SpirvShader: Add flow control info to Block.

src/Pipeline/SpirvShader.cpp

@@ -440,6 +440,20 @@ namespace sw
 				UNIMPLEMENTED("%s", OpcodeName(insn.opcode()).c_str());
 			}
 		}
+
+		// Assign all Block::ins
+		for (auto &it : blocks)
+		{
+			auto &blockId = it.first;
+			auto &block = it.second;
+			for (auto &outId : block.outs)
+			{
+				auto outIt = blocks.find(outId);
+				ASSERT_MSG(outIt != blocks.end(), "Block %d has a non-existent out %d", blockId.value(), outId.value());
+				auto &out = outIt->second;
+				out.ins.emplace(blockId);
+			}
+		}
 	}
 
 	void SpirvShader::DeclareType(InsnIterator insn)
@@ -2513,6 +2527,92 @@ namespace sw
 		}
 	}
 
+	SpirvShader::Block::Block(InsnIterator begin, InsnIterator end) : begin_(begin), end_(end)
+	{
+		// Default to a Simple, this may change later.
+		kind = Block::Simple;
+
+		// Walk the instructions to find the last two of the block.
+		InsnIterator insns[2];
+		for (auto insn : *this)
+		{
+			insns[0] = insns[1];
+			insns[1] = insn;
+		}
+
+		switch (insns[1].opcode())
+		{
+			case spv::OpBranch:
+				branchInstruction = insns[1];
+				outs.emplace(Block::ID(branchInstruction.word(1)));
+
+				switch (insns[0].opcode())
+				{
+					case spv::OpLoopMerge:
+						kind = Loop;
+						mergeInstruction = insns[0];
+						mergeBlock = Block::ID(mergeInstruction.word(1));
+						continueTarget = Block::ID(mergeInstruction.word(2));
+						break;
+
+					default:
+						kind = Block::Simple;
+						break;
+				}
+				break;
+
+			case spv::OpBranchConditional:
+				branchInstruction = insns[1];
+				outs.emplace(Block::ID(branchInstruction.word(2)));
+				outs.emplace(Block::ID(branchInstruction.word(3)));
+
+				switch (insns[0].opcode())
+				{
+					case spv::OpSelectionMerge:
+						kind = StructuredBranchConditional;
+						mergeInstruction = insns[0];
+						mergeBlock = Block::ID(mergeInstruction.word(1));
+						break;
+
+					case spv::OpLoopMerge:
+						kind = Loop;
+						mergeInstruction = insns[0];
+						mergeBlock = Block::ID(mergeInstruction.word(1));
+						continueTarget = Block::ID(mergeInstruction.word(2));
+						break;
+
+					default:
+						kind = UnstructuredBranchConditional;
+						break;
+				}
+				break;
+
+			case spv::OpSwitch:
+				branchInstruction = insns[1];
+				outs.emplace(Block::ID(branchInstruction.word(2)));
+				for (uint32_t w = 4; w < branchInstruction.wordCount(); w += 2)
+				{
+					outs.emplace(Block::ID(branchInstruction.word(w)));
+				}
+
+				switch (insns[0].opcode())
+				{
+					case spv::OpSelectionMerge:
+						kind = StructuredSwitch;
+						mergeInstruction = insns[0];
+						mergeBlock = Block::ID(mergeInstruction.word(1));
+						break;
+
+					default:
+						kind = UnstructuredSwitch;
+						break;
+				}
+				break;
+
+			default:
+				break;
+		}
+	}
 	SpirvRoutine::SpirvRoutine(vk::PipelineLayout const *pipelineLayout) :
 		pipelineLayout(pipelineLayout)
 	{

src/Pipeline/SpirvShader.hpp

@@ -29,6 +29,7 @@
 #include <functional>
 #include <string>
 #include <vector>
+#include <unordered_set>
 #include <unordered_map>
 #include <cstdint>
 #include <type_traits>
@@ -246,15 +247,51 @@ namespace sw
 		{
 		public:
 			using ID = SpirvID<Block>;
+			using Set = std::unordered_set<ID>;
+
+			// Edge represents the graph edge between two blocks.
+			struct Edge
+			{
+				ID from;
+				ID to;
+
+				bool operator == (const Edge& other) const { return from == other.from && to == other.to; }
+
+				struct Hash
+				{
+					std::size_t operator()(const Edge& edge) const noexcept
+					{
+						return std::hash<uint32_t>()(edge.from.value() * 31 + edge.to.value());
+					}
+				};
+			};
 
 			Block() = default;
 			Block(const Block& other) = default;
-			explicit Block(InsnIterator begin, InsnIterator end) : begin_(begin), end_(end) {}
+			explicit Block(InsnIterator begin, InsnIterator end);
 
 			/* range-based-for interface */
 			inline InsnIterator begin() const { return begin_; }
 			inline InsnIterator end() const { return end_; }
 
+			enum Kind
+			{
+				Simple, // OpBranch or other simple terminator.
+				StructuredBranchConditional, // OpSelectionMerge + OpBranchConditional
+				UnstructuredBranchConditional, // OpBranchConditional
+				StructuredSwitch, // OpSelectionMerge + OpSwitch
+				UnstructuredSwitch, // OpSwitch
+				Loop, // OpLoopMerge + [OpBranchConditional | OpBranch]
+			};
+
+			Kind kind;
+			InsnIterator mergeInstruction; // Merge instruction.
+			InsnIterator branchInstruction; //
+			ID mergeBlock; // Structured flow merge block.
+			ID continueTarget; // Loop continue block.
+			Set ins; // Blocks that branch into this block.
+			Set outs; // Blocks that this block branches to.
+
 		private:
 			InsnIterator begin_;
 			InsnIterator end_;