Make aliases explicit in the summary

Summary:
To be able to work accurately on the reference graph when taking decision
about internalizing, promoting, renaming, etc. We need to have the alias
information explicit.

Reviewers: tejohnson

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D18836

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266214

1 files changed, 51 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 321c775531e..e5fb51b1bed 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5848,6 +5848,35 @@ std::error_code ModuleSummaryIndexBitcodeReader::parseEntireSummary() {
       Info->setSummary(std::move(FS));
       break;
     }
+    // FS_ALIAS: [valueid, linkage, valueid]
+    // Aliases must be emitted (and parsed) after all FS_PERMODULE entries, as
+    // they expect all aliasee summaries to be available.
+    case bitc::FS_ALIAS: {
+      unsigned ValueID = Record[0];
+      uint64_t RawLinkage = Record[1];
+      unsigned AliaseeID = Record[2];
+      std::unique_ptr<AliasSummary> AS =
+          llvm::make_unique<AliasSummary>(getDecodedLinkage(RawLinkage));
+      // The module path string ref set in the summary must be owned by the
+      // index's module string table. Since we don't have a module path
+      // string table section in the per-module index, we create a single
+      // module path string table entry with an empty (0) ID to take
+      // ownership.
+      AS->setModulePath(
+          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0)->first());
+
+      GlobalValue::GUID AliaseeGUID = getGUIDFromValueId(AliaseeID);
+      auto *AliaseeInfo = TheIndex->getGlobalValueInfo(AliaseeGUID);
+      if (!AliaseeInfo->summary())
+        return error("Alias expects aliasee summary to be parsed");
+      AS->setAliasee(AliaseeInfo->summary());
+
+      GlobalValue::GUID GUID = getGUIDFromValueId(ValueID);
+      auto *Info = TheIndex->getGlobalValueInfo(GUID);
+      assert(!Info->summary() && "Expected a single summary per VST entry");
+      Info->setSummary(std::move(AS));
+      break;
+    }
     // FS_PERMODULE_GLOBALVAR_INIT_REFS: [valueid, linkage, n x valueid]
     case bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS: {
       unsigned ValueID = Record[0];
@@ -5906,6 +5935,28 @@ std::error_code ModuleSummaryIndexBitcodeReader::parseEntireSummary() {
       Combined = true;
       break;
     }
+    // FS_COMBINED_ALIAS: [modid, linkage, offset]
+    // Aliases must be emitted (and parsed) after all FS_PERMODULE entries, as
+    // they expect all aliasee summaries to be available.
+    case bitc::FS_COMBINED_ALIAS: {
+      uint64_t ModuleId = Record[0];
+      uint64_t RawLinkage = Record[1];
+      uint64_t AliaseeSummaryOffset = Record[2];
+      std::unique_ptr<AliasSummary> AS =
+          llvm::make_unique<AliasSummary>(getDecodedLinkage(RawLinkage));
+      AS->setModulePath(ModuleIdMap[ModuleId]);
+
+      auto *AliaseeInfo = getInfoFromSummaryOffset(AliaseeSummaryOffset);
+      if (!AliaseeInfo->summary())
+        return error("Alias expects aliasee summary to be parsed");
+      AS->setAliasee(AliaseeInfo->summary());
+
+      auto *Info = getInfoFromSummaryOffset(CurRecordBit);
+      assert(!Info->summary() && "Expected a single summary per VST entry");
+      Info->setSummary(std::move(AS));
+      Combined = true;
+      break;
+    }
     // FS_COMBINED_GLOBALVAR_INIT_REFS: [modid, linkage, n x valueid]
     case bitc::FS_COMBINED_GLOBALVAR_INIT_REFS: {
       uint64_t ModuleId = Record[0];