[Wasm GC] rtt.fresh_sub (#3936)

This is the same as rtt.sub, but creates a "new" rtt each time. See

https://docs.google.com/document/d/1DklC3qVuOdLHSXB5UXghM_syCh-4cMinQ50ICiXnK3Q/edit#

The old Literal implementation of rtts becomes a little more complex here,
as it was designed for the original spec where only structure matters. It may
be worth a complete redesign there, but for now as the spec is in flux I think
the approach here is good enough.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 70a593bec..3200e77a7 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -1993,7 +1993,8 @@ void BinaryInstWriter::visitRttCanon(RttCanon* curr) {
 }
 
 void BinaryInstWriter::visitRttSub(RttSub* curr) {
-  o << int8_t(BinaryConsts::GCPrefix) << U32LEB(BinaryConsts::RttSub);
+  o << int8_t(BinaryConsts::GCPrefix);
+  o << U32LEB(curr->fresh ? BinaryConsts::RttFreshSub : BinaryConsts::RttSub);
   parent.writeIndexedHeapType(curr->type.getRtt().heapType);
 }