[PATCH] D62348: ELF: Introduce a separate bit for tracking whether an output section has ever had an input section added to it. NFCI.

[Peter Collingbourne via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL362444: ELF: Introduce a separate bit for tracking whether an output section has ever… (authored by pcc, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D62348?vs=201073&id=202781#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62348/new/

https://reviews.llvm.org/D62348

Files:
  lld/trunk/ELF/LinkerScript.cpp
  lld/trunk/ELF/OutputSections.cpp
  lld/trunk/ELF/OutputSections.h
  lld/trunk/ELF/Writer.cpp


Index: lld/trunk/ELF/OutputSections.cpp
===================================================================
--- lld/trunk/ELF/OutputSections.cpp
+++ lld/trunk/ELF/OutputSections.cpp
@@ -84,9 +84,10 @@
 }
 
 void OutputSection::addSection(InputSection *IS) {
-  if (!isLive()) {
+  if (!HasInputSections) {
     // If IS is the first section to be added to this section,
     // initialize Partition, Type, Entsize and flags from IS.
+    HasInputSections = true;
     Partition = IS->Partition;
     Type = IS->Type;
     Entsize = IS->Entsize;
Index: lld/trunk/ELF/OutputSections.h
===================================================================
--- lld/trunk/ELF/OutputSections.h
+++ lld/trunk/ELF/OutputSections.h
@@ -93,6 +93,11 @@
   bool UsedInExpression = false;
   bool InOverlay = false;
 
+  // Tracks whether the section has ever had an input section added to it, even
+  // if the section was later removed (e.g. because it is a synthetic section
+  // that wasn't needed). This is needed for orphan placement.
+  bool HasInputSections = false;
+
   void finalize();
   template <class ELFT> void writeTo(uint8_t *Buf);
   template <class ELFT> void maybeCompress();
Index: lld/trunk/ELF/Writer.cpp
===================================================================
--- lld/trunk/ELF/Writer.cpp
+++ lld/trunk/ELF/Writer.cpp
@@ -1052,7 +1052,7 @@
 
 static int getRankProximity(OutputSection *A, BaseCommand *B) {
   auto *Sec = dyn_cast<OutputSection>(B);
-  return (Sec && Sec->isLive()) ? getRankProximityAux(A, Sec) : -1;
+  return (Sec && Sec->HasInputSections) ? getRankProximityAux(A, Sec) : -1;
 }
 
 // When placing orphan sections, we want to place them after symbol assignments
@@ -1094,19 +1094,20 @@
   int Proximity = getRankProximity(Sec, *I);
   for (; I != E; ++I) {
     auto *CurSec = dyn_cast<OutputSection>(*I);
-    if (!CurSec || !CurSec->isLive())
+    if (!CurSec || !CurSec->HasInputSections)
       continue;
     if (getRankProximity(Sec, CurSec) != Proximity ||
         Sec->SortRank < CurSec->SortRank)
       break;
   }
 
-  auto IsLiveOutputSec = [](BaseCommand *Cmd) {
+  auto IsOutputSecWithInputSections = [](BaseCommand *Cmd) {
     auto *OS = dyn_cast<OutputSection>(Cmd);
-    return OS && OS->isLive();
+    return OS && OS->HasInputSections;
   };
   auto J = std::find_if(llvm::make_reverse_iterator(I),
-                        llvm::make_reverse_iterator(B), IsLiveOutputSec);
+                        llvm::make_reverse_iterator(B),
+                        IsOutputSecWithInputSections);
   I = J.base();
 
   // As a special case, if the orphan section is the last section, put
@@ -1114,7 +1115,7 @@
   // This matches bfd's behavior and is convenient when the linker script fully
   // specifies the start of the file, but doesn't care about the end (the non
   // alloc sections for example).
-  auto NextSec = std::find_if(I, E, IsLiveOutputSec);
+  auto NextSec = std::find_if(I, E, IsOutputSecWithInputSections);
   if (NextSec == E)
     return E;
 
Index: lld/trunk/ELF/LinkerScript.cpp
===================================================================
--- lld/trunk/ELF/LinkerScript.cpp
+++ lld/trunk/ELF/LinkerScript.cpp
@@ -889,10 +889,9 @@
       Sec->Alignment =
           std::max<uint32_t>(Sec->Alignment, Sec->AlignExpr().getValue());
 
-    // A live output section means that some input section was added to it. It
-    // might have been removed (if it was empty synthetic section), but we at
-    // least know the flags.
-    if (Sec->isLive())
+    // The input section might have been removed (if it was an empty synthetic
+    // section), but we at least know the flags.
+    if (Sec->HasInputSections)
       Flags = Sec->Flags;
 
     // We do not want to keep any special flags for output section


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