From 5fc488229d416116236199fb1187e0015a1a9d53 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 17 Jun 2022 09:38:11 -0700
Subject: [PATCH 1/5] Do not emit recursion groups without GC enabled

We emit nominal types as a single large recursion group, but this produces
invalid modules when --nominal or --hybrid was used without GC enabled. Fix the
bug by always emitting types as though they were structural (i.e. without
recursion groups) when GC is not enabled.
---
 src/wasm/wasm-binary.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index decd78852c8..87712ceb4c8 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -223,7 +223,12 @@ void WasmBinaryWriter::writeTypes() {
   // the type section. With nominal typing there is always one group and with
   // equirecursive typing there is one group per type.
   size_t numGroups = 0;
-  switch (getTypeSystem()) {
+  // MVP types are structural and do not use recursion groups.
+  TypeSystem typeSystem = getTypeSystem();
+  if (!wasm->features.hasGC()) {
+    typeSystem = TypeSystem::Equirecursive;
+  }
+  switch (typeSystem) {
     case TypeSystem::Equirecursive:
       numGroups = indexedTypes.types.size();
       break;
@@ -242,7 +247,7 @@ void WasmBinaryWriter::writeTypes() {
   BYN_TRACE("== writeTypes\n");
   auto start = startSection(BinaryConsts::Section::Type);
   o << U32LEB(numGroups);
-  if (getTypeSystem() == TypeSystem::Nominal) {
+  if (typeSystem == TypeSystem::Nominal) {
     // The nominal recursion group contains every type.
     o << S32LEB(BinaryConsts::EncodedType::Rec)
       << U32LEB(indexedTypes.types.size());

From 96508b9e0bd6d21142df7ff81e9742f148c445b4 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 17 Jun 2022 09:55:00 -0700
Subject: [PATCH 2/5] add missing test

---
 test/lit/nominal-no-gc.wast | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 test/lit/nominal-no-gc.wast

diff --git a/test/lit/nominal-no-gc.wast b/test/lit/nominal-no-gc.wast
new file mode 100644
index 00000000000..92decd8564b
--- /dev/null
+++ b/test/lit/nominal-no-gc.wast
@@ -0,0 +1,15 @@
+;; Write the module with --nominal but without GC
+;; RUN: wasm-opt %s --nominal --disable-gc -g -o %t.wasm
+
+;; We should not get any recursion groups even though we used --nominal
+;; RUN: wasm-opt %t.wasm --hybrid -all -S -o - | filecheck %s
+
+;; CHECK-NOT: rec
+
+(module
+  (type $foo (func))
+  (type $bar (func))
+
+  (func $f1 (type $foo))
+  (func $f2 (type $bar))
+)
\ No newline at end of file

From 94316baff618b964957f48dcc1ca6c8db201df76 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 17 Jun 2022 12:29:58 -0700
Subject: [PATCH 3/5] add missing line terminator

---
 test/lit/nominal-no-gc.wast | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/lit/nominal-no-gc.wast b/test/lit/nominal-no-gc.wast
index 92decd8564b..717f3a7dfe9 100644
--- a/test/lit/nominal-no-gc.wast
+++ b/test/lit/nominal-no-gc.wast
@@ -12,4 +12,4 @@
 
   (func $f1 (type $foo))
   (func $f2 (type $bar))
-)
\ No newline at end of file
+)

From 0bd705c2896f8101a47c7bfd363872cfd2b0f3d8 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 17 Jun 2022 12:31:27 -0700
Subject: [PATCH 4/5] update comment

---
 test/lit/nominal-no-gc.wast | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/test/lit/nominal-no-gc.wast b/test/lit/nominal-no-gc.wast
index 717f3a7dfe9..c562e41002c 100644
--- a/test/lit/nominal-no-gc.wast
+++ b/test/lit/nominal-no-gc.wast
@@ -1,7 +1,9 @@
 ;; Write the module with --nominal but without GC
 ;; RUN: wasm-opt %s --nominal --disable-gc -g -o %t.wasm
 
-;; We should not get any recursion groups even though we used --nominal
+;; We should not get any recursion groups even though we used --nominal. We use
+;; --hybrid -all here to make sure that any rec groups from the binary will
+;; actually show up in the output and cause the test to fail.
 ;; RUN: wasm-opt %t.wasm --hybrid -all -S -o - | filecheck %s
 
 ;; CHECK-NOT: rec

From 2a0fe1004626d10bc7abb9297cdcda47a24f004e Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 17 Jun 2022 17:00:12 -0700
Subject: [PATCH 5/5] Add test with default flags

---
 test/lit/nominal-no-gc.wast | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/lit/nominal-no-gc.wast b/test/lit/nominal-no-gc.wast
index c562e41002c..7247caa5a04 100644
--- a/test/lit/nominal-no-gc.wast
+++ b/test/lit/nominal-no-gc.wast
@@ -6,6 +6,9 @@
 ;; actually show up in the output and cause the test to fail.
 ;; RUN: wasm-opt %t.wasm --hybrid -all -S -o - | filecheck %s
 
+;; Also check that we don't get a failure with the default configuration.
+;; RUN: wasm-opt %t.wasm
+
 ;; CHECK-NOT: rec
 
 (module