Fix LocalCSE's usable local selection (#2638)

Now that we have subtypes, we cannot reuse any local that contains the
same expression, because that local's type can be a supertype. For
example:
```
(local $0 anyref)
(local $1 nullref)
...
(local.set $0 (ref.null))
(local.set $1 (ref.null)) ;; cannot be replaced with (local.get $0)
```

This extends `usables` map's key to contain both `HashedExpression` and
the local's type, so we can get the right usable local in presence of
subtypes.

1 files changed, 0 insertions, 19 deletions

diff --git a/src/ir/hashed.h b/src/ir/hashed.h
index fe0a0b958..3068966c5 100644
--- a/src/ir/hashed.h
+++ b/src/ir/hashed.h
@@ -38,25 +38,6 @@ struct HashedExpression {
     : expr(other.expr), hash(other.hash) {}
 };
 
-struct ExpressionHasher {
-  HashType operator()(const HashedExpression value) const { return value.hash; }
-};
-
-struct ExpressionComparer {
-  bool operator()(const HashedExpression a, const HashedExpression b) const {
-    if (a.hash != b.hash) {
-      return false;
-    }
-    return ExpressionAnalyzer::equal(a.expr, b.expr);
-  }
-};
-
-template<typename T>
-class HashedExpressionMap
-  : public std::
-      unordered_map<HashedExpression, T, ExpressionHasher, ExpressionComparer> {
-};
-
 // A pass that hashes all functions
 
 struct FunctionHasher : public WalkerPass<PostWalker<FunctionHasher>> {