On 06/01/17 11:54, Kyrill Tkachov wrote:
> Hi all,
>
> In this wrong-code issue the RTL tries to load a const_vector:
> (const_vector:V8QI [
> (const_int 1 [0x1])
> (const_int 0 [0])
> (const_int 1 [0x1])
> (const_int 0 [0])
> (const_int 1 [0x1])
> (const_int 0 [0])
> (const_int 1 [0x1])
> (const_int 0 [0])
> ])
>
> into a NEON register. The logic for that is in neon_valid_immediate
> which does a number of tricks
> to decide what value and of what size to do a VMOV on to load the
> correct vector immediate into the register.
> It goes wrong on big-endian. On both big and little-endian this outputs:
> vmov.i16 d18, #0x1
>
> This is wrong on big-endian. The vector layout has to be such as if
> loaded from memory.
> I've tried various approaches of fixing neon_valid_immediate to generate
> the correct immediate but have been unsuccessful,
> resulting in regressions in various parts of the testsuite or making a
> big mess of the function.
>
> Given that armeb is not a target of major concern I believe the safest
> route at this stage is to only allow vector constants
> that will obviously work on big-endian, that is the ones that are just a
> single element duplicated in all lanes.
>
> This patch fixes the execution failures:
> FAIL: gfortran.dg/intrinsic_pack_1.f90
> FAIL: gfortran.dg/c_f_pointer_logical.f03
> FAIL: gcc.dg/torture/pr60183.c
> FAIL: gcc.dg/vect/pr51581-4.c
>
> on armeb-none-eabi.
>
> Ok for trunk?
>
> Thanks,
> Kyrill
>
> 2017-01-06 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR target/71270
> * config/arm/arm.c (neon_valid_immediate): Reject vector constants
> in big-endian mode when they are not a single duplicated value.
>
Ok, but if you plan to close the PR above, please create a new
'enhancement' PR to fix the missed optimization.
R.
> armeb-vec.patch
>
>
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index
> 45e0a3cd11fa650f456f7382ffbbcd1c932b95eb..2beee8ebe94eeadd6fb1d5b119e3b474e1ab902a
> 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -11542,6 +11542,12 @@ neon_valid_immediate (rtx op, machine_mode mode, int
> inverse,
> return 18;
> }
>
> + /* The tricks done in the code below apply for little-endian vector layout.
> + For big-endian vectors only allow vectors of the form { a, a, a..., a }.
> + FIXME: Implement logic for big-endian vectors. */
> + if (BYTES_BIG_ENDIAN && vector && !const_vec_duplicate_p (op))
> + return -1;
> +
> /* Splat vector constant out into a byte vector. */
> for (i = 0; i < n_elts; i++)
> {
>
