On Sat, Sep 28, 2013 at 3:28 AM, Cong Hou <co...@google.com> wrote:
> The current GCC vectorizer requires the following pattern as a simple
> reduction computation:
>
> loop_header:
> a1 = phi < a0, a2 >
> a3 = ...
> a2 = operation (a3, a1)
>
> But a3 can also be defined outside of the loop. For example, the
> following loop can benefit from vectorization but the GCC vectorizer
> fails to vectorize it:
>
>
> int foo(int v)
> {
> int s = 1;
> ++v;
> for (int i = 0; i < 100000; ++i)
> s *= v;
> return s;
> }
>
>
> This patch relaxes the original requirement by also considering the
> following pattern:
>
>
> a3 = ...
> loop_header:
> a1 = phi < a0, a2 >
> a2 = operation (a3, a1)
>
>
> A test case is also added. The patch is tested on x86-64.
>
>
> thanks,
> Cong
>
> ================================
>
> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> index 39c786e..45c1667 100644
> --- a/gcc/ChangeLog
> +++ b/gcc/ChangeLog
> @@ -1,3 +1,9 @@
> +2013-09-27 Cong Hou <co...@google.com>
> +
> + * tree-vect-loop.c: Relax the requirement of the reduction
ChangeLog format is
<tab>* tree-vect-loop.c (vect_is_simple_reduction_1): Relax the
<tab>requirement of the reduction.
Ok with that change.
Thanks,
Richard.
> + pattern so that one operand of the reduction operation can
> + come from outside of the loop.
> +
> 2013-09-25 Tom Tromey <tro...@redhat.com>
>
> * Makefile.in (PARTITION_H, LTO_SYMTAB_H, COMMON_TARGET_DEF_H)
> diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
> index 09644d2..90496a2 100644
> --- a/gcc/testsuite/ChangeLog
> +++ b/gcc/testsuite/ChangeLog
> @@ -1,3 +1,7 @@
> +2013-09-27 Cong Hou <co...@google.com>
> +
> + * gcc.dg/vect/vect-reduc-pattern-3.c: New test.
> +
> 2013-09-25 Marek Polacek <pola...@redhat.com>
>
> PR sanitizer/58413
> diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
> index 2871ba1..3c51c3b 100644
> --- a/gcc/tree-vect-loop.c
> +++ b/gcc/tree-vect-loop.c
> @@ -2091,6 +2091,13 @@ vect_is_slp_reduction (loop_vec_info loop_info,
> gimple phi, gimple first_stmt)
> a3 = ...
> a2 = operation (a3, a1)
>
> + or
> +
> + a3 = ...
> + loop_header:
> + a1 = phi < a0, a2 >
> + a2 = operation (a3, a1)
> +
> such that:
> 1. operation is commutative and associative and it is safe to
> change the order of the computation (if CHECK_REDUCTION is true)
> @@ -2451,6 +2458,7 @@ vect_is_simple_reduction_1 (loop_vec_info
> loop_info, gimple phi,
> if (def2 && def2 == phi
> && (code == COND_EXPR
> || !def1 || gimple_nop_p (def1)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (def1))
> || (def1 && flow_bb_inside_loop_p (loop, gimple_bb (def1))
> && (is_gimple_assign (def1)
> || is_gimple_call (def1)
> @@ -2469,6 +2477,7 @@ vect_is_simple_reduction_1 (loop_vec_info
> loop_info, gimple phi,
> if (def1 && def1 == phi
> && (code == COND_EXPR
> || !def2 || gimple_nop_p (def2)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (def2))
> || (def2 && flow_bb_inside_loop_p (loop, gimple_bb (def2))
> && (is_gimple_assign (def2)
> || is_gimple_call (def2)
> diff --git gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c
> gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c
> new file mode 100644
> index 0000000..06a9416
> --- /dev/null
> +++ gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c
> @@ -0,0 +1,41 @@
> +/* { dg-require-effective-target vect_int } */
> +
> +#include <stdarg.h>
> +#include "tree-vect.h"
> +
> +#define N 10
> +#define RES 1024
> +
> +/* A reduction pattern in which there is no data ref in
> + the loop and one operand is defined outside of the loop. */
> +
> +__attribute__ ((noinline)) int
> +foo (int v)
> +{
> + int i;
> + int result = 1;
> +
> + ++v;
> + for (i = 0; i < N; i++)
> + result *= v;
> +
> + return result;
> +}
> +
> +int
> +main (void)
> +{
> + int res;
> +
> + check_vect ();
> +
> + res = foo (1);
> + if (res != RES)
> + abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
> +/* { dg-final { cleanup-tree-dump "vect" } } */
> +
