[TypeProf][InstrFDO]Omit vtable symbols in indexed profiles by default (#96520)

- The indexed iFDO profiles contains compressed vtable names for `llvm-profdata show --show-vtables` debugging 
   usage. An optimized build doesn't need it and doesn't decompress the blob now [1], since optimized binary has the 
   source code and IR to find vtable symbols.
- The motivation is to avoid increasing profile size when it's not necessary.
- This doesn't change the indexed profile format and thereby doesn't need a version change.

[1] https://github.com/llvm/llvm-project/blob/eac925fb81f26342811ad1765e8f9919628e2254/llvm/include/llvm/ProfileData/InstrProfReader.h#L696-L699

1 files changed, 10 insertions, 4 deletions

diff --git a/llvm/tools/llvm-profdata/llvm-profdata.cpp b/llvm/tools/llvm-profdata/llvm-profdata.cpp
index 6c8ab14..2ce0668 100644
--- a/llvm/tools/llvm-profdata/llvm-profdata.cpp
+++ b/llvm/tools/llvm-profdata/llvm-profdata.cpp
@@ -291,6 +291,11 @@ cl::opt<bool> DropProfileSymbolList(
     cl::desc("Drop the profile symbol list when merging AutoFDO profiles "
              "(only meaningful for -sample)"));
 
+cl::opt<bool> KeepVTableSymbols(
+    "keep-vtable-symbols", cl::init(false), cl::Hidden,
+    cl::sub(MergeSubcommand),
+    cl::desc("If true, keep the vtable symbols in indexed profiles"));
+
 // Temporary support for writing the previous version of the format, to enable
 // some forward compatibility.
 // TODO: Consider enabling this with future version changes as well, to ease
@@ -767,11 +772,12 @@ static void loadInput(const WeightedFile &Input, SymbolRemapper *Remapper,
     });
   }
 
-  const InstrProfSymtab &symtab = Reader->getSymtab();
-  const auto &VTableNames = symtab.getVTableNames();
+  if (KeepVTableSymbols) {
+    const InstrProfSymtab &symtab = Reader->getSymtab();
+    const auto &VTableNames = symtab.getVTableNames();
 
-  for (const auto &kv : VTableNames) {
-    WC->Writer.addVTableName(kv.getKey());
+    for (const auto &kv : VTableNames)
+      WC->Writer.addVTableName(kv.getKey());
   }
 
   if (Reader->hasTemporalProfile()) {