On Wed, 20 Oct 2004 19:48:05 +0900, you wrote:
Hello,
Changelog: Dmitry Timoshkov <dmitry(a)codeweavers.com> Tiny optimizations of bit testing operations.
Testing with gcc 3.3.5:
- BOOL min_or_max_box = (wndPtr->dwStyle & WS_MAXIMIZEBOX) || - (wndPtr->dwStyle & WS_MINIMIZEBOX); + BOOL min_or_max_box = wndPtr->dwStyle & (WS_MAXIMIZEBOX | WS_MINIMIZEBOX);
At moderate optimization levels (-O1) gcc compiles this to identical code.
- if((wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR) != 0) + if (wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR)
At any optimization level, gcc compiles this to identical code.
if ((wndPtr->dwStyle & WS_VSCROLL) && - ((((wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR) != 0) && (ptClient.x <= rcClient.left + GetSystemMetrics(SM_CXVSCROLL))) || - (((wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR) == 0) && (ptClient.x >= rcClient.right - GetSystemMetrics(SM_CXVSCROLL))))) + (((wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR) && (ptClient.x <= rcClient.left + GetSystemMetrics(SM_CXVSCROLL))) || + (!(wndPtr->dwExStyle & WS_EX_LEFTSCROLLBAR) && (ptClient.x >= rcClient.right - GetSystemMetrics(SM_CXVSCROLL)))))
Not different then the previous example.
From the C point of view these bit logics are identical. The compiler finds that out easy.
Rein. -- Rein Klazes rklazes(a)xs4all.nl