[ELF] Linkerscript: implement ALIGNOF

[evgeny777]

Summary

Implemented ALIGNOF + some refactoring done to script methods invocation.

[evgeny777]

Rebased + minor code cleanups

[evgeny777]

Changed file name

[ruiu]

I'm not sure if this refactoring improves things overall. Can you please factor it out and make this patch focus on one thing, which is the ALIGNOF support?

[evgeny777]

Addressed review comments

[ruiu]

LGTM

lld/trunk/ELF/LinkerScript.h

struct PhdrsCommand {
   bool HasPhdrs;
   unsigned Flags;
 };
 
 class LinkerScriptBase {
 public:
   virtual uint64_t getOutputSectionAddress(StringRef Name) = 0;
   virtual uint64_t getOutputSectionSize(StringRef Name) = 0;
+  virtual uint64_t getOutputSectionAlign(StringRef Name) = 0;
   virtual uint64_t getHeaderSize() = 0;
   virtual uint64_t getSymbolValue(StringRef S) = 0;
 };
 
 // ScriptConfiguration holds linker script parse results.
 struct ScriptConfiguration {
   // Used to create symbol assignments outside SECTIONS command.
   std::vector<std::unique_ptr<SymbolAssignment>> Assignments;
public:
   ArrayRef<uint8_t> getFiller(StringRef Name);
   Expr getLma(StringRef Name);
   bool shouldKeep(InputSectionBase<ELFT> *S);
   void assignAddresses();
   int compareSections(StringRef A, StringRef B);
   bool hasPhdrsCommands();
   uint64_t getOutputSectionAddress(StringRef Name) override;
   uint64_t getOutputSectionSize(StringRef Name) override;
+  uint64_t getOutputSectionAlign(StringRef Name) override;
   uint64_t getHeaderSize() override;
   uint64_t getSymbolValue(StringRef S) override;
 
   std::vector<OutputSectionBase<ELFT> *> *OutputSections;
 
 private:
   std::vector<InputSectionBase<ELFT> *>
   getInputSections(const InputSectionDescription *);

lld/trunk/ELF/LinkerScript.cpp

 uint64_t LinkerScript<ELFT>::getOutputSectionSize(StringRef Name) {
   for (OutputSectionBase<ELFT> *Sec : *OutputSections)
     if (Sec->getName() == Name)
       return Sec->getSize();
   error("undefined section " + Name);
   return 0;
 }
 
+template <class ELFT>
+uint64_t LinkerScript<ELFT>::getOutputSectionAlign(StringRef Name) {
+  for (OutputSectionBase<ELFT> *Sec : *OutputSections)
+    if (Sec->getName() == Name)
+      return Sec->getAlignment();
+  error("undefined section " + Name);
+  return 0;
+}
+
 template <class ELFT> uint64_t LinkerScript<ELFT>::getHeaderSize() {
   return Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
 }
 
 template <class ELFT> uint64_t LinkerScript<ELFT>::getSymbolValue(StringRef S) {
   if (SymbolBody *B = Symtab<ELFT>::X->find(S))
     return B->getVA<ELFT>();
   error("symbol not found: " + S);
if (Tok == "DATA_SEGMENT_RELRO_END") {
     return [](uint64_t Dot) { return alignTo(Dot, Target->PageSize); };
   }
   if (Tok == "SIZEOF") {
     expect("(");
     StringRef Name = next();
     expect(")");
     return [=](uint64_t Dot) { return ScriptBase->getOutputSectionSize(Name); };
   }
+  if (Tok == "ALIGNOF") {
+    expect("(");
+    StringRef Name = next();
+    expect(")");
+    return
+        [=](uint64_t Dot) { return ScriptBase->getOutputSectionAlign(Name); };
+  }
   if (Tok == "SIZEOF_HEADERS")
     return [=](uint64_t Dot) { return ScriptBase->getHeaderSize(); };
 
   // Tok is a literal number.
   uint64_t V;
   if (readInteger(Tok, V))
     return [=](uint64_t Dot) { return V; };
 

lld/trunk/test/ELF/linkerscript/alignof.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+
+# RUN: echo "SECTIONS { \
+# RUN:   .aaa         : { *(.aaa) } \
+# RUN:   .bbb         : { *(.bbb) } \
+# RUN:   .ccc         : { *(.ccc) } \
+# RUN:   _aaa = ALIGNOF(.aaa); \
+# RUN:   _bbb = ALIGNOF(.bbb); \
+# RUN:   _ccc = ALIGNOF(.ccc); \
+# RUN: }" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -t %t1 | FileCheck %s
+# CHECK:      SYMBOL TABLE:
+# CHECK:      0000000000000008         *ABS*     00000000 _aaa
+# CHECK-NEXT: 0000000000000010         *ABS*     00000000 _bbb
+# CHECK-NEXT: 0000000000000020         *ABS*     00000000 _ccc
+
+## Check that we error out if trying to get alignment of
+## section that does not exist.
+# RUN: echo "SECTIONS { \
+# RUN:   _aaa = ALIGNOF(.foo); \
+# RUN: }" > %t.script
+# RUN: not ld.lld -o %t1 --script %t.script %t 2>&1 \
+# RUN:  | FileCheck -check-prefix=ERR %s
+# ERR: undefined section .foo
+.global _start
+_start:
+ nop
+
+.section .aaa,"a"
+ .align 8
+ .quad 0
+
+.section .bbb,"a"
+ .align 16
+ .quad 0
+
+.section .ccc,"a"
+ .align 32
+ .quad 0