From db0ca64ff3d8f6ea3e1c0a8dcd6d5387bbc1a4d2 Mon Sep 17 00:00:00 2001
From: Nathaniel Filardo <nfilardo@microsoft.com>
Date: Fri, 20 Nov 2020 12:56:03 +0000
Subject: [PATCH] NFC: Add an AAL Concept, too

While here, pull out some constants to their own header.  Eventually we'll
want to match on AalFeatures in the AAL Concept.
---
 CMakeLists.txt        |  2 +-
 src/aal/aal.h         | 37 ++++-----------------------------
 src/aal/aal_concept.h | 48 +++++++++++++++++++++++++++++++++++++++++++
 src/aal/aal_consts.h  | 37 +++++++++++++++++++++++++++++++++
 src/ds/concept.h      |  2 ++
 5 files changed, 92 insertions(+), 34 deletions(-)
 create mode 100644 src/aal/aal_concept.h
 create mode 100644 src/aal/aal_consts.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 693b82a..df91b70 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,7 +82,7 @@ macro(clangformat_targets)
     file(GLOB_RECURSE ALL_SOURCE_FILES *.cc *.h *.hh)
     # clangformat does not yet understand concepts well; for the moment, don't
     # ask it to format them.  See https://reviews.llvm.org/D79773
-    list(FILTER ALL_SOURCE_FILES EXCLUDE REGEX "src/pal/pal_concept\.h$")
+    list(FILTER ALL_SOURCE_FILES EXCLUDE REGEX "src/[^/]*/[^/]*_concept\.h$")
     add_custom_target(
       clangformat
       COMMAND ${CLANG_FORMAT}
diff --git a/src/aal/aal.h b/src/aal/aal.h
index 69d5480..471b460 100644
--- a/src/aal/aal.h
+++ b/src/aal/aal.h
@@ -1,5 +1,8 @@
 #pragma once
+#include "../ds/concept.h"
 #include "../ds/defines.h"
+#include "aal_concept.h"
+#include "aal_consts.h"
 
 #include <chrono>
 #include <cstdint>
@@ -29,38 +32,6 @@
 
 namespace snmalloc
 {
-  /**
-   * Flags in a bitfield of attributes of this architecture, much like
-   * PalFeatures.
-   */
-  enum AalFeatures : uint64_t
-  {
-    /**
-     * This architecture does not discriminate between integers and pointers,
-     * and so may use bit operations on pointer values.
-     */
-    IntegerPointers = (1 << 0),
-    /**
-     * This architecture cannot access cpu cycles counters.
-     */
-    NoCpuCycleCounters = (1 << 1),
-    /**
-     * This architecture enforces strict pointer provenance; we bound the
-     * pointers given out on malloc() and friends and must, therefore retain
-     * internal high-privilege pointers for recycling memory on free().
-     */
-    StrictProvenance = (1 << 2),
-  };
-
-  enum AalName : int
-  {
-    ARM,
-    PowerPC,
-    X86,
-    X86_SGX,
-    Sparc,
-  };
-
   /**
    * Architecture Abstraction Layer. Includes default implementations of some
    * functions using compiler builtins.  Falls back to the definitions in the
@@ -160,7 +131,7 @@ namespace snmalloc
 {
   using Aal = AAL_Generic<AAL_Arch>;
 
-  template<AalFeatures F, typename AAL = Aal>
+  template<AalFeatures F, SNMALLOC_CONCEPT(ConceptAAL) AAL = Aal>
   constexpr static bool aal_supports = (AAL::aal_features & F) == F;
 } // namespace snmalloc
 
diff --git a/src/aal/aal_concept.h b/src/aal/aal_concept.h
new file mode 100644
index 0000000..e199e07
--- /dev/null
+++ b/src/aal/aal_concept.h
@@ -0,0 +1,48 @@
+#pragma once
+
+#ifdef __cpp_concepts
+#  include "../ds/concept.h"
+#  include "aal_consts.h"
+
+#  include <cstdint>
+#  include <utility>
+
+namespace snmalloc
+{
+  /**
+   * AALs must advertise the bit vector of supported features, their name,
+   * 
+   */
+  template<typename AAL>
+  concept ConceptAAL_static_members = requires()
+  {
+    typename std::integral_constant<uint64_t, AAL::aal_features>;
+    typename std::integral_constant<int, AAL::aal_name>;
+  };
+
+  /**
+   * AALs provide a prefetch operation.
+   */
+  template<typename AAL>
+  concept ConceptAAL_prefetch = requires(void *ptr)
+  {
+    { AAL::prefetch(ptr) } noexcept -> ConceptSame<void>;
+  };
+
+  /**
+   * AALs provide a notion of high-precision timing.
+   */
+  template<typename AAL>
+  concept ConceptAAL_tick = requires()
+  {
+    { AAL::tick() } noexcept -> ConceptSame<uint64_t>;
+  };
+
+  template<typename AAL>
+  concept ConceptAAL =
+    ConceptAAL_static_members<AAL> &&
+    ConceptAAL_prefetch<AAL> &&
+    ConceptAAL_tick<AAL>;
+
+} // namespace snmalloc
+#endif
diff --git a/src/aal/aal_consts.h b/src/aal/aal_consts.h
new file mode 100644
index 0000000..24b31ff
--- /dev/null
+++ b/src/aal/aal_consts.h
@@ -0,0 +1,37 @@
+#pragma once
+#include <cstdint>
+
+namespace snmalloc
+{
+  /**
+   * Flags in a bitfield of attributes of this architecture, much like
+   * PalFeatures.
+   */
+  enum AalFeatures : uint64_t
+  {
+    /**
+     * This architecture does not discriminate between integers and pointers,
+     * and so may use bit operations on pointer values.
+     */
+    IntegerPointers = (1 << 0),
+    /**
+     * This architecture cannot access cpu cycles counters.
+     */
+    NoCpuCycleCounters = (1 << 1),
+    /**
+     * This architecture enforces strict pointer provenance; we bound the
+     * pointers given out on malloc() and friends and must, therefore retain
+     * internal high-privilege pointers for recycling memory on free().
+     */
+    StrictProvenance = (1 << 2),
+  };
+
+  enum AalName : int
+  {
+    ARM,
+    PowerPC,
+    X86,
+    X86_SGX,
+    Sparc,
+  };
+} // namespace snmalloc
diff --git a/src/ds/concept.h b/src/ds/concept.h
index d935417..4e489ed 100644
--- a/src/ds/concept.h
+++ b/src/ds/concept.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <type_traits>
+
 /**
  * C++20 concepts are referenced as if they were types in declarations within
  * template parameters (e.g. "template<FooConcept Foo> ...").  That is, they