[AVR] Add a majority of the backend code

[dylanmckay]

Summary

This adds the majority of the AVR backend.

[dylanmckay]

Ping.

[dylanmckay]

Ping.

[dylanmckay]

Ping.

[arsenm]

lib/Target/AVR/AVRFrameLowering.h

10–13

Remove empty comment block

31

Pointless comment

lib/Target/AVR/AVRISelLowering.h

120–124

C++ style comments

lib/Target/AVR/AVRInstrInfo.cpp

39–44

These are not OK

lib/Target/AVR/AVRInstrInfo.h

24

Missing undef?

lib/Target/AVR/AVRSubtarget.h

69

this->?

[dylanmckay]

First round of code review

[dylanmckay]

lib/Target/AVR/AVRInstrInfo.cpp

39–44

That wasn't meant to make it in here, it's gone now.

lib/Target/AVR/AVRInstrInfo.h

24

Nice catch

[dylanmckay]

Back to you Matt

[dylanmckay]

Ping

[arsenm]

LGTM with some style nits, plus the pass setup seems to be adding a couple of passes I don't see being added

lib/Target/AVR/AVRFrameLowering.h

19–21

C++ style comments

lib/Target/AVR/AVRISelLowering.h

39

Why not all caps like the others?

82–83

I think it's best to not duplicate the comments on overrides. The base class header comment is more likely to be kept up to date

lib/Target/AVR/AVRInstrInfo.cpp

69

brace on case lines

390

Question mark?

462

static_cast

lib/Target/AVR/AVRInstrInfo.h

29–33

C++ comments

lib/Target/AVR/AVRRegisterInfo.cpp

57–69

Some comments about why these registers are reserved might be helpful

171

Fallthrough

lib/Target/AVR/AVRRegisterInfo.h

23–25

C++ comments. Repeat for everywhere else

lib/Target/AVR/AVRSubtarget.cpp

37

Do these actually initialize to 0? I don't think I've seen empty parens like this before

lib/Target/AVR/AVRSubtarget.h

38

Extra lne

48

return on new line like the others here

lib/Target/AVR/AVRTargetMachine.cpp

29

This is only one place, so you can just move the literal there

32

static, Get->get

35

No return after else

97

Don't see this

104

I don't see this file?

lib/Target/AVR/MCTargetDesc/AVRMCTargetDesc.h

23–25

Alphabetize

[dylanmckay]

lib/Target/AVR/AVRRegisterInfo.cpp

57–69

Agree

[dylanmckay]

Second round of Matt's code review

[dylanmckay]

Thanks for the review Matt :)