The module currently stores the target triple as a string. This means
that any code that wants to actually use the triple first has to
instantiate a Triple, which is somewhat expensive. The change in #121652
caused a moderate compile-time regression due to this. While it would be
easy enough to work around, I think that architecturally, it makes more
sense to store the parsed Triple in the module, so that it can always be
directly queried.

For this change, I've opted not to add any magic conversions between
std::string and Triple for backwards-compatibilty purses, and instead
write out needed Triple()s or str()s explicitly. This is because I think
a decent number of them should be changed to work on Triple as well, to
avoid unnecessary conversions back and forth.

The only interesting part in this patch is that the default triple is
Triple("") instead of Triple() to preserve existing behavior. The former
defaults to using the ELF object format instead of unknown object
format. We should fix that as well.

The forwarding header is left in place because of its use in
`polly/lib/External/isl/interface/extract_interface.cc`, but I have
added a GCC warning about the fact it is deprecated, because it is used
in `isl` from where it is included by Polly.

to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636

While there, change a bunch of helper functions to take references to
avoid adding calls to get().

This should conclude the bugpoint yak shaving.

llvm-svn: 325177

This one requires a new small feature in TempFile: the ability to keep
the temporary file with the temporary name.

llvm-svn: 318458

llvm-svn: 318427

This replaces the threading of `std::string &Error` through all of
these APIs with checked Error returns instead. There are very few
places here that actually emit any errors right now, but threading the
APIs through will allow us to replace a bunch of exit(1)'s that are
scattered through this code with proper error handling.

This is more or less NFC, but does move around where a couple of error
messages are printed out.

llvm-svn: 280720

This isn't the right thing to do - it turns out a number of the APIs
that "never fail" just exit(1) if something bad happens. We can and
should thread Error through this instead.

That diff will make more sense with this reverted. Sorry for the
noise.

This reverts r280690

llvm-svn: 280691

This simplifies ListReducer and most of its subclasses by removing the
std::string &Error that was threaded through all of them but almost
never used. If we end up needing error handling in more places here we
can reinstate it using llvm::Error instead of these unwieldy strings.

The 2 cases (out of 12) that actually can hit the error cases are a
little bit awkward now, but those will clean up as I refactor this API
further.

llvm-svn: 280690