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QAnyStringView: move the tag bits to the LSB for Qt 7

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This removes the TODO that was left in the file. It's also applied for
bootstrapped use of QAnyStringView, even though it's currently not used
in the bootstrap lib.

Along with the previous commit of inverting the order of the members,
the code generated by GCC 12 for a visitation compares as:

_Z1f14QAnyStringView:                                           _Z1f14QAnyStringView:
        movabsq $4611686018427387903, %rcx                    |         movq    %rsi, %rax
        movq    %rdi, %rdx                                    |         shrq    $2, %rsi
        movabsq $-4611686018427387904, %rax                   |         andl    $3, %eax
        andq    %rsi, %rax                                    |         cmpq    $2, %rax
        andq    %rcx, %rsi                                    <
        movabsq $-9223372036854775808, %rcx                   <
        cmpq    %rcx, %rax                                    <
        je      .L15                                                    je      .L15
        movabsq $4611686018427387904, %rcx                    |         cmpq    $1, %rax
        cmpq    %rcx, %rax                                    <
        je      .L16                                                    je      .L16
        jmp     _Z1fI20QBasicUtf8StringViewILb0EEEvT_                   jmp     _Z1fI20QBasicUtf8StringViewILb0EEEvT_
.L16:                                                           .L16:
        movq    %rsi, %rdi                                    |         jmp     _Z1fI17QLatin1StringViewEvT_
        movq    %rdx, %rsi                                    <
        jmp     _Z1fI13QLatin1StringEvT_                      <
.L15:                                                           .L15:
        movq    %rsi, %rdi                                    <
        movq    %rdx, %rsi                                    <
        jmp     _Z1fI11QStringViewEvT_                                  jmp     _Z1fI11QStringViewEvT_

Fixes: QTBUG-109086
Change-Id: I51d12ccdc56c4ad2af07fffd172db128ca4105a5
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
This commit is contained in:
Thiago Macieira 2022-12-04 12:30:25 -08:00
parent 497275a8ba
commit 8be744df8a
1 changed files with 17 additions and 10 deletions
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27
src/corelib/text/qanystringview.h
View File

@ -33,20 +33,25 @@ public:
typedef qptrdiff difference_type;
typedef qsizetype size_type;
private:
// TODO: Optimize by inverting and storing the flags in the low bits and
// the size in the high.
static_assert(std::is_same_v<std::size_t, size_t>);
static_assert(sizeof(size_t) == sizeof(qsizetype));
static constexpr size_t SizeMask = (std::numeric_limits<size_t>::max)() / 4;
#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0) || defined(QT_BOOTSTRAPPED)
static constexpr int SizeShift = 2;
static constexpr size_t Latin1Flag = 1;
#else
static constexpr int SizeShift = 0;
static constexpr size_t Latin1Flag = SizeMask + 1;
#endif
static constexpr size_t TwoByteCodePointFlag = Latin1Flag << 1;
static constexpr size_t TypeMask = (std::numeric_limits<size_t>::max)() & ~SizeMask;
static constexpr size_t TypeMask = ~(SizeMask << SizeShift);
static_assert(TypeMask == (Latin1Flag|TwoByteCodePointFlag));
// HI HI LO LO ...
// 0 0 SZ SZ Utf8
// 0 1 SZ SZ Latin1
// 1 0 SZ SZ Utf16
// 1 1 SZ SZ Unused
// Tag bits
// 0 0 Utf8
// 0 1 Latin1
// 1 0 Utf16
// 1 1 Unused
// ^ ^ latin1
// | sizeof code-point == 2
enum Tag : size_t {
@ -130,7 +135,8 @@ private:
Q_ASSERT(sz >= 0);
Q_ASSERT(sz <= qsizetype(SizeMask));
Q_ASSERT(str || !sz);
return std::size_t(sz) | uint(sizeof(Char) == sizeof(char16_t)) * Tag::Utf16
return (std::size_t(sz) << SizeShift)
| uint(sizeof(Char) == sizeof(char16_t)) * Tag::Utf16
| uint(isAsciiOnlyCharsAtCompileTime(str, sz)) * Tag::Latin1;
}
@ -247,7 +253,8 @@ public:
[[nodiscard]] inline QString toString() const; // defined in qstring.h
[[nodiscard]] constexpr qsizetype size() const noexcept { return qsizetype(m_size & SizeMask); }
[[nodiscard]] constexpr qsizetype size() const noexcept
{ return qsizetype((m_size >> SizeShift) & SizeMask); }
[[nodiscard]] constexpr const void *data() const noexcept { return m_data; }
[[nodiscard]] Q_CORE_EXPORT static int compare(QAnyStringView lhs, QAnyStringView rhs, Qt::CaseSensitivity cs = Qt::CaseSensitive) noexcept;