Benjamin Kramer 4861bbca65 Lazily allocate DenseMaps.
This makes lookup slightly more expensive but it's worth it, unused
DenseMaps are common in LLVM code apparently.

1% speedup on clang -O3 bzip2.c
4% speedup on clang -O3 oggenc.c (Release build of clang on i386/linux)

llvm-svn: 127088
2011-03-05 16:43:41 +00:00
..
2011-03-05 16:43:41 +00:00