[llvm] [AMDGPU] Inplace FI elimination during PEI for scalar copy instruction (PR #99556)

[Matt Arsenault via llvm-commits]

================
@@ -2555,12 +2555,33 @@ bool SIRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator MI,
                       TmpResultReg)
                   .addImm(ST.getWavefrontSizeLog2())
                   .addReg(FrameReg);
-              auto Add = BuildMI(*MBB, MI, DL, TII->get(AMDGPU::V_ADD_U32_e32),
-                                 TmpResultReg);
-              Add.addImm(Offset).addReg(TmpResultReg, RegState::Kill);
+
+              MachineInstrBuilder Add;
+              if ((Add = TII->getAddNoCarry(*MBB, MI, DL, TmpResultReg, *RS)) ==
+                  nullptr) {
----------------
arsenm wrote:

It would be easiest to read if we handled the positive cases where this returned an add before the fallback path. 

https://github.com/llvm/llvm-project/pull/99556