message: Remove perf warning for fp[16|32|64] -> uint[8|16].
  This is never a problem and it was added incorrectly in the first place.
diff: @@ -6214,20 +6214,14 @@ static llvm::Value *lTypeConvAtomic(FunctionEmitContext *ctx, llvm::Value *exprV
  cast = ctx->TruncInst(exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_FLOAT16:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from float16 to uint8 is slow. Use \"int8\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_FLOAT:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from float to uint8 is slow. Use \"int8\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_DOUBLE:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from double to uint8 is slow. Use \"int8\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  @@ -6296,20 +6290,14 @@ static llvm::Value *lTypeConvAtomic(FunctionEmitContext *ctx, llvm::Value *exprV
  cast = ctx->TruncInst(exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_FLOAT16:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from float16 to uint16 is slow. Use \"int16\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_FLOAT:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from float to uint16 is slow. Use \"int16\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  case AtomicType::TYPE_DOUBLE:
  - if (fromType->IsVaryingType())
  - PerformanceWarning(pos, "Conversion from double to uint16 is slow. Use \"int16\" if possible");
  cast = ctx->CastInst(llvm::Instruction::FPToUI, // unsigned int
  exprVal, targetType, cOpName);
  break;
  