[MacPorts] #37846: cctools as does not support AVX, consider using llvm

[MacPorts]

#37846: cctools as does not support AVX, consider using llvm
--------------------------+--------------------------------
  Reporter:  wd11@…       |      Owner:  macports-tickets@…
      Type:  defect       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:  2.1.2
Resolution:               |   Keywords:
      Port:  cctools gcc  |
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Comment (by kencu):

 The guts of this behaviour is controlled by cctools `as` `driver.c`.

 For practical purposes, `/usr/bin/as` sends you to `/usr/bin/clang` for
 assember work on 10.10 or later, which on my system matched up to Xcode 7.
 On 10.9 and below, it appears you get the standard GNU assember 1.38
 unless you send the `-q` flag, or have set the `AS_INTEGRATED_ASSEMBER`
 environment variable.

 On older systems, if you have set `AS_INTEGRATED_ASSEMBER`, or if you have
 set the `-q` flag with `-Wa,-q`, then cctools `as` passes off the assembly
 to `clang` in the same directory as `as` is.

 At this moment, you can't set a more specific name for `clang`, and you
 can't specify a full path to `clang`. It's just going to look for `clang`,
 next to `as`, wherever the running copy of `as` is.

 So for a MacPorts install of cctools, `/opt/local/bin/as` which is the
 first one on the path usually will look for `/opt/local/bin/clang`.
 `/usr/bin/as` will look for `/usr/bin/clang`.

 To make the MacPorts cctools `as` work to use `clang` as the assembler,
 there needs to be an `/opt/local/bin/clang` and the only way to get that
 is to `sudo port select` a clang manually, at present.

 So on systems 10.9 or older, you need to select a clang, and then use
 `-Wa,-q` to make it work.

-- 
Ticket URL: <https://trac.macports.org/ticket/37846#comment:22>
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