[PATCH] D27687: [ThinLTO] Thin link efficiency improvement: don't re-export globals (NFC)

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson created this revision.
tejohnson added a reviewer: mehdi_amini.
tejohnson added a subscriber: llvm-commits.

We were reinvoking exportGlobalInModule numerous times redundantly.
No need to re-export globals referenced by a global that was already
exported in the module. This resulted in a large speedup in the thin
link for a big application, particularly when importing aggressiveness
was cranked up.


https://reviews.llvm.org/D27687

Files:
  lib/Transforms/IPO/FunctionImport.cpp


Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -332,16 +332,19 @@
     // Make exports in the source module.
     if (ExportLists) {
       auto &ExportList = (*ExportLists)[ExportModulePath];
-      ExportList.insert(GUID);
-      // Mark all functions and globals referenced by this function as exported
-      // to the outside if they are defined in the same source module.
-      for (auto &Edge : ResolvedCalleeSummary->calls()) {
-        auto CalleeGUID = Edge.first.getGUID();
-        exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
-      }
-      for (auto &Ref : ResolvedCalleeSummary->refs()) {
-        auto GUID = Ref.getGUID();
-        exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
+      auto InsertResult = ExportList.insert(GUID);
+      if (InsertResult.second) {
+        // This is the first time this function was exported from its source
+        // module, so mark all functions and globals it references as exported
+        // to the outside if they are defined in the same source module.
+        for (auto &Edge : ResolvedCalleeSummary->calls()) {
+          auto CalleeGUID = Edge.first.getGUID();
+          exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
+        }
+        for (auto &Ref : ResolvedCalleeSummary->refs()) {
+          auto GUID = Ref.getGUID();
+          exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
+        }
       }
     }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D27687.81140.patch
Type: text/x-patch
Size: 1620 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20161212/57cc973b/attachment.bin>