codegen: complete handling for partial-layout objects

Fixes #41425

Author: vtjnash

src/ccall.cpp

@@ -493,7 +493,7 @@ static Value *julia_to_native(
         assert(!byRef); // don't expect any ABI to pass pointers by pointer
         return boxed(ctx, jvinfo);
     }
-    assert(jl_is_datatype(jlto) && julia_struct_has_layout((jl_datatype_t*)jlto));
+    assert(jl_is_datatype(jlto) && jl_struct_try_layout((jl_datatype_t*)jlto));
 
     typeassert_input(ctx, jvinfo, jlto, jlto_env, argn);
     if (!byRef)

src/cgutils.cpp

@@ -321,7 +321,7 @@ static size_t dereferenceable_size(jl_value_t *jt)
         // Array has at least this much data
         return sizeof(jl_array_t);
     }
-    else if (jl_is_datatype(jt) && ((jl_datatype_t*)jt)->layout) {
+    else if (jl_is_datatype(jt) && jl_struct_try_layout((jl_datatype_t*)jt)) {
         return jl_datatype_size(jt);
     }
     return 0;
@@ -339,7 +339,7 @@ static unsigned julia_alignment(jl_value_t *jt)
         // and this is the guarantee we have for the GC bits
         return 16;
     }
-    assert(jl_is_datatype(jt) && ((jl_datatype_t*)jt)->layout);
+    assert(jl_is_datatype(jt) && jl_struct_try_layout((jl_datatype_t*)jt));
     unsigned alignment = jl_datatype_align(jt);
     if (alignment > JL_HEAP_ALIGNMENT)
         return JL_HEAP_ALIGNMENT;
@@ -555,16 +555,10 @@ static Type *bitstype_to_llvm(jl_value_t *bt, bool llvmcall = false)
 }
 
 static bool jl_type_hasptr(jl_value_t* typ)
-{ // assumes that jl_stored_inline(typ) is true
+{ // assumes that jl_stored_inline(typ) is true (and therefore that layout is defined)
     return jl_is_datatype(typ) && ((jl_datatype_t*)typ)->layout->npointers > 0;
 }
 
-// return whether all concrete subtypes of this type have the same layout
-static bool julia_struct_has_layout(jl_datatype_t *dt)
-{
-    return dt->layout || jl_has_fixed_layout(dt);
-}
-
 static unsigned jl_field_align(jl_datatype_t *dt, size_t i)
 {
     unsigned al = jl_field_offset(dt, i);
@@ -588,11 +582,8 @@ static Type *_julia_struct_to_llvm(jl_codegen_params_t *ctx, jl_value_t *jt, boo
         bool isTuple = jl_is_tuple_type(jt);
         jl_svec_t *ftypes = jl_get_fieldtypes(jst);
         size_t i, ntypes = jl_svec_len(ftypes);
-        if (!julia_struct_has_layout(jst))
+        if (!jl_struct_try_layout(jst))
             return NULL; // caller should have checked jl_type_mappable_to_c already, but we'll be nice
-        if (jst->layout == NULL)
-            jl_compute_field_offsets(jst);
-        assert(jst->layout);
         if (ntypes == 0 || jl_datatype_nbits(jst) == 0)
             return T_void;
         Type *_struct_decl = NULL;
@@ -1904,6 +1895,9 @@ static bool emit_getfield_unknownidx(jl_codectx_t &ctx,
         return true;
     }
     if (nfields == 1) {
+        if (jl_has_free_typevars(jl_field_type(stt, 0))) {
+            return false;
+        }
         (void)idx0();
         *ret = emit_getfield_knownidx(ctx, strct, 0, stt, order);
         return true;

src/codegen.cpp

@@ -933,12 +933,12 @@ static MDNode *best_tbaa(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)->layout;
+    return jl_is_immutable_datatype(t) && ((jl_datatype_t*)t)->isconcretetype;
 }
 
 static bool jl_is_pointerfree(jl_value_t* t)
 {
-    if (!jl_is_immutable_datatype(t))
+    if (!jl_is_concrete_immutable(t))
         return 0;
     const jl_datatype_layout_t *layout = ((jl_datatype_t*)t)->layout;
     return layout && layout->npointers == 0;
@@ -3033,9 +3033,9 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
                 return true;
             }
 
