powerpc support

[richo]

Originally, this was going to be discussed and revisted, however I've been working on this for months, and a rebase on top of master was about 1 flight's worth of work so I just went ahead and did it.

This gets you as far as being able to target powerpc with, eg:

LD_LIBRARY_PATH=./x86_64-unknown-linux-gnu/stage2/lib/ x86_64-unknown-linux-gnu/stage2/bin/rustc -C linker=powerpc-linux-gnu-gcc --target powerpc-unknown-linux-gnu hello.rs

Would really love to get this out before 1.0. r? @alexcrichton

[alexcrichton]

Hm, to stem the flow of these additional target_arch settings, can you change this to be conditional on target_pointer_width?

[richo]

Sorry. Ignore that other comment if it got emailed. Willfix.

[alexcrichton]

This looks pretty good to me, thanks!

I think we're definitely growing a real need for an extension to #[cfg] which allows us to cut down on the huge amount of #[cfg], but we can always worry about that later.

[alexcrichton]

Due to this I think you'll also want to touch the llvm-auto-clean-trigger to ensure LLVM is rebuilt.

[alexcrichton]

As I also requested on #19790, could you analyze the before/after sizes of the compiler? Just want to make sure LLVM isn't bringing too many megabyte wads of powerpc support!

[richo]

Awesome! Thanks so much for taking a look. I'll try to get these issues fixed tonight.

Regarding the size of the compiler:

After:
35M x86_64-unknown-linux-gnu/stage2/lib/librustc_llvm-4e7c5e5c.so
12K x86_64-unknown-linux-gnu/stage2/bin/rustc
3.2M x86_64-unknown-linux-gnu/llvm/Release+Asserts/lib/libLLVMPower*.a

I don't have a before handy, but I can build one before I get home. Comparison numbers from that PR:

Before:
x86_64-unknown-linux-gnu/llvm/Release+Asserts/lib/libLLVMAArch64*.a: 0M
x86_64-unknown-linux-gnu/stage2/lib/librustc_llvm-4e7c5e5c.so: 36,259K
x86_64-unknown-linux-gnu/stage3/bin/rustc: 51,329K

(I'm not sure what the huge discrepancy with the stage3 rustc and my stage2 are, did a bunch of things move out into libs?)

[richo]

I cleaned up the issues in your comments, and grabbed a nightly to check on the sizes of the objects:

From the nightly on rust-lang.org:

42M ./lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_llvm-4e7c5e5c.so
8.0K bin/rustc
(And obviously no powerpc archives).

I guess since I branched, some other LLVM changes must have landed? My librustc_llvm is 7 megs smaller.

[richo]

I finally made time to build the tree that I branched from, for comparison:

goodnight % for i in rust rust-vanilla; do du -hs $i/x86_64-unknown-linux-gnu/stage2/lib/librustc_llvm-*.so; done
42M rust/x86_64-unknown-linux-gnu/stage2/lib/librustc_llvm-4e7c5e5c.so
40M rust-vanilla/x86_64-unknown-linux-gnu/stage2/lib/librustc_llvm-4e7c5e5c.so
goodnight % for i in rust rust-vanilla; do du -hs $i/x86_64-unknown-linux-gnu/stage2/bin/rustc; done
8.0K rust/x86_64-unknown-linux-gnu/stage2/bin/rustc
8.0K rust-vanilla/x86_64-unknown-linux-gnu/stage2/bin/rustc

Is there anything else this needs for an r? @alexcrichton

[brson]

Nice.