Tiny optimizations of bit testing operations

[Rein Klazes]

On Wed, 20 Oct 2004 19:48:05 +0900, you wrote:

> Hello,
> 
> Changelog:
>     Dmitry Timoshkov <dmitry at 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.