[GHC] #15891: Excessive system time during execution of GHC-built executables on macOS

[GHC]

#15891: Excessive system time during execution of GHC-built executables on macOS
---------------------------------+----------------------------------------
        Reporter:  goldfire      |                Owner:  (none)
            Type:  bug           |               Status:  new
        Priority:  normal        |            Milestone:  8.6.3
       Component:  Compiler      |              Version:  8.6.2
      Resolution:                |             Keywords:
Operating System:  MacOS X       |         Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
---------------------------------+----------------------------------------

Comment (by gridaphobe):

 So I tried a build with gcc as the C compiler, to see if the issue was
 somehow related to Apple's build of clang. I kicked it off with

 {{{
 > ./configure CC=gcc-8  # installed with `brew`
 ...
 Configure completed successfully.

    Building GHC version  : 8.7.20181114
           Git commit id  : 89fa34ecd326de879145e6d854306eb17722bf6c

    Build platform        : x86_64-apple-darwin
    Host platform         : x86_64-apple-darwin
    Target platform       : x86_64-apple-darwin

    Bootstrapping using   : /usr/local/bin/ghc
       which is version   : 8.4.4

    Using (for bootstrapping) : clang  # why?
    Using gcc                 : gcc-8
       which is version       : 8.2.0
    Building a cross compiler : NO
    Unregisterised            : NO
    hs-cpp       : gcc-8
    hs-cpp-flags : -E -undef -traditional
    ar           : ar
    ld           : ld
    nm           : nm
    libtool      : libtool
    objdump      : objdump
    ranlib       : ranlib
    windres      :
    dllwrap      :
    genlib       :
    Happy        : /Users/eseidel13/.local/bin/happy (1.19.9)
    Alex         : /Users/eseidel13/.local/bin/alex (3.2.4)
    Perl         : /usr/bin/perl
    sphinx-build :
    xelatex      :

    Using LLVM tools
       clang : clang
       llc   :
       opt   :
    HsColour : /Users/eseidel13/.cabal/bin/HsColour

    Tools to build Sphinx HTML documentation available: NO
    Tools to build Sphinx PDF documentation available: NO
 }}}

 Curiously, even though I specified `CC=gcc-8`, the build insists on using
 `clang` for some portion of bootstrapping. I'm not sure what exactly that
 means.

 The build of `ghc-stage1` went smoothly, as before, but I again started to
 notice a major uptick in system time once ghc-stage1 was used. The build
 also failed during the RTS portion, with

 {{{
   rts_dist_HC rts/dist/build/StgCRun.o

 <unknown>:0:0: error:
      error: this directive must appear between .cfi_startproc and
 .cfi_endproc directives
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15891#comment:6>
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