S/390: Add a new pattern for r{o,x}sbg

S/390: Add a new pattern for r{o,x}sbg

Fixes rXsbg_mode_sXl test failures.

Combine used to give us

(set (reg:SI 65)
    (ior:SI (lshiftrt:SI (reg:SI 3 %r3 [ bD.2238 ])
            (const_int 2 [0x2]))
        (reg:SI 2 %r2 [ aD.2237 ])))

but now we get

(set (reg:SI 65)
    (ior:SI (subreg:SI (zero_extract:DI (reg:DI 69)
                (const_int 32 [0x20])
                (const_int 30 [0x1e])) 4)
        (subreg:SI (reg:DI 68) 4)))

or

(set (reg:SI 65)
    (ior:SI (subreg:SI (and:DI (lshiftrt:DI (reg:DI 69)
                    (const_int 2 [0x2]))
                (const_int 4294967295 [0xffffffff])) 4)
        (subreg:SI (reg:DI 68) 4)))

with an extra subreg, which appears because pseudos, unlike hard
registers, can be accessed only using their natural mode.

This patch adds a special case for that.  Also, it performs r*sbg
bit index computations during gcc run, so that expectations do not
depend on which concrete pattern was matched.

gcc/ChangeLog:

2018-11-16  Ilya Leoshkevich  <iii@linux.ibm.com>

	* config/s390/s390.md
	(*r<noxa>sbg_<mode>_srl_bitmask): Do not delegate arithmetic to
	assembler.
	(*r<noxa>sbg_<mode>_sll): Likewise.
	(*r<noxa>sbg_<mode>_srl): Likewise.
	(*r<noxa>sbg_sidi_srl): New pattern.

gcc/testsuite/ChangeLog:

2018-11-16  Ilya Leoshkevich  <iii@linux.ibm.com>

	* gcc.target/s390/md/rXsbg_mode_sXl.c: Do not use arithmetic in
	r{o,x}sbg expectations.
	* gcc.target/s390/risbg-ll-2.c: Likewise.

From-SVN: r266203