Merge pull request #15213 from xokdvium/unhardcode-alignas-cache-line-size

Unhardcode alignas cache line size

nix-meson-build-support/common/meson.build

@@ -27,6 +27,7 @@ add_project_arguments(
   '-Wignored-qualifiers',
   '-Wimplicit-fallthrough',
   '-Wno-deprecated-declarations',
+  '-Wno-interference-size', # Used for C++ ABI only. We don't provide any guarantees about different march tunings.
   language : 'cpp',
 )
 

src/libexpr/eval.cc

@@ -318,7 +318,6 @@ EvalState::EvalState(
     countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
 
     static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
-    static_assert(sizeof(Counter) == 64, "counters must be 64 bytes");
 
     /* Construct the Nix expression search path. */
     assert(lookupPath.elements.empty());

src/libexpr/include/nix/expr/counter.hh

@@ -11,7 +11,7 @@ namespace nix {
  * variable is set. This is to prevent contention on these counters
  * when multi-threaded evaluation is enabled.
  */
-struct alignas(64) Counter
+struct alignas(std::hardware_destructive_interference_size) Counter
 {
     using value_type = uint64_t;
 

src/libexpr/include/nix/expr/value.hh

@@ -134,7 +134,7 @@ public:
     virtual bool operator==(const ExternalValueBase & b) const noexcept;
 
     /**
-     * Print the value as JSON. Defaults to unconvertable, i.e. throws an error
+     * Print the value as JSON. Defaults to unconvertible, i.e. throws an error
      */
     virtual nlohmann::json
     printValueAsJSON(EvalState & state, bool strict, NixStringContext & context, bool copyToStore = true) const;
@@ -587,7 +587,7 @@ class alignas(16)
     enum PrimaryDiscriminator : int {
         pdUninitialized = 0,
         pdSingleDWord, //< layout: Single/zero field payload
-        /* The order of these enumations must be the same as in InternalType. */
+        /* The order of these enumerations must be the same as in InternalType. */
         pdListN, //< layout: Single untaggable field.
         pdString,
         pdPath,