[llvm] [AArch64][SVE] Share code across SVE prologue/epilogue implementations (NFCI) (PR #162253)

[Benjamin Maxwell via llvm-commits]

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@@ -75,6 +74,8 @@ static bool isPartOfPPRCalleeSaves(MachineBasicBlock::iterator I) {
   case AArch64::LDR_PXI:
     return I->getFlag(MachineInstr::FrameSetup) ||
            I->getFlag(MachineInstr::FrameDestroy);
+  case AArch64::SEH_SavePReg:
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MacDue wrote:

It's not really, `SEH_SavePReg` was placed in the wrong helper originally (`isPartOfZPRCalleeSaves()`), but it was not noticed because the Windows code only used `isPartOfSVECalleeSaves()`. This refactoring exposed this issue, but it was not observable before. 

https://github.com/llvm/llvm-project/pull/162253