Add a 'rolling_buffer' scheduling primitive (apache#9444)

* Add a 'rolling_buffer' scheduling primitive

Co-authored-by: Matthew Barrett <Matthew.Barrett@arm.com>

* Fix lint problems

Change-Id: I5e27a66105fccca84327e41b4c68836ac2515126

* Remove designated initializers

Change-Id: Ic148264239eac7df7d976a6a3e15236935232792

Co-authored-by: Matthew Barrett <Matthew.Barrett@arm.com>

include/tvm/te/schedule.h

@@ -251,6 +251,11 @@ class Stage : public ObjectRef {
    * \return reference to self.
    */
   TVM_DLL Stage& double_buffer();  // NOLINT(*)
+  /*!
+   * \brief Compute current stage with rolling buffering.
+   * \return reference to self.
+   */
+  TVM_DLL Stage& rolling_buffer();  // NOLINT(*)
   /*!
    * \brief whether the stage has been scheduled.
    * \return whether the stage has been scheduled.
@@ -493,6 +498,8 @@ class StageNode : public Object {
   bool is_output{false};
   /*! \brief Whether apply double buffer optimization to this stage */
   bool double_buffer{false};
+  /*! \brief Whether apply rolling buffer optimization to this stage */
+  bool rolling_buffer{false};
   /*!
    * \brief The parent group of the current stage.
    *  The stage cannot be assigned to stages outside the group.

include/tvm/tir/stmt.h

@@ -1284,6 +1284,8 @@ constexpr const char* double_buffer_scope = "double_buffer_scope";
  * \brief Marks region used by double buffer write
  */
 constexpr const char* double_buffer_write = "double_buffer_write";
+/*! \brief Mark realization for rolling buffer optimization */
+constexpr const char* rolling_buffer_scope = "rolling_buffer_scope";
 /*! \brief Mark of scan update scope */
 constexpr const char* scan_update_scope = "scan_update_scope";
 /*! \brief Mark of scan init scope */

python/tvm/te/schedule.py

@@ -511,6 +511,14 @@ def double_buffer(self):
         """
         _ffi_api.StageDoubleBuffer(self)
 
+    def rolling_buffer(self):
+        """Compute the current stage via rolling buffering.
+
+        This can only be applied to intermediate stage.
+        This will change the storage cost of the current stage.
+        """
+        _ffi_api.StageRollingBuffer(self)
+
 
 @tvm._ffi.register_object
 class SpecializedCondition(Object):

python/tvm/tir/transform/transform.py

@@ -206,6 +206,17 @@ def InjectDoubleBuffer():
     return _ffi_api.InjectDoubleBuffer()  # type: ignore
 
 
+def InjectRollingBuffer():
+    """Inject rolling buffer statements.
+
+    Returns
+    -------
+    fpass : tvm.transform.Pass
+        The result pass
+    """
+    return _ffi_api.InjectRollingBuffer()  # type: ignore
+
+
 def StorageRewrite():
     """Rewrite storage allocation pattern.
 

src/te/operation/compute_op.cc

@@ -484,7 +484,8 @@ ComputeLoopNest ComputeLoopNest::Create(const BaseComputeOpNode* self, const Sta
     }
     ret.init_nest = MakeLoopNest(stage, dom_map, begin_loop, true, skip_iter, &(ret.init_vmap),
                                  debug_keep_trivial_loop);
-    ret.init_predicates = MakeBoundCheck(stage, dom_map, ret.init_vmap, true, skip_iter);
+    ret.init_predicates =
+        MakeBoundCheck(stage, dom_map, ret.init_vmap, !stage->rolling_buffer, skip_iter);
     for (auto& e : ret.init_predicates) {
       e = likely(e);
     }

src/te/schedule/schedule_lang.cc

@@ -423,6 +423,13 @@ Stage& Stage::double_buffer() {
   return *this;
 }
 
+Stage& Stage::rolling_buffer() {
+  StageNode* self = operator->();
+  ICHECK(!self->is_output) << "Cannot apply rolling buffer on output";
+  self->rolling_buffer = true;
+  return *this;
+}
+
 Stage CopyStage(const Stage& s) {
   ObjectPtr<StageNode> n = make_object<StageNode>(*s.operator->());
   return Stage(n);
@@ -886,6 +893,8 @@ TVM_REGISTER_GLOBAL("te.StageStorageAlign").set_body_method(&Stage::storage_alig
 
 TVM_REGISTER_GLOBAL("te.StageDoubleBuffer").set_body_method(&Stage::double_buffer);
 
+TVM_REGISTER_GLOBAL("te.StageRollingBuffer").set_body_method(&Stage::rolling_buffer);
+
 TVM_REGISTER_GLOBAL("te.ScheduleNormalize").set_body_method(&Schedule::normalize);
 
 TVM_REGISTER_GLOBAL("te.ScheduleCreateGroup").set_body_method(&Schedule::create_group);

src/te/schedule/schedule_ops.cc

@@ -52,6 +52,10 @@ Stmt MakePipeline(const Stage& s, const std::unordered_map<IterVar, Range>& dom_
     pipeline = SeqStmt({producer, consumer});
   }
 
+  if (s->rolling_buffer) {
+    pipeline = AttrStmt(s->op, tir::attr::rolling_buffer_scope, Bool(true), pipeline);
+  }
+
   return s->op->BuildRealize(s, dom_map, pipeline, s->scope);
 }
 

src/te/schedule/schedule_postproc_to_primfunc.cc

@@ -67,7 +67,8 @@ class TensorToBufferMapper : public StmtExprMutator {
   Stmt VisitStmt_(const AttrStmtNode* op) final {
     auto ret = StmtExprMutator::VisitStmt_(op);
     op = ret.as<AttrStmtNode>();
-    if (op->attr_key == tir::attr::double_buffer_scope) {
+    if (op->attr_key == tir::attr::double_buffer_scope ||
+        op->attr_key == tir::attr::rolling_buffer_scope) {
       Stmt body = op->body;
       Operation operation = Downcast<Operation>(op->node);
       for (int i = operation->num_outputs(); i != 0; --i) {