder.getContext(), "ok");
+    ctx.builder.CreateCondBr(ok, ifok, err);
+    ctx.builder.SetInsertPoint(err);
+    ctx.builder.CreateCall(prepare_call(jlhasnofield_func),
+                          {mark_callee_rooted(ctx, literal_pointer_val(ctx, (jl_value_t*)type)),
+                           mark_callee_rooted(ctx, boxed(ctx, name))});
+    ctx.builder.CreateUnreachable();
+    ctx.f->getBasicBlockList().push_back(ifok);
+    ctx.builder.SetInsertPoint(ifok);
+}
+
 // returns a jl_ppvalue_t location for the global variable m.s
 // if the reference currently bound or assign == true,
 //   pbnd will also be assigned with the binding address
@@ -9011,6 +9049,7 @@ static void init_jit_functions(void)
     add_named_global(jlatomicerror_func, &jl_atomic_error);
     add_named_global(jlthrow_func, &jl_throw);
     add_named_global(jlundefvarerror_func, &jl_undefined_var_error);
+    add_named_global(jlhasnofield_func, &jl_has_no_field_error);
     add_named_global(jlboundserrorv_func, &jl_bounds_error_ints);
     add_named_global(jlboundserror_func, &jl_bounds_error_int);
     add_named_global(jlvboundserror_func, &jl_bounds_error_tuple_int);

src/datatype.c

@@ -1558,8 +1558,7 @@ JL_DLLEXPORT int jl_field_index(jl_datatype_t *t, jl_sym_t *fld, int err)
         }
     }
     if (err)
-        jl_errorf("type %s has no field %s", jl_symbol_name(t->name->name),
-                  jl_symbol_name(fld));
+        jl_has_no_field_error(t->name->name, fld);
     return -1;
 }
 

src/jl_exported_funcs.inc

@@ -510,6 +510,7 @@
     XX(jl_uncompress_argname_n) \
     XX(jl_uncompress_ir) \
     XX(jl_undefined_var_error) \
+    XX(jl_has_no_field_error) \
     XX(jl_value_ptr) \
     XX(jl_ver_is_release) \
     XX(jl_ver_major) \

src/julia.h

@@ -1790,6 +1790,7 @@ JL_DLLEXPORT void JL_NORETURN jl_type_error_rt(const char *fname,
                                                jl_value_t *ty JL_MAYBE_UNROOTED,
                                                jl_value_t *got JL_MAYBE_UNROOTED);
 JL_DLLEXPORT void JL_NORETURN jl_undefined_var_error(jl_sym_t *var);
+JL_DLLEXPORT void JL_NORETURN jl_has_no_field_error(jl_sym_t *type_name, jl_sym_t *var);
 JL_DLLEXPORT void JL_NORETURN jl_atomic_error(char *str);
 JL_DLLEXPORT void JL_NORETURN jl_bounds_error(jl_value_t *v JL_MAYBE_UNROOTED,
                                               jl_value_t *t JL_MAYBE_UNROOTED);

src/rtutils.c

@@ -134,6 +134,11 @@ JL_DLLEXPORT void JL_NORETURN jl_undefined_var_error(jl_sym_t *var)
     jl_throw(jl_new_struct(jl_undefvarerror_type, var));
 }
 
+JL_DLLEXPORT void JL_NORETURN jl_has_no_field_error(jl_sym_t *type_name, jl_sym_t *var)
+{
+    jl_errorf("type %s has no field %s", jl_symbol_name(type_name), jl_symbol_name(var));
+}
+
 JL_DLLEXPORT void JL_NORETURN jl_atomic_error(char *str) // == jl_exceptionf(jl_atomicerror_type, "%s", str)
 {
     jl_value_t *msg = jl_pchar_to_string((char*)str, strlen(str));

test/compiler/codegen.jl

@@ -820,3 +820,15 @@ end
 # issue 48917, hoisting load to above the parent
 f48917(x, w) = (y = (a=1, b=x); z = (; a=(a=(1, w), b=(3, y))))
 @test f48917(1,2) == (a = (a = (1, 2), b = (3, (a = 1, b = 1))),)
+
+# https://github.com/JuliaLang/julia/issues/50317 getproperty allocation on struct with 1 field
+struct Wrapper50317
+    lock::ReentrantLock
+end
+const MONITOR50317 = Wrapper50317(ReentrantLock())
+issue50317() = @noinline MONITOR50317.lock
+issue50317()
+let res = @timed issue50317()
+    @test res.bytes == 0
+    return res # must return otherwise the compiler may eliminate the result entirely
+end