[PATCH] D59842: RegScavenger: Fix !AllowSpill if no regs are available

[Francis Visoiu Mistrih via Phabricator via llvm-commits]

thegameg added a comment.

I would have a slight preference for just:

  diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp
  index bb19110e6d70..b9e30c579e65 100644
  --- a/llvm/lib/CodeGen/RegisterScavenging.cpp
  +++ b/llvm/lib/CodeGen/RegisterScavenging.cpp
  @@ -554,6 +554,11 @@ unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
     if (Available.any())
       Candidates = Available;
  
  +  if (Candidates.none()) {
  +    assert(!AllowSpill && "No candidates for scavenging");
  +    return 0;
  +  }
  +
     // Find the register whose use is furthest away.
     MachineBasicBlock::iterator UseMI;
     unsigned SReg = findSurvivorReg(I, Candidates, 25, UseMI);

with maybe a comment on when this can happen.

Also maybe a MIR test with `$reg = IMPLICIT_DEF` instead of the inline asm would be nicer?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59842/new/

https://reviews.llvm.org/D59842