Make jl_datatype_size reflect non-padded field size

Padding is then added when creating the struct layout, but otherwise
the memory layout should be unchanged. This is an alternative to
the proposal in #46260. LLVM size and julia size should now be
aligned.

src/datatype.c

@@ -475,11 +475,14 @@ void jl_compute_field_offsets(jl_datatype_t *st)
                         zeroinit = ((jl_datatype_t*)fld)->zeroinit;
                     npointers += fld_npointers;
                 }
+                desc[i].size = fsz;
+                fsz = LLT_ALIGN(fsz, al);
             }
             else {
                 fsz = sizeof(void*);
                 if (fsz > MAX_ALIGN)
                     fsz = MAX_ALIGN;
+                desc[i].size = fsz;
                 al = fsz;
                 desc[i].isptr = 1;
                 zeroinit = 1;
@@ -503,7 +506,6 @@ void jl_compute_field_offsets(jl_datatype_t *st)
             }
             homogeneous &= firstty == fld;
             desc[i].offset = sz;
-            desc[i].size = fsz;
             if (__unlikely(max_offset - sz < fsz))
                 throw_ovf(should_malloc, desc, st, sz);
             sz += fsz;
@@ -525,9 +527,7 @@ void jl_compute_field_offsets(jl_datatype_t *st)
             if (al > alignm)
                 alignm = al;
         }
-        st->size = LLT_ALIGN(sz, alignm);
-        if (st->size > sz)
-            haspadding = 1;
+        st->size = sz;
         if (should_malloc && npointers)
             pointers = (uint32_t*)malloc_s(npointers * sizeof(uint32_t));
         else
@@ -1470,6 +1470,7 @@ static inline void memassign_safe(int hasptr, jl_value_t *parent, char *dst, con
         memmove_refs((void**)dst, (void**)src, nptr);
         jl_gc_multi_wb(parent, src);
         src = (jl_value_t*)((char*)src + nptr * sizeof(void*));
+        dst += nptr * sizeof(void*);
         nb -= nptr * sizeof(void*);
     }
     else {