On Fri, Oct 23, 2015 at 5:15 PM, Alan Lawrence <alan.lawre...@arm.com> wrote:
> On 19/10/15 12:49, Richard Biener wrote:
>
>> Err, you should always do the shift in the type of rhs1. You should also
>> avoid the chrec_convert of rhs2 above for shifts.
>
> Err, yes, indeed. Needed to keep the chrec_convert before the
> chrec_fold_multiply, and the rest followed. How's this?
>
> Bootstrapped+check-gcc,g++ on x86, ARM, AArch64.
>
> gcc/ChangeLog (as before):
>
> PR tree-optimization/65963
> * tree-scalar-evolution.c (interpret_rhs_expr): Handle some
> LSHIFT_EXPRs
> as equivalent MULT_EXPRs.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/vect-strided-shift-1.c: New.
> ---
> gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c | 33
> ++++++++++++++++++++++++
> gcc/tree-scalar-evolution.c | 15 +++++++++++
> 2 files changed, 48 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
> b/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
> new file mode 100644
> index 0000000..b1ce2ec
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
> @@ -0,0 +1,33 @@
> +/* PR tree-optimization/65963. */
> +#include "tree-vect.h"
> +
> +#define N 512
> +
> +int in[2*N], out[N];
> +
> +__attribute__ ((noinline)) void
> +loop (void)
> +{
> + for (int i = 0; i < N; i++)
> + out[i] = in[i << 1] + 7;
> +}
> +
> +int
> +main (int argc, char **argv)
> +{
> + check_vect ();
> + for (int i = 0; i < 2*N; i++)
> + {
> + in[i] = i;
> + __asm__ volatile ("" : : : "memory");
> + }
> + loop ();
> + __asm__ volatile ("" : : : "memory");
> + for (int i = 0; i < N; i++)
> + {
> + if (out[i] != i*2 + 7)
> + abort ();
> + }
> + return 0;
> +}
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops in function" 1
> "vect" { target { vect_strided2 } } } } */
> diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
> index 0753bf3..129682f 100644
> --- a/gcc/tree-scalar-evolution.c
> +++ b/gcc/tree-scalar-evolution.c
> @@ -1840,6 +1840,21 @@ interpret_rhs_expr (struct loop *loop, gimple *at_stmt,
> res = chrec_fold_multiply (type, chrec1, chrec2);
> break;
>
> + case LSHIFT_EXPR:
> + /* Handle A<<B as A * (1<<B). */
> + chrec1 = analyze_scalar_evolution (loop, rhs1);
> + chrec2 = analyze_scalar_evolution (loop, rhs2);
> + chrec1 = chrec_convert (type, chrec1, at_stmt);
> + chrec1 = instantiate_parameters (loop, chrec1);
> + chrec2 = instantiate_parameters (loop, chrec2);
> + chrec2 = fold_build2 (LSHIFT_EXPR, TREE_TYPE (rhs1),
> + build_int_cst (TREE_TYPE (rhs1), 1),
'type' instead of TREE_TYPE (rhs1)
> + chrec2);
> + chrec2 = chrec_convert (type, chrec2, at_stmt);
so you can remove this chrec_convert.
Ok with that change.
Richard.
> + res = chrec_fold_multiply (type, chrec1, chrec2);
> + break;
> +
> CASE_CONVERT:
> /* In case we have a truncation of a widened operation that in
> the truncated type has undefined overflow behavior analyze
> --
> 1.9.1
>
