Typed continuations: resume instructions (#6083)

This PR is part of a series that adds basic support for the [typed continuations proposal](https://github.com/wasmfx/specfx).

This particular PR adds support for the `resume` instruction. The most notable missing feature is validation, which is not implemented, yet.

1 files changed, 50 insertions, 0 deletions

diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index ad44acda4..06e9de148 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -17,6 +17,7 @@
 #include "wasm.h"
 #include "ir/branch-utils.h"
 #include "wasm-traversal.h"
+#include "wasm-type.h"
 
 namespace wasm {
 
@@ -1350,6 +1351,55 @@ void StringSliceIter::finalize() {
   }
 }
 
+static void populateResumeSentTypes(Resume* curr, Module* wasm) {
+  if (!wasm) {
+    return;
+  }
+
+  const Signature& contSig =
+    curr->contType.getContinuation().type.getSignature();
+
+  // Let $tag be a tag with type [tgp*] -> [tgr*]. Let $ct be a continuation
+  // type (cont $ft), where $ft is [ctp*] -> [ctr*]. Then an instruction (resume
+  // $ct ... (tag $tag $block) ... ) causes $block to receive values of the
+  // following types when suspending to $tag: tgp* (ref $ct') where ct' = (cont
+  // $ft') and ft' = [tgr*] -> [ctr*].
+  //
+  auto& ctrs = contSig.results;
+  curr->sentTypes.clear();
+  curr->sentTypes.resize(curr->handlerTags.size());
+  for (Index i = 0; i < curr->handlerTags.size(); i++) {
+    auto& tag = curr->handlerTags[i];
+    auto& tagSig = wasm->getTag(tag)->sig;
+
+    auto& tgps = tagSig.params;
+    auto& tgrs = tagSig.results;
+
+    HeapType ftPrime{Signature(tgrs, ctrs)};
+    HeapType ctPrime{Continuation(ftPrime)};
+    Type ctPrimeRef(ctPrime, Nullability::NonNullable);
+
+    if (tgps.size() > 0) {
+      TypeList sentValueTypes;
+      sentValueTypes.reserve(tgps.size() + 1);
+
+      sentValueTypes.insert(sentValueTypes.begin(), tgps.begin(), tgps.end());
+      sentValueTypes.push_back(ctPrimeRef);
+      curr->sentTypes[i] = Type(sentValueTypes);
+    } else {
+      curr->sentTypes[i] = ctPrimeRef;
+    }
+  }
+}
+
+void Resume::finalize(Module* wasm) {
+  const Signature& contSig =
+    this->contType.getContinuation().type.getSignature();
+  type = contSig.results;
+
+  populateResumeSentTypes(this, wasm);
+}
+
 size_t Function::getNumParams() { return getParams().size(); }
 
 size_t Function::getNumVars() { return vars.size(); }