[PATCH] D33772: [LLD][ELF] SHF_LINK_ORDER should sort based on InputSectionDescriptions

[Peter Smith via Phabricator via llvm-commits]

peter.smith updated this revision to Diff 101177.
peter.smith added a comment.

> On trunk we now have



  if (!Script->Opt.HasSections) {
    if (!Config->Relocatable)
      fixSectionAlignments();
    Script->fabricateDefaultCommands();
  } else {
    Script->synchronize();
  }

> Would it be possible to move this block together? That would avoid the need to change synchronize as it would now be earlier too.

I've updated the diff to move the fabricatedDefaultCommands() after ThunkCreation, this permits the block to stay together. Later Today I'm intending to post a set of patches to convert Thunks to insert into InputSectionDescriptions which will hopefully permit synchronize() to be removed.


https://reviews.llvm.org/D33772

Files:
  ELF/OutputSections.cpp
  ELF/Writer.cpp


Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -257,14 +257,6 @@
   if (ErrorCount)
     return;
 
-  if (!Script->Opt.HasSections) {
-    Script->fabricateDefaultCommands();
-    if (!Config->Relocatable)
-      fixSectionAlignments();
-  } else {
-    Script->synchronize();
-  }
-
   for (BaseCommand *Base : Script->Opt.Commands)
     if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       OutputSectionCommands.push_back(Cmd);
@@ -1260,6 +1252,15 @@
       applySynthetic({InX::MipsGot},
                      [](SyntheticSection *SS) { SS->updateAllocSize(); });
   }
+
+  if (!Script->Opt.HasSections) {
+    Script->fabricateDefaultCommands();
+    if (!Config->Relocatable)
+      fixSectionAlignments();
+  } else {
+    Script->synchronize();
+  }
+
   // Fill other section headers. The dynamic table is finalized
   // at the end because some tags like RELSZ depend on result
   // of finalizing other sections.
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -99,8 +99,20 @@
 
 template <class ELFT> void OutputSection::finalize() {
   if ((this->Flags & SHF_LINK_ORDER) && !this->Sections.empty()) {
+    OutputSectionCommand *Cmd = Script->getCmd(this);
+    // Link order may be distributed across several InputSectionDescriptions
+    // but sort must consider them all at once.
+    std::vector<InputSection **> ScriptSections;
+    std::vector<InputSection *> Sections;
+    for (BaseCommand *Base : Cmd->Commands)
+      if (auto *ISD = dyn_cast<InputSectionDescription>(Base))
+        for (InputSection *&IS : ISD->Sections) {
+          ScriptSections.push_back(&IS);
+          Sections.push_back(IS);
+        }
     std::sort(Sections.begin(), Sections.end(), compareByFilePosition);
-    assignOffsets();
+    for (int I = 0, N = Sections.size(); I < N; ++I)
+      *ScriptSections[I] = Sections[I];
 
     // We must preserve the link order dependency of sections with the
     // SHF_LINK_ORDER flag. The dependency is indicated by the sh_link field. We


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