Document more x86 operand modifier.

Document more x86 operand modifier.

Documents operand modifiers which are available in asm stmt but missing in document.

 | Modifier | Description | Available in asm stmt | Existed in documentation |
 | --- | --- | ------- | ----- |
 | L,W,B,Q,S,T | print the opcode suffix for specified size of operand. | Available | Not |
 | C | print opcode suffix for set/cmov insn. | Not | - |
 | c | like C, but print reversed condition | Not | - |
 | F,f | likewise, but for floating-point. | Not | - |
 | O | if HAVE_AS_IX86_CMOV_SUN_SYNTAX, expand to "w.", "l." or "q.", otherwise nothing | Not | - |
 | R | print embedded rounding and sae. | Available | Not |
 | r | print only sae. | Available | Not |
 | z | print the opcode suffix for the size of the current operand. | Available | Existed |
 | Z | likewise, with special suffixes for x87 instructions. | Availble | Not |
 | * | print a star (in certain assembler syntax) | Not | - |
 | A | print an absolute memory reference. | Available | Existed |
 | E | print address with DImode register names if TARGET_64BIT. | Available | Existed |
 | w | print the operand as if it's a "word" (HImode) even if it isn't. | Available | Existed |
 | s | print a shift double count, followed by the assemblers argument delimiter. | Available | Not |
 | b | print the QImode name of the register for the indicated operand %b0 would print %al if operands[0] is reg 0. | Available | Existed |
 | w | likewise, print the HImode name of the register. | Available | Existed |
 | k | likewise, print the SImode name of the register. | Available | Existed |
 | q | likewise, print the DImode name of the register. | Available | Existed |
 | x | likewise, print the V4SFmode name of the register. | Available | Not |
 | t | likewise, print the V8SFmode name of the register. | Available | Not |
 | g | likewise, print the V16SFmode name of the register. | Avaliable | Not |
 | h | print the QImode name for a "high" register, either ah, bh, ch or dh. | Available | Existed |
 | y | print "st(0)" instead of "st" as a register. | Available | Not |
 | d | print duplicated register operand for AVX instruction. | Available | Not |
 | D | print condition for SSE cmp instruction. | Not | - |
 | P | if PIC, print an @PLT suffix. | Available | Existed |
 | p | print raw symbol name. | Available | Existed |
 | X | don't print any sort of PIC '@' suffix for a symbol. | Not | - |
 | & | print some in-use local-dynamic symbol name. | Not | - |
 | H | print a memory address offset by 8; used for sse high-parts | Available | Existed |
 | Y | print condition for XOP pcom* instruction. | Not | - |
 | V | print naked full integer register name without %. | Available | Existed |
 | + | print a branch hint as 'cs' or 'ds' prefix | Not | - |
 | ; | print a semicolon (after prefixes due to bug in older gas). | Not | - |
 | ~ | print "i" if TARGET_AVX2, "f" otherwise. | Not | - |
 | ^ | print addr32 prefix if TARGET_64BIT and Pmode != word_mode | Not | - |
 | M | print addr32 prefix for TARGET_X32 with VSIB address. | Not | - |
 | ! | print NOTRACK prefix for jxx/call/ret instructions if required. | Not | - |
 | N | print maskz if it's constant 0 operand. | Available | Not |
 | I | print comparision predicate operand for sse cmp condition. | Not | - |

gcc/ChangeLog

	PR target/94118
	 * doc/extend.texi (x86Operandmodifiers): Document more x86
	 operand modifier.
	 * gcc/config/i386/i386.c: Add comment for operand modifier N
	 and I.

Modified-by: liuhongt <hongtao.liu@intel.com>