[ThinLTO] Add some stats for read only variable internalization

Summary:
Follow up to D49362 ([ThinLTO] Internalize read only globals). Add a
statistic on the number of read only variables (only counting live
variables since dead variables will be dropped anyway).

Reviewers: evgeny777

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, arphaman, llvm-commits

Differential Revision: https://reviews.llvm.org/D54642

llvm-svn: 347145

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/IR/ModuleSummaryIndex.cpp b/llvm/lib/IR/ModuleSummaryIndex.cpp
index 6c0d3973715..bb5b7d0d3ab 100644
--- a/llvm/lib/IR/ModuleSummaryIndex.cpp
+++ b/llvm/lib/IR/ModuleSummaryIndex.cpp
@@ -14,11 +14,17 @@
 
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "module-summary-index"
+
+STATISTIC(ReadOnlyLiveGVars,
+          "Number of live global variables marked read only");
+
 FunctionSummary FunctionSummary::ExternalNode =
     FunctionSummary::makeDummyFunctionSummary({});
 bool ValueInfo::isDSOLocal() const {
@@ -160,6 +166,14 @@ void ModuleSummaryIndex::propagateConstants(
           GVS->setReadOnly(false);
       propagateConstantsToRefs(S.get());
     }
+#if LLVM_ENABLE_STATS
+  for (auto &P : *this)
+    if (P.second.SummaryList.size())
+      if (auto *GVS = dyn_cast<GlobalVarSummary>(
+              P.second.SummaryList[0]->getBaseObject()))
+        if (isGlobalValueLive(GVS) && GVS->isReadOnly())
+          ReadOnlyLiveGVars++;
+#endif
 }
 
 // TODO: write a graphviz dumper for SCCs (see ModuleSummaryIndex::exportToDot)