[ThinLTO] Add index flag for internalization/promotion status (llvm#164530)

Add an index-wide flag indicating whether index-based internalization
and promotion have completed. This will be used in a follow on change.

Author: teresajohnson

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -1449,6 +1449,9 @@ class ModuleSummaryIndex {
   /// every summary of a GV is synchronized.
   bool WithDSOLocalPropagation = false;
 
+  /// Indicates that summary-based internalization and promotion has run.
+  bool WithInternalizeAndPromote = false;
+
   /// Indicates that we have whole program visibility.
   bool WithWholeProgramVisibility = false;
 
@@ -1653,6 +1656,9 @@ class ModuleSummaryIndex {
   bool withDSOLocalPropagation() const { return WithDSOLocalPropagation; }
   void setWithDSOLocalPropagation() { WithDSOLocalPropagation = true; }
 
+  bool withInternalizeAndPromote() const { return WithInternalizeAndPromote; }
+  void setWithInternalizeAndPromote() { WithInternalizeAndPromote = true; }
+
   bool withWholeProgramVisibility() const { return WithWholeProgramVisibility; }
   void setWithWholeProgramVisibility() { WithWholeProgramVisibility = true; }
 

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -8603,7 +8603,7 @@ getEnableSplitLTOUnitAndUnifiedFlag(BitstreamCursor &Stream,
     case bitc::FS_FLAGS: { // [flags]
       uint64_t Flags = Record[0];
       // Scan flags.
-      assert(Flags <= 0x2ff && "Unexpected bits in flag");
+      assert(Flags <= 0x7ff && "Unexpected bits in flag");
 
       bool EnableSplitLTOUnit = Flags & 0x8;
       bool UnifiedLTO = Flags & 0x200;

llvm/lib/IR/ModuleSummaryIndex.cpp

@@ -111,11 +111,13 @@ uint64_t ModuleSummaryIndex::getFlags() const {
     Flags |= 0x100;
   if (hasUnifiedLTO())
     Flags |= 0x200;
+  if (withInternalizeAndPromote())
+    Flags |= 0x400;
   return Flags;
 }
 
 void ModuleSummaryIndex::setFlags(uint64_t Flags) {
-  assert(Flags <= 0x2ff && "Unexpected bits in flag");
+  assert(Flags <= 0x7ff && "Unexpected bits in flag");
   // 1 bit: WithGlobalValueDeadStripping flag.
   // Set on combined index only.
   if (Flags & 0x1)
@@ -154,6 +156,10 @@ void ModuleSummaryIndex::setFlags(uint64_t Flags) {
   // Set on combined index only.
   if (Flags & 0x200)
     setUnifiedLTO();
+  // 1 bit: WithInternalizeAndPromote flag.
+  // Set on combined index only.
+  if (Flags & 0x400)
+    setWithInternalizeAndPromote();
 }
 
 // Collect for the given module the list of function it defines

llvm/lib/LTO/LTO.cpp

@@ -551,9 +551,11 @@ void llvm::thinLTOInternalizeAndPromoteInIndex(
     function_ref<bool(StringRef, ValueInfo)> isExported,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing) {
+  assert(!Index.withInternalizeAndPromote());
   for (auto &I : Index)
     thinLTOInternalizeAndPromoteGUID(Index.getValueInfo(I), isExported,
                                      isPrevailing);
+  Index.setWithInternalizeAndPromote();
 }
 
 // Requires a destructor for std::vector<InputModule>.

llvm/test/Bitcode/thinlto-deadstrip-flag.ll

@@ -0,0 +1,39 @@
+; REQUIRES: x86-registered-target
+; RUN: opt -module-summary %s -o %t.o
+
+;; By default, the indexing step should perform and set the appropriate index
+;; flags for dead stripping, attribute propagation, DSO local propagation,
+;; and internalization/promotion.
+; RUN: llvm-lto2 run %t.o -o %t.out -thinlto-distributed-indexes \
+; RUN:		-r %t.o,glob,plx
+; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=ALL
+;; The flag value should be 0x461 aka 1121:
+;; 0x1: Dead stripping
+;; 0x20: Attribute propagation
+;; 0x40: DSO local propagation
+;; 0x400: Internalization/promotion
+; ALL: <FLAGS op0=1121/>
+
+;; Ensure dead stripping performed flag is not set on distributed index
+;; when option used to disable dead stripping computation.
+; RUN: llvm-lto2 run %t.o -o %t.out -thinlto-distributed-indexes \
+; RUN:		-r %t.o,glob,plx -compute-dead=false
+; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=NODEAD
+;; Flag should be 0x460 aka 1120.
+; NODEAD: <FLAGS op0=1120/>
+
+;; Disabling attribute propagation should disable that as well as DSO local
+;; propagation.
+; RUN: llvm-lto2 run %t.o -o %t.out -thinlto-distributed-indexes \
+; RUN:		-r %t.o,glob,plx -propagate-attrs=false
+; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=NOPROP
+;; Flag should be 0x401 aka 1025.
+; NOPROP: <FLAGS op0=1025/>
+
+;; Note there isn't currently a way to disable internalization+promotion, which
+;; are performed together.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@glob = global i32 0