Update RMW fields indices in GTO (#8474)

When GTO removes a struct field, RMW operations on later fields need to
have their field indices updated.

Author: tlively

src/passes/GlobalTypeOptimization.cpp

@@ -660,6 +660,28 @@ struct GlobalTypeOptimization : public Pass {
         curr->index = newIndex;
       }
 
+      void visitStructRMW(StructRMW* curr) {
+        if (curr->ref->type == Type::unreachable) {
+          return;
+        }
+
+        auto newIndex = getNewIndex(curr->ref->type.getHeapType(), curr->index);
+        // We must not remove a field that is read from.
+        assert(newIndex != RemovedField);
+        curr->index = newIndex;
+      }
+
+      void visitStructCmpxchg(StructCmpxchg* curr) {
+        if (curr->ref->type == Type::unreachable) {
+          return;
+        }
+
+        auto newIndex = getNewIndex(curr->ref->type.getHeapType(), curr->index);
+        // We must not remove a field that is read from.
+        assert(newIndex != RemovedField);
+        curr->index = newIndex;
+      }
+
       void visitFunction(Function* curr) {
         if (needEHFixups) {
           EHUtils::handleBlockNestedPops(curr, *getModule());

test/lit/passes/gto-removals-rmw.wast

@@ -74,3 +74,47 @@
     )
   )
 )
+
+;; When a field is removed, indexes in RMW and Cmpxchg should be updated.
+(module
+  ;; GTO should remove the first field because it is never read. The second
+  ;; field will then be shifted from index 1 to 0.
+  ;; CHECK:      (rec
+  ;; CHECK-NEXT:  (type $struct (shared (struct (field (mut i32)))))
+  (type $struct (shared (struct (field (mut i64)) (field (mut i32)))))
+
+  ;; CHECK:       (type $1 (func (param (ref $struct))))
+
+  ;; CHECK:      (func $use-field (type $1) (param $ref (ref $struct))
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (struct.atomic.rmw.and $struct 0
+  ;; CHECK-NEXT:    (local.get $ref)
+  ;; CHECK-NEXT:    (i32.const 1)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (struct.atomic.rmw.cmpxchg $struct 0
+  ;; CHECK-NEXT:    (local.get $ref)
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 1)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $use-field (param $ref (ref $struct))
+    ;; Use field 1 with an atomic RMW.
+    (drop
+      (struct.atomic.rmw.and $struct 1
+        (local.get $ref)
+        (i32.const 1)
+      )
+    )
+    ;; Use field 1 with an atomic Cmpxchg.
+    (drop
+      (struct.atomic.rmw.cmpxchg $struct 1
+        (local.get $ref)
+        (i32.const 0)
+        (i32.const 1)
+      )
+    )
+  )
+)