Set default CPU to `avr2`

[dylanmckay]

To be compatible with AVR-GCC

[4ntoine]

Probably fixed in 4ntoine/clang#3 (commit 4ntoine/clang@a13b48e).

now -target-cpu avr2 is added for Clang compiler command-line by default.

[dylanmckay]

I think a default CPU can also be set in LLVM, so I'll leave this issue open until further investigation.

[4ntoine]

if the idea is to set default CPU for AVR target for llc tool then one can just add:

  // set avr2 as default CPU for AVR target
  if (MCPU.empty() && MArch == "avr") {
    MCPU = "avr2";
  }

to https://github.com/dylanmckay/avr-llvm/blob/avr-support/tools/llc/llc.cpp#L218

[4ntoine]

or edit https://github.com/dylanmckay/avr-llvm/blob/avr-support/lib/Target/AVR/AVRTargetMachine.cpp#L28 and https://github.com/dylanmckay/avr-llvm/blob/avr-support/lib/Target/AVR/AVRTargetMachine.cpp#L29 to smth like

LLVMTargetMachine(T, TT, (CPU.empty() ? "avr2" : CPU), FS, Options, RM, CM, OL),
SubTarget(TT, (CPU.empty() ? "avr2" : CPU), FS, *this)

[dylanmckay]

Ah, I had forgotten where abouts that last snippet was in the code. I'm currently at work, but if you want to add that in and submit a pull request, I will accept it.

[dylanmckay]

I'm talking about the AVRTargetMachine class edit that you suggested