[AMDGPU] Use unsigned overflow for S_UADDO_PSEUDO/S_USUBO_PSEUDO (#160142)

Use correct unsigned overflow instructions for
S_UADDO_PSEUDO/S_USUBO_PSEUDO. Note that this issue was hidden because
instruction selection never selected S_UADDO_PSEUDO/S_USUBO_PSEUDO which
will be addressed in #159814.

Signed-off-by: John Lu <[email protected]>

Author: LU-JOHN

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -5953,8 +5953,8 @@ SITargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
     MachineOperand &Src1 = MI.getOperand(3);
 
     unsigned Opc = (MI.getOpcode() == AMDGPU::S_UADDO_PSEUDO)
-                       ? AMDGPU::S_ADD_I32
-                       : AMDGPU::S_SUB_I32;
+                       ? AMDGPU::S_ADD_U32
+                       : AMDGPU::S_SUB_U32;
     // clang-format off
     BuildMI(*BB, MI, DL, TII->get(Opc), Dest0.getReg())
         .add(Src0)