On Thu, 15 Oct 2020, guojiufu wrote:
> Hi,
>
> I just had a check on below patch for PR66552.
> https://gcc.gnu.org/pipermail/gcc-patches/2020-February/540930.html
> It seems this patch works fine now. This patch fixes PR66552 which
> request to optimizes (x shift (n mod C)) to
> (x shift (n bit_and (C - 1))) when C is a constant and power of two.
>
> As tests, bootstrap and regtests pass on ppc64le. Is it ok for trunk?
OK.
Thanks,
Richard.
> Jiufu Guo
>
> gcc/ChangeLog
> 2020-10-14 Li Jia He <heli...@linux.ibm.com>
>
> PR tree-optimization/66552
> * match.pd (x << (n % C) -> x << (n & C-1)): New simplification.
>
> testsuite/ChangeLog
> 2020-10-14 Li Jia He <heli...@linux.ibm.com>
>
> PR tree-optimization/66552
> * testsuite/gcc.dg/pr66552.c: New testcase.
>
>
> ---
> gcc/match.pd | 11 ++++++++++-
> gcc/testsuite/gcc.dg/pr66552.c | 14 ++++++++++++++
> 2 files changed, 24 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr66552.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index c3b88168ac4..9070812fe7b 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -607,12 +607,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> /* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
> i.e. "X % C" into "X & (C - 1)", if X and C are positive.
> Also optimize A % (C << N) where C is a power of 2,
> - to A & ((C << N) - 1). */
> + to A & ((C << N) - 1). And optimize "A shift (B % C)" where C
> + is a power of 2, shift operation included "<<" and ">>" and assume
> + (B % C) will not be negative as shifts negative values would be UB,
> + to "A shift (B & (C - 1))". */
> (match (power_of_two_cand @1)
> INTEGER_CST@1)
> (match (power_of_two_cand @1)
> (lshift INTEGER_CST@1 @2))
> (for mod (trunc_mod floor_mod)
> + (for shift (lshift rshift)
> + (simplify
> + (shift @0 (mod @1 (power_of_two_cand@2 @3)))
> + (if (integer_pow2p (@3) && tree_int_cst_sgn (@3) > 0)
> + (shift @0 (bit_and @1 (minus @2 { build_int_cst (TREE_TYPE (@2),
> + 1); }))))))
> (simplify
> (mod @0 (convert?@3 (power_of_two_cand@1 @2)))
> (if ((TYPE_UNSIGNED (type)
> diff --git a/gcc/testsuite/gcc.dg/pr66552.c b/gcc/testsuite/gcc.dg/pr66552.c
> new file mode 100644
> index 00000000000..7583c9ad25a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr66552.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-lower" } */
> +
> +unsigned a(unsigned x, int n)
> +{
> + return x >> (n % 32);
> +}
> +
> +unsigned b(unsigned x, int n)
> +{
> + return x << (n % 32);
> +}
> +
> +/* { dg-final { scan-tree-dump-not " % " "lower" } } */
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imend
