[GitHub] [tvm] ekalda commented on a diff in pull request #10959: [microNPU] Add a pass to reorder copy and compute nodes

[GitBox <gi...@apache.org>]

ekalda commented on code in PR #10959:
URL: https://github.com/apache/tvm/pull/10959#discussion_r848275763


##########
src/tir/contrib/ethosu/passes.cc:
##########
@@ -110,6 +110,71 @@ tvm::transform::Pass HoistAllocates() {
 
 TVM_REGISTER_GLOBAL("tir.contrib.ethos-u.HoistAllocates").set_body_typed(HoistAllocates);
 
+/*!
+ * \brief Reorders copy and compute nodes in such a way that independent DMA copies,
+ * and computes happen in parallel.
+ */
+class CopyComputeReorderingMutator : public StmtExprMutator {
+ public:
+  CopyComputeReorderingMutator() {}
+
+  PrimFunc operator()(PrimFunc main_func) {
+    auto n{main_func.CopyOnWrite()};
+    n->body = this->VisitStmt(main_func->body);
+    return GetRef<PrimFunc>(n);
+  }
+
+ private:
+  Stmt VisitStmt_(const SeqStmtNode* op) override {
+    if (op->size() <= 1) {
+      return StmtExprMutator::VisitStmt_(op);
+    }
+
+    auto seq_stmt{GetRef<SeqStmt>(op)};
+    std::vector<Stmt> new_seq(seq_stmt->size());
+    std::copy(seq_stmt->seq.begin(), seq_stmt->seq.end(), new_seq.begin());
+    bool previous_stmt_is_copy{true};  // Do not move the first stmt if it is a copy
+
+    for (size_t i{}; i < seq_stmt->size(); ++i) {
+      auto stmt{seq_stmt[i]};
+      auto args{stmt.as<EvaluateNode>()->value.as<CallNode>()->args};
+      bool stmt_is_copy{args[0].as<StringImmNode>()->value == "ethosu_copy"};
+      bool stmt_is_global_copy{stmt_is_copy &&
+                               args[3].as<BufferLoadNode>()->buffer.scope() == "global"};

Review Comment:
   Maybe add a brief comment there why we don't touch copies with scope "local", something along the lines "Copies tagged as "local" copy LUT into the SHRAM which already happens in parallel with copying weights into the weights encoder"



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