[MemProf] Add basic summary section support (#141805)

This patch adds support for a basic MemProf summary section, which is
built along with the indexed MemProf profile (e.g. when reading the raw
or YAML profiles), and serialized through the indexed profile just after
the header.

Currently only 6 fields are written, specifically the number of contexts
(total, cold, hot), and the max context size (cold, warm, hot).

To support forwards and backwards compatibility for added fields in the
indexed profile, the number of fields serialized first. The code is
written to support forwards compatibility (reading newer profiles with
additional summary fields), and comments indicate how to implement
backwards compatibility (reading older profiles with fewer summary
fields) as needed.

Support is added to print the summary as YAML comments when displaying
both the raw and indexed profiles via `llvm-profdata show`. Because they
are YAML comments, the YAML reader ignores these (the summary is always
recomputed when building the indexed profile as described above).

This necessitated moving some options and a couple of interfaces out of
Analysis/MemoryProfileInfo.cpp and into the new
ProfileData/MemProfSummary.cpp file, as we need to classify context
hotness earlier and also compute context ids to build the summary from
older indexed profiles.

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/tools/llvm-profdata/llvm-profdata.cpp b/llvm/tools/llvm-profdata/llvm-profdata.cpp
index 8660eed..a7cbd4b 100644
--- a/llvm/tools/llvm-profdata/llvm-profdata.cpp
+++ b/llvm/tools/llvm-profdata/llvm-profdata.cpp
@@ -22,6 +22,7 @@
 #include "llvm/ProfileData/InstrProfWriter.h"
 #include "llvm/ProfileData/MemProf.h"
 #include "llvm/ProfileData/MemProfReader.h"
+#include "llvm/ProfileData/MemProfSummaryBuilder.h"
 #include "llvm/ProfileData/MemProfYAML.h"
 #include "llvm/ProfileData/ProfileCommon.h"
 #include "llvm/ProfileData/SampleProfReader.h"
@@ -3312,6 +3313,18 @@ static int showMemProfProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
 
   auto Reader = std::move(ReaderOrErr.get());
   memprof::AllMemProfData Data = Reader->getAllMemProfData();
+
+  // For v4 and above the summary is serialized in the indexed profile, and can
+  // be accessed from the reader. Earlier versions build the summary below.
+  // The summary is emitted as YAML comments at the start of the output.
+  if (auto *MemProfSum = Reader->getMemProfSummary()) {
+    MemProfSum->printSummaryYaml(OS);
+  } else {
+    memprof::MemProfSummaryBuilder MemProfSumBuilder;
+    for (auto &Pair : Data.HeapProfileRecords)
+      MemProfSumBuilder.addRecord(Pair.Record);
+    MemProfSumBuilder.getSummary()->printSummaryYaml(OS);
+  }
   // Construct yaml::Output with the maximum column width of 80 so that each
   // Frame fits in one line.
   yaml::Output Yout(OS, nullptr, 80);