aarch64: Fix ICE in aarch64_add_offset_1 [PR94121]

abs_hwi asserts that the argument is not HOST_WIDE_INT_MIN and as the
(invalid) testcase shows, the function can be called with such an offset.
The following patch is IMHO minimal fix, absu_hwi unlike abs_hwi allows even
that value and will return (unsigned HOST_WIDE_INT) HOST_WIDE_INT_MIN
in that case.  The function then uses moffset in two spots which wouldn't
care if the value is (unsigned HOST_WIDE_INT) HOST_WIDE_INT_MIN or
HOST_WIDE_INT_MIN and wouldn't accept it (!moffset and
aarch64_uimm12_shift (moffset)), then in one spot where the signedness of
moffset does matter and using unsigned is the right thing -
moffset < 0x1000000 - and finally has code which will handle even this
value right; the assembler doesn't really care for DImode immediates if
        mov     x1, -9223372036854775808
or
        mov     x1, 9223372036854775808
is used and similarly it doesn't matter if we add or sub it in DImode.

2020-03-11  Jakub Jelinek  <jakub@redhat.com>

	PR target/94121
	* config/aarch64/aarch64.c (aarch64_add_offset_1): Use absu_hwi
	instead of abs_hwi, change moffset type to unsigned HOST_WIDE_INT.

	* gcc.dg/pr94121.c: New test.

gcc/ChangeLog

 2020-03-11  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/94121
+	* config/aarch64/aarch64.c (aarch64_add_offset_1): Use absu_hwi
+	instead of abs_hwi, change moffset type to unsigned HOST_WIDE_INT.
+
 	PR bootstrap/93962
 	* value-prof.c (dump_histogram_value): Use abs_hwi instead of
 	std::abs.

gcc/config/aarch64/aarch64.c

@@ -3713,7 +3713,7 @@ aarch64_add_offset_1 (scalar_int_mode mode, rtx dest,
   gcc_assert (emit_move_imm || temp1 != NULL_RTX);
   gcc_assert (temp1 == NULL_RTX || !reg_overlap_mentioned_p (temp1, src));
 
-  HOST_WIDE_INT moffset = abs_hwi (offset);
+  unsigned HOST_WIDE_INT moffset = absu_hwi (offset);
   rtx_insn *insn;
 
   if (!moffset)

gcc/testsuite/ChangeLog

 2020-03-11  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/94121
+	* gcc.dg/pr94121.c: New test.
+
 	PR middle-end/94111
 	* gcc.dg/dfp/pr94111.c: New test.
 

gcc/testsuite/gcc.dg/pr94121.c

+/* PR target/94121 */
+/* { dg-do compile { target pie } } */
+/* { dg-options "-O2 -fpie -w" } */
+
+#define DIFF_MAX __PTRDIFF_MAX__
+#define DIFF_MIN (-DIFF_MAX - 1)
+
+extern void foo (char *);
+extern char v[];
+
+void
+bar (void)
+{
+  char *p = v;
+  foo (&p[DIFF_MIN]);
+}