[PGO] Add support for writing previous indexed format (#84505)

Enable temporary support to ease use of new llvm-profdata with slightly
older indexed profiles after 16e74fd48988ac95551d0f64e1b36f78a82a89a2,
which bumped the indexed format for type profiling.

1 files changed, 11 insertions, 2 deletions

diff --git a/llvm/tools/llvm-profdata/llvm-profdata.cpp b/llvm/tools/llvm-profdata/llvm-profdata.cpp
index 8400b07..3a7bd06 100644
--- a/llvm/tools/llvm-profdata/llvm-profdata.cpp
+++ b/llvm/tools/llvm-profdata/llvm-profdata.cpp
@@ -291,6 +291,15 @@ cl::opt<bool> DropProfileSymbolList(
     cl::desc("Drop the profile symbol list when merging AutoFDO profiles "
              "(only meaningful for -sample)"));
 
+// 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
+// deployment of newer versions of llvm-profdata.
+cl::opt<bool> DoWritePrevVersion(
+    "write-prev-version", cl::init(false), cl::Hidden,
+    cl::desc("Write the previous version of indexed format, to enable "
+             "some forward compatibility."));
+
 // Options specific to overlap subcommand.
 cl::opt<std::string> BaseFilename(cl::Positional, cl::Required,
                                   cl::desc("<base profile file>"),
@@ -579,8 +588,8 @@ struct WriterContext {
   WriterContext(bool IsSparse, std::mutex &ErrLock,
                 SmallSet<instrprof_error, 4> &WriterErrorCodes,
                 uint64_t ReservoirSize = 0, uint64_t MaxTraceLength = 0)
-      : Writer(IsSparse, ReservoirSize, MaxTraceLength), ErrLock(ErrLock),
-        WriterErrorCodes(WriterErrorCodes) {}
+      : Writer(IsSparse, ReservoirSize, MaxTraceLength, DoWritePrevVersion),
+        ErrLock(ErrLock), WriterErrorCodes(WriterErrorCodes) {}
 };
 
 /// Computer the overlap b/w profile BaseFilename and TestFileName,