[GHC] #15501: Fix unknown symbols/addresses in perf output

[GHC]

#15501: Fix unknown symbols/addresses in perf output
-------------------------------------+-------------------------------------
        Reporter:  last_g            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  Research
       Component:  Compiler          |  needed
  (CodeGen)                          |              Version:  8.5
      Resolution:                    |             Keywords:  perf,
                                     |  symbols, elf, linux
Operating System:  Linux             |         Architecture:
 Type of failure:  Debugging         |  Unknown/Multiple
  information is incorrect           |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  D4713
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Simon Marlow <marlowsd@…>):

 In [changeset:"c23f057f1753634e2bc0612969470efea6443031/ghc"
 c23f057f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c23f057f1753634e2bc0612969470efea6443031"
 Mark code related symbols as @function not @object

 Summary:
 This diff is a part of the bigger project which goal is to improve
 common profiling tools support (perf) for GHC binaries.

 A similar job was already done and reverted in the past:
  *
 https://phabricator.haskell.org/rGHCb1f453e16f0ce11a2ab18cc4c350bdcbd36299a6
  *
 https://phabricator.haskell.org/rGHCf1f3c4f50650110ad0f700d6566a44c515b0548f

 Reasoning:

 `Perf` and similar tools build in memory symbol table from the .symtab
 section of the ELF file to display human-readable function names instead
 of the addresses in the output. `Perf` uses only two types of symbols:
 `@function` and `@notype` but GHC is not capable to produce any
 `@function` symbols so the `perf` output is pretty useless (All the
 haskell symbols that you can see in `perf` now are `@notype` internal
 symbols extracted by mistake/hack).

 The changes:
  * mark code related symbols as @function
  * small hack to mark InfoTable symbols as code if TABLES_NEXT_TO_CODE is
 true

 Limitations:
  * The perf symbolization support is not complete after this patch but
    I'm working on the second patch.
  * Constructor symbols are not supported. To fix that we can issue extra
    local symbols which mark code sections as code and will be only used
    for debug.

 Test Plan:
 tests
 any additional ideas?

 Perf output on stock ghc 8.4.1:
 ```
      9.78%  FibbSlow  FibbSlow            [.] ckY_info
      9.59%  FibbSlow  FibbSlow            [.] cjqd_info
      7.17%  FibbSlow  FibbSlow            [.] c3sg_info
      6.62%  FibbSlow  FibbSlow            [.] c1X_info
      5.32%  FibbSlow  FibbSlow            [.] cjsX_info
      4.18%  FibbSlow  FibbSlow            [.] s3rN_info
      3.82%  FibbSlow  FibbSlow            [.] c2m_info
      3.68%  FibbSlow  FibbSlow            [.] cjlJ_info
      3.26%  FibbSlow  FibbSlow            [.] c3sb_info
      3.19%  FibbSlow  FibbSlow            [.] cjPQ_info
      3.05%  FibbSlow  FibbSlow            [.] cjQd_info
      2.97%  FibbSlow  FibbSlow            [.] cjAB_info
      2.78%  FibbSlow  FibbSlow            [.] cjzP_info
      2.40%  FibbSlow  FibbSlow            [.] cjOS_info
      2.38%  FibbSlow  FibbSlow            [.] s3rK_info
      2.27%  FibbSlow  FibbSlow            [.] cjq0_info
      2.18%  FibbSlow  FibbSlow            [.] cKQ_info
      2.13%  FibbSlow  FibbSlow            [.] cjSl_info
      1.99%  FibbSlow  FibbSlow            [.] s3rL_info
      1.98%  FibbSlow  FibbSlow            [.] c2cC_info
      1.80%  FibbSlow  FibbSlow            [.] s3rO_info
      1.37%  FibbSlow  FibbSlow            [.] c2f2_info
 ...
 ```

 Perf output on patched ghc:
 ```
      7.97%  FibbSlow  FibbSlow            [.] c3rM_info
      6.75%  FibbSlow  FibbSlow            [.] 0x000000000032cfa8
      6.63%  FibbSlow  FibbSlow            [.] cifA_info
      4.98%  FibbSlow  FibbSlow            [.]
 integerzmgmp_GHCziIntegerziType_eqIntegerzh_info
      4.55%  FibbSlow  FibbSlow            [.] chXn_info
      4.52%  FibbSlow  FibbSlow            [.] c3rH_info
      4.45%  FibbSlow  FibbSlow            [.] chZB_info
      4.04%  FibbSlow  FibbSlow            [.] Main_fibbzuslow_info
      4.03%  FibbSlow  FibbSlow            [.] stg_ap_0_fast
      3.76%  FibbSlow  FibbSlow            [.] chXA_info
      3.67%  FibbSlow  FibbSlow            [.] cifu_info
      3.25%  FibbSlow  FibbSlow            [.] ci4r_info
      2.64%  FibbSlow  FibbSlow            [.] s3rf_info
      2.42%  FibbSlow  FibbSlow            [.] s3rg_info
      2.39%  FibbSlow  FibbSlow            [.]
 integerzmgmp_GHCziIntegerziType_eqInteger_info
      2.25%  FibbSlow  FibbSlow            [.]
 integerzmgmp_GHCziIntegerziType_minusInteger_info
      2.17%  FibbSlow  FibbSlow            [.]
 ghczmprim_GHCziClasses_zeze_info
      2.09%  FibbSlow  FibbSlow            [.] cicc_info
      2.03%  FibbSlow  FibbSlow            [.] 0x0000000000331e15
      2.02%  FibbSlow  FibbSlow            [.] s3ri_info
      1.91%  FibbSlow  FibbSlow            [.] 0x0000000000331bb8
      1.89%  FibbSlow  FibbSlow            [.] ci4N_info
 ...
 ```

 Reviewers: simonmar, niteria, bgamari, goldfire

 Reviewed By: simonmar, bgamari

 Subscribers: lelf, rwbarton, thomie, carter

 GHC Trac Issues: #15501

 Differential Revision: https://phabricator.haskell.org/D4713
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15501#comment:2>
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