Sergei Azovskov authored Sep 14, 2018 and Simon Marlow committed Sep 14, 2018

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