From c57de781e45e1561a588c28f3097d696b93bdbc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <pawel.bylica@imapp.pl>
Date: Tue, 14 Oct 2014 20:49:48 +0200
Subject: [PATCH] Use longjmp to return OutOfGas code from main function (WIP)

[#80660432]
---
 evmcc/Compiler.cpp | 15 ++++++++++++---
 evmcc/Compiler.h   |  2 ++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/evmcc/Compiler.cpp b/evmcc/Compiler.cpp
index 00ea5c12e..7b1f6de18 100644
--- a/evmcc/Compiler.cpp
+++ b/evmcc/Compiler.cpp
@@ -6,7 +6,7 @@
 #include <llvm/IR/IRBuilder.h>
 #include <llvm/IR/CFG.h>
 #include <llvm/ADT/PostOrderIterator.h>
-//#include <llvm/Transforms/Scalar.h>
+#include <llvm/IR/IntrinsicInst.h>
 
 #include <libevmface/Instruction.h>
 
@@ -159,6 +159,7 @@ void Compiler::createBasicBlocks(const dev::bytes& bytecode)
 	m_finalBlock = std::make_unique<BasicBlock>("FinalBlock", m_mainFunc);
 	m_badJumpBlock = std::make_unique<BasicBlock>("BadJumpBlock", m_mainFunc);
 	m_jumpTableBlock = std::make_unique<BasicBlock>("JumpTableBlock", m_mainFunc);
+	m_outOfGasBlock = std::make_unique<BasicBlock>("OutOfGas", m_mainFunc);
 
 	for (auto it = directJumpTargets.cbegin(); it != directJumpTargets.cend(); ++it)
 	{
@@ -195,6 +196,7 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 	// Create the basic blocks.
 	auto entryBlock = llvm::BasicBlock::Create(context, "entry", m_mainFunc);
 	builder.SetInsertPoint(entryBlock);
+
 	createBasicBlocks(bytecode);
 
 	// Init runtime structures.
@@ -203,7 +205,12 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 	Ext ext(builder, module.get());
 
 	// Jump to first instruction
-	builder.CreateBr(basicBlocks.begin()->second);
+	auto setjmpFunc = llvm::Intrinsic::getDeclaration(module.get(), llvm::Intrinsic::eh_sjlj_setjmp);
+	auto jmpBufTy = llvm::ArrayType::get(builder.getInt64Ty(), 5);
+	auto jmpBuf = new llvm::GlobalVariable(*module, jmpBufTy, false, llvm::GlobalVariable::PrivateLinkage, llvm::UndefValue::get(jmpBufTy), "jmpBuf");
+	auto setjmpRet = builder.CreateCall(setjmpFunc, builder.CreateBitCast(jmpBuf, Type::BytePtr));
+	auto isNormalFlow = builder.CreateICmpEQ(setjmpRet, builder.getInt32(0));
+	builder.CreateCondBr(isNormalFlow, basicBlocks.begin()->second, m_outOfGasBlock->llvm());
 
 	for (auto basicBlockPairIt = basicBlocks.begin(); basicBlockPairIt != basicBlocks.end(); ++basicBlockPairIt)
 	{
@@ -921,10 +928,12 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 	builder.SetInsertPoint(m_finalBlock->llvm());
 	builder.CreateRet(Constant::get(ReturnCode::Stop));
 
-	// TODO: throw an exception or something
 	builder.SetInsertPoint(m_badJumpBlock->llvm());
 	builder.CreateRet(Constant::get(ReturnCode::BadJumpDestination));
 
+	builder.SetInsertPoint(m_outOfGasBlock->llvm());
+	builder.CreateRet(Constant::get(ReturnCode::OutOfGas));
+
 	builder.SetInsertPoint(m_jumpTableBlock->llvm());
 	if (m_indirectJumpTargets.size() > 0)
 	{
diff --git a/evmcc/Compiler.h b/evmcc/Compiler.h
index 7d0cb4ab6..509cf77df 100644
--- a/evmcc/Compiler.h
+++ b/evmcc/Compiler.h
@@ -59,6 +59,8 @@ private:
 	 */
 	std::unique_ptr<BasicBlock> m_badJumpBlock;
 
+	std::unique_ptr<BasicBlock> m_outOfGasBlock;
+
 	/// Main program function
 	llvm::Function* m_mainFunc = nullptr;
 };