[mlir][sparse][gpu] remove zero init memset

[aartbik]

Summary

avoids quite a big memory fill for each setup

mlir/lib/ExecutionEngine/CudaRuntimeWrappers.cpp

extern "C" MLIR_CUDA_WRAPPERS_EXPORT void mgpuDestroySparseLtEnv() {
   cusparseLt_initiated = false;
 }
 
 extern "C" MLIR_CUDA_WRAPPERS_EXPORT void
 mgpuCreateCuSparseLtDnMat(void *dh, intptr_t rows, intptr_t cols, void *values,
                           int32_t dtp, CUstream /*stream*/) {
   assert(cusparseLt_initiated && "client did not call mgpuCreateSparseLtEnv()");
   auto dnmat_handle = reinterpret_cast<cusparseLtDnMatHandleAndData *>(dh);
-  // CusparseLt expects the descriptors to be zero-initialized.
-  memset(dnmat_handle, 0, sizeof(cusparseLtDnMatHandleAndData));
   dnmat_handle->values = values;
   auto dTp = static_cast<cudaDataType_t>(dtp);
   // Assume row-major when deciding lda.
   const uint32_t alignment = 16;
   CUSPARSE_REPORT_IF_ERROR(cusparseLtDenseDescriptorInit(
       &cusparseLt_env, &(dnmat_handle->mat), rows, cols, /*lda=*/cols,
       alignment, dTp, CUSPARSE_ORDER_ROW))
 }
 
 extern "C" MLIR_CUDA_WRAPPERS_EXPORT void
 mgpuDestroyCuSparseLtDnMat(void *dh, CUstream /*stream*/) {
   auto dnmat_handle = reinterpret_cast<cusparseLtDnMatHandleAndData *>(dh);
   CUSPARSE_REPORT_IF_ERROR(cusparseLtMatDescriptorDestroy(&(dnmat_handle->mat)))
 }
 
 extern "C" MLIR_CUDA_WRAPPERS_EXPORT void
 mgpuCusparseLtCreate2To4SpMat(void *sh, intptr_t rows, intptr_t cols,
                               void *values, int32_t dtp, CUstream /*stream*/) {
   assert(cusparseLt_initiated && "client did not call mgpuCreateSparseLtEnv()");
   auto spmat_handle = reinterpret_cast<cusparseLtSpMatHandleAndData *>(sh);
-  // CusparseLt expects the descriptors to be zero-initialized.
-  memset(spmat_handle, 0, sizeof(cusparseLtSpMatHandleAndData));
   spmat_handle->values = values;
   auto dTp = static_cast<cudaDataType_t>(dtp);
   // Assume row-major when deciding lda.
   const uint32_t alignment = 16;
   CUSPARSE_REPORT_IF_ERROR(cusparseLtStructuredDescriptorInit(
       &cusparseLt_env, &(spmat_handle->mat), rows, cols, /*ld=*/cols, alignment,
       dTp, CUSPARSE_ORDER_ROW, CUSPARSELT_SPARSITY_50_PERCENT))
 }