[GHC] #15723: -prof -fPIC -fexternal-dynamic-refs generates non-PIC relocations for external symbol

[GHC]

#15723: -prof -fPIC -fexternal-dynamic-refs generates non-PIC relocations for
external symbol
-------------------------------------+-------------------------------------
        Reporter:  watashi           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by watashi):

 * cc: simonmar (added)


Old description:

> When compiling code with `-prof -fPIC -fexternal-dynamic-refs`, the
> generated object file may contains R_X86_64_PC32 relocation to symbols
> defined in another object file.
>
> will add more details

New description:

 When compiling code with `-prof -fPIC -fexternal-dynamic-refs`, the
 generated object file may contains R_X86_64_PC32 relocation to symbols
 defined in another object file.

 {{{
 $ cat T15723A.hs T15723B.hs
 module T15723A where

 {-# INLINE foo #-}
 foo :: Int -> Int
 foo x = {-# SCC foo1 #-} bar x

 {-# NOINLINE bar #-}
 bar :: Int -> Int
 bar x = x
 module T15723B where

 import T15723A

 test :: Int -> Int
 test x = {-# SCC test1 #-} foo $ foo x
 $ $HC -prof -prof -fPIC -fexternal-dynamic-refs -O2 -c T15723A.hs
 $ $HC -prof -prof -fPIC -fexternal-dynamic-refs -O2 -c T15723B.hs
 $ objdump -rdS T15723B.o | less
 0000000000000028 <T15723B_test_info>:
   28:   48 8d 45 f0             lea    -0x10(%rbp),%rax
   2c:   4c 39 f8                cmp    %r15,%rax
   2f:   72 70                   jb     a1 <T15723B_test_info+0x79>
   31:   48 83 ec 08             sub    $0x8,%rsp
   35:   48 8d 35 00 00 00 00    lea    0x0(%rip),%rsi        # 3c
 <T15723B_test_info+0x14>
                         38: R_X86_64_PC32       T15723B_test1_EXPR_cc-0x4
   3c:   49 8b bd 60 03 00 00    mov    0x360(%r13),%rdi
   43:   31 c0                   xor    %eax,%eax
   45:   e8 00 00 00 00          callq  4a <T15723B_test_info+0x22>
                         46: R_X86_64_PLT32      pushCostCentre-0x4
   4a:   48 83 c4 08             add    $0x8,%rsp
   4e:   48 ff 40 30             incq   0x30(%rax)
   52:   49 89 85 60 03 00 00    mov    %rax,0x360(%r13)
   59:   48 83 ec 08             sub    $0x8,%rsp
   5d:   48 8d 35 00 00 00 00    lea    0x0(%rip),%rsi        # 64
 <T15723B_test_info+0x3c>
                         60: R_X86_64_PC32       T15723A_foo1_EXPR_cc-0x4
 }}}

 When attempt to link both `T15723A.o` and `T15723B.o` in ghci using `+RTS
 -xp`, the address of `T15723A_foo1_EXPR_cc` can be more than 2G away from
 `T15723B_test_info` and cause link error or segfault.

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15723#comment:1>
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