From 43519798b48a7c83c2aa78d714e9c40af15b0b85 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Wed, 4 Sep 2019 09:35:32 +0000
Subject: [PATCH] [llvm-objcopy] Add objcopy::elf::Object::allocSections to
 simplify loops on SHF_ALLOC sections

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D67142

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@370860 91177308-0d34-0410-b5e6-96231b3b80d8
---
 tools/llvm-objcopy/ELF/Object.cpp | 28 ++++++++--------------------
 tools/llvm-objcopy/ELF/Object.h   | 15 +++++++++++++--
 2 files changed, 21 insertions(+), 22 deletions(-)

diff --git a/tools/llvm-objcopy/ELF/Object.cpp b/tools/llvm-objcopy/ELF/Object.cpp
index f2b606d28d6..44e6bf54b28 100644
--- a/tools/llvm-objcopy/ELF/Object.cpp
+++ b/tools/llvm-objcopy/ELF/Object.cpp
@@ -2101,23 +2101,19 @@ template <class ELFT> Error ELFWriter<ELFT>::finalize() {
 }
 
 Error BinaryWriter::write() {
-  for (const SectionBase &Sec : Obj.sections())
-    if (Sec.Flags & SHF_ALLOC)
-      Sec.accept(*SecWriter);
+  for (const SectionBase &Sec : Obj.allocSections())
+    Sec.accept(*SecWriter);
   return Buf.commit();
 }
 
 Error BinaryWriter::finalize() {
-  // TODO: Create a filter range to construct OrderedSegments from so that this
-  // code can be deduped with assignOffsets above. This should also solve the
-  // todo below for LayoutSections.
   // We need a temporary list of segments that has a special order to it
   // so that we know that anytime ->ParentSegment is set that segment has
   // already had it's offset properly set. We only want to consider the segments
   // that will affect layout of allocated sections so we only add those.
   std::vector<Segment *> OrderedSegments;
-  for (const SectionBase &Sec : Obj.sections())
-    if ((Sec.Flags & SHF_ALLOC) != 0 && Sec.ParentSegment != nullptr)
+  for (const SectionBase &Sec : Obj.allocSections())
+    if (Sec.ParentSegment != nullptr)
       OrderedSegments.push_back(Sec.ParentSegment);
 
   // For binary output, we're going to use physical addresses instead of
@@ -2161,24 +2157,16 @@ Error BinaryWriter::finalize() {
     }
   }
 
-  // TODO: generalize layoutSections to take a range. Pass a special range
-  // constructed from an iterator that skips values for which a predicate does
-  // not hold. Then pass such a range to layoutSections instead of constructing
-  // AllocatedSections here.
-  std::vector<SectionBase *> AllocatedSections;
-  for (SectionBase &Sec : Obj.sections())
-    if (Sec.Flags & SHF_ALLOC)
-      AllocatedSections.push_back(&Sec);
-  layoutSections(make_pointee_range(AllocatedSections), Offset);
+  layoutSections(Obj.allocSections(), Offset);
 
   // Now that every section has been laid out we just need to compute the total
   // file size. This might not be the same as the offset returned by
   // layoutSections, because we want to truncate the last segment to the end of
   // its last section, to match GNU objcopy's behaviour.
   TotalSize = 0;
-  for (SectionBase *Sec : AllocatedSections)
-    if (Sec->Type != SHT_NOBITS)
-      TotalSize = std::max(TotalSize, Sec->Offset + Sec->Size);
+  for (const SectionBase &Sec : Obj.allocSections())
+    if (Sec.Type != SHT_NOBITS)
+      TotalSize = std::max(TotalSize, Sec.Offset + Sec.Size);
 
   if (Error E = Buf.allocate(TotalSize))
     return E;
diff --git a/tools/llvm-objcopy/ELF/Object.h b/tools/llvm-objcopy/ELF/Object.h
index 42844dae3b4..70be6bed422 100644
--- a/tools/llvm-objcopy/ELF/Object.h
+++ b/tools/llvm-objcopy/ELF/Object.h
@@ -57,8 +57,8 @@ class SectionTableRef {
       : Sections(Secs) {}
   SectionTableRef(const SectionTableRef &) = default;
 
-  iterator begin() { return iterator(Sections.data()); }
-  iterator end() { return iterator(Sections.data() + Sections.size()); }
+  iterator begin() const { return iterator(Sections.data()); }
+  iterator end() const { return iterator(Sections.data() + Sections.size()); }
   size_t size() const { return Sections.size(); }
 
   SectionBase *getSection(uint32_t Index, Twine ErrMsg);
@@ -994,6 +994,10 @@ class Object {
   std::vector<SegPtr> Segments;
   std::vector<SecPtr> RemovedSections;
 
+  static bool sectionIsAlloc(const SectionBase &Sec) {
+    return Sec.Flags & ELF::SHF_ALLOC;
+  };
+
 public:
   template <class T>
   using Range = iterator_range<
@@ -1032,6 +1036,13 @@ class Object {
   ConstRange<SectionBase> sections() const {
     return make_pointee_range(Sections);
   }
+  iterator_range<
+      filter_iterator<pointee_iterator<std::vector<SecPtr>::const_iterator>,
+                      decltype(&sectionIsAlloc)>>
+  allocSections() const {
+    return make_filter_range(make_pointee_range(Sections), sectionIsAlloc);
+  }
+
   SectionBase *findSection(StringRef Name) {
     auto SecIt =
         find_if(Sections, [&](const SecPtr &Sec) { return Sec->Name == Name; });