[ARM]: Correct the grouping of operands in MVE vector scatter store intrinsics (PR94735).

[ARM]: Correct the grouping of operands in MVE vector scatter store intrinsics (PR94735).

The operands in RTL patterns of MVE vector scatter store intrinsics are wrongly grouped,
because of which few vector loads and stores instructions are wrongly getting optimized
out with -O2.

A new predicate "mve_scatter_memory" is defined in this patch, this predicate returns TRUE on
matching: (mem(reg)) for MVE scatter store intrinsics.
This patch fixes the issue by adding define_expand pattern with "mve_scatter_memory" predicate
and calls the corresponding define_insn by passing register_operand as first argument.
This register_operand is extracted from the operand with "mve_scatter_memory" predicate in
define_expand pattern.

gcc/ChangeLog:

2020-06-01  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	PR target/94735
	* config/arm/predicates.md (mve_scatter_memory): Define to
	match (mem (reg)) for scatter store memory.
	* config/arm/mve.md (mve_vstrbq_scatter_offset_<supf><mode>): Modify
	define_insn to define_expand.
	(mve_vstrbq_scatter_offset_p_<supf><mode>): Likewise.
	(mve_vstrhq_scatter_offset_<supf><mode>): Likewise.
	(mve_vstrhq_scatter_shifted_offset_p_<supf><mode>): Likewise.
	(mve_vstrhq_scatter_shifted_offset_<supf><mode>): Likewise.
	(mve_vstrdq_scatter_offset_p_<supf>v2di): Likewise.
	(mve_vstrdq_scatter_offset_<supf>v2di): Likewise.
	(mve_vstrdq_scatter_shifted_offset_p_<supf>v2di): Likewise.
	(mve_vstrdq_scatter_shifted_offset_<supf>v2di): Likewise.
	(mve_vstrhq_scatter_offset_fv8hf): Likewise.
	(mve_vstrhq_scatter_offset_p_fv8hf): Likewise.
	(mve_vstrhq_scatter_shifted_offset_fv8hf): Likewise.
	(mve_vstrhq_scatter_shifted_offset_p_fv8hf): Likewise.
	(mve_vstrwq_scatter_offset_fv4sf): Likewise.
	(mve_vstrwq_scatter_offset_p_fv4sf): Likewise.
	(mve_vstrwq_scatter_offset_p_<supf>v4si): Likewise.
	(mve_vstrwq_scatter_offset_<supf>v4si): Likewise.
	(mve_vstrwq_scatter_shifted_offset_fv4sf): Likewise.
	(mve_vstrwq_scatter_shifted_offset_p_fv4sf): Likewise.
	(mve_vstrwq_scatter_shifted_offset_p_<supf>v4si): Likewise.
	(mve_vstrwq_scatter_shifted_offset_<supf>v4si): Likewise.
	(mve_vstrbq_scatter_offset_<supf><mode>_insn): Define insn for scatter
	stores.
	(mve_vstrbq_scatter_offset_p_<supf><mode>_insn): Likewise.
	(mve_vstrhq_scatter_offset_<supf><mode>_insn): Likewise.
	(mve_vstrhq_scatter_shifted_offset_p_<supf><mode>_insn): Likewise.
	(mve_vstrhq_scatter_shifted_offset_<supf><mode>_insn): Likewise.
	(mve_vstrdq_scatter_offset_p_<supf>v2di_insn): Likewise.
	(mve_vstrdq_scatter_offset_<supf>v2di_insn): Likewise.
	(mve_vstrdq_scatter_shifted_offset_p_<supf>v2di_insn): Likewise.
	(mve_vstrdq_scatter_shifted_offset_<supf>v2di_insn): Likewise.
	(mve_vstrhq_scatter_offset_fv8hf_insn): Likewise.
	(mve_vstrhq_scatter_offset_p_fv8hf_insn): Likewise.
	(mve_vstrhq_scatter_shifted_offset_fv8hf_insn): Likewise.
	(mve_vstrhq_scatter_shifted_offset_p_fv8hf_insn): Likewise.
	(mve_vstrwq_scatter_offset_fv4sf_insn): Likewise.
	(mve_vstrwq_scatter_offset_p_fv4sf_insn): Likewise.
	(mve_vstrwq_scatter_offset_p_<supf>v4si_insn): Likewise.
	(mve_vstrwq_scatter_offset_<supf>v4si_insn): Likewise.
	(mve_vstrwq_scatter_shifted_offset_fv4sf_insn): Likewise.
	(mve_vstrwq_scatter_shifted_offset_p_fv4sf_insn): Likewise.
	(mve_vstrwq_scatter_shifted_offset_p_<supf>v4si_insn): Likewise.
	(mve_vstrwq_scatter_shifted_offset_<supf>v4si_insn): Likewise.

gcc/testsuite/ChangeLog:

2020-06-01  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	PR target/94735
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_base.c: New test.
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_base_p.c: Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_offset.c: Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_offset_p.c: Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_shifted_offset.c:
	Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vstore_scatter_shifted_offset_p.c:
	Likewise.