[RELAY] Fixes to MergeCompilerRegions (apache#5195)

* [RELAY] Fixed issues with MergeCompilerRegions

This PR addresses a few outstanding issues with
the implementation of MergeCompilerRegions. In
particular, it now handles TupleGetItem nodes properly
and other minor bugs related to region merging have
been fixed.

Change-Id: I07783afc56183a6f798a510209f23b0a5f252255

* Fixed issue using pre-merged regions

Change-Id: I0a844ac59bda1089ae0c67cef52f0b0c7ab2cbd7

* Removed some debugging logic

Change-Id: Ib6f2eede6f38bbb270073eb8d4c4dc19f60832c6

* Remove default annotations

Change-Id: I9b7696a51c95871491cbea33c40f92ec327e417f

* Annotate default 'if's

Change-Id: I0098bd1bf6788dd6366810dcefa84f1ebbffaab0

* Clang format

Change-Id: I944365cd3080a97a9261f643a8f1efa5a63cf82b

* Use src/dest in merge

Change-Id: Ie43113492bda8f1ce63eaf9615cb645bb9e2ee86

* Fixed partition test

Change-Id: I46f9e349b1a813a9140f7e4f8a2241687e2df73b

* Removed comments

Change-Id: I309afdd1951d7e796e41d13788aa487707e0ac4c

src/relay/analysis/annotated_region_set.cc

@@ -70,12 +70,12 @@ void AnnotatedRegionSetNode::MergeRegions(AnnotatedRegion src,
   regions_.erase(src);
 }
 
-void AnnotatedRegionSetNode::AddToRegion(AnnotatedRegion region, const Expr& expr) {
-  auto region2 = GetRegion(expr);
-  if (region2.defined()) {
-    MergeRegions(region, region2);
+void AnnotatedRegionSetNode::AddToRegion(AnnotatedRegion dest, const Expr& expr) {
+  auto src = GetRegion(expr);
+  if (src.defined()) {
+    MergeRegions(src, dest);
   } else {
-    region->nodes.insert(expr);
+    dest->nodes.insert(expr);
   }
 }
 

src/relay/analysis/annotated_region_set.h

@@ -178,10 +178,10 @@ class AnnotatedRegionSetNode : public Object {
   /*!
    * \brief Add an expression to a region.
    *
-   * \param region The region to add the expression to.
+   * \param dest The region to add the expression to.
    * \param expr The expression.
    */
-  void AddToRegion(AnnotatedRegion region, const Expr& expr);
+  void AddToRegion(AnnotatedRegion dest, const Expr& expr);
 
   /*!
    * \brief Make a new region.

src/relay/transforms/annotate_target.cc

@@ -32,6 +32,9 @@ namespace tvm {
 namespace relay {
 namespace annotate_target {
 
+// Cache compiler_begin op for equivalence check.
+static const Op& compiler_begin_op = Op::Get("annotation.compiler_begin");
+
 // A helper class to insert annotation boundaries for a program region that will
 // be handled by a specific compiler.
 class AnnotateTargetWrapper : public ExprMutator {
@@ -52,6 +55,13 @@ class AnnotateTargetWrapper : public ExprMutator {
         return fannotate[op](call->attrs, call->args);
       }
     }
+    if (expr->IsInstance<TupleGetItemNode>()) {
+      TupleGetItem get = Downcast<TupleGetItem>(expr);
+      if (get->tuple->IsInstance<CallNode>() &&
+          get->tuple.as<CallNode>()->op == compiler_begin_op) {
+        return true;
+      }
+    }
     return false;
   }
 
@@ -110,9 +120,14 @@ class AnnotateTargetWrapper : public ExprMutator {
     auto new_e = ExprMutator::VisitExpr_(op);
 
     auto get = Downcast<TupleGetItem>(new_e);
-    return TupleGetItem(
-      InsertEnd(get->tuple),
-      get->index);
+    if (IsSupported(get->tuple)) {
+      const auto* begin_op =
+        runtime::Registry::Get("relay.op.annotation._make.compiler_begin");
+      CHECK(begin_op);
+      return TupleGetItem((*begin_op)(InsertEnd(get->tuple), target_), get->index);
+    } else {
+      return TupleGetItem(InsertEnd(get->tuple), get->index);
+    }
   }
 
   Expr VisitExpr_(const FunctionNode* op) {