[llvm] Update call graph ELF section type. (llvm#164461)

Make call graph section to have a dedicated type instead of the generic
progbits type.

Author: Prabhuk

llvm/docs/Extensions.rst

@@ -601,6 +601,35 @@ sees fit (generally the section that would provide the best locality).
 
 .. _CFI jump table: https://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#forward-edge-cfi-for-indirect-function-calls
 
+``SHT_LLVM_CALL_GRAPH`` Section (Call Graph)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This section is used to store the call graph. It has a type of
+``SHT_LLVM_CALL_GRAPH`` (0x6fff4c0f). Details of call graph section layout
+are described in :doc:`CallGraphSection`.
+
+For example:
+
+.. code-block:: gas
+
+  .section  ".llvm.callgraph","",@llvm_call_graph
+  .byte   0
+  .byte   7
+  .quad   .Lball
+  .quad   0
+  .byte   3
+  .quad   foo
+  .quad   bar
+  .quad   baz
+  .byte   3
+  .quad   4524972987496481828
+  .quad   3498816979441845844
+  .quad   8646233951371320954
+
+This indicates that ``ball`` calls ``foo``, ``bar`` and ``baz`` directly;
+``ball`` indirectly calls functions whose types are ``4524972987496481828``,
+``3498816979441845844`` and ``8646233951371320954``.
+
 CodeView-Dependent
 ------------------
 

llvm/include/llvm/BinaryFormat/ELF.h

@@ -1185,6 +1185,7 @@ enum : unsigned {
   SHT_LLVM_LTO = 0x6fff4c0c,                // .llvm.lto for fat LTO.
   SHT_LLVM_JT_SIZES = 0x6fff4c0d,           // LLVM jump tables sizes.
   SHT_LLVM_CFI_JUMP_TABLE = 0x6fff4c0e,     // LLVM CFI jump table.
+  SHT_LLVM_CALL_GRAPH = 0x6fff4c0f,         // LLVM Call Graph Section.
   // Android's experimental support for SHT_RELR sections.
   // https://android.googlesource.com/platform/bionic/+/b7feec74547f84559a1467aca02708ff61346d2a/libc/include/elf.h#512
   SHT_ANDROID_RELR = 0x6fffff00,   // Relocation entries; only offsets.

llvm/lib/MC/MCAsmInfoELF.cpp

@@ -197,6 +197,8 @@ void MCAsmInfoELF::printSwitchToSection(const MCSection &Section,
     OS << "llvm_jt_sizes";
   else if (Sec.Type == ELF::SHT_LLVM_CFI_JUMP_TABLE)
     OS << "llvm_cfi_jump_table";
+  else if (Sec.Type == ELF::SHT_LLVM_CALL_GRAPH)
+    OS << "llvm_call_graph";
   else
     OS << "0x" << Twine::utohexstr(Sec.Type);
 

llvm/lib/MC/MCObjectFileInfo.cpp

@@ -554,7 +554,7 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
       Ctx->getELFSection(".sframe", ELF::SHT_GNU_SFRAME, ELF::SHF_ALLOC);
 
   CallGraphSection =
-      Ctx->getELFSection(".llvm.callgraph", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".llvm.callgraph", ELF::SHT_LLVM_CALL_GRAPH, 0);
 
   StackSizesSection = Ctx->getELFSection(".stack_sizes", ELF::SHT_PROGBITS, 0);
 
@@ -1172,7 +1172,7 @@ MCObjectFileInfo::getCallGraphSection(const MCSection &TextSec) const {
   }
 
   return Ctx->getELFSection(
-      ".llvm.callgraph", ELF::SHT_PROGBITS, Flags, 0, GroupName,
+      ".llvm.callgraph", ELF::SHT_LLVM_CALL_GRAPH, Flags, 0, GroupName,
       /*IsComdat=*/true, ElfSec.getUniqueID(),
       static_cast<const MCSymbolELF *>(TextSec.getBeginSymbol()));
 }

llvm/lib/MC/MCParser/ELFAsmParser.cpp

@@ -637,6 +637,8 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {
       Type = ELF::SHT_LLVM_JT_SIZES;
     else if (TypeName == "llvm_cfi_jump_table")
       Type = ELF::SHT_LLVM_CFI_JUMP_TABLE;
+    else if (TypeName == "llvm_call_graph")
+      Type = ELF::SHT_LLVM_CALL_GRAPH;
     else if (TypeName.getAsInteger(0, Type))
       return TokError("unknown section type");
   }

llvm/lib/Object/ELF.cpp

@@ -322,6 +322,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LTO);
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_JT_SIZES)
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CFI_JUMP_TABLE)
+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_SFRAME);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -744,6 +744,7 @@ void ScalarEnumerationTraits<ELFYAML::ELF_SHT>::enumeration(
   ECase(SHT_LLVM_BB_ADDR_MAP);
   ECase(SHT_LLVM_OFFLOADING);
   ECase(SHT_LLVM_LTO);
+  ECase(SHT_LLVM_CALL_GRAPH);
   ECase(SHT_GNU_SFRAME);
   ECase(SHT_GNU_ATTRIBUTES);
   ECase(SHT_GNU_HASH);

llvm/test/CodeGen/ARM/call-graph-section-addrtaken.ll

@@ -27,7 +27,7 @@ entry:
 !1 = !{i64 0, !"_ZTSFivE.generalized"}
 !2 = !{i64 0, !"_ZTSFviE.generalized"}
 
-; CHECK: .section .llvm.callgraph,"o",%progbits,.text
+; CHECK: .section .llvm.callgraph,"o",%llvm_call_graph,.text
 ;; Version
 ; CHECK-NEXT: .byte   0
 ;; Flags -- Potential indirect target so LSB is set to 1. Other bits are 0.

llvm/test/CodeGen/ARM/call-graph-section-assembly.ll

@@ -36,7 +36,7 @@ entry:
 !4 = !{!5}
 !5 = !{i64 0, !"_ZTSFPvS_E.generalized"}
 
-; CHECK: .section .llvm.callgraph,"o",%progbits,.text
+; CHECK: .section .llvm.callgraph,"o",%llvm_call_graph,.text
 ;; Version
 ; CHECK-NEXT: .byte   0
 ;; Flags

llvm/test/CodeGen/X86/call-graph-section-addrtaken.ll

@@ -27,7 +27,7 @@ entry:
 !1 = !{i64 0, !"_ZTSFivE.generalized"}
 !2 = !{i64 0, !"_ZTSFviE.generalized"}
 
-; CHECK: .section .llvm.callgraph,"o",@progbits,.text
+; CHECK: .section .llvm.callgraph,"o",@llvm_call_graph,.text
 ;; Version
 ; CHECK-NEXT: .byte   0
 ;; Flags -- Potential indirect target so LSB is set to 1. Other bits are 0.