[Stack Switching] Fix ctor-eval handling of unhandled resumes (#8556)

The logic for this was in the wrong place. It should be where we handle
a non-constant operation, as it is something that stops us and prevents
precomputing. (Before, it was down by a branch, but a branch is a very
special case in which we can ignore the branch, because we know it
goes to the toplevel block, skipping what is after it.)

Fixes #8553

Author: kripken

src/tools/wasm-ctor-eval.cpp

@@ -1173,6 +1173,14 @@ EvalCtorOutcome evalCtor(EvallingModuleRunner& instance,
           std::cout << "  ...stopping due to non-constant flow\n";
         }
         break;
+      } else if (flow.suspendTag) {
+        // A suspend reached the exit of the function, so it is unhandled in
+        // it. TODO: We could support the case of the calling function
+        // handling it.
+        if (!quiet) {
+          std::cout << "  ...stopping due to unhandled suspend\n";
+        }
+        break;
       }
 
       if (flow.breakTo == RETURN_CALL_FLOW) {
@@ -1235,18 +1243,8 @@ EvalCtorOutcome evalCtor(EvallingModuleRunner& instance,
       results = flow.values;
 
       if (flow.breaking()) {
-        if (flow.suspendTag) {
-          // A suspend reached the exit of the function, so it is unhandled in
-          // it. TODO: We could support the case of the calling function
-          // handling it.
-          if (!quiet) {
-            std::cout << "  ...stopping due to unhandled suspend\n";
-          }
-          return EvalCtorOutcome();
-        }
-
         // We are returning out of the function (either via a return, or via a
-        // break to |block|, which has the same outcome. That means we don't
+        // break to |block|, which has the same outcome). That means we don't
         // need to execute any more lines, and can consider them to be
         // executed.
         if (!quiet) {

test/lit/ctor-eval/cont-unhandled.wast

@@ -0,0 +1,54 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: foreach %s %t wasm-ctor-eval --ctors=ctor --kept-exports=ctor,main --quiet -all -S -o - | filecheck %s
+
+;; Test that we properly stop precomputing at an unhandled suspend. $ctor will
+;; decrement $global, and we apply that to the global. We should remove that
+;; decrement from the export, which will only contain the suspend that we
+;; stopped at. (After that, $main will print the same value, 99, as if we didn't
+;; precompute.)
+
+(module
+ ;; CHECK:      (type $none-none (func))
+
+ ;; CHECK:      (type $i32-none (func (param i32)))
+ (type $i32-none (func (param i32)))
+ (type $none-none (func))
+
+ ;; CHECK:      (import "fuzzing-support" "log-i32" (func $log (type $i32-none) (param i32)))
+ (import "fuzzing-support" "log-i32" (func $log (type $i32-none)))
+
+ ;; CHECK:      (global $global (mut i32) (i32.const 99))
+ (global $global (mut i32) (i32.const 100))
+
+ ;; CHECK:      (tag $tag (type $none-none))
+ (tag $tag (type $none-none))
+
+ (export "ctor" (func $ctor))
+ ;; CHECK:      (export "ctor" (func $ctor_3))
+
+ ;; CHECK:      (export "main" (func $main))
+ (export "main" (func $main))
+
+ (func $ctor (type $none-none)
+  (global.set $global
+   (i32.sub
+    (global.get $global)
+    (i32.const 1)
+   )
+  )
+  (suspend $tag)
+ )
+
+ ;; CHECK:      (func $main (type $none-none)
+ ;; CHECK-NEXT:  (call $log
+ ;; CHECK-NEXT:   (global.get $global)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $main (type $none-none)
+  (global.get $global)
+  (call $log)
+ )
+)
+;; CHECK:      (func $ctor_3 (type $none-none)
+;; CHECK-NEXT:  (suspend $tag)
+;; CHECK-NEXT: )