bug#24703: Store references in 8-byte chunks in compiled code

[Mark H Weaver]

The 8-byte chunks may appear out of order.  For example, in
'bash-static' we have this reference to:

  /gnu/store/7z3hpynjsbidxkq78xi5qi6lbcm8ndhp-glibc-intermediate-2.23

where the chunks are found in the following order:

1_/gnu/sto
2_________________ynjsbidx
3_________re/7z3hp
4_________________________________i6lbcm8n
5_________________________kq78xi5q
6_________________________________________dhp-glib
7_________________________________________________c-interm
8_________________________________________________________ediate-2
9_________________________________________________________________.23/lib/

Here's an excerpt of "objdump -d" output, annotated to show the 8-byte
constant as a string, and its position within the larger string.

======== /gnu/store/0010wvgs40kdq8chzsh403qm7la9jxq7-bash-static-4.3.42/bin/bash
  46b2c3:       48 b9 2f 67 6e 75 2f    movabs $0x6f74732f756e672f,%rcx ; 
"/gnu/sto" (1)
  46b2ca:       73 74 6f 
  46b2cd:       48 01 d8                add    %rbx,%rax
  46b2d0:       48 bb 79 6e 6a 73 62    movabs $0x78646962736a6e79,%rbx ; 
"ynjsbidx" (3)
  46b2d7:       69 64 78 
  46b2da:       48 89 48 01             mov    %rcx,0x1(%rax)
  46b2de:       48 b9 72 65 2f 37 7a    movabs $0x7068337a372f6572,%rcx ; 
"re/7z3hp" (2)
  46b2e5:       33 68 70 
  46b2e8:       48 89 58 11             mov    %rbx,0x11(%rax)
  46b2ec:       48 89 48 09             mov    %rcx,0x9(%rax)
  46b2f0:       48 bb 69 36 6c 62 63    movabs $0x6e386d63626c3669,%rbx ; 
"i6lbcm8n" (5)
  46b2f7:       6d 38 6e 
  46b2fa:       48 b9 6b 71 37 38 78    movabs $0x713569783837716b,%rcx ; 
"kq78xi5q" (4)
  46b301:       69 35 71 
  46b304:       48 89 48 19             mov    %rcx,0x19(%rax)
  46b308:       48 89 58 21             mov    %rbx,0x21(%rax)
  46b30c:       48 b9 64 68 70 2d 67    movabs $0x62696c672d706864,%rcx ; 
"dhp-glib" (6)
  46b313:       6c 69 62 
  46b316:       48 bb 63 2d 69 6e 74    movabs $0x6d7265746e692d63,%rbx ; 
"c-interm" (7)
  46b31d:       65 72 6d 
  46b320:       48 89 48 29             mov    %rcx,0x29(%rax)
  46b324:       ba 76 00 00 00          mov    $0x76,%edx
  46b329:       48 89 58 31             mov    %rbx,0x31(%rax)
  46b32d:       48 b9 65 64 69 61 74    movabs $0x322d657461696465,%rcx ; 
"ediate-2" (8)
  46b334:       65 2d 32 
  46b337:       48 bb 2e 32 33 2f 6c    movabs $0x2f62696c2f33322e,%rbx ; 
".23/lib/" (9)
  46b33e:       69 62 2f 
  46b341:       48 89 58 41             mov    %rbx,0x41(%rax)
  46b345:       31 f6                   xor    %esi,%esi
  46b347:       31 ff                   xor    %edi,%edi
  46b349:       c6 00 3a                movb   $0x3a,(%rax)
  46b34c:       48 89 48 39             mov    %rcx,0x39(%rax)
  46b350:       c7 40 49 67 63 6f 6e    movl   $0x6e6f6367,0x49(%rax)
  46b357:       66 89 50 4d             mov    %dx,0x4d(%rax)