[Parser] Do not require a memory for GC string ops (#6363)

We previously required a memory to exist while parsing all `StringNew` and
`StringEncode` instructions, even though some variants of the instructions use
GC arrays instead. Require a memory only for those instructions that use one.

3 files changed, 55 insertions, 12 deletions

diff --git a/src/parser/contexts.h b/src/parser/contexts.h
index 6505d11a4..4c15c0308 100644
--- a/src/parser/contexts.h
+++ b/src/parser/contexts.h
@@ -2448,9 +2448,21 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
                          StringNewOp op,
                          bool try_,
                          Name* mem) {
-    auto m = getMemory(pos, mem);
-    CHECK_ERR(m);
-    return withLoc(pos, irBuilder.makeStringNew(op, try_, *m));
+    Name memName;
+    switch (op) {
+      case StringNewUTF8:
+      case StringNewWTF8:
+      case StringNewLossyUTF8:
+      case StringNewWTF16: {
+        auto m = getMemory(pos, mem);
+        CHECK_ERR(m);
+        memName = *m;
+        break;
+      }
+      default:
+        break;
+    }
+    return withLoc(pos, irBuilder.makeStringNew(op, try_, memName));
   }
 
   Result<> makeStringConst(Index pos,
@@ -2469,9 +2481,21 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
                             const std::vector<Annotation>& annotations,
                             StringEncodeOp op,
                             Name* mem) {
-    auto m = getMemory(pos, mem);
-    CHECK_ERR(m);
-    return withLoc(pos, irBuilder.makeStringEncode(op, *m));
+    Name memName;
+    switch (op) {
+      case StringEncodeUTF8:
+      case StringEncodeLossyUTF8:
+      case StringEncodeWTF8:
+      case StringEncodeWTF16: {
+        auto m = getMemory(pos, mem);
+        CHECK_ERR(m);
+        memName = *m;
+        break;
+      }
+      default:
+        break;
+    }
+    return withLoc(pos, irBuilder.makeStringEncode(op, memName));
   }
 
   Result<> makeStringConcat(Index pos,
diff --git a/src/parser/parsers.h b/src/parser/parsers.h
index 987f0f5aa..4c210624f 100644
--- a/src/parser/parsers.h
+++ b/src/parser/parsers.h
@@ -2330,9 +2330,18 @@ Result<> makeStringNew(Ctx& ctx,
                        const std::vector<Annotation>& annotations,
                        StringNewOp op,
                        bool try_) {
-  auto mem = maybeMemidx(ctx);
-  CHECK_ERR(mem);
-  return ctx.makeStringNew(pos, annotations, op, try_, mem.getPtr());
+  switch (op) {
+    case StringNewUTF8:
+    case StringNewWTF8:
+    case StringNewLossyUTF8:
+    case StringNewWTF16: {
+      auto mem = maybeMemidx(ctx);
+      CHECK_ERR(mem);
+      return ctx.makeStringNew(pos, annotations, op, try_, mem.getPtr());
+    }
+    default:
+      return ctx.makeStringNew(pos, annotations, op, try_, nullptr);
+  }
 }
 
 template<typename Ctx>
@@ -2359,9 +2368,18 @@ Result<> makeStringEncode(Ctx& ctx,
                           Index pos,
                           const std::vector<Annotation>& annotations,
                           StringEncodeOp op) {
-  auto mem = maybeMemidx(ctx);
-  CHECK_ERR(mem);
-  return ctx.makeStringEncode(pos, annotations, op, mem.getPtr());
+  switch (op) {
+    case StringEncodeUTF8:
+    case StringEncodeLossyUTF8:
+    case StringEncodeWTF8:
+    case StringEncodeWTF16: {
+      auto mem = maybeMemidx(ctx);
+      CHECK_ERR(mem);
+      return ctx.makeStringEncode(pos, annotations, op, mem.getPtr());
+    }
+    default:
+      return ctx.makeStringEncode(pos, annotations, op, nullptr);
+  }
 }
 
 template<typename Ctx>
diff --git a/test/lit/passes/string-lowering-instructions.wast b/test/lit/passes/string-lowering-instructions.wast
index d1b8172e2..97186fba7 100644
--- a/test/lit/passes/string-lowering-instructions.wast
+++ b/test/lit/passes/string-lowering-instructions.wast
@@ -1,6 +1,7 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
 ;; RUN: foreach %s %t wasm-opt --string-lowering  -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --new-wat-parser --string-lowering  -all -S -o - | filecheck %s
 
 (module
   (rec