Add feature gate for "rust-intrinsic".

This commit implemented a feature gate to check `intrinsics`.

gcc/rust/ChangeLog:

	* checks/errors/rust-feature-gate.cc: Add implementation for
	`void FeatureGate::visit (AST::ExternBlock &block)`. Add `valid_feature`
	construction process in `FeatureGate::check`.
	* checks/errors/rust-feature-gate.h: Add declaration for
	`void FeatureGate::visit (AST::ExternBlock &block)`. Add private
	variable `valid_feature`.
	* checks/errors/rust-feature.h: Change `issue` to `m_issue`.

gcc/testsuite/ChangeLog:

	* rust/compile/const-issue1440.rs: Add crate feature: `intrinsics`.
	* rust/compile/feature_intrinsics.rs: New file.
	* rust/compile/issue-1031.rs: Add crate feature: `intrinsics`.
	* rust/compile/issue-1130.rs: Add crate feature: `intrinsics`.
	* rust/compile/issue-1131.rs: Add crate feature: `intrinsics`.
	* rust/compile/issue-1237.rs: Add crate feature: `intrinsics`.
	* rust/compile/issue-1289.rs: Add crate feature: `intrinsics`.
	* rust/compile/rust-const-blog-issue.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/intrinsics-3.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/intrinsics-4.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/intrinsics-5.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/intrinsics-6.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/intrinsics-7.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/issue-1024.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/issue-1075.rs: Add crate feature: `intrinsics`.
	* rust/compile/torture/issue-1432.rs: Add crate feature: `intrinsics`.
	* rust/compile/unsafe10.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/atomic_load.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/atomic_store.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/copy_nonoverlapping1.rs: Add crate feature:
	`intrinsics`.
	* rust/execute/torture/issue-1120.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/issue-1133.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/issue-1232.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/slice-magic.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/slice-magic2.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/str-layout1.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/transmute1.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/wrapping_op1.rs: Add crate feature: `intrinsics`.
	* rust/execute/torture/wrapping_op2.rs: Add crate feature: `intrinsics`.

Signed-off-by: Xiao Ma <mxlol233@outlook.com>

3 files changed, 62 insertions, 11 deletions

diff --git a/gcc/rust/checks/errors/rust-feature-gate.cc b/gcc/rust/checks/errors/rust-feature-gate.cc
index 31ce367..bd01b52 100644
--- a/gcc/rust/checks/errors/rust-feature-gate.cc
+++ b/gcc/rust/checks/errors/rust-feature-gate.cc
@@ -17,14 +17,15 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-feature-gate.h"
-#include "rust-feature.h"
+#include "rust-abi.h"
 
 namespace Rust {
 
 void
 FeatureGate::check (AST::Crate &crate)
 {
-  std::vector<Feature> valid_features;
+  valid_features.clear ();
+
   for (const auto &attr : crate.inner_attrs)
     {
       if (attr.get_path ().as_string () == "feature")
@@ -39,20 +40,22 @@ FeatureGate::check (AST::Crate &crate)
 		option.parse_to_meta_item ());
 	      for (const auto &item : meta_item->get_items ())
 		{
-		  const auto &name = item->as_string ();
-		  auto tname = Feature::as_name (name);
+		  const auto &name_str = item->as_string ();
+		  auto tname = Feature::as_name (name_str);
 		  if (!tname.is_none ())
-		    valid_features.push_back (Feature::create (tname.get ()));
+		    {
+		      auto name = tname.get ();
+		      valid_features.insert (name);
+		    }
+
 		  else
 		    rust_error_at (item->get_locus (), "unknown feature '%s'",
-				   name.c_str ());
+				   name_str.c_str ());
 		}
 	    }
 	}
     }
-  valid_features.shrink_to_fit ();
 
