Add new EliminateAvailableExternally module pass, which is performed in

[oota-llvm.git] / lib / Transforms / IPO / PassManagerBuilder.cpp

diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 963f1bb13aafb4712bdc5317eb9c9a18fe9fe084..a067a4b45254edd073610d7c1e2bdb37c0144b7c 100644 (file)
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -105,6 +105,7 @@ PassManagerBuilder::PassManagerBuilder() {
     VerifyInput = false;
     VerifyOutput = false;
     MergeFunctions = false;
+    PrepareForLTO = false;
 }
 
 PassManagerBuilder::~PassManagerBuilder() {
@@ -401,6 +402,17 @@ void PassManagerBuilder::populateModulePassManager(
     // GlobalOpt already deletes dead functions and globals, at -O2 try a
     // late pass of GlobalDCE.  It is capable of deleting dead cycles.
     if (OptLevel > 1) {
+      if (!PrepareForLTO) {
+        // Remove avail extern fns and globals definitions if we aren't
+        // compiling an object file for later LTO. For LTO we want to preserve
+        // these so they are eligible for inlining at link-time. Note if they
+        // are unreferenced they will be removed by GlobalDCE below, so
+        // this only impacts referenced available externally globals.
+        // Eventually they will be suppressed during codegen, but eliminating
+        // here enables more opportunity for GlobalDCE as it may make
+        // globals referenced by available external functions dead.
+        MPM.add(createEliminateAvailableExternallyPass());
+      }
       MPM.add(createGlobalDCEPass());         // Remove dead fns and globals.
       MPM.add(createConstantMergePass());     // Merge dup global constants
     }