I've put some work into the Google Benchmark library in order to make it easier
to benchmark libc++. These changes have already been upstreamed into
Google Benchmark and this patch applies the changes to the in-tree version.
The main improvement in the addition of a 'compare_bench.py' script which
makes it very easy to compare benchmarks. For example to compare the native
STL to libc++ you would run:
`$ compare_bench.py ./util_smartptr.native.out ./util_smartptr.libcxx.out`
And the output would look like:
RUNNING: ./util_smartptr.native.out
Benchmark Time CPU Iterations
----------------------------------------------------------------
BM_SharedPtrCreateDestroy 62 ns 62 ns 10937500
BM_SharedPtrIncDecRef 31 ns 31 ns 23972603
BM_WeakPtrIncDecRef 28 ns 28 ns 23648649
RUNNING: ./util_smartptr.libcxx.out
Benchmark Time CPU Iterations
----------------------------------------------------------------
BM_SharedPtrCreateDestroy 46 ns 46 ns 14957265
BM_SharedPtrIncDecRef 31 ns 31 ns 22435897
BM_WeakPtrIncDecRef 34 ns 34 ns 21084337
Comparing ./util_smartptr.native.out to ./util_smartptr.libcxx.out
Benchmark Time CPU
-----------------------------------------------------
BM_SharedPtrCreateDestroy -0.26 -0.26
BM_SharedPtrIncDecRef +0.00 +0.00
BM_WeakPtrIncDecRef +0.21 +0.21
llvm-svn: 278147
Eric Fiselier