[AArch64] Add a couple of SVE ACLE comparison folds

[AArch64] Add a couple of SVE ACLE comparison folds

When writing vector-length specific SVE code, it's useful to be able
to store an svbool_t predicate in a GNU vector of unsigned chars.
This patch makes sure that there is no overhead when converting
to that form and then immediately reading it back again.

2019-12-02  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-sve-builtins.h
	(gimple_folder::force_vector): Declare.
	* config/aarch64/aarch64-sve-builtins.cc
	(gimple_folder::force_vector): New function.
	* config/aarch64/aarch64-sve-builtins-base.cc
	(svcmp_impl::fold): Likewise.
	(svdup_impl::fold): Handle svdup_z too.

gcc/testsuite/
	* gcc.target/aarch64/sve/acle/general/eqne_dup_1.c: New test.
	* gcc.target/aarch64/sve/acle/asm/dup_f16.c (dup_0_f16_z): Expect
	the call to be folded to zero.
	* gcc.target/aarch64/sve/acle/asm/dup_f32.c (dup_0_f32_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_f64.c (dup_0_f64_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_s8.c (dup_0_s8_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_s16.c (dup_0_s16_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_s32.c (dup_0_s32_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_s64.c (dup_0_s64_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_u8.c (dup_0_u8_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_u16.c (dup_0_u16_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_u32.c (dup_0_u32_z): Likewise.
	* gcc.target/aarch64/sve/acle/asm/dup_u64.c (dup_0_u64_z): Likewise.

From-SVN: r278907