Compare binaryen fuzz-exec to JS VMs (#1856)

The main fuzz_opt.py script compares JS VMs, and separately runs binaryen's fuzz-exec that compares the binaryen interpreter to itself (before and after opts). This PR lets us directly compare binaryen's interpreter output to JS VMs. This found a bunch of minor things we can do better on both sides, giving more fuzz coverage.

To enable this, a bunch of tiny fixes were needed:

*    Add --fuzz-exec-before which is like --fuzz-exec but just runs the code before opts are run, instead of before and after.
*    Normalize double printing (so JS and C++ print comparable things). This includes negative zero in JS, which we never printed properly til now.
*    Various improvements to how we print fuzz-exec logging - remove unuseful things, and normalize the others across JS and C++.
*    Properly legalize the wasm when --emit-js-wrapper (i.e., we will run the code from JS), and use that in the JS wrapper code.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/shell-interface.h b/src/shell-interface.h
index fc6a5897c..071cc614d 100644
--- a/src/shell-interface.h
+++ b/src/shell-interface.h
@@ -200,7 +200,7 @@ struct ShellExternalInterface : ModuleInstance::ExternalInterface {
   }
 
   void trap(const char* why) override {
-    std::cerr << "[trap " << why << "]\n";
+    std::cout << "[trap " << why << "]\n";
     throw TrapException();
   }
 };