AMDGPU/GlobalISel: Preserve flags when splitting select

RegBankSelect was losing flags on selects.

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

@@ -2357,8 +2357,9 @@ void AMDGPURegisterBankInfo::applyMappingImpl(
 
     setRegsToType(MRI, DefRegs, HalfTy);
 
-    B.buildSelect(DefRegs[0], CondRegs[0], Src1Regs[0], Src2Regs[0]);
-    B.buildSelect(DefRegs[1], CondRegs[0], Src1Regs[1], Src2Regs[1]);
+    auto Flags = MI.getFlags();
+    B.buildSelect(DefRegs[0], CondRegs[0], Src1Regs[0], Src2Regs[0], Flags);
+    B.buildSelect(DefRegs[1], CondRegs[0], Src1Regs[1], Src2Regs[1], Flags);
 
     MRI.setRegBank(DstReg, AMDGPU::VGPRRegBank);
     MI.eraseFromParent();