aarch64: Add vector floating point extend pattern [PR113880, PR113869]

aarch64: Add vector floating point extend pattern [PR113880, PR113869]

This patch adds vector floating point extend pattern for V2SF->V2DF and
V4HF->V4SF conversions by renaming the existing aarch64_float_extend_lo_<Vwide>
pattern to the standard optab one, i.e., extend<mode><Vwide>2. This allows the
vectorizer to vectorize certain floating point widening operations for the
aarch64 target.

	PR target/113880
	PR target/113869

gcc/ChangeLog:

	* config/aarch64/aarch64-builtins.cc (VAR1): Remap float_extend_lo_
	builtin codes to standard optab ones.
	* config/aarch64/aarch64-simd.md (aarch64_float_extend_lo_<Vwide>): Rename
	to...
	(extend<mode><Vwide>2): ... This.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/extend-vec.c: New test.

Signed-off-by: Pengxuan Zheng <quic_pzheng@quicinc.com>