[Bug translator/16596] Support DW_OP_GNU_entry_value in location expressions

["mjw at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16596

--- Comment #4 from Mark Wielaard <mjw at redhat dot com> ---
Note that for the example in comment #3 we cannot use the simple unwinding
approach number 2 from the description because r2 isn't saved at all. Looking
at the CFI:

 [ 7a590] FDE length=68 cie=[ 79ab0]
   CIE_pointer:              498352
   initial_location:         0xffffffff811e1110 <handle_mm_fault>
   address_range:            0xf4f

   Program:
     advance_loc 6 to 0x6
     def_cfa_offset 16
     offset r6 (rbp) at cfa-16
     advance_loc 6 to 0xc
     def_cfa_register r6 (rbp)
     advance_loc 4 to 0x10
     offset r15 (r15) at cfa-24
     offset r14 (r14) at cfa-32
     advance_loc 5 to 0x15
     offset r13 (r13) at cfa-40
     advance_loc 6 to 0x1b
     offset r12 (r12) at cfa-48
     offset r3 (rbx) at cfa-56
     advance_loc2 1039 to 0x42a
     remember_state
     restore r3 (rbx)
     advance_loc 2 to 0x42c
     restore r12 (r12)
     advance_loc 2 to 0x42e
     restore r13 (r13)
     advance_loc 2 to 0x430
     restore r14 (r14)
     advance_loc 2 to 0x432
     restore r15 (r15)
     advance_loc 1 to 0x433
     restore r6 (rbp)
     def_cfa r7 (rsp) at offset 8
     advance_loc 5 to 0x438
     restore_state
     nop
     nop
     nop
     nop
     nop
     nop
     nop

(I didn't save the CIE, but that didn't save it either.)

Unfortunately I don't have access anymore to this setup so cannot see whether
unwinding and finding the matching DW_TAG_call_site_parameter would work
(approach 1 in the description).

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