Optimize LocalCSE hash computations using a stack. NFC (#4091)

Before, we'd compute the hash of a child, then store that in a map, then
the parent would find the child's hash in the map using the pointer to the
child. But as we do a simple postorder walk, we can use a stack, and
avoid hashing the child pointers.

This makes it 10% faster or so.

1 files changed, 35 insertions, 0 deletions

diff --git a/src/ir/properties.h b/src/ir/properties.h
index 4909dfbc8..dbf2715ef 100644
--- a/src/ir/properties.h
+++ b/src/ir/properties.h
@@ -310,6 +310,41 @@ inline Expression* getFallthrough(Expression* curr,
   }
 }
 
+inline Index getNumChildren(Expression* curr) {
+  Index ret = 0;
+
+#define DELEGATE_ID curr->_id
+
+#define DELEGATE_START(id)                                                     \
+  auto* cast = curr->cast<id>();                                               \
+  WASM_UNUSED(cast);
+
+#define DELEGATE_GET_FIELD(id, name) cast->name
+
+#define DELEGATE_FIELD_CHILD(id, name) ret++;
+
+#define DELEGATE_FIELD_OPTIONAL_CHILD(id, name)                                \
+  if (cast->name) {                                                            \
+    ret++;                                                                     \
+  }
+
+#define DELEGATE_FIELD_INT(id, name)
+#define DELEGATE_FIELD_INT_ARRAY(id, name)
+#define DELEGATE_FIELD_LITERAL(id, name)
+#define DELEGATE_FIELD_NAME(id, name)
+#define DELEGATE_FIELD_NAME_VECTOR(id, name)
+#define DELEGATE_FIELD_SCOPE_NAME_DEF(id, name)
+#define DELEGATE_FIELD_SCOPE_NAME_USE(id, name)
+#define DELEGATE_FIELD_SCOPE_NAME_USE_VECTOR(id, name)
+#define DELEGATE_FIELD_SIGNATURE(id, name)
+#define DELEGATE_FIELD_TYPE(id, name)
+#define DELEGATE_FIELD_ADDRESS(id, name)
+
+#include "wasm-delegations-fields.def"
+
+  return ret;
+}
+
 // Returns whether the resulting value here must fall through without being
 // modified. For example, a tee always does so. That is, this returns false if
 // and only if the return value may have some computation performed on it to