On Thu, Sep 03, 2015 at 05:25:43PM +0100, Kyrill Tkachov wrote:
> >void g(void);
> >void f(int *x) { if (*x & 2) g(); }
> A testcase I was looking at is:
> int
> foo (int a)
> {
> return (a & 7) != 0;
> }
>
> For me this generates:
> and w0, w0, 7
> cmp w0, wzr
> cset w0, ne
> ret
>
> when it could be:
> tst w0, 7
> cset w0, ne
> ret
Interesting, thanks.
That testcase with 4 (instead of 7) results in a single ubfx (a zero_extract)
(this case is written differently before combine already, however).
With 6 it does what you want (combine does not handle it as an extract,
no matter what the docs say); and 7 is as you say (combine tries the extract,
there is no insn like that).
Segher
