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QThread::currentThreadId: fix build on x32 (ILP32) ABI

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On this ABI, pointers are 32-bit, so Qt::HANDLE (void *) is a 32-bit
variable and the "movq" instruction is inappropriate.

There's a GCC extended inline assembler modifier for the instruction
size suffix (%z0) but Clang seems not to understand it. Instead, I just
removed the suffix: we can do that because this is a memory load
instruction, which implies the destination is a general purpose register
(also required by the "=r" constraint) and therefore the assembler can
determine the size of the memory load from the name of the selected
register.

Note: I did not verify this compiles on x32 at all, much less that it
loads the right thing from memory.

Fixes: QTBUG-122674
Pick-to: 6.6 6.5
Change-Id: I01ec3c774d9943adb903fffd17b6513d146e89ce
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 08349ef0fe3902504987d12ebe0ed9674ed1e486)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Thiago Macieira 2024-02-22 16:53:51 -06:00 committed by Qt Cherry-pick Bot
parent 5fea2d374b
commit f5738ab463
1 changed files with 3 additions and 3 deletions
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6
src/corelib/thread/qthread.h
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@ -151,13 +151,13 @@ inline Qt::HANDLE QThread::currentThreadId() noexcept
static_assert(sizeof(tid) == sizeof(void*));
// See https://akkadia.org/drepper/tls.pdf for x86 ABI
#if defined(Q_PROCESSOR_X86_32) && ((defined(Q_OS_LINUX) && defined(__GLIBC__)) || defined(Q_OS_FREEBSD)) // x86 32-bit always uses GS
__asm__("movl %%gs:%c1, %0" : "=r" (tid) : "i" (2 * sizeof(void*)) : );
__asm__("mov %%gs:%c1, %0" : "=r" (tid) : "i" (2 * sizeof(void*)) : );
#elif defined(Q_PROCESSOR_X86_64) && defined(Q_OS_DARWIN)
// 64bit macOS uses GS, see https://github.com/apple/darwin-xnu/blob/master/libsyscall/os/tsd.h
__asm__("movq %%gs:0, %0" : "=r" (tid) : : );
__asm__("mov %%gs:0, %0" : "=r" (tid) : : );
#elif defined(Q_PROCESSOR_X86_64) && ((defined(Q_OS_LINUX) && defined(__GLIBC__)) || defined(Q_OS_FREEBSD))
// x86_64 Linux, BSD uses FS
__asm__("movq %%fs:%c1, %0" : "=r" (tid) : "i" (2 * sizeof(void*)) : );
__asm__("mov %%fs:%c1, %0" : "=r" (tid) : "i" (2 * sizeof(void*)) : );
#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