From 0cba3d90054716d6c62f1f312818ba54e553c839 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <pawel.bylica@imapp.pl>
Date: Tue, 7 Oct 2014 17:27:45 +0200
Subject: [PATCH] Improve basic blocks linking implementation

---
 evmcc/BasicBlock.cpp |  4 +++-
 evmcc/BasicBlock.h   |  2 ++
 evmcc/Compiler.cpp   | 32 ++++++++++++++------------------
 evmcc/Stack.cpp      |  2 +-
 4 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/evmcc/BasicBlock.cpp b/evmcc/BasicBlock.cpp
index 19e1d68ec..9bdd6d31d 100644
--- a/evmcc/BasicBlock.cpp
+++ b/evmcc/BasicBlock.cpp
@@ -6,9 +6,11 @@
 namespace evmcc
 {
 
+const char* BasicBlock::NamePrefix = "Instr.";
+
 BasicBlock::BasicBlock(ProgramCounter _beginInstIdx, llvm::Function* _mainFunc):
 	m_beginInstIdx(_beginInstIdx),
-	m_llvmBB(llvm::BasicBlock::Create(_mainFunc->getContext(), {"Instr.", std::to_string(_beginInstIdx)}, _mainFunc))
+	m_llvmBB(llvm::BasicBlock::Create(_mainFunc->getContext(), {NamePrefix, std::to_string(_beginInstIdx)}, _mainFunc))
 {}
 
 }
\ No newline at end of file
diff --git a/evmcc/BasicBlock.h b/evmcc/BasicBlock.h
index 793dfaea2..83df5da24 100644
--- a/evmcc/BasicBlock.h
+++ b/evmcc/BasicBlock.h
@@ -13,6 +13,8 @@ class BasicBlock
 public:
 	using State = std::vector<llvm::Value*>;
 
+	static const char* NamePrefix;
+
 	explicit BasicBlock(ProgramCounter _beginInstIdx, llvm::Function* _mainFunc);
 
 	BasicBlock(const BasicBlock&) = delete;
diff --git a/evmcc/Compiler.cpp b/evmcc/Compiler.cpp
index e5fe6db8b..2ae7ab1e7 100644
--- a/evmcc/Compiler.cpp
+++ b/evmcc/Compiler.cpp
@@ -797,14 +797,13 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 void Compiler::linkBasicBlocks()
 {
 	/// Helper function that finds basic block given LLVM basic block pointer
-	auto findBB = [this](llvm::BasicBlock* _llvmBB)
+	auto findBasicBlock = [this](llvm::BasicBlock* _llbb) -> BasicBlock&
 	{
-		for (auto&& bb : basicBlocks)
-		{
-			if (bb.second.llvm() == _llvmBB)
-				return &bb.second;
-		}
-		return (BasicBlock*)nullptr;
+		// Name is used to get basic block index (index of first instruction)
+		// TODO: If basicBlocs are still a map - multikey map can be used
+		auto&& idxStr = _llbb->getName().substr(sizeof(BasicBlock::NamePrefix) - 2);
+		auto idx = std::stoul(idxStr);
+		return basicBlocks.find(idx)->second;
 	};
 
 	// Link basic blocks
@@ -813,19 +812,16 @@ void Compiler::linkBasicBlocks()
 		BasicBlock& bb = p.second;
 		llvm::BasicBlock* llvmBB = bb.llvm();
 
-		size_t i = 0;
-		for (auto& inst : *llvmBB)
+		size_t valueIdx = 0;
+		auto firstNonPhi = llvmBB->getFirstNonPHI();
+		for (auto instIt = llvmBB->begin(); &*instIt != firstNonPhi; ++instIt, ++valueIdx)
 		{
-			if (auto phi = llvm::dyn_cast<llvm::PHINode>(&inst))
+			auto phi = llvm::cast<llvm::PHINode>(instIt);
+			for (auto predIt = llvm::pred_begin(llvmBB); predIt != llvm::pred_end(llvmBB); ++predIt)
 			{
-				for (auto preIt = llvm::pred_begin(llvmBB); preIt != llvm::pred_end(llvmBB); ++preIt)
-				{
-					llvm::BasicBlock* preBB = *preIt;
-					auto pbb = findBB(preBB);
-					assert(i < pbb->getState().size()); // TODO: Report error
-					phi->addIncoming(*(pbb->getState().rbegin() + i), preBB);
-				}
-				++i;
+				auto& predBB = findBasicBlock(*predIt);
+				assert(valueIdx < predBB.getState().size()); // TODO: Report error
+				phi->addIncoming(*(predBB.getState().rbegin() + valueIdx), predBB);
 			}
 		}
 	}
diff --git a/evmcc/Stack.cpp b/evmcc/Stack.cpp
index 86b39316c..fc359f103 100644
--- a/evmcc/Stack.cpp
+++ b/evmcc/Stack.cpp
@@ -23,7 +23,7 @@ llvm::Value* BBStack::pop()
 		// Create PHI node
 		auto i256Ty = llvm::Type::getIntNTy(m_block->llvm()->getContext(), 256);
 		auto llvmBB = m_block->llvm();
-		if (llvmBB->getInstList().empty())
+		if (llvmBB->empty())
 			return llvm::PHINode::Create(i256Ty, 0, {}, m_block->llvm());
 		return llvm::PHINode::Create(i256Ty, 0, {}, llvmBB->getFirstNonPHI());
 	}