-            if (jl_is_datatype(utt) && utt->layout) {
+            if (jl_is_datatype(utt) && jl_struct_try_layout(utt)) {
                 ssize_t idx = jl_field_index(utt, name, 0);
-                if (idx != -1) {
+                if (idx != -1 && !jl_has_free_typevars(jl_field_type(utt, idx))) {
                     *ret = emit_getfield_knownidx(ctx, obj, idx, utt, order);
                     return true;
                 }
@@ -3063,14 +3063,16 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
             }
 
             if (jl_is_datatype(utt)) {
-                if (jl_is_structtype(utt) && utt->layout) {
+                if (jl_struct_try_layout(utt)) {
                     size_t nfields = jl_datatype_nfields(utt);
                     // integer index
                     size_t idx;
                     if (fld.constant && (idx = jl_unbox_long(fld.constant) - 1) < nfields) {
-                        // known index
-                        *ret = emit_getfield_knownidx(ctx, obj, idx, utt, order);
-                        return true;
+                        if (!jl_has_free_typevars(jl_field_type(utt, idx))) {
+                            // known index
+                            *ret = emit_getfield_knownidx(ctx, obj, idx, utt, order);
+                            return true;
+                        }
                     }
                     else {
                         // unknown index
@@ -3115,8 +3117,6 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
                 }
             }
         }
-        // TODO: attempt better codegen for approximate types, if the types
-        // and offsets of some fields are independent of parameters.
         // TODO: generic getfield func with more efficient calling convention
         return false;
     }
@@ -3155,7 +3155,7 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
         }
 
         jl_datatype_t *uty = (jl_datatype_t*)jl_unwrap_unionall(obj.typ);
-        if (jl_is_structtype(uty) && uty->layout) {
+        if (jl_is_datatype(uty) && jl_struct_try_layout(uty)) {
             ssize_t idx = -1;
             if (fld.constant && fld.typ == (jl_value_t*)jl_symbol_type) {
                 idx = jl_field_index(uty, (jl_sym_t*)fld.constant, 0);

src/datatype.c

@@ -220,27 +220,36 @@ unsigned jl_special_vector_alignment(size_t nfields, jl_value_t *t)
     return next_power_of_two(size);
 }
 
-STATIC_INLINE int jl_is_datatype_make_singleton(jl_datatype_t *d)
+STATIC_INLINE int jl_is_datatype_make_singleton(jl_datatype_t *d) JL_NOTSAFEPOINT
 {
     return (!d->name->abstract && jl_datatype_size(d) == 0 && d != jl_symbol_type && d->name != jl_array_typename &&
             d->isconcretetype && !d->name->mutabl);
 }
 
-STATIC_INLINE void jl_maybe_allocate_singleton_instance(jl_datatype_t *st)
+STATIC_INLINE void jl_maybe_allocate_singleton_instance(jl_datatype_t *st) JL_NOTSAFEPOINT
 {
     if (jl_is_datatype_make_singleton(st)) {
         // It's possible for st to already have an ->instance if it was redefined
-        if (!st->instance) {
-            jl_task_t *ct = jl_current_task;
-            st->instance = jl_gc_alloc(ct->ptls, 0, st);
-            jl_gc_wb(st, st->instance);
-        }
+        if (!st->instance)
+            st->instance = jl_gc_permobj(0, st);
     }
 }
 
