[Custom Descriptors] Update TypeMerging (#7666)

Update type merging to consider the existence of descriptor and
described types as part of the top-level structure of a type. This
prevents types with and without descriptors from incorrectly being
merged together.

Author: tlively

scripts/test/fuzzing.py

@@ -120,6 +120,7 @@
     'struct.new-desc.wast',
     'remove-unused-types-descriptors.wast',
     'unsubtyping-desc.wast',
+    'type-merging-desc.wast',
     # TODO: fix split_wast() on tricky escaping situations like a string ending
     #       in \\" (the " is not escaped - there is an escaped \ before it)
     'string-lifting-section.wast',

src/passes/TypeMerging.cpp

@@ -591,6 +591,13 @@ bool shapeEq(HeapType a, HeapType b) {
   if (a.isShared() != b.isShared()) {
     return false;
   }
+  // Ignore supertype because we want to be able to merge into parents.
+  if (!!a.getDescriptorType() != !!b.getDescriptorType()) {
+    return false;
+  }
+  if (!!a.getDescribedType() != !!b.getDescribedType()) {
+    return false;
+  }
   auto aKind = a.getKind();
   auto bKind = b.getKind();
   if (aKind != bKind) {
@@ -614,6 +621,9 @@ bool shapeEq(HeapType a, HeapType b) {
 size_t shapeHash(HeapType a) {
   size_t digest = hash(a.isOpen());
   rehash(digest, a.isShared());
+  // Ignore supertype because we want to be able to merge into parents.
+  rehash(digest, !!a.getDescriptorType());
+  rehash(digest, !!a.getDescribedType());
   auto kind = a.getKind();
   rehash(digest, kind);
   switch (kind) {

test/lit/passes/type-merging-desc.wast

@@ -0,0 +1,75 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: foreach %s %t wasm-opt -all --closed-world --preserve-type-order \
+;; RUN:     --type-merging --remove-unused-types -S -o - | filecheck %s
+
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $A (struct))
+    (type $A (struct))
+    ;; CHECK:       (type $B (descriptor $C (struct)))
+    (type $B (descriptor $C (struct)))
+    ;; CHECK:       (type $C (describes $B (struct)))
+    (type $C (describes $B (struct)))
+  )
+
+  ;; The types have different shapes and should not be merged.
+  ;; CHECK:      (global $A (ref null $A) (ref.null none))
+  (global $A (ref null $A) (ref.null none))
+  ;; CHECK:      (global $B (ref null $B) (ref.null none))
+  (global $B (ref null $B) (ref.null none))
+  ;; CHECK:      (global $C (ref null $C) (ref.null none))
+  (global $C (ref null $C) (ref.null none))
+)
+
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $A (descriptor $A.desc (struct (field i32))))
+    (type $A (descriptor $A.desc (struct (field i32))))
+    ;; CHECK:       (type $A.desc (describes $A (struct)))
+    (type $A.desc (describes $A (struct)))
+
+    ;; CHECK:       (type $B (descriptor $B.desc (struct (field f64))))
+    (type $B (descriptor $B.desc (struct (field f64))))
+    ;; CHECK:       (type $B.desc (describes $B (struct)))
+    (type $B.desc (describes $B (struct)))
+  )
+
+  ;; $A and $B have different shapes and should not be merged, so therefore
+  ;; $A.desc and $B.desc should not be merged.
+  ;; CHECK:      (global $A (ref null $A) (ref.null none))
+  (global $A (ref null $A) (ref.null none))
+  ;; CHECK:      (global $A.desc (ref null $A.desc) (ref.null none))
+  (global $A.desc (ref null $A.desc) (ref.null none))
+  ;; CHECK:      (global $B (ref null $B) (ref.null none))
+  (global $B (ref null $B) (ref.null none))
+  ;; CHECK:      (global $B.desc (ref null $A.desc) (ref.null none))
+  (global $B.desc (ref null $B.desc) (ref.null none))
+)
+
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $A (descriptor $A.desc (struct)))
+    (type $A (descriptor $A.desc (struct)))
+    ;; CHECK:       (type $A.desc (describes $A (struct (field i32))))
+    (type $A.desc (describes $A (struct (field i32))))
+
+    ;; CHECK:       (type $B (descriptor $B.desc (struct)))
+    (type $B (descriptor $B.desc (struct)))
+    ;; CHECK:       (type $B.desc (describes $B (struct (field f64))))
+    (type $B.desc (describes $B (struct (field f64))))
+  )
+
+  ;; $A.desc and $B.desc have different shapes and should not be merged, so
+  ;; therefore $A and $B should not be merged.
+  ;; CHECK:      (global $A (ref null $A) (ref.null none))
+  (global $A (ref null $A) (ref.null none))
+  ;; CHECK:      (global $A.desc (ref null $A.desc) (ref.null none))
+  (global $A.desc (ref null $A.desc) (ref.null none))
+  ;; CHECK:      (global $B (ref null $A) (ref.null none))
+  (global $B (ref null $B) (ref.null none))
+  ;; CHECK:      (global $B.desc (ref null $B.desc) (ref.null none))
+  (global $B.desc (ref null $B.desc) (ref.null none))
+)