[SIMD] wasm-ctor-eval: Fix relaxed SIMD in expressions (#7508)

The previous fix #7495 handled functions computing something with
relaxed SIMD, in which case an exception is thrown, but we also need to
handle relaxed SIMD inside a function, since wasm-ctor-eval can
partially-evaluate code. In that case we get NONCONSTANT_FLOW.

Turns out adding --kept-exports is enough to test this, as keeping the
exports around forces partial evaluation of their contents.

Author: kripken

src/tools/wasm-ctor-eval.cpp

@@ -1115,7 +1115,14 @@ EvalCtorOutcome evalCtor(EvallingModuleRunner& instance,
         break;
       } catch (NonconstantException& fail) {
         if (!quiet) {
-          std::cout << "  ...stopping due to non-constant code\n";
+          std::cout << "  ...stopping due to non-constant func\n";
+        }
+        break;
+      }
+
+      if (flow.breakTo == NONCONSTANT_FLOW) {
+        if (!quiet) {
+          std::cout << "  ...stopping due to non-constant flow\n";
         }
         break;
       }

test/lit/ctor-eval/relaxed.wast

@@ -1,5 +1,5 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
-;; RUN: wasm-ctor-eval %s --ctors=return,drop,passthrough --quiet -all -S -o - | filecheck %s
+;; RUN: wasm-ctor-eval %s --ctors=return,drop,passthrough --kept-exports=return,drop,passthrough --quiet -all -S -o - | filecheck %s
 
 ;; The relaxed SIMD operation here cannot be optimized by wasm-ctor-eval, as we
 ;; do not know how the VM that the code will run on should execute it. We can
@@ -10,6 +10,8 @@
 
  ;; CHECK:      (type $1 (func))
 
+ ;; CHECK:      (export "return" (func $return))
+
  ;; CHECK:      (export "drop" (func $drop))
 
  ;; CHECK:      (export "passthrough" (func $passthrough))