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Fix MSVC2017 compilation with enabled relaxed constexpr on 32-bit target

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The problem is that qCountLeadingZeroBits is calling qPopulationCount
which is only conditionally constexpr, so qCountLeadingZeroBits can only
be marked constexpr if qPopulationCount is also.

On MSVC2017 64bit this is not a problem because it uses builtins function
in this case. (which is not constexpr, but it works because the compiler
is not forced to diagnose the problem because of the "?:" operator.

The error being fixed is:

  qalgorithms.h(847): error C3615: constexpr function 'qCountLeadingZeroBits' cannot result in a constant expression
  qalgorithms.h(858): note: failure was caused by call of undefined function or one not declared 'constexpr'
  qalgorithms.h(858): note: see usage of 'qPopulationCount'

Task-number: QTBUG-67259
Change-Id: I65a3dfae12ca49394bec14ffefdd41a07fee1c32
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Olivier Goffart 2018-03-23 11:34:10 +01:00 committed by Olivier Goffart (Woboq GmbH)
parent e83f1900f6
commit c59cb98095
1 changed files with 6 additions and 4 deletions
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10
src/corelib/tools/qalgorithms.h
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@ -590,6 +590,7 @@ Q_DECL_CONSTEXPR Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) Q_DECL_NO
}
#elif defined(Q_CC_MSVC) && !defined(Q_OS_WINCE) && !defined(Q_PROCESSOR_ARM)
#define QT_POPCOUNT_CONSTEXPR
#define QT_POPCOUNT_RELAXED_CONSTEXPR
#define QT_HAS_BUILTIN_CTZ
Q_ALWAYS_INLINE unsigned long qt_builtin_ctz(quint32 val)
{
@ -676,6 +677,7 @@ Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) Q_DECL_NOTHROW
#ifndef QT_POPCOUNT_CONSTEXPR
#define QT_POPCOUNT_CONSTEXPR Q_DECL_CONSTEXPR
#define QT_POPCOUNT_RELAXED_CONSTEXPR Q_DECL_RELAXED_CONSTEXPR
#endif
} //namespace QAlgorithmsPrivate
@ -819,7 +821,7 @@ Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint32 v) Q_DECL_NOT
#endif
}
Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) Q_DECL_NOTHROW
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) Q_DECL_NOTHROW
{
#if defined(QT_HAS_BUILTIN_CLZ)
return v ? QAlgorithmsPrivate::qt_builtin_clz(v)-24U : 8U;
@ -831,7 +833,7 @@ Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) Q_DECL_NOTH
#endif
}
Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) Q_DECL_NOTHROW
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) Q_DECL_NOTHROW
{
#if defined(QT_HAS_BUILTIN_CLZS)
return v ? QAlgorithmsPrivate::qt_builtin_clzs(v) : 16U;
@ -844,7 +846,7 @@ Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) Q_DECL_NOT
#endif
}
Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) Q_DECL_NOTHROW
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) Q_DECL_NOTHROW
{
#if defined(QT_HAS_BUILTIN_CLZLL)
return v ? QAlgorithmsPrivate::qt_builtin_clzll(v) : 64U;
@ -859,7 +861,7 @@ Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) Q_DECL_NOT
#endif
}
Q_DECL_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(unsigned long v) Q_DECL_NOTHROW
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(unsigned long v) Q_DECL_NOTHROW
{
return qCountLeadingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
}