Merge #969

969: Add builtin macros framework r=CohenArthur a=CohenArthur

This PR adds bases to define new builtin macro functions.

Since we operate at the `insert_macro_def` level, this requires builtin macros to be defined, as is the case in the rust standard library:

```rust
    macro_rules! assert {
        ($cond:expr $(,)?) => {{ /* compiler built-in */ }};
        ($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }};
    }
```

Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

6 files changed, 135 insertions, 6 deletions

diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
index 080b9dd..9de93fe 100644
--- a/gcc/rust/Make-lang.in
+++ b/gcc/rust/Make-lang.in
@@ -75,6 +75,7 @@ GRS_OBJS = \
     rust/rust-compile-resolve-path.o \
     rust/rust-macro-expand.o \
     rust/rust-macro-invoc-lexer.o \
+    rust/rust-macro-builtins.o \
     rust/rust-hir-full-test.o \
     rust/rust-hir-map.o \
     rust/rust-attributes.o \
diff --git a/gcc/rust/ast/rust-macro.h b/gcc/rust/ast/rust-macro.h
index 995b255..9f8f19c 100644
--- a/gcc/rust/ast/rust-macro.h
+++ b/gcc/rust/ast/rust-macro.h
@@ -361,9 +361,26 @@ class MacroRulesDefinition : public MacroItem
   DelimType delim_type;
   // MacroRules rules;
   std::vector<MacroRule> rules; // inlined form
-
   Location locus;
 
+  std::function<ASTFragment (Location, MacroInvocData &)>
+    associated_transcriber;
+  // Since we can't compare std::functions, we need to use an extra boolean
+  bool is_builtin_rule;
+
+  /**
+   * Default function to use as an associated transcriber. This function should
+   * never be called, hence the gcc_unreachable().
+   * If this function is used, then the macro is not builtin and the compiler
+   * should make use of the actual rules. If the macro is builtin, then another
+   * associated transcriber should be used
+   */
+  static ASTFragment dummy_builtin (Location, MacroInvocData &)
+  {
+    gcc_unreachable ();
+    return ASTFragment::create_empty ();
+  }
+
   /* NOTE: in rustc, macro definitions are considered (and parsed as) a type
    * of macro, whereas here they are considered part of the language itself.
    * I am not aware of the implications of this decision. The rustc spec does
@@ -377,7 +394,17 @@ public:
 			std::vector<MacroRule> rules,
 			std::vector<Attribute> outer_attrs, Location locus)
     : outer_attrs (std::move (outer_attrs)), rule_name (std::move (rule_name)),
-      delim_type (delim_type), rules (std::move (rules)), locus (locus)
+      delim_type (delim_type), rules (std::move (rules)), locus (locus),
+      associated_transcriber (dummy_builtin), is_builtin_rule (false)
+  {}
+
+  MacroRulesDefinition (Identifier builtin_name, DelimType delim_type,
+			std::function<ASTFragment (Location, MacroInvocData &)>
+			  associated_transcriber)
+    : outer_attrs (std::vector<Attribute> ()), rule_name (builtin_name),
+      delim_type (delim_type), rules (std::vector<MacroRule> ()),
+      locus (Location ()), associated_transcriber (associated_transcriber),
+      is_builtin_rule (true)
   {}
 
   void accept_vis (ASTVisitor &vis) override;
@@ -400,6 +427,20 @@ public:
   std::vector<MacroRule> &get_rules () { return rules; }
   const std::vector<MacroRule> &get_rules () const { return rules; }
 