-  // TODO (mxlol233): add the real feature gate stuff.
   auto &items = crate.items;
   for (auto it = items.begin (); it != items.end (); it++)
     {
@@ -60,4 +63,46 @@ FeatureGate::check (AST::Crate &crate)
       item->accept_vis (*this);
     }
 }
+
+void
+FeatureGate::gate (Feature::Name name, Location loc,
+		   const std::string &error_msg)
+{
+  if (!valid_features.count (name))
+    {
+      auto feature = Feature::create (name);
+      auto issue = feature.issue ();
+      if (issue > 0)
+	{
+	  const char *fmt_str
+	    = "%s. see issue %ld "
+	      "<https://github.com/rust-lang/rust/issues/%ld> for more "
+	      "information. add `#![feature(%s)]` to the crate attributes to "
+	      "enable.";
+	  rust_error_at (loc, fmt_str, error_msg.c_str (), issue, issue,
+			 feature.as_string ().c_str ());
+	}
+      else
+	{
+	  const char *fmt_str
+	    = "%s. add `#![feature(%s)]` to the crate attributes to enable.";
+	  rust_error_at (loc, fmt_str, error_msg.c_str (),
+			 feature.as_string ().c_str ());
+	}
+    }
+}
+
+void
+FeatureGate::visit (AST::ExternBlock &block)
+{
+  if (block.has_abi ())
+    {
+      const auto abi = block.get_abi ();
+
+      if (get_abi_from_string (abi) == ABI::INTRINSIC)
+	gate (Feature::Name::INTRINSICS, block.get_locus (),
+	      "intrinsics are subject to change");
+    }
+}
+
 } // namespace Rust
\ No newline at end of file
diff --git a/gcc/rust/checks/errors/rust-feature-gate.h b/gcc/rust/checks/errors/rust-feature-gate.h
index dc95c6b..6768c4c 100644
--- a/gcc/rust/checks/errors/rust-feature-gate.h
+++ b/gcc/rust/checks/errors/rust-feature-gate.h
@@ -21,6 +21,7 @@
 
 #include "rust-ast-visitor.h"
 #include "rust-ast-full.h"
+#include "rust-feature.h"
 
 namespace Rust {
 
@@ -136,7 +137,7 @@ public:
   void visit (AST::TraitImpl &impl) override {}
   void visit (AST::ExternalStaticItem &item) override {}
   void visit (AST::ExternalFunctionItem &item) override {}
-  void visit (AST::ExternBlock &block) override {}
+  void visit (AST::ExternBlock &block) override;
   void visit (AST::MacroMatchFragment &match) override {}
   void visit (AST::MacroMatchRepetition &match) override {}
   void visit (AST::MacroMatcher &matcher) override {}
@@ -186,6 +187,10 @@ public:
   void visit (AST::SliceType &type) override {}
   void visit (AST::InferredType &type) override {}
   void visit (AST::BareFunctionType &type) override {}
+
+private:
+  void gate (Feature::Name name, Location loc, const std::string &error_msg);
+  std::set<Feature::Name> valid_features;
 };
 } // namespace Rust
 #endif
\ No newline at end of file
diff --git a/gcc/rust/checks/errors/rust-feature.h b/gcc/rust/checks/errors/rust-feature.h
index 1425e26..7bd76c0 100644
--- a/gcc/rust/checks/errors/rust-feature.h
+++ b/gcc/rust/checks/errors/rust-feature.h
@@ -47,6 +47,7 @@ public:
   Name name () { return m_name; }
   const std::string &description () { return m_description; }
   State state () { return m_state; }
+  uint64_t issue () { return m_issue; }
 
   static Optional<Name> as_name (const std::string &name);
   static Feature create (Name name);
@@ -57,7 +58,7 @@ private:
 	   const Optional<CompileOptions::Edition> &edition,
 	   const char *description)
     : m_state (state), m_name (name), m_name_str (name_str),
-      m_rustc_since (rustc_since), issue (issue_number), edition (edition),
+      m_rustc_since (rustc_since), m_issue (issue_number), edition (edition),
       m_description (description)
   {}
 
@@ -65,7 +66,7 @@ private:
   Name m_name;
   std::string m_name_str;
   std::string m_rustc_since;
-  uint64_t issue;
+  uint64_t m_issue;
   Optional<CompileOptions::Edition> edition;
   std::string m_description;