[PATCH] D38128: Handle COPYs of physregs better (regalloc hints)

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa updated this revision to Diff 124559.
jonpa added a comment.

Patch updated to include a TargetRegisterInfo hook 'enableMultipleCopyHints()' that returns false per default, which gives NFC to trunk. OnlySystemZ returns true for now. It is up to all target maintainers to enable this and review test changes, which hopefully will be done
soon so that the hook can be removed again.

Some minor changes compared to last version in order to get the NFC to trunk when returning false in enableMultipleCopyHints():

- reinstate the mri.isAllocatable() check for the hint, which was dropped for some reason (makes a small difference on the resulting weight in some rare cases).
- If target has created a simple hint, it must be cleared before the best hint from CopyHints is inserted, so a new clearSimpleHint() method in MachineRegisterInfo was needed. Not sure that all those different methods for manipulating hints are really needed in the end once all targets have been converted. In particular, I am curious why AMDGPU sets those hints (of generic type) when they will be recomputed always here...
- A new temporary variable CopyHint::HintOrder, in order to properly mimic the current behavior on trunk for NFC. This is because on trunk, the best hint is kept in the order of discovery, which is not what the CopyHints set was doing.

These hacks aren't very pretty, so PLEASE EVERYONE: HELP REMOVE THEM BY ENABLING THE MULTIPLE COPY HINTS!

@nemanjai: You approved this for Power PC, but one more test has changed now (licm-tocReg.ll), so please get the previous test changes from here on Phabricator (which apply fine) and review the new one, and then return true in enableMultipleCopyHints() once this is approved.

@tstellard, @efriedman: Thanks for helping reviewing the tests on your targets. I have not enabled those targets as I have not checked on those tests on latest trunk. I hope you can download those tests from here on Phabricator and make sure eveything's green as you enable this.

Please let me know if this is ok to commit.


https://reviews.llvm.org/D38128

Files:
  include/llvm/CodeGen/MachineRegisterInfo.h
  include/llvm/CodeGen/TargetRegisterInfo.h
  lib/CodeGen/CalcSpillWeights.cpp
  lib/CodeGen/TargetRegisterInfo.cpp
  lib/Target/SystemZ/SystemZRegisterInfo.h
  test/CodeGen/SystemZ/call-03.ll
  test/CodeGen/SystemZ/swift-return.ll
  test/CodeGen/SystemZ/swifterror.ll

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