qalgorithms.h: fix mistake that MSVC has constexpr bitops in C++17 mode

<bit> exists in C++20 and is properly both constexpr and optimized. But
in C++17 mode, we don't have constexpr bitops and instead elect to have
performance at runtime instead. But somewhere along the line, either
when they were added, when C++20 <bit> support was, or in any of the
bugfixes for other compilers, the nesting of #ifdef got messed up and we
declared that we had constexpr builtins for MSVC in C++17 too.

The macro QT_HAS_CONSTEXPR_BUILTINS isn't supposed to be used by anyone
else... but we ended up not being able to use it ourselves either. So
I'm renaming it to a more precise label.

Pick-to: 6.5
Change-Id: I9671dee8ceb64aa9b9cafffd1741b9b4060c9753
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/auto/widgets/kernel/qsizepolicy/tst_qsizepolicy.cpp b/tests/auto/widgets/kernel/qsizepolicy/tst_qsizepolicy.cpp
index 5b64f122e2..f59471a6e6 100644
--- a/tests/auto/widgets/kernel/qsizepolicy/tst_qsizepolicy.cpp
+++ b/tests/auto/widgets/kernel/qsizepolicy/tst_qsizepolicy.cpp
@@ -95,7 +95,7 @@ void tst_QSizePolicy::constExpr()
     {
       // QTBUG-69983: For ControlType != QSizePolicy::DefaultType, qCountTrailingZeroBits()
       // is used, which MSVC 15.8.1 does not consider constexpr due to built-ins
-#  if defined(QT_HAS_CONSTEXPR_BUILTINS) && (!defined(Q_CC_MSVC) || _MSC_VER < 1915)
+#  if defined(QT_HAS_CONSTEXPR_BITOPS)
       constexpr auto sp = QSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed, QSizePolicy::CheckBox);
 #  else
       constexpr auto sp = QSizePolicy(QSizePolicy::Minimum, QSizePolicy::Expanding, QSizePolicy::DefaultType);