Fix TypeRefining-GUFA on unreachable StructCmpxchg

src/ir/possible-contents.cpp

@@ -1776,6 +1776,7 @@ void TNHOracle::scan(Function* func,
     void visitStructCmpxchg(StructCmpxchg* curr) {
       notePossibleTrap(curr->ref);
     }
+    // TODO: visitStructWait
     void visitArrayGet(ArrayGet* curr) { notePossibleTrap(curr->ref); }
     void visitArraySet(ArraySet* curr) { notePossibleTrap(curr->ref); }
     void visitArrayLoad(ArrayLoad* curr) { notePossibleTrap(curr->ref); }

src/ir/struct-utils.h

@@ -287,6 +287,8 @@ struct StructScanner : public WalkerPass<PostWalker<SubType>> {
     noteExpressionOrCopy(curr->replacement, type, index, info);
   }
 
+  // TODO: visitStructWait
+
   void visitRefCast(RefCast* curr) {
     if (curr->desc) {
       // We may try to read a descriptor from anything arriving in |curr->ref|,

src/passes/GlobalTypeOptimization.cpp

@@ -838,6 +838,8 @@ struct GlobalTypeOptimization : public Pass {
         assert(newIndex != RemovedField);
         curr->index = newIndex;
       }
+
+      // TODO: visitStructWait
     };
 
     PassRunner runner(getPassRunner());

src/passes/TypeRefining.cpp

@@ -551,7 +551,12 @@ struct TypeRefining : public Pass {
       }
 
       void visitStructCmpxchg(StructCmpxchg* curr) {
-        if (curr->type == Type::unreachable) {
+        if (curr->ref->type == Type::unreachable) {
+          // Ignore unreachable code. Note that we check curr->ref, not curr,
+          // as curr may be unreachable because of another operand than the ref
+          // and the replacement value (the expected value may be the
+          // unreachable one). In that case, the replacement must still validate
+          // as if it were written, so we must fix it up below.
           return;
         }
         auto type = curr->ref->type.getHeapType();
@@ -563,6 +568,8 @@ struct TypeRefining : public Pass {
         curr->replacement = fixType(curr->replacement, fieldType);
       }
 
+      // TODO: visitStructWait
+
       bool refinalize = false;
 
       // Fix up a given value so it fits into the type the location it is

test/lit/passes/type-refining-gufa-rmw.wast

@@ -415,3 +415,62 @@
   )
  )
 )
+
+(module
+ ;; NRML:      (type $struct (sub (struct (field (mut (ref null $struct))))))
+ ;; GUFA:      (rec
+ ;; GUFA-NEXT:  (type $struct (sub (struct (field (mut nullref)))))
+ (type $struct (sub (struct (field (mut (ref null $struct))))))
+
+ ;; NRML:      (type $1 (func (param (ref null $struct))))
+
+ ;; NRML:      (func $test (type $1) (param $struct (ref null $struct))
+ ;; NRML-NEXT:  (drop
+ ;; NRML-NEXT:   (struct.new_default $struct)
+ ;; NRML-NEXT:  )
+ ;; NRML-NEXT:  (drop
+ ;; NRML-NEXT:   (struct.atomic.rmw.cmpxchg acqrel acqrel $struct 0
+ ;; NRML-NEXT:    (local.get $struct)
+ ;; NRML-NEXT:    (unreachable)
+ ;; NRML-NEXT:    (local.get $struct)
+ ;; NRML-NEXT:   )
+ ;; NRML-NEXT:  )
+ ;; NRML-NEXT: )
+ ;; GUFA:       (type $1 (func (param (ref null $struct))))
+
+ ;; GUFA:      (func $test (type $1) (param $struct (ref null $struct))
+ ;; GUFA-NEXT:  (drop
+ ;; GUFA-NEXT:   (struct.new_default $struct)
+ ;; GUFA-NEXT:  )
+ ;; GUFA-NEXT:  (drop
+ ;; GUFA-NEXT:   (struct.atomic.rmw.cmpxchg acqrel acqrel $struct 0
+ ;; GUFA-NEXT:    (local.get $struct)
+ ;; GUFA-NEXT:    (unreachable)
+ ;; GUFA-NEXT:    (block (result nullref)
+ ;; GUFA-NEXT:     (drop
+ ;; GUFA-NEXT:      (local.get $struct)
+ ;; GUFA-NEXT:     )
+ ;; GUFA-NEXT:     (ref.null none)
+ ;; GUFA-NEXT:    )
+ ;; GUFA-NEXT:   )
+ ;; GUFA-NEXT:  )
+ ;; GUFA-NEXT: )
+ (func $test (param $struct (ref null $struct))
+  ;; Use the type, writing only nulls.
+  (drop
+   (struct.new_default $struct)
+  )
+  ;; An unreachable cmpxchg, but where the ref and value are not unreachable.
+  ;; The value must still validate as if it were written, so we will fix it up
+  ;; with a null, as the field is refined to a null (in GUFA mode, which
+  ;; does that refining).
+  (drop
+   (struct.atomic.rmw.cmpxchg acqrel acqrel $struct 0
+    (local.get $struct)
+    (unreachable)
+    (local.get $struct)
+   )
+  )
+ )
+)
+