tiling: Track the branch completion status via the output stages

Tiles may produce output on only a single branch when multiple branches are active. Track the completion using a new BranchComplete() helper, which traverses the pipeline till the output stage and returns a flag if the stage has completed all its output. In the split stage, do not inject tiles into a branch if the output is complete. Signed-off-by: Naushir Patuck <[email protected]>
raspberrypi · Jul 15, 2024 · ee4585c · ee4585c
1 parent 8f30e45
commit ee4585c
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Showing 7 changed files with 66 additions and 10 deletions.
diff --git a/src/libpisp/backend/tiling/output_stage.cpp b/src/libpisp/backend/tiling/output_stage.cpp
@@ -21,7 +21,7 @@ using namespace tiling;
 // the offset/length from the LH edge).
 
 OutputStage::OutputStage(char const *name, Stage *upstream, Config const &config, int struct_offset)
-	: BasicStage(name, upstream->GetPipeline(), upstream, struct_offset), config_(config)
+	: BasicStage(name, upstream->GetPipeline(), upstream, struct_offset), config_(config), branch_complete_(false)
 {
 	pipeline_->AddOutputStage(this);
 }
@@ -118,7 +118,21 @@ void OutputStage::PushCropDown(Interval interval, [[maybe_unused]] Dir dir)
 	PISP_LOG(debug, "(" << name_ << ") Exit with interval " << output_interval_);
 }
 
-bool OutputStage::Done(Dir dir) const
+void OutputStage::Reset()
 {
-	return output_interval_.End() >= GetOutputImageSize()[dir];
+	BasicStage::Reset();
+	branch_complete_ = false;
+}
+
+bool OutputStage::BranchComplete() const
+{
+	return branch_complete_;
+}
+
+bool OutputStage::Done(Dir dir)
+{
+	if (output_interval_.End() >= GetOutputImageSize()[dir])
+		branch_complete_ = true;
+
+	return branch_complete_;
 }
diff --git a/src/libpisp/backend/tiling/output_stage.hpp b/src/libpisp/backend/tiling/output_stage.hpp
@@ -30,10 +30,13 @@ class OutputStage : public BasicStage
 	virtual int PushEndDown(int input_end, Dir dir);
 	virtual void PushEndUp(int output_end, Dir dir);
 	virtual void PushCropDown(Interval interval, Dir dir);
-	bool Done(Dir dir) const;
+	virtual void Reset();
+	bool BranchComplete() const;
+	bool Done(Dir dir);
 
 private:
 	Config config_;
+	bool branch_complete_;
 };
 
 } // namespace tiling
diff --git a/src/libpisp/backend/tiling/pipeline.cpp b/src/libpisp/backend/tiling/pipeline.cpp
@@ -80,7 +80,10 @@ int Pipeline::tileDirection(Dir dir, void *mem, size_t num_items, size_t item_si
 		if (num_tiles == num_items)
 			throw std::runtime_error("Too many tiles!");
 		for (auto s : outputs_)
-			s->PushStartUp(s->GetOutputInterval().End(), dir);
+		{
+			if (!s->BranchComplete())
+				s->PushStartUp(s->GetOutputInterval().End(), dir);
+		}
 		for (auto s : inputs_)
 			s->PushEndDown(s->GetInputInterval().offset + config_.max_tile_size[dir], dir);
 		for (auto s : inputs_)

