[PATCH] D49465: [ARM] Enable tail calls for all Thumb1 targets.

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.
efriedma added reviewers: chill, rengolin, SjoerdMeijer.
Herald added a reviewer: javed.absar.
Herald added subscribers: chrib, kristof.beyls.

It isn't really profitable in general, but it's profitable in cases where there we don't need to spill LR and the callee is a function pointer.

This also implements reversing the transform after isel if it isn't profitable; it's hard to tell during isel whether we'll be forced to spill LR.  Based off the old implementation in r294000, with a hacky fix for the problem of arguments on the stack. I'm not completely happy with the check for this, but it seems like the least-bad alternative.

Depends on https://reviews.llvm.org/D49459.


Repository:
  rL LLVM

https://reviews.llvm.org/D49465

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMSubtarget.cpp
  lib/Target/ARM/Thumb1FrameLowering.cpp
  test/CodeGen/ARM/thumb_indirect_calls.ll
  test/CodeGen/ARM/v8m-tail-call.ll

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