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[0/5] C-SKY port

This patch series is a new port for C-SKY ABI V2 processors.  It's
based on the original work by C-SKY with cleanup, modernization, and
bug-fixing by Mentor Graphics.  The supported targets are csky-elf and
csky-linux-* (both glibc and uClibc).  At this time we're only
supporting the C and C++ languages, but we've built all the other
front ends except Ada where we're still trying to sort out build
environment issues.

C-SKY proposes Han Mao <> and Yunhai Shang
<> as maintainers for this port.  We expect that
C-SKY will also be providing a public link to the processor and ABI
documentation at some point.  Meanwhile, here's brief overview
of the architecture from the compiler's point of view:

This is a 32-bit target with mixed 16- and 32-bit instructions and
support for both endiannesses.  There are 5 different architecture
variants.  The ck801 variant is substantially different from the
others in terms of code generation -- it has only a few 32-bit
instructions and a restricted register set, so it's almost analagous
to a Thumb-only ARM core.  ck802 and ck803 have more 32-bit
instructions and 16 registers, while ck807 and ck810 are Linux-capable
with 32 registers.

The ABI is fairly standard; arguments are passed in r0-r3 with the
overflow on the stack, return values in r0-r1, etc.  There is no
dedicated frame pointer register.

The ELF target is configured to build 16(!) multilibs and the Linux
targets 8, to account for hard/soft float variants and endiannesses.
We've been testing all of them with QEMU (user-mode for the Linux
targets, since we don't have a stable kernel yet) and the results are
quite good now.

I've split the patch set up into 5 pieces, with part 2 having the bulk
of the new code:

[1] Configury
[2] Backend implementation
[3] Documentation
[4] Testsuite
[5] libgcc

We also have a couple small patches to target-independent code to fix
bugs, which we'll post separately.


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