void BytecodeWriter::outputConstants(bool isFunction) {
ConstantTotalBytes -= Out.size();
if (isFunction) FunctionConstantTotalBytes -= Out.size();
- BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out);
+ BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out,
+ true /* Elide block if empty */);
unsigned NumPlanes = Table.getNumPlanes();
SymTabBytes -= Out.size();
- BytecodeBlock SymTabBlock(BytecodeFormat::SymbolTable, Out);
+ BytecodeBlock SymTabBlock(BytecodeFormat::SymbolTable, Out,
+ true/* ElideIfEmpty*/);
for (SymbolTable::const_iterator TI = MST.begin(); TI != MST.end(); ++TI) {
SymbolTable::type_const_iterator I = MST.type_begin(TI->first);
-// BytecodeBlock - Little helper class that helps us do backpatching of bytecode
-// block sizes really easily. It backpatches when it goes out of scope.
-//
+/// BytecodeBlock - Little helper class is used by the bytecode writer to help
+/// do backpatching of bytecode block sizes really easily. It backpatches when
+/// it goes out of scope.
+///
class BytecodeBlock {
unsigned Loc;
std::deque<unsigned char> &Out;
+ /// ElideIfEmpty - If this is true and the bytecode block ends up being empty,
+ /// the block can remove itself from the output stream entirely.
+ bool ElideIfEmpty;
+
BytecodeBlock(const BytecodeBlock &); // do not implement
void operator=(const BytecodeBlock &); // do not implement
public:
- inline BytecodeBlock(unsigned ID, std::deque<unsigned char> &o) : Out(o) {
+ inline BytecodeBlock(unsigned ID, std::deque<unsigned char> &o,
+ bool elideIfEmpty = false)
+ : Out(o), ElideIfEmpty(elideIfEmpty) {
output(ID, Out);
- output((unsigned)0, Out); // Reserve the space for the block size...
+ output(0U, Out); // Reserve the space for the block size...
Loc = Out.size();
}
inline ~BytecodeBlock() { // Do backpatch when block goes out
// of scope...
+ if (Loc == Out.size() && ElideIfEmpty) {
+ // If the block is empty, and we are allowed to, do not emit the block at
+ // all!
+ Out.resize(Out.size()-8);
+ return;
+ }
+
//cerr << "OldLoc = " << Loc << " NewLoc = " << NewLoc << " diff = "
// << (NewLoc-Loc) << endl;
- output((unsigned)(Out.size()-Loc), Out, (int)Loc-4);
+ output(unsigned(Out.size()-Loc), Out, int(Loc-4));
align32(Out); // Blocks must ALWAYS be aligned
}
};