This patch pattern-matches a partial gather load followed by a sign or
zero extension into an extending gather load.  (The partial gather load
is already an extending load; we just don't rely on the upper bits of
the elements.)

2019-11-16  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (SVE_2BHSI, SVE_2HSDI, SVE_4BHI)
	(SVE_4HSI): New mode iterators.
	(ANY_EXTEND2): New code iterator.
	* config/aarch64/aarch64-sve.md
	(@aarch64_gather_load_<ANY_EXTEND:optab><VNx4_WIDE:mode><VNx4_NARROW:mode>):
	Extend to...
	(@aarch64_gather_load_<ANY_EXTEND:optab><SVE_4HSI:mode><SVE_4BHI:mode>):
	...this, handling extension to partial modes as well as full modes.
	Describe the extension as a predicated rather than unpredicated
	extension.
	(@aarch64_gather_load_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>):
	Likewise extend to...
	(@aarch64_gather_load_<ANY_EXTEND:optab><SVE_2HSDI:mode><SVE_2BHSI:mode>):
	...this, making the same adjustments.
	(*aarch64_gather_load_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>_sxtw):
	Likewise extend to...
	(*aarch64_gather_load_<ANY_EXTEND:optab><SVE_2HSDI:mode><SVE_2BHSI:mode>_sxtw)
	...this, making the same adjustments.
	(*aarch64_gather_load_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>_uxtw):
	Likewise extend to...
	(*aarch64_gather_load_<ANY_EXTEND:optab><SVE_2HSDI:mode><SVE_2BHSI:mode>_uxtw)
	...this, making the same adjustments.
	(*aarch64_gather_load_<ANY_EXTEND:optab><SVE_2HSDI:mode><SVE_2BHSI:mode>_<ANY_EXTEND2:su>xtw_unpacked):
	New pattern.
	(*aarch64_ldff1_gather<mode>_sxtw): Canonicalize to a constant
	extension predicate.
	(@aarch64_ldff1_gather_<ANY_EXTEND:optab><VNx4_WIDE:mode><VNx4_NARROW:mode>)
	(@aarch64_ldff1_gather_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>)
	(*aarch64_ldff1_gather_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>_uxtw):
	Describe the extension as a predicated rather than unpredicated
	extension.
	(*aarch64_ldff1_gather_<ANY_EXTEND:optab><VNx2_WIDE:mode><VNx2_NARROW:mode>_sxtw):
	Likewise.  Canonicalize to a constant extension predicate.
	* config/aarch64/aarch64-sve-builtins-base.cc
	(svld1_gather_extend_impl::expand): Add an extra predicate for
	the extension.
	(svldff1_gather_extend_impl::expand): Likewise.

gcc/testsuite/
	* gcc.target/aarch64/sve/gather_load_extend_1.c: New test.
	* gcc.target/aarch64/sve/gather_load_extend_2.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_3.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_4.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_5.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_6.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_7.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_8.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_9.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_10.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_11.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_extend_12.c: Likewise.

From-SVN: r278346