[GHC] #10375: arm: ghci hits an illegal instruction

[GHC]

#10375: arm: ghci hits an illegal instruction
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        Reporter:  erikd             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.10.3
       Component:  GHCi              |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:  arm
 Type of failure:  GHCi crash        |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by erikd):

 Got some help from the llvm-dev mailing list. People there pointed out
 that this:

 {{{
 (gdb) disassemble
 Dump of assembler code for function stg_ap_v_fast:
    0x03ff9db4 <+0>:     push    {r7, lr}
    0x03ff9db6 <+2>:     sub     sp, #32
    0x03ff9db8 <+4>:     add     r7, sp, #0
    0x03ff9dba <+6>:     ldr     r3, [pc, #508]  ; (0x3ff9fb8
 <stg_ap_v_fast+516>)
 => 0x03ff9dbc <+8>:     ldr     r3, [r3, #0]
    0x03ff9dbe <+10>:    and.w   r3, r3, #
 }}}

 show the CPU executing Thumb instructions.

 Thumb instructions are encoded in two btyes (and hence instructions with
 addresses that are even) while Arm instructions are encoded in 4 bytes (so
 instructions should be aligned at 4 bytes offsets).

 This could be that GDB getting the CPU mode incorrect. Not sure how to
 figure out if that is the case or even if and how that could happen.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10375#comment:44>
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