[Strings] wasm-ctor-eval: Stop on seeing a string view, which we cannot precompute (#6561)

Author: kripken

src/tools/wasm-ctor-eval.cpp

@@ -93,6 +93,14 @@ class EvallingModuleRunner : public ModuleRunnerBase<EvallingModuleRunner> {
     //       serialize them.)
     throw FailToEvalException("table.set: TODO");
   }
+
+  Flow visitStringAs(StringAs* curr) {
+    // TODO: It is not clear how we can handle string.as, since it can lead to
+    //       us needing string_views in globals, but string.as is not a constant
+    //       instruction, so we cannot generate such globals atm. Perhaps we
+    //       could generate them in the start function?
+    throw FailToEvalException("string.as: TODO");
+  }
 };
 
 // Build an artificial `env` module based on a module's imports, so that the

test/lit/ctor-eval/string_view.wast

@@ -0,0 +1,32 @@
+;; 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=test --kept-exports=test --quiet -all -S -o - | filecheck %s
+
+;; We cannot precompute string views atm.
+
+(module
+ ;; CHECK:      (type $0 (func))
+
+ ;; CHECK:      (export "test" (func $test))
+ (export "test" (func $test))
+
+ ;; CHECK:      (func $test (type $0)
+ ;; CHECK-NEXT:  (local $temp-view (ref stringview_wtf16))
+ ;; CHECK-NEXT:  (local.set $temp-view
+ ;; CHECK-NEXT:   (string.as_wtf16
+ ;; CHECK-NEXT:    (string.const "test")
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $test
+  (local $temp-view (ref stringview_wtf16))
+  ;; This code will remain: we cannot precompute a value that we store in a
+  ;; global, as string.as is not a constant instruction that can appear in a
+  ;; global.
+  (local.set $temp-view
+   (string.as_wtf16
+    (string.const "test")
+   )
+  )
+ )
+)
+