InsertPointGuard helper class for IRBuilder

evmcc/GasMeter.cpp

@@ -8,6 +8,7 @@
 #include <libevm/FeeStructure.h>
 
 #include "Type.h"
+#include "Utils.h"
 
 namespace evmcc
 {
@@ -81,17 +82,14 @@ GasMeter::GasMeter(llvm::IRBuilder<>& _builder, llvm::Module* _module):
 	m_gas = new llvm::GlobalVariable(*_module, Type::i256, false, llvm::GlobalVariable::ExternalLinkage, nullptr, "gas");
 	m_gas->setUnnamedAddr(true); // Address is not important
 
-	auto pt = m_builder.GetInsertPoint();
-	auto bb = m_builder.GetInsertBlock();
 	m_gasCheckFunc = llvm::Function::Create(llvm::FunctionType::get(Type::Void, Type::i256, false), llvm::Function::PrivateLinkage, "gas.check", _module);
-	auto gasCheckBB = llvm::BasicBlock::Create(_builder.getContext(), {}, m_gasCheckFunc);
-	m_builder.SetInsertPoint(gasCheckBB);
+	InsertPointGuard guard(m_builder); 
+	m_builder.SetInsertPoint(llvm::BasicBlock::Create(_builder.getContext(), {}, m_gasCheckFunc));
 	llvm::Value* cost = m_gasCheckFunc->arg_begin();
 	llvm::Value* gas = m_builder.CreateLoad(m_gas);
 	gas = m_builder.CreateSub(gas, cost);
 	m_builder.CreateStore(gas, m_gas);
 	m_builder.CreateRetVoid();
-	m_builder.SetInsertPoint(bb, pt);
 }
 
 void GasMeter::count(Instruction _inst)

evmcc/Memory.cpp

@@ -54,30 +54,32 @@ llvm::Function* Memory::createRequireFunc(llvm::Module* _module, GasMeter& _gasM
 	auto resizeBB = llvm::BasicBlock::Create(func->getContext(), "resize", func);
 	auto returnBB = llvm::BasicBlock::Create(func->getContext(), "return", func);
 
+	InsertPointGuard guard(m_builder); // Restores insert point at function exit
+
 	// BB "check"
-	llvm::IRBuilder<> builder(checkBB);
+	m_builder.SetInsertPoint(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?
+	auto size = m_builder.CreateLoad(m_size, "size");
+	auto resizeNeeded = m_builder.CreateICmpULE(size, sizeRequired, "resizeNeeded");
+	m_builder.CreateCondBr(resizeNeeded, resizeBB, returnBB); // OPT branch weights?
 
 	// BB "resize"
-	builder.SetInsertPoint(resizeBB);
+	m_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);
+	auto wordsRequired = m_builder.CreateUDiv(m_builder.CreateAdd(sizeRequired, Constant::get(31)), Constant::get(32), "wordsRequired");
+	auto words = m_builder.CreateUDiv(m_builder.CreateAdd(size, Constant::get(31)), Constant::get(32), "words");
+	auto newWords = m_builder.CreateSub(wordsRequired, words, "addtionalWords");
+	_gasMeter.checkMemory(newWords, m_builder);
 	// Resize
-	builder.CreateStore(sizeRequired, m_size);
-	auto newData = builder.CreateCall(m_resize, m_size, "newData");
-	builder.CreateStore(newData, m_data);
-	builder.CreateBr(returnBB);
+	m_builder.CreateStore(sizeRequired, m_size);
+	auto newData = m_builder.CreateCall(m_resize, m_size, "newData");
+	m_builder.CreateStore(newData, m_data);
+	m_builder.CreateBr(returnBB);
 
 	// BB "return"
-	builder.SetInsertPoint(returnBB);
-	builder.CreateRetVoid();
+	m_builder.SetInsertPoint(returnBB);
+	m_builder.CreateRetVoid();
 	return func;
 }
 
@@ -90,8 +92,7 @@ llvm::Function* Memory::createFunc(bool _isStore, llvm::Type* _valueType, llvm::
 	auto funcType = _isStore ? llvm::FunctionType::get(Type::Void, storeArgs, false) : llvm::FunctionType::get(Type::i256, Type::i256, false);
 	auto func = llvm::Function::Create(funcType, llvm::Function::PrivateLinkage, name, _module);
 
-	auto origBB = m_builder.GetInsertBlock();
-	auto origPt = m_builder.GetInsertPoint();
+	InsertPointGuard guard(m_builder); // Restores insert point at function exit
 
 	m_builder.SetInsertPoint(llvm::BasicBlock::Create(func->getContext(), {}, func));
 	llvm::Value* index = func->arg_begin();
@@ -116,8 +117,6 @@ llvm::Function* Memory::createFunc(bool _isStore, llvm::Type* _valueType, llvm::
 		m_builder.CreateRet(ret);
 	}
 
-	m_builder.SetInsertPoint(origBB, origPt);
-
 	return func;
 }
 

evmcc/Memory.h

@@ -45,11 +45,11 @@ private:
 	llvm::GlobalVariable* m_returnDataOffset;
 	llvm::GlobalVariable* m_returnDataSize;
 
+	llvm::Function* m_resize;
+	llvm::Function* m_require;
 	llvm::Function* m_loadWord;
 	llvm::Function* m_storeWord;
 	llvm::Function* m_storeByte;
-	llvm::Function* m_require;
-	llvm::Function* m_resize;
 
 	llvm::Function* m_memDump;
 };

evmcc/Utils.h

@@ -1,7 +1,7 @@
 
 #pragma once
 
-#include <cstdint>
+#include <llvm/IR/IRBuilder.h>
 
 #include <libdevcore/Common.h>
 
@@ -22,4 +22,26 @@ static_assert(sizeof(i256) == 32, "Wrong i265 size");
 dev::u256 llvm2eth(i256);
 i256 eth2llvm(dev::u256);
 
+struct InsertPointGuard
+{
+	InsertPointGuard(llvm::IRBuilder<>& _builder) :
+		m_builder(_builder),
+		m_insertBB(m_builder.GetInsertBlock()),
+		m_insertPt(m_builder.GetInsertPoint())
+	{}
+
+	~InsertPointGuard()
+	{
+		m_builder.SetInsertPoint(m_insertBB, m_insertPt);
+	}
+
+private:
+	llvm::IRBuilder<>& m_builder;
+	llvm::BasicBlock* m_insertBB;
+	llvm::BasicBlock::iterator m_insertPt;
+
+	InsertPointGuard(const InsertPointGuard&) = delete;
+	void operator=(InsertPointGuard) = delete;
+};
+
 }