From a667b70dbedb0b9864ec4ffa0a7c90c1d08f578e Mon Sep 17 00:00:00 2001
From: Evgeniy Stepanov <eugeni.stepanov@gmail.com>
Date: Fri, 2 Jun 2017 18:24:17 +0000
Subject: [PATCH] Move summary dead stripping before regular LTO.

This way dead stripping results are recorded in combined summary and
can be used in regular LTO passes.

Differential Revision: https://reviews.llvm.org/D33615

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304577 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/LTO/LTO.cpp               | 26 +++++++++++++-------------
 test/ThinLTO/X86/deadstrip.ll | 16 +++++++++++++++-
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/lib/LTO/LTO.cpp b/lib/LTO/LTO.cpp
index 2bd3af6e92d..92145aaf667 100644
--- a/lib/LTO/LTO.cpp
+++ b/lib/LTO/LTO.cpp
@@ -622,6 +622,19 @@ unsigned LTO::getMaxTasks() const {
 }
 
 Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
+  // Compute "dead" symbols, we don't want to import/export these!
+  DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
+  for (auto &Res : GlobalResolutions) {
+    if (Res.second.VisibleOutsideThinLTO &&
+        // IRName will be defined if we have seen the prevailing copy of
+        // this value. If not, no need to preserve any ThinLTO copies.
+        !Res.second.IRName.empty())
+      GUIDPreservedSymbols.insert(GlobalValue::getGUID(
+          GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
+  }
+
+  computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
+
   // Save the status of having a regularLTO combined module, as
   // this is needed for generating the ThinLTO Task ID, and
   // the CombinedModule will be moved at the end of runRegularLTO.
@@ -974,19 +987,6 @@ Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
 
   if (Conf.OptLevel > 0) {
-    // Compute "dead" symbols, we don't want to import/export these!
-    DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
-    for (auto &Res : GlobalResolutions) {
-      if (Res.second.VisibleOutsideThinLTO &&
-          // IRName will be defined if we have seen the prevailing copy of
-          // this value. If not, no need to preserve any ThinLTO copies.
-          !Res.second.IRName.empty())
-        GUIDPreservedSymbols.insert(GlobalValue::getGUID(
-            GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
-    }
-
-    computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
-
     ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
                              ImportLists, ExportLists);
 
diff --git a/test/ThinLTO/X86/deadstrip.ll b/test/ThinLTO/X86/deadstrip.ll
index 0c85322eb56..c19ccb01be3 100644
--- a/test/ThinLTO/X86/deadstrip.ll
+++ b/test/ThinLTO/X86/deadstrip.ll
@@ -22,6 +22,20 @@
 ; RUN: llvm-dis < %t.out.1.3.import.bc | FileCheck %s --check-prefix=CHECK2
 ; RUN: llvm-nm %t.out.1 | FileCheck %s --check-prefix=CHECK2-NM
 
+; RUN: llvm-bcanalyzer -dump %t.out.index.bc | FileCheck %s --check-prefix=COMBINED
+; Live, NotEligibleForImport, Internal
+; COMBINED-DAG: <COMBINED {{.*}} op2=55
+; Live, Internal
+; COMBINED-DAG: <COMBINED {{.*}} op2=39
+; Live, External
+; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; (Dead)
+; COMBINED-DAG: <COMBINED {{.*}} op2=0
+; COMBINED-DAG: <COMBINED {{.*}} op2=0
+; COMBINED-DAG: <COMBINED {{.*}} op2=0
+
 ; Dead-stripping on the index allows to internalize these,
 ; and limit the import of @baz thanks to early pruning.
 ; CHECK-NOT: available_externally {{.*}} @baz()
@@ -35,7 +49,7 @@
 ; Make sure we didn't internalize @boo, which is reachable via
 ; llvm.global_ctors
 ; CHECK2: define void @boo()
-; We should have eventually revoved @baz since it was internalized and unused
+; We should have eventually removed @baz since it was internalized and unused
 ; CHECK2-NM-NOT: _baz
 
 ; The final binary should not contain any of the dead functions,