[PATCH] Fix redundant load missed by fre [tree-optimization 92980]

[Andrew Pinski]

On Tue, Dec 17, 2019 at 6:33 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> Hi:
>   This patch is to simplify A * C + (-D) -> (A - D/C) * C when C is a
> power of 2 and D mod C == 0.
>   bootstrap and make check is ok.

I don't see why D has to be negative here.


>TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
+     && TYPE_UNSIGNED (TREE_TYPE (@0))

This is the wrong check here.
Use INTEGRAL_TYPE_P .

>+ (plus (mult @0 integer_pow2p@1) INTEGER_CST@2)

 You might want a :s here for the mult and/or plus.

unsigned HOST_WIDE_INT d = tree_to_uhwi (@2);
...
Maybe use wide_int math instead of HOST_WIDE_INT here, then you don't
need the tree_fits_uhwi_p check.

Add a testcase should tests the pattern directly rather than indirectly.

Also we are in stage 3 which means bug fixes only so this might/should
wait until stage 1.

Thanks,
Andrew Pinski

>
> changelog
> gcc/
>         * gcc/match.pd (A * C + (-D) = (A - D/C) * C. when C is a
>         power of 2 and D mod C == 0): Add new simplification.
>
> gcc/testsuite
>         * gcc.dg/pr92980.c: New test.
>
> --
> BR,
> Hongtao