If these blocks are empty, there is no reason to even emit the bytecode blocks.
This saves about 15K in 176.gcc, coupled with another patch that I'm working on.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10889 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bytecode/Writer/WriterInternals.h b/lib/Bytecode/Writer/WriterInternals.h
index 51ec362..15dbeff 100644
--- a/lib/Bytecode/Writer/WriterInternals.h
+++ b/lib/Bytecode/Writer/WriterInternals.h
@@ -50,27 +50,41 @@
-// 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
}
};