[llvm] [X86][IPRA] Add getIPRACSRegs since frame registers are risked to be optimized out. (PR #109597)

[Shengchen Kan via llvm-commits]

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@@ -103,15 +103,18 @@ void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
   // saved registers.
   SavedRegs.resize(TRI.getNumRegs());
 
-  // When interprocedural register allocation is enabled caller saved registers
-  // are preferred over callee saved registers.
+  // Get the callee saved register list...
+  const MCPhysReg *CSRegs = nullptr;
+
+  // When interprocedural register allocation is enabled, callee saved register
+  // lit should be null, since caller saved registers are preferred over callee
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KanRobert wrote:

lit -> list, null -> empty ?

https://github.com/llvm/llvm-project/pull/109597