[SampleFDO] Add FunctionOffsetTable in compact binary format profile.

The patch saves a function offset table which maps function name index to the
offset of its function profile to the start of the binary profile. By using
the function offset table, for those function profiles which will not be used
when compiling a module, the profile reader does't have to read them. For
profile size around 10~20M, it saves ~10% compile time.

Differential Revision: https://reviews.llvm.org/D51863

llvm-svn: 342283

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index b9b055d36f7..41ed0614af0 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -1515,6 +1515,7 @@ bool SampleProfileLoader::doInitialization(Module &M) {
     return false;
   }
   Reader = std::move(ReaderOrErr.get());
+  Reader->collectFuncsToUse(M);
   ProfileIsValid = (Reader->read() == sampleprof_error::success);
   return true;
 }