gisel update for g_merge

Author: broxigarchen

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

@@ -639,7 +639,7 @@ bool AMDGPUInstructionSelector::selectG_MERGE_VALUES(MachineInstr &MI) const {
   LLT SrcTy = MRI->getType(MI.getOperand(1).getReg());
 
   const unsigned SrcSize = SrcTy.getSizeInBits();
-  if (SrcSize < 32)
+  if (SrcSize < 16)
     return selectImpl(MI, *CoverageInfo);
 
   const DebugLoc &DL = MI.getDebugLoc();