[Committed] PR target/110843: Check TARGET_AVX512VL for V2DI rotates in STV.

[Committed] PR target/110843: Check TARGET_AVX512VL for V2DI rotates in STV.

This patch resolves PR target/110843, an ICE caused by my enhancement to
support AVX512 DImode and SImode rotates in the scalar-to-vector (STV) pass.
Although the vprotate instructions are available on all TARGET_AVX512F
microarchitectures, the V2DI and V4SI variants are only available on the
TARGET_AVX512VL subset, leading to problems when command line options
enable AVX512 (i.e. AVX512F) but not the required AVX512VL functionality.
The simple fix is to update/correct the target checks.

2023-07-31  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR target/110843
	* config/i386/i386-features.cc (compute_convert_gain): Check
	TARGET_AVX512VL (not TARGET_AVX512F) when considering V2DImode
	and V4SImode rotates in STV.
	(general_scalar_chain::convert_rotate): Likewise.

gcc/testsuite/ChangeLog
	PR target/110843
	* gcc.target/i386/pr110843.c: New test case.