[NFCI]Remove EntryCount from FunctionSummary and clean up surrounding synthetic count passes. (#107471)

The primary motivation is to remove `EntryCount` from `FunctionSummary`.
This frees 8 bytes out of `sizeof(FunctionSummary)` (136 bytes as of
https://github.com/llvm/llvm-project/commit/64498c54831bed9cf069e0923b9b73678c6451d8).

While I'm at it, this PR clean up {SummaryBasedOptimizations,
SyntheticCountsPropagation} since they were not used and there are no
plans to further invest on them.

With this patch, bitcode writer writes a placeholder 0 at the byte
offset of `EntryCount` and bitcode reader can parse the function entry
count at the correct byte offset. Added a TODO to stop writing
`EntryCount` and bump bitcode version

1 files changed, 0 insertions, 4 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index b1aa89a..6807256 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -32,7 +32,6 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/RuntimeLibcalls.h"
 #include "llvm/LTO/LTOBackend.h"
-#include "llvm/LTO/SummaryBasedOptimizations.h"
 #include "llvm/Linker/IRMover.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Object/IRObjectFile.h"
@@ -1693,9 +1692,6 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
     if (!ModuleToDefinedGVSummaries.count(Mod.first))
       ModuleToDefinedGVSummaries.try_emplace(Mod.first);
 
-  // Synthesize entry counts for functions in the CombinedIndex.
-  computeSyntheticCounts(ThinLTO.CombinedIndex);
-
   FunctionImporter::ImportListsTy ImportLists(ThinLTO.ModuleMap.size());
   DenseMap<StringRef, FunctionImporter::ExportSetTy> ExportLists(
       ThinLTO.ModuleMap.size());