[mlir][sparse] Simplifying code in expInsert

[wrengr]

Summary

Just some minor cleanup

[aartbik]

mlir/lib/ExecutionEngine/SparseTensorUtils.cpp

339

Note that llvm style is no fan of putting const on locals (I am, but just noting).

[wrengr]

mlir/lib/ExecutionEngine/SparseTensorUtils.cpp

339

I'll bear that in mind. (I prefer it since it helps clarify intent and catch bugs, but I'll try not to offend the style guardians :)

mlir/lib/ExecutionEngine/SparseTensorUtils.cpp

public:
   /// to all-zero/false while only iterating over the nonzero elements.
   void expInsert(uint64_t *cursor, V *values, bool *filled, uint64_t *added,
                  uint64_t count) override {
     if (count == 0)
       return;
     // Sort.
     std::sort(added, added + count);
     // Restore insertion path for first insert.
-    uint64_t rank = getRank();
+    const uint64_t lastDim = getRank() - 1;
     uint64_t index = added[0];
-    cursor[rank - 1] = index;
+    cursor[lastDim] = index;
     lexInsert(cursor, values[index]);
     assert(filled[index]);
     values[index] = 0;
     filled[index] = false;
     // Subsequent insertions are quick.
     for (uint64_t i = 1; i < count; i++) {
       assert(index < added[i] && "non-lexicographic insertion");
       index = added[i];
-      cursor[rank - 1] = index;
-      insPath(cursor, rank - 1, added[i - 1] + 1, values[index]);
+      cursor[lastDim] = index;
+      insPath(cursor, lastDim, added[i - 1] + 1, values[index]);
       assert(filled[index]);
-      values[index] = 0.0;
+      values[index] = 0;
       filled[index] = false;
     }
   }
 
   /// Finalizes lexicographic insertions.
   void endInsert() override {
     if (values.empty())
       endDim(0);