From 7e7fd554168d49819e248e4e0f1d80ba32ff49d5 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka@google.com>
Date: Thu, 6 Aug 2020 05:28:03 -0700
Subject: [PATCH] [StackSafety] Change how callee searched in index

Handle other than local linkage types.
---
 lib/Analysis/StackSafetyAnalysis.cpp     | 64 ++++++++++++++++++------
 test/Analysis/StackSafetyAnalysis/ipa.ll |  4 +-
 2 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/lib/Analysis/StackSafetyAnalysis.cpp b/lib/Analysis/StackSafetyAnalysis.cpp
index f61363909c5..0a8a4cc446b 100644
--- a/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/lib/Analysis/StackSafetyAnalysis.cpp
@@ -52,6 +52,10 @@ STATISTIC(NumCombinedParamAccessesAfter,
           "Number of total param accesses after generateParamAccessSummary.");
 STATISTIC(NumCombinedDataFlowNodes,
           "Number of total nodes in combined index for dataflow processing.");
+STATISTIC(NumIndexCalleeUnhandled, "Number of index callee which are unhandled.");
+STATISTIC(NumIndexCalleeMultipleWeak, "Number of index callee non-unique weak.");
+STATISTIC(NumIndexCalleeMultipleExternal, "Number of index callee non-unique external.");
+
 
 static cl::opt<int> StackSafetyMaxIterations("stack-safety-max-iterations",
                                              cl::init(20), cl::Hidden);
@@ -604,7 +608,45 @@ StackSafetyDataFlowAnalysis<CalleeTy>::run() {
   return Functions;
 }
 
-FunctionSummary *resolveCallee(GlobalValueSummary *S) {
+FunctionSummary *findCalleeFunctionSummary(ValueInfo VI, StringRef ModuleId) {
+  if (!VI)
+    return nullptr;
+  auto SummaryList = VI.getSummaryList();
+  GlobalValueSummary* S = nullptr;
+  for (const auto& GVS : SummaryList) {
+    if (!GVS->isLive())
+      continue;
+    if (const AliasSummary *AS = dyn_cast<AliasSummary>(GVS.get()))
+      if (!AS->hasAliasee())
+        continue;
+    if (!isa<FunctionSummary>(GVS->getBaseObject()))
+      continue;
+    if (GlobalValue::isLocalLinkage(GVS->linkage())) {
+      if (GVS->modulePath() == ModuleId) {
+        S = GVS.get();
+        break;
+      }
+    } else if (GlobalValue::isExternalLinkage(GVS->linkage())) {
+      if (S) {
+        ++NumIndexCalleeMultipleExternal;
+        return nullptr;
+      }
+      S = GVS.get();
+    } else if (GlobalValue::isWeakLinkage(GVS->linkage())) {
+      if (S) {
+        ++NumIndexCalleeMultipleWeak;
+        return nullptr;
+      }
+      S = GVS.get();
+    } else if (GlobalValue::isAvailableExternallyLinkage(GVS->linkage()) ||
+               GlobalValue::isLinkOnceLinkage(GVS->linkage())) {
+      if (SummaryList.size() == 1)
+        S = GVS.get();
+      // According thinLTOResolvePrevailingGUID these are unlikely prevailing.
+    } else {
+      ++NumIndexCalleeUnhandled;
+    }
+  };
   while (S) {
     if (!S->isLive() || !S->isDSOLocal())
       return nullptr;
@@ -636,15 +678,6 @@ const Function *findCalleeInModule(const GlobalValue *GV) {
   return nullptr;
 }
 
-GlobalValueSummary *getGlobalValueSummary(const ModuleSummaryIndex *Index,
-                                          uint64_t ValueGUID) {
-  auto VI = Index->getValueInfo(ValueGUID);
-  if (!VI || VI.getSummaryList().empty())
-    return nullptr;
-  auto &Summary = VI.getSummaryList()[0];
-  return Summary.get();
-}
-
 const ConstantRange *findParamAccess(const FunctionSummary &FS,
                                      uint32_t ParamNo) {
   assert(FS.isLive());
@@ -668,10 +701,9 @@ void resolveAllCalls(UseInfo<GlobalValue> &Use,
 
     if (!Index)
       return Use.updateRange(FullSet);
-    GlobalValueSummary *GVS =
-        getGlobalValueSummary(Index, C.first.Callee->getGUID());
-
-    FunctionSummary *FS = resolveCallee(GVS);
+    FunctionSummary *FS =
+        findCalleeFunctionSummary(Index->getValueInfo(C.first.Callee->getGUID()),
+                                  C.first.Callee->getParent()->getModuleIdentifier());
     ++NumModuleCalleeLookupTotal;
     if (!FS) {
       ++NumModuleCalleeLookupFailed;
@@ -997,8 +1029,8 @@ void llvm::generateParamAccessSummary(ModuleSummaryIndex &Index) {
           US.Range = PS.Use;
           for (auto &Call : PS.Calls) {
             assert(!Call.Offsets.isFullSet());
-            FunctionSummary *S = resolveCallee(
-                Index.findSummaryInModule(Call.Callee, FS->modulePath()));
+            FunctionSummary *S =
+                findCalleeFunctionSummary(Call.Callee, FS->modulePath());
             ++NumCombinedCalleeLookupTotal;
             if (!S) {
               ++NumCombinedCalleeLookupFailed;
diff --git a/test/Analysis/StackSafetyAnalysis/ipa.ll b/test/Analysis/StackSafetyAnalysis/ipa.ll
index 6be426f6bbd..a610f1bb5f2 100644
--- a/test/Analysis/StackSafetyAnalysis/ipa.ll
+++ b/test/Analysis/StackSafetyAnalysis/ipa.ll
@@ -469,14 +469,12 @@ entry:
   ret void
 }
 
-; FIXME: LTO should match NOLTO
 define void @TestCrossModuleTwice() #0 {
 ; CHECK-DAG: @TestCrossModuleTwice dso_preemptable{{$}}
 ; CHECK-NEXT: args uses:
 ; CHECK-NEXT: allocas uses:
 ; LOCAL-NEXT: z[1]: empty-set, @Write1DiffModule(arg0, [0,1)){{$}}
-; NOLTO-NEXT: z[1]: [0,1), @Write1DiffModule(arg0, [0,1)){{$}}
-; LTO-NEXT: z[1]: full-set, @Write1DiffModule(arg0, [0,1)){{$}}
+; GLOBAL-NEXT: z[1]: [0,1), @Write1DiffModule(arg0, [0,1)){{$}}
 ; CHECK-EMPTY:
 entry:
   %z = alloca i8, align 4