Implement fast paths for removeFirst() and removeLast()

This avoids lots of the code and checks in remove() making the methods a lot faster. Change-Id: If99c39f5b55672b341f9331b5903bf77e9e67477 Reviewed-by: Andrei Golubev <[email protected]> Reviewed-by: Thiago Macieira <[email protected]>
zoldalis · Nov 9, 2020 · f438286 · f438286
1 parent 13fcd02
commit f438286
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Showing 2 changed files with 64 additions and 2 deletions.
diff --git a/src/corelib/tools/qarraydataops.h b/src/corelib/tools/qarraydataops.h
@@ -429,6 +429,19 @@ struct QPodArrayOps
         this->size -= (e - b);
     }
 
+    void eraseFirst()
+    {
+        Q_ASSERT(this->size);
+        ++this->ptr;
+        --this->size;
+    }
+
+    void eraseLast()
+    {
+        Q_ASSERT(this->size);
+        --this->size;
+    }
+
     void assign(T *b, T *e, parameter_type t)
     {
         Q_ASSERT(b <= e);
@@ -830,6 +843,22 @@ struct QGenericArrayOps
         } while (b != e);
     }
 
+    void eraseFirst()
+    {
+        Q_ASSERT(this->size);
+        this->begin()->~T();
+        ++this->ptr;
+        --this->size;
+    }
+
+    void eraseLast()
+    {
+        Q_ASSERT(this->size);
+        (--this->end())->~T();
+        --this->size;
+    }
+
+
     void assign(T *b, T *e, parameter_type t)
     {
         Q_ASSERT(b <= e);
@@ -1300,6 +1329,21 @@ struct QCommonArrayOps : QArrayOpsSelector<T>::Type
             Base::erase(GrowsForwardTag{}, b, e);
         }
     }
+
+    void eraseFirst()
+    {
+        Q_ASSERT(this->isMutable());
+        Q_ASSERT(this->size);
+        Base::eraseFirst();
+    }
+
+    void eraseLast()
+    {
+        Q_ASSERT(this->isMutable());
+        Q_ASSERT(this->size);
+        Base::eraseLast();
+    }
+
 };
 
 } // namespace QtPrivate

diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
@@ -377,8 +377,8 @@ class QList
     }
 
     void remove(qsizetype i, qsizetype n = 1);
-    void removeFirst() { Q_ASSERT(!isEmpty()); remove(0); }
-    void removeLast() { Q_ASSERT(!isEmpty()); remove(size() - 1); }
+    void removeFirst();
+    void removeLast();
     value_type takeFirst() { Q_ASSERT(!isEmpty()); value_type v = std::move(first()); remove(0); return v; }
     value_type takeLast() { Q_ASSERT(!isEmpty()); value_type v = std::move(last()); remove(size() - 1); return v; }
 
@@ -655,8 +655,26 @@ inline void QList<T>::remove(qsizetype i, qsizetype n)
         // we're detached and we can just move data around
         d->erase(d->begin() + i, d->begin() + i + n);
     }
+
+template <typename T>
+inline void QList<T>::removeFirst()
+{
+    Q_ASSERT(!isEmpty());
+    if (d->needsDetach())
+        d.detach();
+    d->eraseFirst();
 }
 
+template <typename T>
+inline void QList<T>::removeLast()
+{
+    Q_ASSERT(!isEmpty());
+    if (d->needsDetach())
+        detach();
+    d->eraseLast();
+}
+
+
 template<typename T>
 inline T QList<T>::value(qsizetype i, parameter_type defaultValue) const
 {