[PATCH] D117426: [AVR] Only push and clear R1 in interrupts when necessary

[Ayke via Phabricator via llvm-commits]

aykevl created this revision.
aykevl added reviewers: dylanmckay, benshi001.
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`r1` is a reserved register, but LLVM gives the APIs to know when it is used or not. So this patch uses these APIs to only save/clear/restore `r1` in interrupts when necessary.

The main issue here was getting inline assembly to work. One could argue that this is the job of Clang, but for consistency I've made sure that `r1` is always usable in inline assembly even if that means clearing it when it might not be needed.

Information on inline assembly in AVR can be found here:

https://www.nongnu.org/avr-libc/user-manual/inline_asm.html#asm_code

Essentially, this seems to suggest that `r1` can be freely used in avr-gcc inline assembly, even without specifying it as an input operand.

---

This patch depends on D117425 <https://reviews.llvm.org/D117425>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117426

Files:
  llvm/lib/Target/AVR/AVRExpandPseudoInsts.cpp
  llvm/lib/Target/AVR/AVRFrameLowering.cpp
  llvm/lib/Target/AVR/AVRISelDAGToDAG.cpp
  llvm/lib/Target/AVR/AVRISelLowering.cpp
  llvm/lib/Target/AVR/AVRInstrInfo.td
  llvm/test/CodeGen/AVR/interrupts.ll
  llvm/test/CodeGen/AVR/pseudo/NEGWRd.mir
  llvm/test/CodeGen/AVR/pseudo/ROLBrd.mir
  llvm/test/CodeGen/AVR/zeroreg.ll

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