[Stack Switching] Fix the effects of ContBind (#7850)

It alters global state (modifies the input continuation).

Author: kripken

src/ir/effects.h

@@ -1107,6 +1107,12 @@ class EffectAnalyzer {
     void visitContBind(ContBind* curr) {
       // traps when curr->cont is null ref.
       parent.implicitTrap = true;
+
+      // The input continuation is modified, as it will trap if resumed. This is
+      // a globally-noticeable effect, which we model as a call for now, but we
+      // could in theory use something more refined here (|modifiesContinuation|
+      // perhaps, to parallel |writesMemory| etc.).
+      parent.calls = true;
     }
     void visitSuspend(Suspend* curr) {
       // Similar to resume/call: Suspending means that we execute arbitrary

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

@@ -9,6 +9,13 @@
  ;; CHECK:      (type $cont (cont $func))
  (type $cont (cont $func))
 
+  ;; CHECK:      (type $func-i32 (func (param i32)))
+  (type $func-i32 (func (param i32)))
+  ;; CHECK:      (type $cont-i32 (cont $func-i32))
+  (type $cont-i32 (cont $func-i32))
+
+ ;; CHECK:      (type $4 (func (param (ref $cont-i32))))
+
  ;; CHECK:      (elem declare func $cont.new)
 
  ;; CHECK:      (func $cont.new (type $func)
@@ -36,5 +43,37 @@
    )
   )
  )
+
+ ;; CHECK:      (func $cont.bind (type $4) (param $cont-i32 (ref $cont-i32))
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (cont.bind $cont-i32 $cont
+ ;; CHECK-NEXT:    (i32.const 42)
+ ;; CHECK-NEXT:    (local.get $cont-i32)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (cont.bind $cont-i32 $cont
+ ;; CHECK-NEXT:    (i32.const 42)
+ ;; CHECK-NEXT:    (local.get $cont-i32)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $cont.bind (param $cont-i32 (ref $cont-i32))
+  ;; We cannot optimize here: Each of these has a side effect of modifying the
+  ;; continuation they were given, as it will trap if resumed, and in fact the
+  ;; second cont.bind here should trap, which we should not remove.
+  (drop
+   (cont.bind $cont-i32 $cont
+    (i32.const 42)
+    (local.get $cont-i32)
+   )
+  )
+  (drop
+   (cont.bind $cont-i32 $cont
+    (i32.const 42)
+    (local.get $cont-i32)
+   )
+  )
+ )
 )