Documentation for gcc 9.1 changes

[Andrew Roberts]

Hello,

looking at the changes for configuration in gcc 9.1, I noticed:

1) New configure options

OTOOL/OTOOL_FOR_TARGET: Which I assume from google is the Darwin ldd 
replacement

GDC_FOR_TARGET: Which with a bit of guess work I assume is the 
Gnu_D_Compiler

Is this stuff documented anywhere?

2) D language documentation

Also looking at the D documentation it appears missing in action:

No manual here: https://gcc.gnu.org/onlinedocs/

and the release notes just say: "Support for the D programming language 
has been added to GCC, implementing version 2.076 of the language and 
run-time library."

If this stuff is documented elsewhere a link to said documentation would 
be useful.

3) Stdlibc++

Release notes reference parallel algorithms requiring TBB 2018 or newer, 
again guess work suggests this is Thread Building Blocks. It would be 
nice to explicitly say that, and provide links to implementations.

How is TBB detected and selected? I didn't see any configure switches 
relating to this either in the toplevel configure or stdc++ configure 
files. Can it be built in tree etc?

Also while TBB may not be a prerequisite should it be at least 
documented on that page: https://gcc.gnu.org/install/prerequisites.html 
(or somewhere)

The TBB release notes (written by Intel) seem to limit things to Intel 
or compatible processors, wikipedia suggests a wider range (sparc?, 
powerpc). Is ARM supported? Again it would be nice to document what 
range of systems this can work on.

Thanks

Andrew