[AMDGPU] Use a named predicate instead of a magic number.

llvm/trunk/lib/Target/AMDGPU/AMDGPUAtomicOptimizer.cpp

void AMDGPUAtomicOptimizer::optimizeAtomic(Instruction &I,
   Type *const VecTy = VectorType::get(B.getInt32Ty(), 2);
 
   // This is the value in the atomic operation we need to combine in order to
   // reduce the number of atomic operations.
   Value *const V = I.getOperand(ValIdx);
 
   // We need to know how many lanes are active within the wavefront, and we do
   // this by doing a ballot of active lanes.
-  CallInst *const Ballot =
-      B.CreateIntrinsic(Intrinsic::amdgcn_icmp,
-                        {B.getInt64Ty(), B.getInt32Ty()},
-                        {B.getInt32(1), B.getInt32(0), B.getInt32(33)});
+  CallInst *const Ballot = B.CreateIntrinsic(
+      Intrinsic::amdgcn_icmp, {B.getInt64Ty(), B.getInt32Ty()},
+      {B.getInt32(1), B.getInt32(0), B.getInt32(CmpInst::ICMP_NE)});
 
   // We need to know how many lanes are active within the wavefront that are
   // below us. If we counted each lane linearly starting from 0, a lane is
   // below us only if its associated index was less than ours. We do this by
   // using the mbcnt intrinsic.
   Value *const BitCast = B.CreateBitCast(Ballot, VecTy);
   Value *const ExtractLo = B.CreateExtractElement(BitCast, B.getInt32(0));
   Value *const ExtractHi = B.CreateExtractElement(BitCast, B.getInt32(1));