RISC-V: Bugfix for vls mode aggregated in GPR calling convention

According to the issue as below.

https://hub.fgit.cf/riscv-non-isa/riscv-elf-psabi-doc/pull/416



When the mode size of vls integer mode is less than 2 * XLEN, we will
take the gpr for both the args and the return values. Instead of the
reference. For example the below code:

typedef short v8hi __attribute__ ((vector_size (16)));

v8hi __attribute__((noinline))
add (v8hi a, v8hi b)
{
  v8hi r = a + b;
  return r;
}

Before this patch:
add:
  vsetivli zero,8,e16,m1,ta,ma
  vle16.v  v1,0(a1) <== arg by reference
  vle16.v  v2,0(a2) <== arg by reference
  vadd.vv  v1,v1,v2
  vse16.v  v1,0(a0) <== return by reference
  ret

After this patch:
add:
  addi     sp,sp,-32
  sd       a0,0(sp)  <== arg by register a0 - a3
  sd       a1,8(sp)
  sd       a2,16(sp)
  sd       a3,24(sp)
  addi     a5,sp,16
  vsetivli zero,8,e16,m1,ta,ma
  vle16.v  v2,0(sp)
  vle16.v  v1,0(a5)
  vadd.vv  v1,v1,v2
  vse16.v  v1,0(sp)
  ld       a0,0(sp)  <== return by a0 - a1.
  ld       a1,8(sp)
  addi     sp,sp,32
  jr       ra

For vls floating point, we take the same rules as integer and passed by
the gpr or reference.

The riscv regression passed for this patch.

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_v_vls_mode_aggregate_gpr_count): New function to
	calculate the gpr count required by vls mode.
	(riscv_v_vls_to_gpr_mode): New function convert vls mode to gpr mode.
	(riscv_pass_vls_aggregate_in_gpr): New function to return the rtx of gpr
	for vls mode.
	(riscv_get_arg_info): Add vls mode handling.
	(riscv_pass_by_reference): Return false if arg info has no zero gpr count.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls/def.h: Add new helper macro.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-1.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-10.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-2.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-3.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-4.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-5.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-6.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-7.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-8.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-9.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-1.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-2.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-3.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-4.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-5.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/calling-convention-run-6.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>