ELF: Respect MEMORY command when specified without a SECTIONS command.

[pcc]

Summary

We were previously ignoring the MEMORY command unless SECTIONS was also
specified. Fix it.

[MaskRay]

lld/test/ELF/linkerscript/memory-no-sections.test

2

Add a file-level comment about the purpose.

lld/ELF/Writer.cpp

 private:
   void copyLocalSymbols();
   void addSectionSymbols();
   void sortSections();
   void resolveShfLinkOrder();
   void finalizeAddressDependentContent();
   void optimizeBasicBlockJumps();
   void sortInputSections();
+  void sortOrphanSections();
   void finalizeSections();
   void checkExecuteOnly();
   void setReservedSymbolSections();
 
   SmallVector<PhdrEntry *, 0> createPhdrs(Partition &part);
   void addPhdrForSection(Partition &part, unsigned shType, unsigned pType,
                          unsigned pFlags);
   void assignFileOffsets();
std::stable_sort(
         compareSections);
   }
 
   // Process INSERT commands and update output section attributes. From this
   // point onwards the order of script->sectionCommands is fixed.
   script->processInsertCommands();
   script->adjustOutputSections();
 
-  if (!script->hasSectionsCommand)
-    return;
+  if (script->hasSectionsCommand)
+    sortOrphanSections();
 
+  script->adjustSectionsAfterSorting();
+}
+
+template <class ELFT> void Writer<ELFT>::sortOrphanSections() {
   // Orphan sections are sections present in the input files which are
   // not explicitly placed into the output file by the linker script.
   //
   // The sections in the linker script are already in the correct
   // order. We have to figuere out where to insert the orphan
   // sections.
   //
   // The order of the sections in the script is arbitrary and may not agree with
while (nonScriptI != e) {
     // and insert them with one rotate.
     unsigned rank = orphan->sortRank;
     auto end = std::find_if(nonScriptI + 1, e, [=](SectionCommand *cmd) {
       return cast<OutputDesc>(cmd)->osec.sortRank != rank;
     });
     std::rotate(pos, nonScriptI, end);
     nonScriptI = end;
   }
-
-  script->adjustSectionsAfterSorting();
 }
 
 static bool compareByFilePosition(InputSection *a, InputSection *b) {
   InputSection *la = a->flags & SHF_LINK_ORDER ? a->getLinkOrderDep() : nullptr;
   InputSection *lb = b->flags & SHF_LINK_ORDER ? b->getLinkOrderDep() : nullptr;
   // SHF_LINK_ORDER sections with non-zero sh_link are ordered before
   // non-SHF_LINK_ORDER sections and SHF_LINK_ORDER sections with zero sh_link.
   if (!la || !lb)

lld/test/ELF/linkerscript/memory-no-sections.test

+REQUIRES: x86
+
+## Check that we respect MEMORY commands in linker scripts without
+## SECTIONS commands.
+
+RUN: split-file %s %ts
+RUN: llvm-mc -filetype=obj -triple=x86_64 %ts/asm.s -o %t.o
+RUN: ld.lld -o %t -T %ts/script %t.o
+RUN: llvm-readelf -S %t | FileCheck %s
+
+CHECK: .text             PROGBITS        0000000000001000
+CHECK: .data             PROGBITS        0000000010000000
+
+#--- script
+
+MEMORY {
+  flash (rx!w): org = 0x1000, len = 0x3000
+  ram (rwx): org = 0x10000000, len = 0x1000
+}
+
+#--- asm.s
+
+.text
+.byte 1
+.data
+.byte 2