Canonicalize types based on hashing than HirIds and TyTy equality

When we compile types for GCC we need to make sure we canonicalize them,
this means that for any user defined type such as Structs or Tuples we want
all expressions or declarations to use the same tree. Even if we have
duplicate tree's we can end up confusing the middle-end and lose out on
optimizations as we will be using view_convert_exprs to maintain the
consistancy which will marshall between the objects unnessecarily.

The old method for doing this kept mappings of HirIds which was fine for
simple cases but when generics are involved new Id's are generated so this
meant we ended up having a vector of pairs {TyTy::BaseType, tree} and we
did a liner search to find the relevant TyTy::BaseType that we equaled to.

This was not only slow but did not handle the cases for generic associated
types or nested generics. So we needed a more general faster implementation
therefore hashing. This patch takes the gcc/tree.h type_hash_canon code
and adds in hashing for RECORD and UNION types. This means we will generate
a duplicate type then hash it and look for an existing type.

This patch will also allow us to fix how we implement monomorphization of
functions by nesting the hashes behind DefId's.

1 files changed, 139 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-context.cc b/gcc/rust/backend/rust-compile-context.cc
new file mode 100644
index 0000000..463ac27
--- /dev/null
+++ b/gcc/rust/backend/rust-compile-context.cc
@@ -0,0 +1,139 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-compile-context.h"
+#include "rust-compile-type.h"
+
+namespace Rust {
+namespace Compile {
+
+Context::Context (::Backend *backend)
+  : backend (backend), resolver (Resolver::Resolver::get ()),
+    tyctx (Resolver::TypeCheckContext::get ()),
+    mappings (Analysis::Mappings::get ()), mangler (Mangler ())
+{
+  setup_builtins ();
+}
+
+void
+Context::setup_builtins ()
+{
+  auto builtins = resolver->get_builtin_types ();
+  for (auto it = builtins.begin (); it != builtins.end (); it++)
+    {
+      HirId ref;
+      bool ok = tyctx->lookup_type_by_node_id ((*it)->get_node_id (), &ref);
+      rust_assert (ok);
+
+      TyTy::BaseType *lookup;
+      ok = tyctx->lookup_type (ref, &lookup);
+      rust_assert (ok);
+
+      TyTyResolveCompile::compile (this, lookup);
+    }
+}
+
+hashval_t
+Context::type_hasher (tree type)
+{
+  inchash::hash hstate;
+
+  hstate.add_int (TREE_CODE (type));
+
+  if (TYPE_NAME (type))
+    {
+      hashval_t record_name_hash
+	= IDENTIFIER_HASH_VALUE (DECL_NAME (TYPE_NAME (type)));
+      hstate.add_object (record_name_hash);
+    }
+
+  if (TREE_TYPE (type))
+    hstate.add_object (TYPE_HASH (TREE_TYPE (type)));
+
+  for (tree t = TYPE_ATTRIBUTES (type); t; t = TREE_CHAIN (t))
+    /* Just the identifier is adequate to distinguish.  */
+    hstate.add_object (IDENTIFIER_HASH_VALUE (TREE_PURPOSE (t)));
+
+  switch (TREE_CODE (type))
+    {
+    case METHOD_TYPE:
+      hstate.add_object (TYPE_HASH (TYPE_METHOD_BASETYPE (type)));
+      /* FALLTHROUGH. */
+    case FUNCTION_TYPE:
+      for (tree t = TYPE_ARG_TYPES (type); t; t = TREE_CHAIN (t))
+	if (TREE_VALUE (t) != error_mark_node)
+	  hstate.add_object (TYPE_HASH (TREE_VALUE (t)));
+      break;
+
+    case OFFSET_TYPE:
+      hstate.add_object (TYPE_HASH (TYPE_OFFSET_BASETYPE (type)));
+      break;
+
+      case ARRAY_TYPE: {
+	if (TYPE_DOMAIN (type))
+	  hstate.add_object (TYPE_HASH (TYPE_DOMAIN (type)));
+	if (!AGGREGATE_TYPE_P (TREE_TYPE (type)))
+	  {
+	    unsigned typeless = TYPE_TYPELESS_STORAGE (type);
+	    hstate.add_object (typeless);
+	  }
+      }
+      break;
+
+      case INTEGER_TYPE: {
+	tree t = TYPE_MAX_VALUE (type);
+	if (!t)
+	  t = TYPE_MIN_VALUE (type);
+	for (int i = 0; i < TREE_INT_CST_NUNITS (t); i++)
+	  hstate.add_object (TREE_INT_CST_ELT (t, i));
+	break;
+      }
+
+    case REAL_TYPE:
+      case FIXED_POINT_TYPE: {
+	unsigned prec = TYPE_PRECISION (type);
+	hstate.add_object (prec);
+	break;
+      }
+
+    case VECTOR_TYPE:
+      hstate.add_poly_int (TYPE_VECTOR_SUBPARTS (type));
+      break;
+
+    case RECORD_TYPE:
+    case UNION_TYPE:
+      case QUAL_UNION_TYPE: {
+	for (tree t = TYPE_FIELDS (type); t; t = TREE_CHAIN (t))
+	  {
+	    hashval_t name_hash = IDENTIFIER_HASH_VALUE (DECL_NAME (t));
+	    hashval_t type_hash = type_hasher (TREE_TYPE (t));
+	    hstate.add_object (name_hash);
+	    hstate.add_object (type_hash);
+	  }
+      }
+      break;
+
+    default:
+      break;
+    }
+
+  return hstate.end ();
+}
+
+} // namespace Compile
+} // namespace Rust