[llvm] [AMDGPU] Save/Restore SCC bit across waterfall loop. (PR #68363)

[Matt Arsenault via llvm-commits]

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@@ -5094,6 +5094,39 @@ unsigned SIInstrInfo::getVALUOp(const MachineInstr &MI) const {
       "Unexpected scalar opcode without corresponding vector one!");
 }
 
+bool SIInstrInfo::isSCCDefinedBefore(MachineBasicBlock &MBB,
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arsenm wrote:

These functions are just recreating computeRegisterLiveness. However, I don't think you really need that in the first place. You could just unconditionally copy and restore and let PeepholeOpt deal with it later if it was unnecessary 

https://github.com/llvm/llvm-project/pull/68363