Re: Add utility functions for rtx broadcast/duplicate constants

[Jeff Law]

On 08/20/2015 04:34 AM, Richard Sandiford wrote:

Several pieces of code want to know whether all elements of a CONST_VECTOR
are equal, and I'm about to add some more to simplify-rtx.c.  This patch
adds some utility functions for that.

I don't think we're really helping ourselves by having the shift
amount in "v16qi << 3" be:

     (const_vector:V16QI [
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
         (const_int 3)
     ])

so I wanted to leave open the possibility of using:

     (const:V16QI (vec_duplicate:V16QI (const_int 3)))

in future.  The interface therefore passes back the duplicated element
rather than leaving callers to use CONST_VECTOR_ELT (c, 0)
(== XVECEXP (c, 0, 0)).

unwrap_const_vec_duplicate is mostly for code that handles vector
operations equivalently to scalar ops.  The follow-on simplify-rtx.c
code makes more use of this.  It also came in useful for the tilegx/
tilepro predicates.

Tested on x86_64-linux-gnu, arm-linux-gnueabi and aarch64-linux-gnu.
I also built cross-compilers for s390x-linux-gnu, spu-elf, tilepro-elf
and tilegx-elf and checked by hand that the affected code still worked.
(Well, except for the SPU case.  That's handling vector constants in
which the elements are symbolic addresses, such as
{ &foo, &foo, &foo, &foo }.  Such vectors don't seem to be treated as
constants at the gimple level and the initial rtl code that we generate
is too complex for later optimisations to convert back to a constant,
so I wasn't sure how best to trigger it.)

OK to install?

Thanks,
Richard

gcc/
        * rtl.h (rtvec_all_equal_p): Declare.
        (const_vec_duplicate_p, unwrap_const_vec_duplicate): New functions.
        * rtl.c (rtvec_all_equal_p): New function.
        * expmed.c (expand_mult): Use unwrap_const_vec_duplicate.
        * config/aarch64/aarch64.c (aarch64_vect_float_const_representable_p)
        (aarch64_simd_dup_constant): Use const_vec_duplicate_p.
        * config/arm/arm.c (neon_vdup_constant): Likewise.
        * config/s390/s390.c (s390_contiguous_bitmask_vector_p): Likewise.
        * config/tilegx/constraints.md (W, Y): Likewise.
        * config/tilepro/constraints.md (W, Y): Likewise.
        * config/spu/spu.c (spu_legitimate_constant_p): Likewise.
        (classify_immediate): Use unwrap_const_vec_duplicate.
        * config/tilepro/predicates.md (reg_or_v4s8bit_operand): Likewise.
        (reg_or_v2s8bit_operand): Likewise.
        * config/tilegx/predicates.md (reg_or_v8s8bit_operand): Likewise.
        (reg_or_v4s8bit_operand): Likewise.

OK.
Jeff