fix

Author: xingmingyyj

paddle/phi/kernels/cpu/trunc_grad_kernel.cc

@@ -25,7 +25,7 @@ void TruncGradKernel(const Context& dev_ctx,
  DenseTensor* in_grad) {
  T* dx_data = dev_ctx.template Alloc<T>(in_grad);
 
- int64_t numel = static_cast<int>(in_grad->numel());
+ int64_t numel = in_grad->numel();
  memset(dx_data, 0.0, numel * sizeof(T));
 }