From 22c66e12e4c6841d51f505073a01e60917cf3174 Mon Sep 17 00:00:00 2001
From: Lars Knoll <lars.knoll@qt.io>
Date: Mon, 1 Mar 2021 11:51:21 +0100
Subject: Provide an inline implementation of currentThreadId() on Windows

As this method is rather critical for performance of some central
parts of Qt, it really should be inline whereever possible. This
commit adds an inline implementation for Windows 32 and 64 bit.

Amends 5e9b2ade678f37e43bfc2e3484f54cbbb5844d2e

Change-Id: Iea51ef905b1cb7f91ca64b718d79bdc4f5c02c3a
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/thread/qthread.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/corelib/thread/qthread.h b/src/corelib/thread/qthread.h
index ab32891a59..e5db44638d 100644
--- a/src/corelib/thread/qthread.h
+++ b/src/corelib/thread/qthread.h
@@ -49,6 +49,10 @@
 #  include <future> // for std::async
 #  include <functional> // for std::invoke; no guard needed as it's a C++98 header
 #endif
+// internal compiler error with mingw 8.1
+#if defined(Q_CC_MSVC) && defined(Q_PROCESSOR_X86)
+#include <intrin.h>
+#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -194,6 +198,27 @@ inline Qt::HANDLE QThread::currentThreadId() noexcept
 #elif defined(Q_PROCESSOR_X86_64) && (defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD)) && !defined(Q_OS_ANDROID)
     // x86_64 Linux, BSD uses FS
     __asm__("movq %%fs:0, %0" : "=r" (tid) : : );
+#elif defined(Q_PROCESSOR_X86_64) && defined(Q_OS_WIN)
+    // See https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
+    // First get the pointer to the TIB
+    quint8 *tib;
+# if defined(Q_CC_MINGW) // internal compiler error when using the intrinsics
+    __asm__("movq %%gs:0x30, %0" : "=r" (tib) : :);
+# else
+    tib = reinterpret_cast<quint8 *>(__readgsqword(0x30));
+# endif
+    // Then read the thread ID
+    tid = *reinterpret_cast<Qt::HANDLE *>(tib + 0x48);
+#elif defined(Q_PROCESSOR_X86_32) && defined(Q_OS_WIN)
+    // First get the pointer to the TIB
+    quint8 *tib;
+# if defined(Q_CC_MINGW) // internal compiler error when using the intrinsics
+    __asm__("movl %%fs:0x18, %0" : "=r" (tib) : :);
+# else
+    tib = reinterpret_cast<quint8 *>(__readfsdword(0x18));
+# endif
+    // Then read the thread ID
+    tid = *reinterpret_cast<Qt::HANDLE *>(tib + 0x24);
 #else
     tid = currentThreadIdImpl();
 #endif
-- 
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