On Wed, Nov 15, 2017 at 3:39 PM, Wilco Dijkstra <wilco.dijks...@arm.com> wrote:
> Richard Biener wrote:
>> On Tue, Oct 17, 2017 at 6:32 PM, Wilco Dijkstra <wilco.dijks...@arm.com>
>> wrote:
>
>>> (if (flag_reciprocal_math)
>>> - /* Convert (A/B)/C to A/(B*C) */
>>> + /* Convert (A/B)/C to A/(B*C). */
>>> (simplify
>>> (rdiv (rdiv:s @0 @1) @2)
>>> - (rdiv @0 (mult @1 @2)))
>>> + (rdiv @0 (mult @1 @2)))
>>> +
>>> + /* Canonicalize x / (C1 * y) to (x * C2) / y. */
>>> + (if (optimize)
>>
>> why if (optimize) here? The pattern you removed has no
>> such check. As discussed this may undo CSE of C1 * y
>> so please check for a single-use on the mult with :s
>
> I think that came from an earlier version of this patch. I've removed it
> and added a single use check.
>
>>> + (simplify
>>> + (rdiv @0 (mult @1 REAL_CST@2))
>>> + (if (!real_zerop (@1))
>>
>> why this check? The pattern below didn't have it.
>
> Presumably to avoid the change when dividing by zero. I've removed it, here is
> the updated version. This passes bootstrap and regress:
Ok.
Richard.
>
> ChangeLog
> 2017-11-15 Wilco Dijkstra <wdijk...@arm.com>
> Jackson Woodruff <jackson.woodr...@arm.com>
>
> gcc/
> PR 71026/tree-optimization
> * match.pd: Canonicalize constant multiplies in division.
>
> gcc/testsuite/
> PR 71026/tree-optimization
> * gcc.dg/cse_recip.c: New test.
> --
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index
> b5042b783c0830a2da08c44bed39842a17911844..ea7d90ed977cfff991d74bee54e91ecb209b6030
> 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -344,10 +344,18 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (negate @0)))
>
> (if (flag_reciprocal_math)
> - /* Convert (A/B)/C to A/(B*C) */
> + /* Convert (A/B)/C to A/(B*C). */
> (simplify
> (rdiv (rdiv:s @0 @1) @2)
> - (rdiv @0 (mult @1 @2)))
> + (rdiv @0 (mult @1 @2)))
> +
> + /* Canonicalize x / (C1 * y) to (x * C2) / y. */
> + (simplify
> + (rdiv @0 (mult:s @1 REAL_CST@2))
> + (with
> + { tree tem = const_binop (RDIV_EXPR, type, build_one_cst (type), @2); }
> + (if (tem)
> + (rdiv (mult @0 { tem; } ) @1))))
>
> /* Convert A/(B/C) to (A/B)*C */
> (simplify
> @@ -646,15 +654,6 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (if (tem)
> (rdiv { tem; } @1)))))
>
> -/* Convert C1/(X*C2) into (C1/C2)/X */
> -(simplify
> - (rdiv REAL_CST@0 (mult @1 REAL_CST@2))
> - (if (flag_reciprocal_math)
> - (with
> - { tree tem = const_binop (RDIV_EXPR, type, @0, @2); }
> - (if (tem)
> - (rdiv { tem; } @1)))))
> -
> /* Simplify ~X & X as zero. */
> (simplify
> (bit_and:c (convert? @0) (convert? (bit_not @0)))
> diff --git a/gcc/testsuite/gcc.dg/cse_recip.c
> b/gcc/testsuite/gcc.dg/cse_recip.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..88cba9930c0eb1fdee22a797eff110cd9a14fcda
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/cse_recip.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -fdump-tree-optimized-raw" } */
> +
> +void
> +cse_recip (float x, float y, float *a)
> +{
> + a[0] = y / (5 * x);
> + a[1] = y / (3 * x);
> + a[2] = y / x;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "rdiv_expr" 1 "optimized" } } */
>
>
>
>
