Add 32-bit big-endian PowerPC support

[briansmith]

No description provided.

[briansmith]

@erichte-ibm PTAL.

[briansmith]

error[E0463]: can't find crate for `profiler_builtins`
  |
  = note: the compiler may have been built without the profiler runtime

We need the change to rust-lang/rust analogous to rust-lang/rust#105389 for this target and probably for the 64-bit big-endian version too.

[codecov]

Codecov Report

Merging #1676 (13650a3) into main (baa823b) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1676      +/-   ##
==========================================
+ Coverage   95.98%   95.99%   +0.01%     
==========================================
  Files         134      134              
  Lines       19953    19953              
  Branches      199      199              
==========================================
+ Hits        19151    19153       +2     
+ Misses        765      763       -2     
  Partials       37       37              

Files	Coverage Δ
src/lib.rs	34.61% <ø> (ø)

... and 2 files with indirect coverage changes

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[briansmith]

@runlevel5 Perhaps you know who should look at this?

[runlevel5]

@runlevel5 Perhaps you know who should look at this?

@classilla I am wondering if you could help Brian review this Pull Request? Many thanks in advance

[pkubaj]

This commit probably introduces misdetection of powerpc64 (big-endian). The reason is that __powerpc__ is defined on both 64-bits and 32-bits. Since you check for __powerpc__ before checking for __powerpc64__ it will go first. The solution would be to explicitly check #if defined(__powerpc__) && !defined(__powerpc64__) or simply move the __powerpc__ check below __powerpc64__.

[pkubaj]

Also, this line:

#elif (defined(__PPC64__) || defined(__powerpc64__)) && \
      (defined(_LITTLE_ENDIAN) || defined(_BIG_ENDIAN))

It's not necessary to check endianness here, there were no middle-endian PPC and I doubt ring even supports middle-endian :)

[classilla]

What @pkubaj said. Please note that I have relatively few 32-bit systems now running anything other than old versions of Mac OS or Mac OS X.