[01/nn] Add gen_(const_)vec_duplicate helpers

[Richard Sandiford]

Jeff Law <law@redhat.com> writes:
> On 10/23/2017 05:16 AM, Richard Sandiford wrote:
>> This patch adds helper functions for generating constant and
>> non-constant vector duplicates.  These routines help with SVE because
>> it is then easier to use:
>> 
>>    (const:M (vec_duplicate:M X))
>> 
>> for a broadcast of X, even if the number of elements in M isn't known
>> at compile time.  It also makes it easier for general rtx code to treat
>> constant and non-constant duplicates in the same way.
>> 
>> In the target code, the patch uses gen_vec_duplicate instead of
>> gen_rtx_VEC_DUPLICATE if handling constants correctly is potentially
>> useful.  It might be that some or all of the call sites only handle
>> non-constants in practice, in which case the change is a harmless
>> no-op (and a saving of a few characters).
>> 
>> Otherwise, the target changes use gen_const_vec_duplicate instead
>> of gen_rtx_CONST_VECTOR if the constant is obviously a duplicate.
>> They also include some changes to use CONSTxx_RTX for easy global
>> constants.
>> 
>> 
>> 2017-10-23  Richard Sandiford  <richard.sandiford@linaro.org>
>> 	    Alan Hayward  <alan.hayward@arm.com>
>> 	    David Sherwood  <david.sherwood@arm.com>
>> 
>> gcc/
>> 	* emit-rtl.h (gen_const_vec_duplicate): Declare.
>> 	(gen_vec_duplicate): Likewise.
>> 	* emit-rtl.c (gen_const_vec_duplicate_1): New function, split
>> 	out from...
>> 	(gen_const_vector): ...here.
>> 	(gen_const_vec_duplicate, gen_vec_duplicate): New functions.
>> 	(gen_rtx_CONST_VECTOR): Use gen_const_vec_duplicate for constants
>> 	whose elements are all equal.
>> 	* optabs.c (expand_vector_broadcast): Use gen_const_vec_duplicate.
>> 	* simplify-rtx.c (simplify_const_unary_operation): Likewise.
>> 	(simplify_relational_operation): Likewise.
>> 	* config/aarch64/aarch64.c (aarch64_simd_gen_const_vector_dup):
>> 	Likewise.
>> 	(aarch64_simd_dup_constant): Use gen_vec_duplicate.
>> 	(aarch64_expand_vector_init): Likewise.
>> 	* config/arm/arm.c (neon_vdup_constant): Likewise.
>> 	(neon_expand_vector_init): Likewise.
>> 	(arm_expand_vec_perm): Use gen_const_vec_duplicate.
>> 	(arm_block_set_unaligned_vect): Likewise.
>> 	(arm_block_set_aligned_vect): Likewise.
>> 	* config/arm/neon.md (neon_copysignf<mode>): Likewise.
>> 	* config/i386/i386.c (ix86_expand_vec_perm): Likewise.
>> 	(expand_vec_perm_even_odd_pack): Likewise.
>> 	(ix86_vector_duplicate_value): Use gen_vec_duplicate.
>> 	* config/i386/sse.md (one_cmpl<mode>2): Use CONSTM1_RTX.
>> 	* config/ia64/ia64.c (ia64_expand_vecint_compare): Use
>> 	gen_const_vec_duplicate.
>> 	* config/ia64/vect.md (addv2sf3, subv2sf3): Use CONST1_RTX.
>> 	* config/mips/mips.c (mips_gen_const_int_vector): Use
>> 	gen_const_vec_duplicate.
>> 	(mips_expand_vector_init): Use CONST0_RTX.
>> 	* config/powerpcspe/altivec.md (abs<mode>2, nabs<mode>2): Likewise.
>> 	(define_split): Use gen_const_vec_duplicate.
>> 	* config/rs6000/altivec.md (abs<mode>2, nabs<mode>2): Use CONST0_RTX.
>> 	(define_split): Use gen_const_vec_duplicate.
>> 	* config/s390/vx-builtins.md (vec_genmask<mode>): Likewise.
>> 	(vec_ctd_s64, vec_ctd_u64, vec_ctsl, vec_ctul): Likewise.
>> 	* config/spu/spu.c (spu_const): Likewise.
> I'd started looking at this a couple times when it was originally
> submitted, but never seemed to get through it.  It seems like a nice
> cleanup.
>
> So in gen_const_vector we had an assert to verify that const_tiny_rtx
> was set up.  That seems to have been lost.  It's probably not a big
> deal, but I mention it in case the loss was unintentional.

This morphed into:

+static rtx
+gen_const_vector (machine_mode mode, int constant)
+{
+  machine_mode inner = GET_MODE_INNER (mode);
+
+  gcc_assert (!DECIMAL_FLOAT_MODE_P (inner));
+
+  rtx el = const_tiny_rtx[constant][(int) inner];
+  gcc_assert (el);

but it wasn't obvious due to the way the unified diff mixed up the
functions.  I should have posted that one as context, sorry...

Richard