On Wed, Jan 24, 2018 at 10:56 PM, Kugan Vivekanandarajah
<kugan.vivekanandara...@linaro.org> wrote:
> Hi All,
>
> Here is a patch for popcount builtin detection similar to LLVM. I
> would like to queue this for review for next stage 1.
>
> 1. This is done part of loop-distribution and effective for -O3 and above.
> 2. This does not distribute loop to detect popcount (like
> memcpy/memmove). I dont think that happens in practice. Please correct
> me if I am wrong.
But then it has no business inside loop distribution but instead is
doing final value
replacement, right? You are pattern-matching the whole loop after all. I think
final value replacement would already do the correct thing if you
teached number of
iteration analysis that niter for
<bb 3> [local count: 955630224]:
# b_11 = PHI <b_5(5), b_8(6)>
_1 = b_11 + -1;
b_8 = _1 & b_11;
if (b_8 != 0)
goto <bb 6>; [89.00%]
else
goto <bb 8>; [11.00%]
<bb 6> [local count: 850510900]:
goto <bb 3>; [100.00%]
is related to popcount (b_5).
Richard.
> Bootstrapped and regression tested on aarch64-linux-gnu with no new
> regressions.
>
> Thanks,
> Kugan
>
> gcc/ChangeLog:
>
> 2018-01-25 Kugan Vivekanandarajah <kug...@linaro.org>
>
> PR middle-end/82479
> * tree-loop-distribution.c (handle_popcount): New.
> (pass_loop_distribution::execute): Use handle_popcount.
>
> gcc/testsuite/ChangeLog:
>
> 2018-01-25 Kugan Vivekanandarajah <kug...@linaro.org>
>
> PR middle-end/82479
> * gcc.dg/tree-ssa/popcount.c: New test.
