[PATCH] D123434: [lld-macho][nfc] Simplify unwind section lookup

[Jez Ng via Phabricator via llvm-commits]

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Previously, we stored a pointer from the ObjFile to its compact unwind
section in order to avoid iterating over the file's sections a second
time. However, given the small number of sections (not subsections) per
file, this caching was really quite unnecessary. We will soon do lookups
for more sections (such as the `__eh_frame` section), so let's simplify
the code first.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123434

Files:
  lld/MachO/InputFiles.cpp
  lld/MachO/InputFiles.h


Index: lld/MachO/InputFiles.h
===================================================================
--- lld/MachO/InputFiles.h
+++ lld/MachO/InputFiles.h
@@ -151,8 +151,6 @@
   std::vector<CallGraphEntry> callGraph;
 
 private:
-  Section *compactUnwindSection = nullptr;
-
   template <class LP> void parseLazy();
   template <class SectionHeader> void parseSections(ArrayRef<SectionHeader>);
   template <class LP>
@@ -165,7 +163,7 @@
   void parseRelocations(ArrayRef<SectionHeader> sectionHeaders,
                         const SectionHeader &, Section &);
   void parseDebugInfo();
-  void registerCompactUnwind();
+  void registerCompactUnwind(Section &compactUnwindSection);
 };
 
 // command-line -sectcreate file
Index: lld/MachO/InputFiles.cpp
===================================================================
--- lld/MachO/InputFiles.cpp
+++ lld/MachO/InputFiles.cpp
@@ -343,8 +343,6 @@
       section.subsections.push_back({0, isec});
     } else if (auto recordSize = getRecordSize(segname, name)) {
       splitRecords(*recordSize);
-      if (name == section_names::compactUnwind)
-        compactUnwindSection = §ion;
     } else if (segname == segment_names::llvm) {
       if (config->callGraphProfileSort && name == section_names::cgProfile)
         checkError(parseCallGraph(data, callGraph));
@@ -916,8 +914,19 @@
       parseRelocations(sectionHeaders, sectionHeaders[i], *sections[i]);
 
   parseDebugInfo();
+
+  Section *ehFrameSection = nullptr;
+  Section *compactUnwindSection = nullptr;
+  for (Section *sec : sections) {
+    Section **s = StringSwitch<Section **>(sec->name)
+                      .Case(section_names::compactUnwind, &compactUnwindSection)
+                      .Case(section_names::ehFrame, &ehFrameSection)
+                      .Default(nullptr);
+    if (s)
+      *s = sec;
+  }
   if (compactUnwindSection)
-    registerCompactUnwind();
+    registerCompactUnwind(*compactUnwindSection);
 }
 
 template <class LP> void ObjFile::parseLazy() {
@@ -980,8 +989,8 @@
 }
 
 // Create pointers from symbols to their associated compact unwind entries.
-void ObjFile::registerCompactUnwind() {
-  for (const Subsection &subsection : compactUnwindSection->subsections) {
+void ObjFile::registerCompactUnwind(Section &compactUnwindSection) {
+  for (const Subsection &subsection : compactUnwindSection.subsections) {
     ConcatInputSection *isec = cast<ConcatInputSection>(subsection.isec);
     // Hack!! Since each CUE contains a different function address, if ICF
     // operated naively and compared the entire contents of each CUE, entries


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