Add a fast path to isSubType (#4453)

We call this very frequently in the interpreter.

This is a 25% speedup on the benchmark in #4452

1 files changed, 8 insertions, 0 deletions

diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index 1b6313ad7..a63c66770 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -1049,6 +1049,10 @@ Type Type::get(unsigned byteSize, bool float_) {
 }
 
 bool Type::isSubType(Type left, Type right) {
+  // As an optimization, in the common case do not even construct a SubTyper.
+  if (left == right) {
+    return true;
+  }
   return SubTyper().isSubType(left, right);
 }
 
@@ -1220,6 +1224,10 @@ bool HeapType::isNominal() const {
 }
 
 bool HeapType::isSubType(HeapType left, HeapType right) {
+  // As an optimization, in the common case do not even construct a SubTyper.
+  if (left == right) {
+    return true;
+  }
   return SubTyper().isSubType(left, right);
 }