[Stack Switching] Mark ContNew as generative (#7849)

Each `cont.new` generates a new continuation, so we cannot e.g.
LocalCSE them.

Author: kripken

scripts/test/fuzzing.py

@@ -109,6 +109,7 @@
     'O3_stack-switching.wast',
     'coalesce-locals-stack-switching.wast',
     'dce-stack-switching.wast',
+    'local-cse-cont.wast',
     'precompute-stack-switching.wast',
     'unsubtyping-stack-switching.wast',
     'vacuum-stack-switching.wast',

src/ir/properties.cpp

@@ -38,6 +38,7 @@ struct GenerativityScanner : public PostWalker<GenerativityScanner> {
   void visitArrayNewData(ArrayNewData* curr) { generative = true; }
   void visitArrayNewElem(ArrayNewElem* curr) { generative = true; }
   void visitArrayNewFixed(ArrayNewFixed* curr) { generative = true; }
+  void visitContNew(ContNew* curr) { generative = true; }
 };
 
 } // anonymous namespace

test/lit/passes/local-cse-cont.wast

@@ -0,0 +1,40 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; NOTE: This test was ported using port_passes_tests_to_lit.py and could be cleaned up.
+
+;; RUN: foreach %s %t wasm-opt --local-cse -all -S -o - | filecheck %s
+
+(module
+ ;; CHECK:      (type $func (func))
+ (type $func (func))
+ ;; CHECK:      (type $cont (cont $func))
+ (type $cont (cont $func))
+
+ ;; CHECK:      (elem declare func $cont.new)
+
+ ;; CHECK:      (func $cont.new (type $func)
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (cont.new $cont
+ ;; CHECK-NEXT:    (ref.func $cont.new)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (cont.new $cont
+ ;; CHECK-NEXT:    (ref.func $cont.new)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $cont.new (type $func)
+  ;; We cannot CSE here, as each of these emits a unique continuation.
+  (drop
+   (cont.new $cont
+    (ref.func $cont.new)
+   )
+  )
+  (drop
+   (cont.new $cont
+    (ref.func $cont.new)
+   )
+  )
+ )
+)
+