[PATCH, PowerPC] Accept 'U' and 'X' constraints in inline asm

Inline asm may specify 'U' and 'X' constraints to print a 'u' for an
update-form memory reference, or an 'x' for an indexed-form memory
reference.  However, these are really only useful in GCC internal code
generation.  In inline asm the operand of the memory constraint is
typically just a register containing the address, so 'U' and 'X' make
no sense.

This patch quietly accepts 'U' and 'X' in inline asm patterns, but
otherwise does nothing.  If we ever unexpectedly see a non-register,
we'll assert and sort it out afterwards.

I've added a new test for these constraints; the test case should be
used for other asm-constraints changes down the road.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217622 91177308-0d34-0410-b5e6-96231b3b80d8
Add missing colon to RUN line...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217623 91177308-0d34-0410-b5e6-96231b3b80d8
Misc cleanups to the FileSytem api.

The main difference is the removal of

std::error_code exists(const Twine &path, bool &result);

It was an horribly redundant interface since a file not existing is also a valid
error_code. Now we have an access function that returns just an error_code. This
is the only function that has to be implemented for Unix and Windows. The
functions can_write, exists and can_execute an now just wrappers.

One still has to be very careful using these function to avoid introducing
race conditions (Time of check to time of use).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217625 91177308-0d34-0410-b5e6-96231b3b80d8