+// return whether all concrete subtypes of this type have the same layout
+int jl_struct_try_layout(jl_datatype_t *dt)
+{
+    if (dt->layout)
+        return 1;
+    else if (!jl_has_fixed_layout(dt))
+        return 0;
+    jl_compute_field_offsets(dt);
+    assert(dt->layout);
+    return 1;
+}
+
 int jl_datatype_isinlinealloc(jl_datatype_t *ty, int pointerfree) JL_NOTSAFEPOINT
 {
-    if (ty->name->mayinlinealloc && ty->layout) {
+    if (ty->name->mayinlinealloc && (ty->isconcretetype || ((jl_datatype_t*)jl_unwrap_unionall(ty->name->wrapper))->layout)) { // TODO: use jl_struct_try_layout(dt) (but it is a safepoint)
         if (ty->layout->npointers > 0) {
             if (pointerfree)
                 return 0;
@@ -348,28 +357,31 @@ void jl_compute_field_offsets(jl_datatype_t *st)
     if (st->name->wrapper == NULL)
         return; // we got called too early--we'll be back
     jl_datatype_t *w = (jl_datatype_t*)jl_unwrap_unionall(st->name->wrapper);
-    assert(st->types && w->types);
-    size_t i, nfields = jl_svec_len(st->types);
-    assert(st->name->n_uninitialized <= nfields);
     if (st == w && st->layout) {
         // this check allows us to force re-computation of the layout for some types during init
         st->layout = NULL;
         st->size = 0;
         st->zeroinit = 0;
         st->has_concrete_subtype = 1;
     }
+    int isbitstype = st->isconcretetype && st->name->mayinlinealloc;
     // If layout doesn't depend on type parameters, it's stored in st->name->wrapper
     // and reused by all subtypes.
     if (w->layout) {
         st->layout = w->layout;
         st->size = w->size;
         st->zeroinit = w->zeroinit;
         st->has_concrete_subtype = w->has_concrete_subtype;
-        if (jl_is_layout_opaque(st->layout)) { // e.g. jl_array_typename
-            return;
+        if (!jl_is_layout_opaque(st->layout)) { // e.g. jl_array_typename
+            st->isbitstype = isbitstype && st->layout->npointers == 0;
+            jl_maybe_allocate_singleton_instance(st);
         }
+        return;
     }
-    else if (nfields == 0) {
+    assert(st->types && w->types);
+    size_t i, nfields = jl_svec_len(st->types);
+    assert(st->name->n_uninitialized <= nfields);
+    if (nfields == 0) {
         // if we have no fields, we can trivially skip the rest
         if (st == jl_symbol_type || st == jl_string_type) {
             // opaque layout - heap-allocated blob
@@ -404,7 +416,6 @@ void jl_compute_field_offsets(jl_datatype_t *st)
         }
     }
 
-    int isbitstype = st->isconcretetype && st->name->mayinlinealloc;
     for (i = 0; isbitstype && i < nfields; i++) {
         jl_value_t *fld = jl_field_type(st, i);
         isbitstype = jl_isbits(fld);

src/jltypes.c

@@ -223,7 +223,9 @@ int jl_has_fixed_layout(jl_datatype_t *dt)
 {
     if (dt->layout || dt->isconcretetype)
         return 1;
-    if (jl_is_tuple_type(dt))
+    if (dt->name->abstract)
+        return 0;
+    if (jl_is_tuple_type(dt) || jl_is_namedtuple_type(dt))
         return 0; // TODO: relax more?
     jl_svec_t *types = jl_get_fieldtypes(dt);
     size_t i, l = jl_svec_len(types);
@@ -242,9 +244,10 @@ int jl_type_mappable_to_c(jl_value_t *ty)
     assert(!jl_is_typevar(ty) && jl_is_type(ty));
     if (jl_is_structtype(ty)) {
         jl_datatype_t *jst = (jl_datatype_t*)ty;
-        return jst->layout || jl_has_fixed_layout(jst);
+        return jl_has_fixed_layout(jst);
     }
-    if (jl_is_tuple_type(jl_unwrap_unionall(ty)))
+    ty = jl_unwrap_unionall(ty);
+    if (jl_is_tuple_type(ty) || jl_is_namedtuple_type(ty))
         return 0; // TODO: relax some?
     return 1; // as boxed or primitive
 }
@@ -1437,7 +1440,7 @@ static jl_value_t *inst_datatype_inner(jl_datatype_t *dt, jl_svec_t *p, jl_value
     jl_gc_wb(ndt, ndt->parameters);
     ndt->types = NULL; // to be filled in below
     if (istuple) {
-        ndt->types = p;
+        ndt->types = p; // TODO: this may need to filter out certain types
     }
     else if (isnamedtuple) {
         jl_value_t *names_tup = jl_svecref(p, 0);
@@ -1463,19 +1466,16 @@ static jl_value_t *inst_datatype_inner(jl_datatype_t *dt, jl_svec_t *p, jl_value
             jl_gc_wb(ndt, ndt->types);
         }
         else {
-            ndt->types = jl_emptysvec;
+            ndt->types = jl_emptysvec; // XXX: this is essentially always false
         }
     }
-    ndt->size = 0;
-    jl_precompute_memoized_dt(ndt, cacheable);
-
-    if (jl_is_primitivetype(dt)) {
-        ndt->size = dt->size;
-        ndt->layout = dt->layout;
-        ndt->isbitstype = ndt->isconcretetype;
-    }
 
