[PATCH] D31957: AMDGPU: Slightly simplify prolog reserved register handling

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
Herald added subscribers: t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, kzhuravl.

Rely on MachineRegisterInfo's knowledge of used physical
registers. Use addPhysRegUsed to avoid manually trying to avoid
re-picking the same registers rather than specially avoiding it.

      

Move flat_scratch initialization earlier, so the uses are visible
when making these decisions.

      

This will make it easier to add another reserved register
 at the end for the stack pointer rather than handling another
 special case.


https://reviews.llvm.org/D31957

Files:
  lib/Target/AMDGPU/SIFrameLowering.cpp

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