[ThinLTO] Create AliasSummary when building index

Summary:
Previously we were creating the alias summary on the fly while writing
the summary to bitcode. This moves the creation of these summaries to
the module summary index builder where we build the rest of the summary
index.

This is going to be necessary for setting the NoRename flag for values
possibly used in inline asm or module level asm.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26049

llvm-svn: 285379

2 files changed, 27 insertions, 7 deletions

diff --git a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
index c107deb0a6e..f13ae844442 100644
--- a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -78,10 +78,9 @@ static CalleeInfo::HotnessType getHotness(uint64_t ProfileCount,
 static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
                                    const Function &F, BlockFrequencyInfo *BFI,
                                    ProfileSummaryInfo *PSI) {
-  // Summary not currently supported for anonymous functions, they must
-  // be renamed.
-  if (!F.hasName())
-    return;
+  // Summary not currently supported for anonymous functions, they should
+  // have been named.
+  assert(F.hasName());
 
   unsigned NumInsts = 0;
   // Map from callee ValueId to profile count. Used to accumulate profile
@@ -111,9 +110,11 @@ static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
       }
       // Check if this is a direct call to a known function.
       if (CalledFunction) {
-        // Skip nameless and intrinsics.
-        if (!CalledFunction->hasName() || CalledFunction->isIntrinsic())
+        // Skip intrinsics.
+        if (CalledFunction->isIntrinsic())
           continue;
+        // We should have named any anonymous globals
+        assert(CalledFunction->hasName());
         auto ScaledCount = BFI ? BFI->getBlockProfileCount(&BB) : None;
         // Use the original CalledValue, in case it was an alias. We want
         // to record the call edge to the alias in that case. Eventually
@@ -166,6 +167,17 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
   Index.addGlobalValueSummary(V.getName(), std::move(GVarSummary));
 }
 
+static void computeAliasSummary(ModuleSummaryIndex &Index,
+                                const GlobalAlias &A) {
+  GlobalValueSummary::GVFlags Flags(A);
+  std::unique_ptr<AliasSummary> AS = llvm::make_unique<AliasSummary>(Flags);
+  auto *Aliasee = A.getBaseObject();
+  auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
+  assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
+  AS->setAliasee(AliaseeSummary);
+  Index.addGlobalValueSummary(A.getName(), std::move(AS));
+}
+
 ModuleSummaryIndex llvm::buildModuleSummaryIndex(
     const Module &M,
     std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
@@ -204,6 +216,12 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
       continue;
     computeVariableSummary(Index, G);
   }
+
+  // Compute summaries for all aliases defined in module, and save in the
+  // index.
+  for (const GlobalAlias &A : M.aliases())
+    computeAliasSummary(Index, A);
+
   return Index;
 }
 
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 2972688992f..62008c42d3d 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3434,7 +3434,9 @@ void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
     auto AliasId = VE.getValueID(&A);
     auto AliaseeId = VE.getValueID(Aliasee);
     NameVals.push_back(AliasId);
-    NameVals.push_back(getEncodedGVSummaryFlags(A));
+    auto *Summary = Index->getGlobalValueSummary(A);
+    AliasSummary *AS = cast<AliasSummary>(Summary);
+    NameVals.push_back(getEncodedGVSummaryFlags(AS->flags()));
     NameVals.push_back(AliaseeId);
     Stream.EmitRecord(bitc::FS_ALIAS, NameVals, FSAliasAbbrev);
     NameVals.clear();