+  bool is_builtin () const { return is_builtin_rule; }
+  const std::function<ASTFragment (Location, MacroInvocData &)> &
+  get_builtin_transcriber () const
+  {
+    rust_assert (is_builtin ());
+    return associated_transcriber;
+  }
+  void set_builtin_transcriber (
+    std::function<ASTFragment (Location, MacroInvocData &)> transcriber)
+  {
+    associated_transcriber = transcriber;
+    is_builtin_rule = true;
+  }
+
 protected:
   /* Use covariance to implement clone function as returning this object rather
    * than base */
diff --git a/gcc/rust/expand/rust-macro-builtins.cc b/gcc/rust/expand/rust-macro-builtins.cc
new file mode 100644
index 0000000..b7bbd32
--- /dev/null
+++ b/gcc/rust/expand/rust-macro-builtins.cc
@@ -0,0 +1,30 @@
+// 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-macro-builtins.h"
+#include "rust-diagnostics.h"
+
+namespace Rust {
+AST::ASTFragment
+MacroBuiltin::assert (Location invoc_locus, AST::MacroInvocData &invoc)
+{
+  rust_debug ("assert!() called");
+
+  return AST::ASTFragment::create_empty ();
+}
+} // namespace Rust
diff --git a/gcc/rust/expand/rust-macro-builtins.h b/gcc/rust/expand/rust-macro-builtins.h
new file mode 100644
index 0000000..f279d39
--- /dev/null
+++ b/gcc/rust/expand/rust-macro-builtins.h
@@ -0,0 +1,34 @@
+// 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/>.
+
+#ifndef RUST_MACRO_BUILTINS_H
+#define RUST_MACRO_BUILTINS_H
+
+#include "rust-ast.h"
+#include "rust-location.h"
+
+namespace Rust {
+class MacroBuiltin
+{
+public:
+  static AST::ASTFragment assert (Location invoc_locus,
+				  AST::MacroInvocData &invoc);
+};
+} // namespace Rust
+
+#endif // RUST_MACRO_BUILTINS_H
diff --git a/gcc/rust/expand/rust-macro-expand.cc b/gcc/rust/expand/rust-macro-expand.cc
index b54aa01..7552e82 100644
--- a/gcc/rust/expand/rust-macro-expand.cc
+++ b/gcc/rust/expand/rust-macro-expand.cc
@@ -3194,8 +3194,14 @@ MacroExpander::expand_invoc (AST::MacroInvocation &invoc)
   bool ok = mappings->lookup_macro_def (resolved_node, &rules_def);
   rust_assert (ok);
 
-  auto fragment
-    = expand_decl_macro (invoc.get_locus (), invoc_data, *rules_def, false);
+  auto fragment = AST::ASTFragment::create_empty ();
+
+  if (rules_def->is_builtin ())
+    fragment
+      = rules_def->get_builtin_transcriber () (invoc.get_locus (), invoc_data);
+  else
+    fragment
+      = expand_decl_macro (invoc.get_locus (), invoc_data, *rules_def, false);
 
   // lets attach this fragment to the invocation
   invoc.set_fragment (std::move (fragment));
@@ -3229,8 +3235,14 @@ MacroExpander::expand_invoc_semi (AST::MacroInvocationSemi &invoc)
   bool ok = mappings->lookup_macro_def (resolved_node, &rules_def);
   rust_assert (ok);
 
-  auto fragment
-    = expand_decl_macro (invoc.get_locus (), invoc_data, *rules_def, true);
+  auto fragment = AST::ASTFragment::create_empty ();
+
+  if (rules_def->is_builtin ())
+    fragment
+      = rules_def->get_builtin_transcriber () (invoc.get_locus (), invoc_data);
+  else
+    fragment
+      = expand_decl_macro (invoc.get_locus (), invoc_data, *rules_def, true);
 
   // lets attach this fragment to the invocation
   invoc.set_fragment (std::move (fragment));
diff --git a/gcc/rust/util/rust-hir-map.cc b/gcc/rust/util/rust-hir-map.cc
index 1348e29..1c0e8fc 100644
--- a/gcc/rust/util/rust-hir-map.cc
+++ b/gcc/rust/util/rust-hir-map.cc
@@ -19,6 +19,7 @@
 #include "rust-hir-map.h"
 #include "rust-ast-full.h"
 #include "rust-hir-full.h"
+#include "rust-macro-builtins.h"
 
 namespace Rust {
 namespace Analysis {
@@ -741,6 +742,16 @@ Mappings::iterate_trait_items (
 void
 Mappings::insert_macro_def (AST::MacroRulesDefinition *macro)
 {
+  static std::map<std::string, std::function<AST::ASTFragment (
+				 Location, AST::MacroInvocData &)>>
+    builtin_macros = {
+      {"assert", MacroBuiltin::assert},
+    };
+
+  auto builtin = builtin_macros.find (macro->get_rule_name ());
+  if (builtin != builtin_macros.end ())
+    macro->set_builtin_transcriber (builtin->second);
+
   auto it = macroMappings.find (macro->get_node_id ());
   rust_assert (it == macroMappings.end ());