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Remove unnecessary jump dest map. Create jump table block on demand.

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This commit is contained in:
Paweł Bylica 2015-01-08 10:05:24 +01:00
parent ed614c5d2a
commit c21237f7b0
3 changed files with 34 additions and 36 deletions
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7
libevmjit/BasicBlock.h
View file

@ -67,6 +67,9 @@ public:
ProgramCounter begin() { return m_beginInstIdx; }
ProgramCounter end() { return m_endInstIdx; }
bool isJumpDest() const { return m_isJumpDest; }
void markAsJumpDest() { m_isJumpDest = true; }
LocalStack& localStack() { return m_stack; }
/// Optimization: propagates values between local stacks in basic blocks
@ -109,6 +112,10 @@ private:
/// How many items higher is the current stack than the initial one.
/// May be negative.
int m_tosOffset = 0;
/// Is the basic block a valid jump destination.
/// JUMPDEST is the first instruction of the basic block.
bool m_isJumpDest = false;
};
}

54
libevmjit/Compiler.cpp
View file

@ -95,10 +95,27 @@ void Compiler::createBasicBlocks(bytes const& _bytecode)
m_stopBB = llvm::BasicBlock::Create(m_mainFunc->getContext(), "Stop", m_mainFunc);
m_badJumpBlock = std::unique_ptr<BasicBlock>(new BasicBlock("BadJumpBlock", m_mainFunc, m_builder));
m_jumpTableBlock = std::unique_ptr<BasicBlock>(new BasicBlock("JumpTableBlock", m_mainFunc, m_builder));
for (auto it = indirectJumpTargets.cbegin(); it != indirectJumpTargets.cend(); ++it)
m_jumpDests[*it] = basicBlocks.find(*it)->second.llvm();
basicBlocks.find(*it)->second.markAsJumpDest();
}
BasicBlock& Compiler::getJumpTableBlock()
{
if (!m_jumpTableBlock)
{
m_jumpTableBlock.reset(new BasicBlock("JumpTable", m_mainFunc, m_builder));
InsertPointGuard g{m_builder};
m_builder.SetInsertPoint(m_jumpTableBlock->llvm());
auto dest = m_jumpTableBlock->localStack().pop();
auto switchInstr = m_builder.CreateSwitch(dest, m_badJumpBlock->llvm());
for (auto&& p : basicBlocks)
{
if (p.second.isJumpDest())
switchInstr->addCase(Constant::get(p.first), p.second.llvm());
}
}
return *m_jumpTableBlock;
}
std::unique_ptr<llvm::Module> Compiler::compile(bytes const& _bytecode, std::string const& _id)
@ -144,21 +161,6 @@ std::unique_ptr<llvm::Module> Compiler::compile(bytes const& _bytecode, std::str
m_builder.SetInsertPoint(m_badJumpBlock->llvm());
m_builder.CreateRet(Constant::get(ReturnCode::BadJumpDestination));
m_builder.SetInsertPoint(m_jumpTableBlock->llvm());
if (m_jumpDests.size() > 0)
{
auto dest = m_jumpTableBlock->localStack().pop();
auto switchInstr = m_builder.CreateSwitch(dest, m_badJumpBlock->llvm(), m_jumpDests.size());
for (auto it = m_jumpDests.cbegin(); it != m_jumpDests.cend(); ++it)
{
auto& bb = *it;
auto dest = Constant::get(it->first);
switchInstr->addCase(dest, it->second);
}
}
else
m_builder.CreateBr(m_badJumpBlock->llvm());
removeDeadBlocks();
dumpCFGifRequired("blocks-init.dot");
@ -552,16 +554,14 @@ void Compiler::compileBasicBlock(BasicBlock& _basicBlock, bytes const& _bytecode
if (c.ult(_bytecode.size()))
{
auto v = c.getZExtValue();
auto it = m_jumpDests.find(v);
if (it != m_jumpDests.end())
targetBlock = it->second;
auto it = basicBlocks.find(v);
if (it != basicBlocks.end() && it->second.isJumpDest())
targetBlock = it->second.llvm();
}
if (!targetBlock)
{
targetBlock = m_badJumpBlock->llvm();
}
}
if (inst == Instruction::JUMP)
{
@ -574,7 +574,7 @@ void Compiler::compileBasicBlock(BasicBlock& _basicBlock, bytes const& _bytecode
else
{
stack.push(target);
m_builder.CreateBr(m_jumpTableBlock->llvm());
m_builder.CreateBr(getJumpTableBlock().llvm());
}
}
else // JUMPI
@ -594,7 +594,6 @@ void Compiler::compileBasicBlock(BasicBlock& _basicBlock, bytes const& _bytecode
m_builder.CreateCondBr(cond, m_jumpTableBlock->llvm(), _nextBasicBlock);
}
}
break;
}
@ -830,13 +829,6 @@ void Compiler::removeDeadBlocks()
}
}
while (sthErased);
// Remove jump table block if no predecessors
if (llvm::pred_begin(m_jumpTableBlock->llvm()) == llvm::pred_end(m_jumpTableBlock->llvm()))
{
m_jumpTableBlock->llvm()->eraseFromParent();
m_jumpTableBlock.reset();
}
}
void Compiler::dumpCFGifRequired(std::string const& _dotfilePath)

7
libevmjit/Compiler.h
View file

@ -47,6 +47,8 @@ private:
void compileBasicBlock(BasicBlock& _basicBlock, bytes const& _bytecode, class RuntimeManager& _runtimeManager, class Arith256& _arith, class Memory& _memory, class Ext& _ext, class GasMeter& _gasMeter, llvm::BasicBlock* _nextBasicBlock);
BasicBlock& getJumpTableBlock();
void removeDeadBlocks();
/// Dumps basic block graph in graphviz format to a file, if option dumpCFG is enabled.
@ -65,10 +67,7 @@ private:
llvm::IRBuilder<> m_builder;
/// Maps a program counter pc to a basic block that starts at pc (if any).
std::map<ProgramCounter, BasicBlock> basicBlocks = {};
/// Map of jump destinations
std::map<ProgramCounter, llvm::BasicBlock*> m_jumpDests = {};
std::map<ProgramCounter, BasicBlock> basicBlocks;
/// Stop basic block - terminates execution with STOP code (0)
llvm::BasicBlock* m_stopBB = nullptr;