[MC] Add assembler support for .cg_profile.

Object FIle Representation
At codegen time this is emitted into the ELF file a pair of symbol indices and a weight. In assembly it looks like:

.cg_profile a, b, 32
.cg_profile freq, a, 11
.cg_profile freq, b, 20

When writing an ELF file these are put into a SHT_LLVM_CALL_GRAPH_PROFILE (0x6fff4c02) section as (uint32_t, uint32_t, uint64_t) tuples as (from symbol index, to symbol index, weight).

Differential Revision: https://reviews.llvm.org/D44965

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333823 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 57 insertions, 0 deletions

diff --git a/tools/llvm-readobj/ELFDumper.cpp b/tools/llvm-readobj/ELFDumper.cpp
index 6ca28e273cc..993d4aaa81e 100644
--- a/tools/llvm-readobj/ELFDumper.cpp
+++ b/tools/llvm-readobj/ELFDumper.cpp
@@ -100,6 +100,7 @@ using namespace ELF;
   using Elf_Vernaux = typename ELFT::Vernaux;                                  \
   using Elf_Verdef = typename ELFT::Verdef;                                    \
   using Elf_Verdaux = typename ELFT::Verdaux;                                  \
+  using Elf_CGProfile = typename ELFT::CGProfile;                              \
   using uintX_t = typename ELFT::uint;
 
 namespace {
@@ -164,6 +165,8 @@ public:
 
   void printHashHistogram() override;
 
+  void printCGProfile() override;
+
   void printNotes() override;
 
   void printELFLinkerOptions() override;
@@ -210,6 +213,7 @@ private:
   const Elf_Hash *HashTable = nullptr;
   const Elf_GnuHash *GnuHashTable = nullptr;
   const Elf_Shdr *DotSymtabSec = nullptr;
+  const Elf_Shdr *DotCGProfileSec = nullptr;
   StringRef DynSymtabName;
   ArrayRef<Elf_Word> ShndxTable;
 
@@ -257,9 +261,11 @@ public:
   void getSectionNameIndex(const Elf_Sym *Symbol, const Elf_Sym *FirstSym,
                            StringRef &SectionName,
                            unsigned &SectionIndex) const;
+  StringRef getStaticSymbolName(uint32_t Index) const;
 
   void printSymbolsHelper(bool IsDynamic) const;
   const Elf_Shdr *getDotSymtabSec() const { return DotSymtabSec; }
+  const Elf_Shdr *getDotCGProfileSec() const { return DotCGProfileSec; }
   ArrayRef<Elf_Word> getShndxTable() const { return ShndxTable; }
   StringRef getDynamicStringTable() const { return DynamicStringTable; }
   const DynRegionInfo &getDynRelRegion() const { return DynRelRegion; }
@@ -319,6 +325,7 @@ public:
                            bool IsDynamic) = 0;
   virtual void printProgramHeaders(const ELFFile<ELFT> *Obj) = 0;
   virtual void printHashHistogram(const ELFFile<ELFT> *Obj) = 0;
+  virtual void printCGProfile(const ELFFile<ELFT> *Obj) = 0;
   virtual void printNotes(const ELFFile<ELFT> *Obj) = 0;
   virtual void printELFLinkerOptions(const ELFFile<ELFT> *Obj) = 0;
   virtual void printMipsGOT(const MipsGOTParser<ELFT> &Parser) = 0;
@@ -349,6 +356,7 @@ public:
                           size_t Offset) override;
   void printProgramHeaders(const ELFO *Obj) override;
   void printHashHistogram(const ELFFile<ELFT> *Obj) override;
+  void printCGProfile(const ELFFile<ELFT> *Obj) override;
   void printNotes(const ELFFile<ELFT> *Obj) override;
   void printELFLinkerOptions(const ELFFile<ELFT> *Obj) override;
   void printMipsGOT(const MipsGOTParser<ELFT> &Parser) override;
@@ -410,6 +418,7 @@ public:
   void printDynamicRelocations(const ELFO *Obj) override;
   void printProgramHeaders(const ELFO *Obj) override;
   void printHashHistogram(const ELFFile<ELFT> *Obj) override;
+  void printCGProfile(const ELFFile<ELFT> *Obj) override;
   void printNotes(const ELFFile<ELFT> *Obj) override;
   void printELFLinkerOptions(const ELFFile<ELFT> *Obj) override;
   void printMipsGOT(const MipsGOTParser<ELFT> &Parser) override;
@@ -737,6 +746,16 @@ StringRef ELFDumper<ELFT>::getSymbolVersion(StringRef StrTab,
 }
 
 template <typename ELFT>
+StringRef ELFDumper<ELFT>::getStaticSymbolName(uint32_t Index) const {
+  StringRef StrTable = unwrapOrError(Obj->getStringTableForSymtab(*DotSymtabSec));
+  Elf_Sym_Range Syms = unwrapOrError(Obj->symbols(DotSymtabSec));
+  if (Index >= Syms.size())
+    reportError("Invalid symbol index");
+  const Elf_Sym *Sym = &Syms[Index];
+  return unwrapOrError(Sym->getName(StrTable));
+}
+
+template <typename ELFT>
 std::string ELFDumper<ELFT>::getFullSymbolName(const Elf_Sym *Symbol,
                                                StringRef StrTable,
                                                bool IsDynamic) const {
@@ -1390,6 +1409,10 @@ ELFDumper<ELFT>::ELFDumper(const ELFFile<ELFT> *Obj, ScopedPrinter &Writer)
         reportError("Multiple SHT_GNU_verneed");
       dot_gnu_version_r_sec = &Sec;
       break;
+    case ELF::SHT_LLVM_CALL_GRAPH_PROFILE:
+      if (DotCGProfileSec != nullptr)
+        reportError("Multiple .note.llvm.cgprofile");
+      DotCGProfileSec = &Sec;
     }
   }
 
