From f0f5833c4ca42ba907f5b9cd86d68a66d2225bfd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <pawel.bylica@imapp.pl>
Date: Tue, 14 Oct 2014 15:12:11 +0200
Subject: [PATCH] Private mem.require function that preallocates memory and
 counts gas fee

---
 evmcc/Memory.cpp | 46 ++++++++++++++++++++++++++++++++++++++++++++--
 evmcc/Memory.h   |  4 ++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/evmcc/Memory.cpp b/evmcc/Memory.cpp
index 4d4a34928..cbc349250 100644
--- a/evmcc/Memory.cpp
+++ b/evmcc/Memory.cpp
@@ -43,6 +43,43 @@ Memory::Memory(llvm::IRBuilder<>& _builder, llvm::Module* _module, GasMeter& _ga
 	m_loadWord = createFunc(false, Type::i256, _module, _gasMeter);
 	m_storeWord = createFunc(true, Type::i256, _module, _gasMeter);
 	m_storeByte = createFunc(true, Type::Byte, _module, _gasMeter);
+
+	m_require = createRequireFunc(_module, _gasMeter);
+}
+
+llvm::Function* Memory::createRequireFunc(llvm::Module* _module, GasMeter& _gasMeter)
+{
+	auto func = llvm::Function::Create(llvm::FunctionType::get(Type::Void, Type::i256, false), llvm::Function::PrivateLinkage, "mem.require", _module);
+
+	auto checkBB = llvm::BasicBlock::Create(func->getContext(), "check", func);
+	auto resizeBB = llvm::BasicBlock::Create(func->getContext(), "resize", func);
+	auto returnBB = llvm::BasicBlock::Create(func->getContext(), "return", func);
+
+	// BB "check"
+	llvm::IRBuilder<> builder(checkBB);
+	llvm::Value* sizeRequired = func->arg_begin();
+	sizeRequired->setName("sizeRequired");
+	auto size = builder.CreateLoad(m_size, "size");
+	auto resizeNeeded = builder.CreateICmpULE(size, sizeRequired, "resizeNeeded");
+	builder.CreateCondBr(resizeNeeded, resizeBB, returnBB); // OPT branch weights?
+
+	// BB "resize"
+	builder.SetInsertPoint(resizeBB);
+	// Check gas first
+	auto wordsRequired = builder.CreateUDiv(builder.CreateAdd(sizeRequired, Constant::get(31)), Constant::get(32), "wordsRequired");
+	auto words = builder.CreateUDiv(builder.CreateAdd(size, Constant::get(31)), Constant::get(32), "words");
+	auto newWords = builder.CreateSub(wordsRequired, words, "addtionalWords");
+	_gasMeter.checkMemory(newWords, builder);
+	// Resize
+	builder.CreateStore(sizeRequired, m_size);
+	auto newData = builder.CreateCall(m_resize, m_size, "newData");
+	builder.CreateStore(newData, m_data);
+	builder.CreateBr(returnBB);
+
+	// BB "return"
+	builder.SetInsertPoint(returnBB);
+	builder.CreateRetVoid();
+	return func;
 }
 
 llvm::Function* Memory::createFunc(bool _isStore, llvm::Type* _valueType, llvm::Module* _module, GasMeter& _gasMeter)
@@ -131,10 +168,15 @@ llvm::Value* Memory::getSize()
 	return m_builder.CreateLoad(m_size);
 }
 
+void Memory::require(llvm::Value* _size)
+{
+	m_builder.CreateCall(m_require, _size);
+}
+
 void Memory::registerReturnData(llvm::Value* _index, llvm::Value* _size)
 {
-	auto lastWord = m_builder.CreateAdd(_index, m_builder.CreateSub(_size, Constant::get(32)), "lastWord");
-	loadWord(lastWord); // Make sure that memory is allocated and count gas
+	auto sizeRequired = m_builder.CreateAdd(_index, _size, "sizeRequired");
+	require(sizeRequired); // Make sure that memory is allocated and count gas
 
 	m_builder.CreateStore(_index, m_returnDataOffset);
 	m_builder.CreateStore(_size, m_returnDataSize);
diff --git a/evmcc/Memory.h b/evmcc/Memory.h
index c01bd6ef8..e973d1016 100644
--- a/evmcc/Memory.h
+++ b/evmcc/Memory.h
@@ -20,6 +20,8 @@ public:
 	void storeByte(llvm::Value* _addr, llvm::Value* _byte);
 	llvm::Value* getSize();
 
+	void require(llvm::Value* _size);
+
 	void registerReturnData(llvm::Value* _index, llvm::Value* _size);
 	static dev::bytesConstRef getReturnData();
 
@@ -27,6 +29,7 @@ public:
 
 private:
 	llvm::Function* createFunc(bool _isStore, llvm::Type* _type, llvm::Module* _module, GasMeter& _gasMeter);
+	llvm::Function* createRequireFunc(llvm::Module* _module, GasMeter& _gasMeter);
 
 private:
 	llvm::IRBuilder<>& m_builder;
@@ -41,6 +44,7 @@ private:
 	llvm::Function* m_loadWord;
 	llvm::Function* m_storeWord;
 	llvm::Function* m_storeByte;
+	llvm::Function* m_require;
 	llvm::Function* m_resize;
 
 	llvm::Function* m_memDump;