[ThinLTO] Add summary entries for index-based WPD

Summary:
If LTOUnit splitting is disabled, the module summary analysis computes
the summary information necessary to perform single implementation
devirtualization during the thin link with the index and no IR. The
information collected from the regular LTO IR in the current hybrid WPD
algorithm is summarized, including:
1) For vtable definitions, record the function pointers and their offset
within the vtable initializer (subsumes the information collected from
IR by tryFindVirtualCallTargets).
2) A record for each type metadata summarizing the vtable definitions
decorated with that metadata (subsumes the TypeIdentiferMap collected
from IR).

Also added are the necessary bitcode records, and the corresponding
assembly support.

The follow-on index-based WPD patch is D55153.

Depends on D53890.

Reviewers: pcc

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

Differential Revision: https://reviews.llvm.org/D54815

llvm-svn: 364960

1 files changed, 67 insertions, 5 deletions

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 33dbbea5f8c..96e1d493aaf 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -214,7 +214,8 @@ private:
                                            const Function &F);
   void writeModuleLevelReferences(const GlobalVariable &V,
                                   SmallVector<uint64_t, 64> &NameVals,
-                                  unsigned FSModRefsAbbrev);
+                                  unsigned FSModRefsAbbrev,
+                                  unsigned FSModVTableRefsAbbrev);
 
   void assignValueId(GlobalValue::GUID ValGUID) {
     GUIDToValueIdMap[ValGUID] = ++GlobalValueId;
@@ -3605,6 +3606,19 @@ static void writeTypeIdSummaryRecord(SmallVector<uint64_t, 64> &NameVals,
                                       W.second);
 }
 
+static void writeTypeIdCompatibleVtableSummaryRecord(
+    SmallVector<uint64_t, 64> &NameVals, StringTableBuilder &StrtabBuilder,
+    const std::string &Id, const TypeIdCompatibleVtableInfo &Summary,
+    ValueEnumerator &VE) {
+  NameVals.push_back(StrtabBuilder.add(Id));
+  NameVals.push_back(Id.size());
+
+  for (auto &P : Summary) {
+    NameVals.push_back(P.AddressPointOffset);
+    NameVals.push_back(VE.getValueID(P.VTableVI.getValue()));
+  }
+}
+
 // Helper to emit a single function summary record.
 void ModuleBitcodeWriterBase::writePerModuleFunctionSummaryRecord(
     SmallVector<uint64_t, 64> &NameVals, GlobalValueSummary *Summary,
@@ -3649,7 +3663,7 @@ void ModuleBitcodeWriterBase::writePerModuleFunctionSummaryRecord(
 // and emit them in a summary record.
 void ModuleBitcodeWriterBase::writeModuleLevelReferences(
     const GlobalVariable &V, SmallVector<uint64_t, 64> &NameVals,
-    unsigned FSModRefsAbbrev) {
+    unsigned FSModRefsAbbrev, unsigned FSModVTableRefsAbbrev) {
   auto VI = Index->getValueInfo(V.getGUID());
   if (!VI || VI.getSummaryList().empty()) {
     // Only declarations should not have a summary (a declaration might however
@@ -3663,6 +3677,10 @@ void ModuleBitcodeWriterBase::writeModuleLevelReferences(
   NameVals.push_back(getEncodedGVSummaryFlags(VS->flags()));
   NameVals.push_back(getEncodedGVarFlags(VS->varflags()));
 
+  auto VTableFuncs = VS->vTableFuncs();
+  if (!VTableFuncs.empty())
+    NameVals.push_back(VS->refs().size());
+
   unsigned SizeBeforeRefs = NameVals.size();
   for (auto &RI : VS->refs())
     NameVals.push_back(VE.getValueID(RI.getValue()));
@@ -3670,8 +3688,20 @@ void ModuleBitcodeWriterBase::writeModuleLevelReferences(
   // been initialized from a DenseSet.
   llvm::sort(NameVals.begin() + SizeBeforeRefs, NameVals.end());
 
-  Stream.EmitRecord(bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS, NameVals,
-                    FSModRefsAbbrev);
+  if (!VTableFuncs.empty()) {
+    // VTableFuncs pairs should already be sorted by offset.
+    for (auto &P : VTableFuncs) {
+      NameVals.push_back(VE.getValueID(P.FuncVI.getValue()));
+      NameVals.push_back(P.VTableOffset);
+    }
+  }
+
+  if (VTableFuncs.empty())
+    Stream.EmitRecord(bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS, NameVals,
+                      FSModRefsAbbrev);
+  else
+    Stream.EmitRecord(bitc::FS_PERMODULE_VTABLE_GLOBALVAR_INIT_REFS, NameVals,
+                      FSModVTableRefsAbbrev);
   NameVals.clear();
 }
 
@@ -3752,6 +3782,17 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned FSModRefsAbbrev = Stream.EmitAbbrev(std::move(Abbv));
 
+  // Abbrev for FS_PERMODULE_VTABLE_GLOBALVAR_INIT_REFS.
+  Abbv = std::make_shared<BitCodeAbbrev>();
+  Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE_VTABLE_GLOBALVAR_INIT_REFS));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // valueid
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // flags
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // numrefs
+  // numrefs x valueid, n x (valueid , offset)
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  unsigned FSModVTableRefsAbbrev = Stream.EmitAbbrev(std::move(Abbv));
+
   // Abbrev for FS_ALIAS.
   Abbv = std::make_shared<BitCodeAbbrev>();
   Abbv->Add(BitCodeAbbrevOp(bitc::FS_ALIAS));
@@ -3760,6 +3801,16 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // valueid
   unsigned FSAliasAbbrev = Stream.EmitAbbrev(std::move(Abbv));
 
+  // Abbrev for FS_TYPE_ID_METADATA
+  Abbv = std::make_shared<BitCodeAbbrev>();
+  Abbv->Add(BitCodeAbbrevOp(bitc::FS_TYPE_ID_METADATA));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // typeid strtab index
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // typeid length
+  // n x (valueid , offset)
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  unsigned TypeIdCompatibleVtableAbbrev = Stream.EmitAbbrev(std::move(Abbv));
+
   SmallVector<uint64_t, 64> NameVals;
   // Iterate over the list of functions instead of the Index to
   // ensure the ordering is stable.
@@ -3784,7 +3835,8 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
   // Capture references from GlobalVariable initializers, which are outside
   // of a function scope.
   for (const GlobalVariable &G : M.globals())
-    writeModuleLevelReferences(G, NameVals, FSModRefsAbbrev);
+    writeModuleLevelReferences(G, NameVals, FSModRefsAbbrev,
+                               FSModVTableRefsAbbrev);
 
   for (const GlobalAlias &A : M.aliases()) {
     auto *Aliasee = A.getBaseObject();
@@ -3802,6 +3854,16 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
     NameVals.clear();
   }
 
+  if (!Index->typeIdCompatibleVtableMap().empty()) {
+    for (auto &S : Index->typeIdCompatibleVtableMap()) {
+      writeTypeIdCompatibleVtableSummaryRecord(NameVals, StrtabBuilder, S.first,
+                                               S.second, VE);
+      Stream.EmitRecord(bitc::FS_TYPE_ID_METADATA, NameVals,
+                        TypeIdCompatibleVtableAbbrev);
+      NameVals.clear();
+    }
+  }
+
   Stream.ExitBlock();
 }