@@ -1534,6 +1557,10 @@ template <class ELFT> void ELFDumper<ELFT>::printHashHistogram() {
   ELFDumperStyle->printHashHistogram(Obj);
 }
 
+template <class ELFT> void ELFDumper<ELFT>::printCGProfile() {
+  ELFDumperStyle->printCGProfile(Obj);
+}
+
 template <class ELFT> void ELFDumper<ELFT>::printNotes() {
   ELFDumperStyle->printNotes(Obj);
 }
@@ -2721,6 +2748,8 @@ std::string getSectionTypeString(unsigned Arch, unsigned Type) {
     return "LLVM_ODRTAB";
   case SHT_LLVM_LINKER_OPTIONS:
     return "LLVM_LINKER_OPTIONS";
+  case SHT_LLVM_CALL_GRAPH_PROFILE:
+    return "LLVM_CALL_GRAPH_PROFILE";
   // FIXME: Parse processor specific GNU attributes
   case SHT_GNU_ATTRIBUTES:
     return "ATTRIBUTES";
@@ -3374,6 +3403,11 @@ void GNUStyle<ELFT>::printHashHistogram(const ELFFile<ELFT> *Obj) {
   }
 }
 
+template <class ELFT>
+void GNUStyle<ELFT>::printCGProfile(const ELFFile<ELFT> *Obj) {
+  OS << "GNUStyle::printCGProfile not implemented\n";
+}
+
 static std::string getGNUNoteTypeName(const uint32_t NT) {
   static const struct {
     uint32_t ID;
@@ -4138,6 +4172,24 @@ void LLVMStyle<ELFT>::printHashHistogram(const ELFFile<ELFT> *Obj) {
 }
 
 template <class ELFT>
+void LLVMStyle<ELFT>::printCGProfile(const ELFFile<ELFT> *Obj) {
+  ListScope L(W, "CGProfile");
+  if (!this->dumper()->getDotCGProfileSec())
+    return;
+  auto CGProfile =
+      unwrapOrError(Obj->template getSectionContentsAsArray<Elf_CGProfile>(
+          this->dumper()->getDotCGProfileSec()));
+  for (const Elf_CGProfile &CGPE : CGProfile) {
+    DictScope D(W, "CGProfileEntry");
+    W.printNumber("From", this->dumper()->getStaticSymbolName(CGPE.cgp_from),
+                  CGPE.cgp_from);
+    W.printNumber("To", this->dumper()->getStaticSymbolName(CGPE.cgp_to),
+                  CGPE.cgp_to);
+    W.printNumber("Weight", CGPE.cgp_weight);
+  }
+}
+
+template <class ELFT>
 void LLVMStyle<ELFT>::printNotes(const ELFFile<ELFT> *Obj) {
   W.startLine() << "printNotes not implemented!\n";
 }
diff --git a/tools/llvm-readobj/ObjDumper.h b/tools/llvm-readobj/ObjDumper.h
index 2bf4dfe5a40..e13646588e7 100644
--- a/tools/llvm-readobj/ObjDumper.h
+++ b/tools/llvm-readobj/ObjDumper.h
@@ -47,6 +47,7 @@ public:
   virtual void printVersionInfo() {}
   virtual void printGroupSections() {}
   virtual void printHashHistogram() {}
+  virtual void printCGProfile() {}
   virtual void printNotes() {}
   virtual void printELFLinkerOptions() {}
 
diff --git a/tools/llvm-readobj/llvm-readobj.cpp b/tools/llvm-readobj/llvm-readobj.cpp
index 4b8a1b32471..f871dc90950 100644
--- a/tools/llvm-readobj/llvm-readobj.cpp
+++ b/tools/llvm-readobj/llvm-readobj.cpp
@@ -284,6 +284,8 @@ namespace opts {
   cl::alias HashHistogramShort("I", cl::desc("Alias for -elf-hash-histogram"),
                                cl::aliasopt(HashHistogram));
 
+  cl::opt<bool> CGProfile("elf-cg-profile", cl::desc("Display callgraph profile section"));
+
   cl::opt<OutputStyleTy>
       Output("elf-output-style", cl::desc("Specify ELF dump style"),
              cl::values(clEnumVal(LLVM, "LLVM default style"),
@@ -441,6 +443,8 @@ static void dumpObject(const ObjectFile *Obj, ScopedPrinter &Writer) {
       Dumper->printGroupSections();
     if (opts::HashHistogram)
       Dumper->printHashHistogram();
+    if (opts::CGProfile)
+      Dumper->printCGProfile();
     if (opts::Notes)
       Dumper->printNotes();
   }