[Bug tdep/31453] New: [gdb/tdep, arm] FAIL: gdb.arch/pr25124.exp: disassemble thumb instruction (1st try)

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31453

            Bug ID: 31453
           Summary: [gdb/tdep, arm] FAIL: gdb.arch/pr25124.exp:
                    disassemble thumb instruction (1st try)
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tdep
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

On arm-linux, I ran into:
...
(gdb) x /i main+8^M
   0x4e1 <main+7>:      vrhadd.u16      d14, d14, d31^M
(gdb) FAIL: gdb.arch/pr25124.exp: disassemble thumb instruction (1st try)
...

Likewise, this fails:
...
$ gdb -q -batch outputs/gdb.arch/pr25124/pr25124 -ex "disassemble main"
Dump of assembler code for function main:
   0x000004d9 <-1>:     bx      pc
   0x000004db <+1>:     nop
   0x000004dd <+3>:     movs    r0, r0
   0x000004df <+5>:     b.n     0xc22
   0x000004e1 <+7>:     vrhadd.u16      d14, d14, d31
End of assembler dump.
...

This is a regression due to PR gas/31115 (reported on 2.39, found this with
2.40, presumably also present in 2.41, and still unfixed), which makes gas
produce a low_pc with the thumb bit set:
...
 <1><24>: Abbrev Number: 2 (DW_TAG_subprogram)
    <25>   DW_AT_name        : (indirect string, offset: 0x65): main
    <29>   DW_AT_external    : 1
    <29>   DW_AT_type        : <0x2f>
    <2a>   DW_AT_low_pc      : 0x4d9
    <2e>   DW_AT_high_pc     : 12
 <1><2f>: Abbrev Number: 3 (DW_TAG_unspecified_type)
...

With this workaround in gdb:
...
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 486be7e4921..b4c8c41f5f8 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -9974,6 +9974,9 @@ read_func_scope (struct die_info *die, struct dwarf2_cu
*cu)
   lowpc = per_objfile->relocate (unrel_low);
   highpc = per_objfile->relocate (unrel_high);

+  lowpc = gdbarch_addr_bits_remove (gdbarch, lowpc);
+  highpc = gdbarch_addr_bits_remove (gdbarch, highpc);
+
   /* If we have any template arguments, then we must allocate a
      different sort of symbol.  */
   for (child_die = die->child; child_die; child_die = child_die->sibling)
...
the test-case passes, and the disassembly command produces sane output:
...
$ gdb -q -batch outputs/gdb.arch/pr25124/pr25124 -ex "disassemble main"
Dump of assembler code for function main:
   0x000004d8 <+0>:     bx      pc
   0x000004da <+2>:     nop
   0x000004dc <+4>:     mov     r0, #0
   0x000004e0 <+8>:     bx      lr
End of assembler dump.
...

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