From 89d1cf92be0636a219ee6415eead387241963dcf Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Thu, 12 Dec 2019 18:36:31 -0800
Subject: Make local.tee's type its local's type (#2511)

According to the current spec, `local.tee`'s return type should be the
same as its local's type. (Discussions on whether we should change this
rule is going on in WebAssembly/reference-types#55, but here I will
assume this spec does not change. If this changes, we should change many
parts of Binaryen transformation anyway...)

But currently in Binaryen `local.tee`'s type is computed from its
value's type. This didn't make any difference in the MVP, but after we
have subtype relationship in #2451, this can become a problem. For
example:
```
(func $test (result funcref) (local $0 anyref)
  (local.tee $0
    (ref.func $test)
  )
)
```
This shouldn't validate in the spec, but this will pass Binaryen
validation with the current `local.tee` implementation.

This makes `local.tee`'s type computed from the local's type, and makes
`LocalSet::makeTee` get a type parameter, to which we should pass the
its corresponding local's type. We don't embed the local type in the
class `LocalSet` because it may increase memory size.

This also fixes the type of `local.get` to be the local type where
`local.get` and `local.set` pair is created from `local.tee`.
---
 src/wasm-builder.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'src/wasm-builder.h')

diff --git a/src/wasm-builder.h b/src/wasm-builder.h
index 22fa0e642..918e6a4ab 100644
--- a/src/wasm-builder.h
+++ b/src/wasm-builder.h
@@ -232,14 +232,15 @@ public:
     auto* ret = allocator.alloc<LocalSet>();
     ret->index = index;
     ret->value = value;
+    ret->makeSet();
     ret->finalize();
     return ret;
   }
-  LocalSet* makeLocalTee(Index index, Expression* value) {
+  LocalSet* makeLocalTee(Index index, Expression* value, Type type) {
     auto* ret = allocator.alloc<LocalSet>();
     ret->index = index;
     ret->value = value;
-    ret->setTee(true);
+    ret->makeTee(type);
     return ret;
   }
   GlobalGet* makeGlobalGet(Name name, Type type) {
-- 
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