From edbae93e0265c13136276d2a30cd9ba8766b3c53 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 6 Nov 2025 16:03:37 -0800
Subject: [PATCH 1/2] fix

---
 src/tools/fuzzing/fuzzing.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/tools/fuzzing/fuzzing.cpp b/src/tools/fuzzing/fuzzing.cpp
index 02dba6d7962..a5cd11202f3 100644
--- a/src/tools/fuzzing/fuzzing.cpp
+++ b/src/tools/fuzzing/fuzzing.cpp
@@ -323,8 +323,11 @@ void TranslateToFuzzReader::pickPasses(OptimizationOptions& options) {
 
   // Prune things that error in JS if we call them (like SIMD), some of the
   // time. This alters the wasm/JS boundary quite a lot, so testing both forms
-  // is useful.
-  if (oneIn(2)) {
+  // is useful. Note that we do not do this if there is an imported module,
+  // because in that case legalization could alter the contract between the two
+  // (that is, if the first module has an i64 param, we must call it like that,
+  // and not as two i32s which we'd get after legalization).
+  if (!importedModule && oneIn(2)) {
     options.passes.push_back("legalize-and-prune-js-interface");
   }
 

From 06d84bae1515527047c153ffde71afd8e4f2f2c4 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 7 Nov 2025 15:40:53 -0800
Subject: [PATCH 2/2] Pick passes *after* setting flags, so we can see the
 flags

---
 src/tools/wasm-opt.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index ec3bafa03e7..310544c9451 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -346,15 +346,15 @@ For more on how to optimize effectively, see
   if (translateToFuzz) {
     TranslateToFuzzReader reader(
       wasm, options.extra["infile"], options.passOptions.closedWorld);
-    if (fuzzPasses) {
-      reader.pickPasses(options);
-    }
     reader.setAllowMemory(fuzzMemory);
     reader.setAllowOOB(fuzzOOB);
     reader.setPreserveImportsAndExports(fuzzPreserveImportsAndExports);
     if (!fuzzImport.empty()) {
       reader.setImportedModule(fuzzImport);
     }
+    if (fuzzPasses) {
+      reader.pickPasses(options);
+    }
     reader.build();
     if (options.passOptions.validate) {
       if (!WasmValidator().validate(wasm, options.passOptions)) {