VAX: Ensure PIC mode address is adjustable with aligned bit-field insns

VAX: Ensure PIC mode address is adjustable with aligned bit-field insns

With the `*insv_aligned', `*extzv_aligned' and `*extv_aligned' insns we
are going to adjust the bit-field location if it is in memory, so only
allow such location addresses that can be offset, excluding external
symbol references in the PIC mode in particular.

This fixes an ICE like:

during RTL pass: final
In file included from .../gcc/testsuite/gcc.dg/torture/vshuf-v16qi.c:11:
.../gcc/testsuite/gcc.dg/torture/vshuf-main.inc: In function 'test_13':
.../gcc/testsuite/gcc.dg/torture/vshuf-main.inc:27:1: internal compiler error: in change_address_1, at emit-rtl.c:2275
.../gcc/testsuite/gcc.dg/torture/vshuf-16.inc:16:1: note: in expansion of macro 'T'
.../gcc/testsuite/gcc.dg/torture/vshuf-main.inc:28:1: note: in expansion of macro 'TESTS'
0x10a34b33 change_address_1
	.../gcc/emit-rtl.c:2275
0x10a358af adjust_address_1(rtx_def*, machine_mode, poly_int<1u, long>, int, int, int, poly_int<1u, long>)
	.../gcc/emit-rtl.c:2409
0x11d2505f output_97
	.../gcc/config/vax/vax.md:806
0x10adec4b get_insn_template(int, rtx_insn*)
	.../gcc/final.c:2070
0x10ae1c5b final_scan_insn_1
	.../gcc/final.c:3039
0x10ae2257 final_scan_insn(rtx_insn*, _IO_FILE*, int, int, int*)
	.../gcc/final.c:3152
0x10ade9a3 final_1
	.../gcc/final.c:2020
0x10ae6157 rest_of_handle_final
	.../gcc/final.c:4658
0x10ae6697 execute
	.../gcc/final.c:4736
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compiler exited with status 1
FAIL: gcc.dg/torture/vshuf-v16qi.c   -O2  (internal compiler error)

triggered by an RTL instruction like:

(insn 97 96 98 (set (reg:SI 5 %r5 [88])
        (zero_extract:SI (mem/c:SI (symbol_ref:SI ("b") <var_decl 0x7ffff7f801b0 b>) [0 b+0 S4 A128])
            (const_int 8 [0x8])
            (const_int 24 [0x18]))) ".../gcc/testsuite/gcc.dg/torture/vshuf-main.inc":28:1 97 {*extzv_aligned}
     (nil))

and removes these regressions:

FAIL: gcc.dg/torture/vshuf-v16qi.c   -O2  (internal compiler error)
FAIL: gcc.dg/torture/vshuf-v16qi.c   -O2  (test for excess errors)
FAIL: gcc.dg/torture/vshuf-v4hi.c   -O2  (internal compiler error)
FAIL: gcc.dg/torture/vshuf-v4hi.c   -O2  (test for excess errors)
FAIL: gcc.dg/torture/vshuf-v8hi.c   -O2  (internal compiler error)
FAIL: gcc.dg/torture/vshuf-v8hi.c   -O2  (test for excess errors)
FAIL: gcc.dg/torture/vshuf-v8qi.c   -O2  (internal compiler error)
FAIL: gcc.dg/torture/vshuf-v8qi.c   -O2  (test for excess errors)

However expand typically presents pseudo-registers rather than memory
references to these insns, so a further rework is required to make a
better use of the code variant they are supposed to produce.  This at
least fixes the problem at hand.

	gcc/
	* config/vax/vax.md (*insv_aligned, *extzv_aligned)
	(*extv_aligned): Also make sure the memory address of a bit-field
	location can be adjusted in the PIC mode.