Fix ivar offset calculation with alignment.

When upgrading legacy ivars, pick a sensible guess.
When calculating ivar offsets, use the supplied alignment.

ivar.c

@@ -5,9 +5,9 @@
 #include "objc/runtime.h"
 #include "objc/objc-arc.h"
 #include "class.h"
-#include "ivar.h"
 #include "visibility.h"
 #include "gc_ops.h"
+#include "legacy.h"
 
 ptrdiff_t objc_alignof_type(const char *);
 ptrdiff_t objc_sizeof_type(const char *);
@@ -78,18 +78,14 @@ PRIVATE void objc_compute_ivar_offsets(Class class)
 				// We only need to do the realignment for things that are
 				// bigger than a pointer, and we don't need to do it in GC mode
 				// where we don't add any extra padding.
-				if (!isGCEnabled && (ivar_size > sizeof(void*)))
+				if (!isGCEnabled && (ivar->align > __alignof__(void*)))
 				{
 					long offset = ivar_start + *ivar->offset + sizeof(intptr_t);
-					// For now, assume that nothing needs to be more than 16-byte aligned.
-					// This is not correct for AVX vectors, but we probably
-					// can't do anything about that for now (as malloc is only
-					// giving us 16-byte aligned memory)
-					long fudge = 16 - (offset % 16);
+					long fudge = ivar->align - (offset % ivar->align);
 					*ivar->offset += fudge;
 					class->instance_size += fudge;
 					cumulative_fudge += fudge;
-					assert((ivar_start + *ivar->offset + sizeof(intptr_t)) % 16 == 0);
+					assert((ivar_start + *ivar->offset + sizeof(intptr_t)) % ivar->align == 0);
 				}
 				*ivar->offset += ivar_start;
 			}

legacy.c

@@ -38,8 +38,15 @@ static struct objc_ivar_list *upgradeIvarList(struct legacy_gnustep_objc_class *
 	n->count = l->count;
 	for (int i=0 ; i<l->count ; i++)
 	{
+		int nextOffset = (i+1 < l->count) ? l->ivar_list[i+1].offset : cls->instance_size;
+		if (nextOffset < 0)
+		{
+			nextOffset = -nextOffset;
+		}
+		const char *type = l->ivar_list[i].type;
+		int size = nextOffset - l->ivar_list[i].offset;
 		n->ivar_list[i].name = l->ivar_list[i].name;
-		n->ivar_list[i].type = l->ivar_list[i].type;
+		n->ivar_list[i].type = type;
 		if (objc_test_class_flag_legacy(cls, objc_class_flag_new_abi))
 		{
 			n->ivar_list[i].offset = cls->ivar_offsets[i];
@@ -48,8 +55,11 @@ static struct objc_ivar_list *upgradeIvarList(struct legacy_gnustep_objc_class *
 		{
 			n->ivar_list[i].offset = &l->ivar_list[i].offset;
 		}
-		const char *type = l->ivar_list[i].type;
 		n->ivar_list[i].align = ((type == NULL) || type[0] == 0) ? __alignof__(void*) : objc_alignof_type(type);
+		if (type[0] == '\0')
+		{
+			n->ivar_list[i].align = size;
+		}
 		ivarSetOwnership(&n->ivar_list[i], ownershipForIvar(cls, i));
 	}
 	return n;