[Bug target/56110] Sub-optimal code: unnecessary CMP after AND

[tilman@code-monkey.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56110

--- Comment #1 from Tilman Sauerbeck <tilman@code-monkey.de> 2013-02-16 16:49:34 UTC ---
Changing the literal in the test function so that it fits in 8 bits makes gcc
go with the TST instruction instead of AND+CMP:

unsigned f2 (unsigned x, unsigned m)
{
    if (m & 0x80)
        x >>= 8;

    return x;
}

=>
    tst    r1, #128
    movne    r0, r0, lsr #8
    bx    lr

So I guess I shouldn't ask why gcc generates AND+CMP instead of ANDS, but why
it chooses not to use TST.