[PATCH] D85760: [DebugInstrRef][7/9] NFC: Separate collection of machine/variable values

[Jeremy Morse via Phabricator via llvm-commits]

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This patch adjusts _when_ something happens in LiveDebugValues / InstrRefBasedLDV, to make it more amenable to dealing with DBG_INSTR_REF instructions. There's no functional change.

In the current base InstrRefBasedLDV implementation, we collect the machine value-number transfer function for blocks at the same time as the variable-value transfer function. After solving machine value numbers, the variable-value transfer function is updated so that DBG_VALUEs of live-in registers have the correct value. The same would need to be done for DBG_INSTR_REFs, to connect instruction-references with machine value numbers.

Rather than writing more code for that, this patch makes things slightly simpler:

- We collect the (machine-value-number) transfer function and solve for machine value numbers,
- Then step through the MachineInstrs again collecting the variable value transfer function.

The change is that linking up variable values with how they're defined (as being in a register, or as an instruction reference) is done as we step through the MachineInstrs, instead of on-the-fly. This is slower (in terms of compile time performance) but makes the next patch much easier to understand.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85760

Files:
  llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp

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