[Custom Descriptors] Support in Precompute (#7678)

Now that we support interpretation of ref.get_desc and the descriptor
casts, test that Precompute handles them properly.

Author: tlively

scripts/test/fuzzing.py

@@ -123,6 +123,7 @@
     'type-merging-desc.wast',
     'heap2local-desc.wast',
     'minimize-rec-groups-desc.wast',
+    'precompute-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/Precompute.cpp

@@ -240,12 +240,6 @@ class PrecomputingExpressionRunner
     // string.encode_wtf16_array anyhow.)
     return Flow(NONCONSTANT_FLOW);
   }
-
-  Flow visitRefGetDesc(RefGetDesc* curr) {
-    // TODO: Implement this. For now, return nonconstant so that we skip it and
-    //       do not error.
-    return Flow(NONCONSTANT_FLOW);
-  }
 };
 
 struct Precompute

test/lit/passes/precompute-desc.wast

@@ -0,0 +1,85 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+
+;; RUN: wasm-opt %s --remove-unused-names --precompute-propagate --fuzz-exec -all -S -o - \
+;; RUN:   | filecheck %s
+
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $struct (descriptor $desc (struct)))
+    (type $struct (descriptor $desc (struct)))
+    ;; CHECK:       (type $desc (describes $struct (struct)))
+    (type $desc (describes $struct (struct)))
+  )
+
+  ;; CHECK:      (global $desc (ref (exact $desc)) (struct.new_default $desc))
+  (global $desc (ref (exact $desc)) (struct.new $desc))
+  ;; CHECK:      (global $struct (ref $struct) (struct.new_default $struct
+  ;; CHECK-NEXT:  (global.get $desc)
+  ;; CHECK-NEXT: ))
+  (global $struct (ref $struct) (struct.new $struct (global.get $desc)))
+
+  ;; CHECK:      (func $eq-descs (type $0) (result i32)
+  ;; CHECK-NEXT:  (i32.const 1)
+  ;; CHECK-NEXT: )
+  (func $eq-descs (result i32)
+    (ref.eq
+      (ref.get_desc $struct
+        (struct.new $struct
+          (global.get $desc)
+        )
+      )
+      (global.get $desc)
+    )
+  )
+
+  ;; CHECK:      (func $different-descs (type $0) (result i32)
+  ;; CHECK-NEXT:  (i32.const 0)
+  ;; CHECK-NEXT: )
+  (func $different-descs (result i32)
+    (ref.eq
+      (ref.get_desc $struct
+        (struct.new $struct
+          (struct.new $desc)
+        )
+      )
+      (global.get $desc)
+    )
+  )
+
+  ;; CHECK:      (func $br-on-cast-desc (type $0) (result i32)
+  ;; CHECK-NEXT:  (i32.const 1)
+  ;; CHECK-NEXT: )
+  (func $br-on-cast-desc (result i32)
+    (ref.eq
+      (block $l (result eqref)
+        (drop
+          (br_on_cast_desc $l eqref (ref $struct)
+            (global.get $struct)
+            (global.get $desc)
+          )
+        )
+        (ref.null none)
+      )
+      (global.get $struct)
+    )
+  )
+
+  ;; CHECK:      (func $br-on-cast-desc-fail (type $0) (result i32)
+  ;; CHECK-NEXT:  (i32.const 0)
+  ;; CHECK-NEXT: )
+  (func $br-on-cast-desc-fail (result i32)
+    (ref.eq
+      (block $l (result eqref)
+        (drop
+          (br_on_cast_desc_fail $l eqref (ref $struct)
+            (global.get $struct)
+            (global.get $desc)
+          )
+        )
+        (ref.null none)
+      )
+      (global.get $struct)
+    )
+  )
+)