[lld] r246496 - Start allocating space for common symbols.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Mon Aug 31 17:07:18 2015
New Revision: 246496

URL: http://llvm.org/viewvc/llvm-project?rev=246496&view=rev
Log:
Start allocating space for common symbols.

Modified:
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/elf2/symbols.s

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=246496&r1=246495&r2=246496&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Aug 31 17:07:18 2015
@@ -60,6 +60,7 @@ public:
 
   // Returns the size of the section in the output file.
   uintX_t getSize() { return Header.sh_size; }
+  void setSize(uintX_t Val) { Header.sh_size = Val; }
   uintX_t getFlags() { return Header.sh_flags; }
   uintX_t getFileOff() { return Header.sh_offset; }
   uintX_t getAlign() { return Header.sh_addralign; }
@@ -149,6 +150,7 @@ template <class ELFT> class Writer {
 public:
   typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
+  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
   Writer(SymbolTable *T)
       : SymTable(*T), StringTable(T->getStringBuilder()) {}
   void run();
@@ -397,6 +399,18 @@ template <bool Is64Bits> struct DenseMap
 // Create output section objects and add them to OutputSections.
 template <class ELFT> void Writer<ELFT>::createSections() {
   SmallDenseMap<SectionKey<ELFT::Is64Bits>, OutputSection<ELFT> *> Map;
+  auto getSection = [&](StringRef Name, uint32_t sh_type,
+                        uintX_t sh_flags) -> OutputSection<ELFT> * {
+    SectionKey<ELFT::Is64Bits> Key{Name, sh_type, sh_flags};
+    OutputSection<ELFT> *&Sec = Map[Key];
+    if (!Sec) {
+      Sec = new (CAlloc.Allocate())
+          OutputSection<ELFT>(Key.Name, Key.sh_type, Key.sh_flags);
+      addOutputSection(Sec);
+    }
+    return Sec;
+  };
+
   const SymbolTable &Symtab = SymTable.getSymTable();
   for (const std::unique_ptr<ObjectFileBase> &FileB : Symtab.ObjectFiles) {
     auto &File = cast<ObjectFile<ELFT>>(*FileB);
@@ -404,17 +418,27 @@ template <class ELFT> void Writer<ELFT>:
       if (!C)
         continue;
       const Elf_Shdr *H = C->getSectionHdr();
-      SectionKey<ELFT::Is64Bits> Key{C->getSectionName(), H->sh_type,
-                                     H->sh_flags};
-      OutputSection<ELFT> *&Sec = Map[Key];
-      if (!Sec) {
-        Sec = new (CAlloc.Allocate())
-            OutputSection<ELFT>(Key.Name, Key.sh_type, Key.sh_flags);
-        addOutputSection(Sec);
-      }
+      OutputSection<ELFT> *Sec =
+          getSection(C->getSectionName(), H->sh_type, H->sh_flags);
       Sec->addChunk(C);
     }
   }
+
+  OutputSection<ELFT> *BSSSec =
+      getSection(".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
+  uintX_t Off = BSSSec->getSize();
+  // FIXME: Try to avoid the extra walk over all global symbols.
+  for (auto &P : Symtab.getSymbols()) {
+    SymbolBody *Body = P.second->Body;
+    auto *C = dyn_cast<DefinedCommon<ELFT>>(Body);
+    if (!C)
+      continue;
+    const Elf_Sym &Sym = C->Sym;
+    uintX_t Align = Sym.st_value;
+    Off = RoundUpToAlignment(Off, Align);
+    Off += Sym.st_size;
+  }
+  BSSSec->setSize(Off);
 }
 
 template <bool Is64Bits>

Modified: lld/trunk/test/elf2/symbols.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/symbols.s?rev=246496&r1=246495&r2=246496&view=diff
==============================================================================
--- lld/trunk/test/elf2/symbols.s (original)
+++ lld/trunk/test/elf2/symbols.s Mon Aug 31 17:07:18 2015
@@ -41,12 +41,22 @@ abs = 0x123
 // CHECK-NEXT: ]
 // CHECK-NEXT: Address: 0x1000
 
+// CHECK:      Name: .bss (14)
+// CHECK-NEXT: Type: SHT_NOBITS (0x8)
+// CHECK-NEXT: Flags [ (0x3)
+// CHECK-NEXT:   SHF_ALLOC (0x2)
+// CHECK-NEXT:   SHF_WRITE (0x1)
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x1004
+// CHECK-NEXT: Offset: 0x1004
+// CHECK-NEXT: Size: 4
+
 // CHECK:      Name: foobar
 // CHECK-NEXT: Type: SHT_NOBITS
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x1004
+// CHECK-NEXT: Address: 0x1008
 
 // CHECK:      Symbols [
 // CHECK-NEXT:   Symbol {
@@ -105,7 +115,7 @@ abs = 0x123
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed
-// CHECK-NEXT:     Value: 0x1004
+// CHECK-NEXT:     Value: 0x1008
 // CHECK-NEXT:     Size: 0
 // CHECK-NEXT:     Binding: Global (0x1)
 // CHECK-NEXT:     Type: None
@@ -114,7 +124,7 @@ abs = 0x123
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed3
-// CHECK-NEXT:     Value: 0x100C
+// CHECK-NEXT:     Value: 0x1010
 // CHECK-NEXT:     Size: 4
 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None
@@ -123,7 +133,7 @@ abs = 0x123
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed2
-// CHECK-NEXT:     Value: 0x1008
+// CHECK-NEXT:     Value: 0x100C
 // CHECK-NEXT:     Size: 0
 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None