LLVM upgrades

[alexcrichton]

This includes some of @brson's patches, plus one of mine. A multithreaded-llvm is necessary for running rusti tests in parallel, and in general is a good idea for running rustc in parallel.

[alexcrichton]

It turns out that this change completely breaks rusti. After a lot of debugging, it turned out that the MCJIT of LLVM was also completely broken. After bisecting the LLVM revision which broke it, I realized I could update to the most current LLVM instead. Indeed, this fixed the MCJIT when I check out the changes from https://github.com/chapuni/llvm.

@brson, can you pull in the upstream LLVM changes into your branch? I could do so as well, but I'm not sure how many patches are custom to rust. I don't mind testing to make sure that LLVM passes by pushing through try.

I don't think that bors will be able to handle this request normally. It'll need to be pushed to incoming manually, and then the bots need to all get their llvm workspaces wiped.

[brson]

@alexcrichton I rebased onto llvm trunk and pushed a rust commit that you can cherry-pick to my 'llvm' branch https://github.com/brson/rust/tree/llvm. Still testing it here.

[brson]

@alexcrichton Thanks for porting rustllvm. Sadly this branch doesn't build for me:

compile_and_link: x86_64-unknown-linux-gnu/stage1/lib/rustc/x86_64-unknown-linux-gnu/lib/libstd.so
/home/brian/dev/rust2/src/libstd/ptr.rs:130:8: 130:51 warning: unused import [-W unused-imports (default)]
/home/brian/dev/rust2/src/libstd/ptr.rs:130     use memcpy64 = unstable::intrinsics::memmove64;
                                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
rustc: /opt/dev/rust2/src/llvm/lib/IR/Attributes.cpp:119: llvm::StringRef llvm::Attribute::getKindAsString() const: Assertion `isStringAttribute() && "Invalid attribute type to get the kind as a string!"' failed.
Stack dump:
0.      Running pass 'Function Pass Manager' on module 'std.rc'.
1.      Running pass 'Module Verifier' on function '@_ZN8unstable10intrinsics12cosf32_1247416_54d9ca723652f656_07preE'
Aborted
make: *** [x86_64-unknown-linux-gnu/stage1/lib/rustc/x86_64-unknown-linux-gnu/lib/libstd.so] Error 134

[alexcrichton]

@brson I've been debugging this today, I've got a fix on the way, just going to make sure that it passes check-stage2-rusti first

[alexcrichton]

The build failures/bugs are probably best explained by the commits

[alexcrichton]

Just to keep this updated, this is currently blocked on a mysterious windows failure which comes from the upstream LLVM changes.