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Optimize code in QTaggedPointer

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Don't execute instructions that will never do anything.

Directly add the tag to the pointer in the constructor to avoid
additional masking operations, and avoid a masking op that is in
practice a no-op in setTag().

Do the same optimization in QTagPreservingPointerToPointer.

Pick-to: dev
Change-Id: Ia364f89cbe6ccc876ec9bda0c239fc4f57c10501
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
This commit is contained in:
Lars Knoll 2020-11-25 11:36:24 +01:00
parent 98c82fb445
commit 2721728c90
2 changed files with 6 additions and 7 deletions
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2
src/corelib/kernel/qpropertyprivate.h
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@ -283,7 +283,7 @@ public:
void setPointer(T *ptr)
{
*d = (reinterpret_cast<quintptr>(ptr) & QTaggedPointer<T, Tag>::pointerMask()) | (*d & QTaggedPointer<T, Tag>::tagMask());
*d = reinterpret_cast<quintptr>(ptr) | (*d & QTaggedPointer<T, Tag>::tagMask());
}
T *get() const

11
src/corelib/tools/qtaggedpointer.h
View File

@ -83,14 +83,13 @@ public:
constexpr QTaggedPointer(std::nullptr_t) noexcept : QTaggedPointer() {}
explicit QTaggedPointer(T *pointer, Tag tag = Tag()) noexcept
: d(quintptr(pointer))
: d(quintptr(pointer) | quintptr(tag))
{
static_assert(sizeof(Type*) == sizeof(QTaggedPointer));
Q_ASSERT_X((quintptr(pointer) & tagMask()) == 0,
"QTaggedPointer<T, Tag>", "Pointer is not aligned");
setTag(tag);
Q_ASSERT_X((quintptr(pointer) & tagMask()) == 0, "QTaggedPointer<T, Tag>", "Pointer is not aligned");
Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0,
"QTaggedPointer<T, Tag>::setTag", "Tag is larger than allowed by number of available tag bits");
}
Type &operator*() const noexcept
@ -125,7 +124,7 @@ public:
Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0,
"QTaggedPointer<T, Tag>::setTag", "Tag is larger than allowed by number of available tag bits");
d = (d & pointerMask()) | (static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & tagMask());
d = (d & pointerMask()) | static_cast<quintptr>(tag);
}
Tag tag() const noexcept