Properly compute source mappings for immutables.

libevmasm/Assembly.cpp

@@ -48,11 +48,11 @@ using namespace solidity::evmasm;
 using namespace solidity::langutil;
 using namespace solidity::util;
 
-AssemblyItem const& Assembly::append(AssemblyItem const& _i)
+AssemblyItem const& Assembly::append(AssemblyItem _i)
 {
 	assertThrow(m_deposit >= 0, AssemblyException, "Stack underflow.");
 	m_deposit += static_cast<int>(_i.deposit());
-	m_items.emplace_back(_i);
+	m_items.emplace_back(move(_i));
 	if (!m_items.back().location().isValid() && m_currentSourceLocation.isValid())
 		m_items.back().setLocation(m_currentSourceLocation);
 	m_items.back().m_modifierDepth = m_currentModifierDepth;
@@ -68,7 +68,7 @@ unsigned Assembly::codeSize(unsigned subTagSize) const
 			ret += i.second.size();
 
 		for (AssemblyItem const& i: m_items)
-			ret += i.bytesRequired(tagSize);
+			ret += i.bytesRequired(tagSize, Precision::Approximate);
 		if (numberEncodingSize(ret) <= tagSize)
 			return static_cast<unsigned>(ret);
 	}
@@ -696,8 +696,11 @@ LinkerObject const& Assembly::assemble() const
 			break;
 		case PushImmutable:
 			ret.bytecode.push_back(static_cast<uint8_t>(Instruction::PUSH32));
+			// Maps keccak back to the "identifier" string of that immutable.
 			ret.immutableReferences[i.data()].first = m_immutables.at(i.data());
+			// Record the bytecode offset of the PUSH32 argument.
 			ret.immutableReferences[i.data()].second.emplace_back(ret.bytecode.size());
+			// Advance bytecode by 32 bytes (default initialized).
 			ret.bytecode.resize(ret.bytecode.size() + 32);
 			break;
 		case VerbatimBytecode:
@@ -705,6 +708,7 @@ LinkerObject const& Assembly::assemble() const
 			break;
 		case AssignImmutable:
 		{
+			// Expect 2 elements on stack (source, dest_base)
 			auto const& offsets = immutableReferencesBySub[i.data()].second;
 			for (size_t i = 0; i < offsets.size(); ++i)
 			{