fix #16752: threadvar now works with importcpp types; osx now uses native TLS (--tlsEmulation:off), which can be orders of magnitude faster (#16750)

* osx now uses native TLS, which can be orders of magnitude faster

* add {.cppNonPod.}

* improve test

* changelog, docs, disable part of windows test

compiler/ast.nim

@@ -265,6 +265,10 @@ type
     sfShadowed,       # a symbol that was shadowed in some inner scope
     sfThread,         # proc will run as a thread
                       # variable is a thread variable
+    sfCppNonPod,      # tells compiler to treat such types as non-pod's, so that
+                      # `thread_local` is used instead of `__thread` for
+                      # {.threadvar.} + `--threads`. Only makes sense for importcpp types.
+                      # This has a performance impact so isn't set by default.
     sfCompileTime,    # proc can be evaluated at compile time
     sfConstructor,    # proc is a C++ constructor
     sfDispatcher,     # copied method symbol is the dispatcher

compiler/ccgthreadvars.nim

@@ -7,8 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
-## Thread var support for crappy architectures that lack native support for
-## thread local storage. (**Thank you Mac OS X!**)
+## Thread var support for architectures that lack native support for
+## thread local storage.
 
 # included from cgen.nim
 
@@ -35,7 +35,11 @@ proc declareThreadVar(m: BModule, s: PSym, isExtern: bool) =
     if isExtern: m.s[cfsVars].add("extern ")
     elif lfExportLib in s.loc.flags: m.s[cfsVars].add("N_LIB_EXPORT_VAR ")
     else: m.s[cfsVars].add("N_LIB_PRIVATE ")
-    if optThreads in m.config.globalOptions: m.s[cfsVars].add("NIM_THREADVAR ")
+    if optThreads in m.config.globalOptions:
+      let sym = s.typ.sym
+      if sym != nil and sfCppNonPod in sym.flags:
+        m.s[cfsVars].add("NIM_THREAD_LOCAL ")
+      else: m.s[cfsVars].add("NIM_THREADVAR ")
     m.s[cfsVars].add(getTypeDesc(m, s.loc.t))
     m.s[cfsVars].addf(" $1;$n", [s.loc.r])
 

compiler/options.nim

@@ -380,11 +380,12 @@ proc hasWarn*(conf: ConfigRef, note: TNoteKind): bool =
 
 proc hcrOn*(conf: ConfigRef): bool = return optHotCodeReloading in conf.globalOptions
 
-template depConfigFields*(fn) {.dirty.} =
-  fn(target)
-  fn(options)
-  fn(globalOptions)
-  fn(selectedGC)
+when false:
+  template depConfigFields*(fn) {.dirty.} = # deadcode
+    fn(target)
+    fn(options)
+    fn(globalOptions)
+    fn(selectedGC)
 
 const oldExperimentalFeatures* = {implicitDeref, dotOperators, callOperator, parallel}
 

compiler/pragmas.nim

@@ -65,7 +65,7 @@ const
     wPure, wHeader, wCompilerProc, wCore, wFinal, wSize, wShallow,
     wIncompleteStruct, wCompleteStruct, wByCopy, wByRef,
     wInheritable, wGensym, wInject, wRequiresInit, wUnchecked, wUnion, wPacked,
-    wBorrow, wGcSafe, wPartial, wExplain, wPackage}
+    wCppNonPod, wBorrow, wGcSafe, wPartial, wExplain, wPackage}
   fieldPragmas* = declPragmas + {
     wGuard, wBitsize, wCursor, wRequiresInit, wNoalias} - {wExportNims, wNodecl} # why exclude these?
   varPragmas* = declPragmas + {wVolatile, wRegister, wThreadVar,
@@ -843,6 +843,8 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
         else: invalidPragma(c, it)
       of wImportCpp:
         processImportCpp(c, sym, getOptionalStr(c, it, "$1"), it.info)
+      of wCppNonPod:
+        incl(sym.flags, sfCppNonPod)
       of wImportJs:
         if c.config.backend != backendJs:
           localError(c.config, it.info, "`importjs` pragma requires the JavaScript target")

compiler/wordrecg.nim

@@ -38,7 +38,8 @@ type
     wCursor = "cursor", wNoalias = "noalias",
 
     wImmediate = "immediate", wConstructor = "constructor", wDestructor = "destructor", 
-    wDelegator = "delegator", wOverride = "override", wImportCpp = "importcpp", 
+    wDelegator = "delegator", wOverride = "override", wImportCpp = "importcpp",
+    wCppNonPod = "cppNonPod", 
     wImportObjC = "importobjc", wImportCompilerProc = "importcompilerproc",
     wImportc = "importc", wImportJs = "importjs", wExportc = "exportc", wExportCpp = "exportcpp", 
     wExportNims = "exportnims",