x86: Optimize EVEX vector load/store instructions

x86: Optimize EVEX vector load/store instructions

When there is no write mask, we can encode lower 16 128-bit/256-bit
EVEX vector register load and store instructions as VEX vector register
load and store instructions with -O1.

gas/

	PR gas/24348
	* config/tc-i386.c (optimize_encoding): Encode 128-bit and
	256-bit EVEX vector register load/store instructions as VEX
	vector register load/store instructions for -O1.
	* doc/c-i386.texi: Update -O1 documentation.
	* testsuite/gas/i386/i386.exp: Run PR gas/24348 tests.
	* testsuite/gas/i386/optimize-1.s: Add tests for EVEX vector
	load/store instructions.
	* testsuite/gas/i386/optimize-2.s: Likewise.
	* testsuite/gas/i386/optimize-3.s: Likewise.
	* testsuite/gas/i386/optimize-5.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-2.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-3.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-4.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-5.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-6.s: Likewise.
	* testsuite/gas/i386/optimize-1.d: Updated.
	* testsuite/gas/i386/optimize-2.d: Likewise.
	* testsuite/gas/i386/optimize-3.d: Likewise.
	* testsuite/gas/i386/optimize-4.d: Likewise.
	* testsuite/gas/i386/optimize-5.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-2.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-3.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-4.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-5.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-6.d: Likewise.
	* testsuite/gas/i386/optimize-7.d: New file.
	* testsuite/gas/i386/optimize-7.s: Likewise.
	* testsuite/gas/i386/x86-64-optimize-8.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-8.s: Likewise.

opcodes/

	PR gas/24348
	* i386-opc.tbl: Add Optimize to vmovdqa32, vmovdqa64, vmovdqu8,
	vmovdqu16, vmovdqu32 and vmovdqu64.
	* i386-tbl.h: Regenerated.