     jl_datatype_t *primarydt = ((jl_datatype_t*)jl_unwrap_unionall(tn->wrapper));
+    jl_precompute_memoized_dt(ndt, cacheable);
+    ndt->size = 0;
+    if (primarydt->layout)
+        jl_compute_field_offsets(ndt);
+
     if (istuple || isnamedtuple) {
         ndt->super = jl_any_type;
     }
@@ -1516,7 +1516,7 @@ static jl_value_t *inst_datatype_inner(jl_datatype_t *dt, jl_svec_t *p, jl_value
     // leading to incorrect layouts and data races (#40050: the A{T} should be
     // an isbitstype singleton of size 0)
     if (cacheable) {
-        if (!jl_is_primitivetype(dt) && ndt->types != NULL && ndt->isconcretetype) {
+        if (dt->layout == NULL && !jl_is_primitivetype(dt) && ndt->types != NULL && ndt->isconcretetype) {
             jl_compute_field_offsets(ndt);
         }
         jl_cache_type_(ndt);

src/julia_internal.h

@@ -388,7 +388,7 @@ STATIC_INLINE jl_gc_tracked_buffer_t *jl_gc_alloc_buf(jl_ptls_t ptls, size_t sz)
     return jl_gc_alloc(ptls, sz, (void*)jl_buff_tag);
 }
 
-STATIC_INLINE jl_value_t *jl_gc_permobj(size_t sz, void *ty)
+STATIC_INLINE jl_value_t *jl_gc_permobj(size_t sz, void *ty) JL_NOTSAFEPOINT
 {
     const size_t allocsz = sz + sizeof(jl_taggedvalue_t);
     unsigned align = (sz == 0 ? sizeof(void*) : (allocsz <= sizeof(void*) * 2 ?
@@ -539,6 +539,7 @@ jl_datatype_t *jl_mk_builtin_func(jl_datatype_t *dt, const char *name, jl_fptr_a
 int jl_obviously_unequal(jl_value_t *a, jl_value_t *b);
 JL_DLLEXPORT jl_array_t *jl_find_free_typevars(jl_value_t *v);
 int jl_has_fixed_layout(jl_datatype_t *t);
+int jl_struct_try_layout(jl_datatype_t *dt);
 int jl_type_mappable_to_c(jl_value_t *ty);
 jl_svec_t *jl_outer_unionall_vars(jl_value_t *u);
 jl_value_t *jl_type_intersection_env_s(jl_value_t *a, jl_value_t *b, jl_svec_t **penv, int *issubty);

test/compiler/codegen.jl

@@ -580,3 +580,16 @@ g40612(a, b) = a[]|a[] === b[]|b[]
 @test g40612(Union{Bool,Missing}[missing], Union{Bool,Missing}[missing])
 @test g40612(Union{Bool,Missing}[true], Union{Bool,Missing}[true])
 @test g40612(Union{Bool,Missing}[false], Union{Bool,Missing}[false])
+
+# issue #41438
+struct A41438{T}
+  x::Ptr{T}
+end
+struct B41438{T}
+  x::T
+end
+f41438(y) = y[].x
+@test A41438.body.layout != C_NULL
+@test B41438.body.layout === C_NULL
+@test f41438(Ref{A41438}(A41438(C_NULL))) === C_NULL
+@test f41438(Ref{B41438}(B41438(C_NULL))) === C_NULL