From ec3bca8fab723563bc9fb99ce9d5161652ce6945 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Mon, 8 May 2023 18:52:47 +0200
Subject: [PATCH] =?UTF-8?q?Windows:=20use=20=5F=5Fdeclspec(thread)=20TLS?=
 =?UTF-8?q?=20implementation,=20it=20is=20MUCH=20faster=E2=80=A6=20(#21810?=
 =?UTF-8?q?)?=
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* Windows: use __declspec(thread) TLS implementation, it is MUCH faster than _Thread_local [backport]

* Update lib/nimbase.h

* better fix
---
 lib/nimbase.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/nimbase.h b/lib/nimbase.h
index b9b2695c9a..570b50b081 100644
--- a/lib/nimbase.h
+++ b/lib/nimbase.h
@@ -125,7 +125,13 @@ __AVR__
   NIM_THREADVAR declaration based on
   http://stackoverflow.com/questions/18298280/how-to-declare-a-variable-as-thread-local-portably
 */
-#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112 && !defined __STDC_NO_THREADS__
+#if defined _WIN32
+#  if defined _MSC_VER || defined __DMC__ || defined __BORLANDC__
+#    define NIM_THREADVAR __declspec(thread)
+#  else
+#    define NIM_THREADVAR __thread
+#  endif
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112 && !defined __STDC_NO_THREADS__
 #  define NIM_THREADVAR _Thread_local
 #elif defined _WIN32 && ( \
        defined _MSC_VER || \