diff --git a/src/libpisp/backend/tiling/split_stage.cpp b/src/libpisp/backend/tiling/split_stage.cpp
@@ -49,7 +49,13 @@ void SplitStage::PushStartUp(int output_start, Dir dir)
 		input_interval_ = Interval(output_start);
 	else
 		input_interval_ |= output_start;
-	if (count_ == downstream_.size())
+
+	unsigned int branch_incomplete_count = 0;
+	for (auto const &d : downstream_)
+		if (!d->BranchComplete())
+			branch_incomplete_count++;
+
+	if (count_ == branch_incomplete_count)
 	{
 		count_ = 0;
 		PISP_LOG(debug, "(" << name_ << ") Exit - call PushStartUp with " << input_interval_.offset);
@@ -67,6 +73,8 @@ int SplitStage::PushEndDown(int input_end, Dir dir)
 	input_interval_.SetEnd(0);
 	for (auto d : downstream_)
 	{
+		if (d->BranchComplete())
+			continue;
 		int branch_end = d->PushEndDown(input_end, dir);
 		// (It is OK for a branch to make no progress at all - so long as another branch does!)
 		if (branch_end > input_interval_.End())
@@ -82,7 +90,8 @@ int SplitStage::PushEndDown(int input_end, Dir dir)
 	}
 
 	for (auto d : downstream_)
-		d->PushEndDown(input_interval_.End(), dir);
+		if (!d->BranchComplete())
+			d->PushEndDown(input_interval_.End(), dir);
 
 	PushEndUp(input_interval_.End(), dir);
 	return input_interval_.End();
@@ -105,6 +114,8 @@ void SplitStage::PushCropDown(Interval interval, Dir dir)
 	input_interval_ = interval;
 	for (auto d : downstream_)
 	{
+		if (d->BranchComplete())
+			continue;
 		PISP_LOG(debug, "(" << name_ << ") Exit with interval " << interval);
 		d->PushCropDown(interval, dir);
 	}
@@ -113,3 +124,11 @@ void SplitStage::PushCropDown(Interval interval, Dir dir)
 void SplitStage::CopyOut([[maybe_unused]] void *dest, [[maybe_unused]] Dir dir)
 {
 }
+
+bool SplitStage::BranchComplete() const
+{
+	bool done = true;
+	for (auto d : downstream_)
+		done &= d->BranchComplete();
+	return done;
+}
diff --git a/src/libpisp/backend/tiling/split_stage.hpp b/src/libpisp/backend/tiling/split_stage.hpp
@@ -26,6 +26,7 @@ class SplitStage : public Stage
 	virtual void PushEndUp(int output_end, Dir dir);
 	virtual void PushCropDown(Interval interval, Dir dir);
 	virtual void CopyOut(void *dest, Dir dir);
+	virtual bool BranchComplete() const;
 
 private:
 	Stage *upstream_;

diff --git a/src/libpisp/backend/tiling/stages.cpp b/src/libpisp/backend/tiling/stages.cpp
@@ -74,8 +74,22 @@ void BasicStage::CopyOut(void *dest, Dir dir)
 	if (struct_offset_ >= 0)
 	{
 		Region *region = (Region *)((uint8_t *)dest + struct_offset_);
-		region->input[dir] = input_interval_;
-		region->crop[dir] = crop_;
-		region->output[dir] = output_interval_;
+		if (!BranchComplete())
+		{
+			region->input[dir] = input_interval_;
+			region->crop[dir] = crop_;
+			region->output[dir] = output_interval_;
+		}
+		else
+		{
+			region->input[dir] = {};
+			region->crop[dir] = {};
+			region->output[dir] = {};
+		}
 	}
 }
+
+bool BasicStage::BranchComplete() const
+{
+	return downstream_->BranchComplete();
+}
diff --git a/src/libpisp/backend/tiling/stages.hpp b/src/libpisp/backend/tiling/stages.hpp
@@ -36,6 +36,7 @@ class Stage
 	virtual void PushEndUp(int output_end, Dir dir) = 0;
 	virtual void PushCropDown(Interval interval, Dir dir) = 0;
 	virtual void CopyOut(void *dest, Dir dir) = 0;
+	virtual bool BranchComplete() const = 0;
 	void MergeRegions(void *dest, void *x_src, void *y_src) const;
 
 protected:
@@ -55,6 +56,7 @@ class BasicStage : public Stage
 	virtual void SetDownstream(Stage *downstream);
 	virtual void Reset();
 	virtual void CopyOut(void *dest, Dir dir);
+	virtual bool BranchComplete() const;
 
 protected:
 	Stage *upstream_;