NaN fuzzing improvements (#1913)

* make DE_NAN avoid creating nan literals in the first place
* add a reducer option `--denan` to not introduce nans in destructive reduction
* add a `Literal::isNaN()` method
* also remove the default exception logging from the fuzzer js glue, which is a source of non-useful VM differences (like nan nondeterminism)
* added an option `--no-fuzz-nans` to make it easy to avoid nans when fuzzing (without hacking the source and recompiling).

Background: trying to get fuzzing on jsc working despite this open issue: https://bugs.webkit.org/show_bug.cgi?id=175691

1 files changed, 11 insertions, 0 deletions

diff --git a/src/wasm/literal.cpp b/src/wasm/literal.cpp
index 5f358fa6b..4ec256aae 100644
--- a/src/wasm/literal.cpp
+++ b/src/wasm/literal.cpp
@@ -144,6 +144,17 @@ bool Literal::operator!=(const Literal& other) const {
   return !(*this == other);
 }
 
+bool Literal::isNaN() {
+  if (type == Type::f32 && std::isnan(getf32())) {
+    return true;
+  }
+  if (type == Type::f64 && std::isnan(getf64())) {
+    return true;
+  }
+  // TODO: SIMD?
+  return false;
+}
+
 uint32_t Literal::NaNPayload(float f) {
   assert(std::isnan(f) && "expected a NaN");
   // SEEEEEEE EFFFFFFF FFFFFFFF FFFFFFFF