[PATCH] D28440: [ThinLTO] Import static functions from the same module as caller

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson updated this revision to Diff 84177.
tejohnson added a comment.

Slight update to enable importing a local from another module when
there is a single summary for that GUID - in that case this must be
due to indirect call profile metadata. This was flagged by
test/Transforms/PGOProfile/thinlto_indirect_call_promotion.ll.

Note if there are multiple matching locals and there is indirect call
profile data pointing to them, we wouldn't know which to import
anyway (the profile data uses the same GUID).


https://reviews.llvm.org/D28440

Files:
  lib/Transforms/IPO/FunctionImport.cpp
  test/ThinLTO/X86/local_name_conflict.ll


Index: test/ThinLTO/X86/local_name_conflict.ll
===================================================================
--- test/ThinLTO/X86/local_name_conflict.ll
+++ test/ThinLTO/X86/local_name_conflict.ll
@@ -1,14 +1,25 @@
+; Test handling when two files with the same source file name contain
+; static functions with the same name (which will have the same GUID
+; in the combined index.
+
 ; Do setup work for all below tests: generate bitcode and combined index
 ; RUN: opt -module-summary -module-hash %s -o %t.bc
 ; RUN: opt -module-summary -module-hash %p/Inputs/local_name_conflict1.ll -o %t2.bc
 ; RUN: opt -module-summary -module-hash %p/Inputs/local_name_conflict2.ll -o %t3.bc
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t4.bc %t.bc %t2.bc %t3.bc
 
-; Make sure foo is promoted and renamed without complaint in both
-; Inputs/local_name_conflict1.ll and Inputs/local_name_conflict2.ll
-; FIXME: Once the importer is fixed to import the correct copy of the
-; local, we should be able to verify that via an import action.
-; RUN: llvm-lto -thinlto-action=promote %t2.bc -thinlto-index=%t4.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=EXPORTSTATIC
+; This module will import b() which should cause the copy of foo from
+; that module (%t3.bc) to be imported. Check that the imported reference's
+; promoted name matches the imported copy.
+; RUN: llvm-lto -thinlto-action=import %t.bc -thinlto-index=%t4.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=IMPORT
+; IMPORT: call i32 @foo.llvm.[[HASH:[0-9A-F]+]]
+; IMPORT: define available_externally hidden i32 @foo.llvm.[[HASH]]()
+
+; The copy in %t2.bc should not be exported/promoted/renamed
+; RUN: llvm-lto -thinlto-action=promote %t2.bc -thinlto-index=%t4.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=NOEXPORTSTATIC
+; NOEXPORTSTATIC: define internal i32 @foo()
+
+; Make sure foo is promoted and renamed without complaint in %t3.bc.
 ; RUN: llvm-lto -thinlto-action=promote %t3.bc -thinlto-index=%t4.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=EXPORTSTATIC
 ; EXPORTSTATIC: define hidden i32 @foo.llvm.
 
Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -124,7 +124,7 @@
 static const GlobalValueSummary *
 selectCallee(const ModuleSummaryIndex &Index,
              const GlobalValueSummaryList &CalleeSummaryList,
-             unsigned Threshold) {
+             unsigned Threshold, StringRef CallerModulePath) {
   auto It = llvm::find_if(
       CalleeSummaryList,
       [&](const std::unique_ptr<GlobalValueSummary> &SummaryPtr) {
@@ -145,6 +145,21 @@
 
         auto *Summary = cast<FunctionSummary>(GVSummary);
 
+        // If this is a local function, make sure we import the copy
+        // in the caller's module. The only time a local function can
+        // share an entry in the index is if there is a local with the same name
+        // in another module that had the same source file name (in a different
+        // directory), where each was compiled in their own directory so there
+        // was not distinguishing path.
+        // However, do the import from another module if there is only one
+        // entry in the list - in that case this must be a reference due
+        // to indirect call profile data, since a function pointer can point to
+        // a local in another module.
+        if (GlobalValue::isLocalLinkage(Summary->linkage()) &&
+            CalleeSummaryList.size() > 1 &&
+            Summary->modulePath() != CallerModulePath)
+          return false;
+
         if (Summary->instCount() > Threshold)
           return false;
 
@@ -163,11 +178,13 @@
 /// null if there's no match.
 static const GlobalValueSummary *selectCallee(GlobalValue::GUID GUID,
                                               unsigned Threshold,
-                                              const ModuleSummaryIndex &Index) {
+                                              const ModuleSummaryIndex &Index,
+                                              StringRef CallerModulePath) {
   auto CalleeSummaryList = Index.findGlobalValueSummaryList(GUID);
   if (CalleeSummaryList == Index.end())
     return nullptr; // This function does not have a summary
-  return selectCallee(Index, CalleeSummaryList->second, Threshold);
+  return selectCallee(Index, CalleeSummaryList->second, Threshold,
+                      CallerModulePath);
 }
 
 using EdgeInfo = std::tuple<const FunctionSummary *, unsigned /* Threshold */,
@@ -202,7 +219,8 @@
     const auto NewThreshold =
         Threshold * GetBonusMultiplier(Edge.second.Hotness);
 
-    auto *CalleeSummary = selectCallee(GUID, NewThreshold, Index);
+    auto *CalleeSummary =
+        selectCallee(GUID, NewThreshold, Index, Summary.modulePath());
     if (!CalleeSummary) {
       DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");
       continue;


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