xtensa: Implement l(ceil|floor)sfsi2 insn patterns and their scaled variants

xtensa: Implement l(ceil|floor)sfsi2 insn patterns and their scaled variants

By using the previously unused CEIL|FLOOR.S floating-point coprocessor
instructions.  In addition, two instruction operand format codes are added
to output the scale value as assembler source.

     /* example */
     int test0(float a) {
       return __builtin_lceilf(a);
     }
     int test1(float a) {
       return __builtin_lceilf(a * 2);
     }
     int test2(float a) {
       return __builtin_lfloorf(a);
     }
     int test3(float a) {
       return __builtin_lfloorf(a * 32768);
     }

     ;; result
     test0:
     	entry	sp, 32
     	wfr	f0, a2
     	ceil.s	a2, f0, 0
     	retw.n
     test1:
     	entry	sp, 32
     	wfr	f0, a2
     	ceil.s	a2, f0, 1
     	retw.n
     test2:
     	entry	sp, 32
     	wfr	f0, a2
     	floor.s	a2, f0, 0
     	retw.n
     test3:
     	entry	sp, 32
     	wfr	f0, a2
     	floor.s	a2, f0, 15
     	retw.n

However, because the rounding-half behavior (e.g., the rule that determines
whether 1.5 should be rounded to 1 or 2) of the two is inconsistent;
the lroundsfsi2 pattern is explicitly specified that rounding to nearest
integer and away from zero, but the other hand, the ROUND.S instruction is
not specified that by the ISA and is implementation-dependent.

Therefore lroundsfsi2 cannot be implemented by ROUND.S.

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (printx, print_operand):
	Add two instruction operand format codes 'U' and 'V',
	whose represent scale factors of 0 to 15th positive/negative
	power of two.
	* config/xtensa/xtensa.md (c_enum "unspec"):
	Add UNSPEC_CEIL and UNSPEC_FLOOR.
	(int_iterator ANY_ROUND, int_attr m_round):
	New integer iterator and its attribute.
	(fix<s_fix>_truncsfsi2, *fix<s_fix>_truncsfsi2_2x,
	*fix<s_fix>_truncsfsi2_scaled, float<s_float>sisf2,
	*float<s_float>sisf2_scaled):
	Use output templates with the operand formats added above,
	instead of individual output statements.
	(l<m_round>sfsi2, *l<m_round>sfsi2_2x, *l<m_round>sfsi2_scaled):
	New insn patterns.