[yaml2obj] - Teach tool to produce SHT_GROUP section with a custom type.

Currently, it is possible to use yaml2obj for producing SHT_GROUP sections
of type GRP_COMDAT. For LLD test case I need to produce an object with
a broken (different from GRP_COMDAT) type.

The patch teaches tool to do such things.

Differential revision: https://reviews.llvm.org/D50761

llvm-svn: 339764

test/tools/yaml2obj/elf-comdat-broken.yaml

@@ -0,0 +1,34 @@
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj -sections -elf-section-groups %t | FileCheck %s
+
+--- !ELF
+FileHeader:
+  Class:               ELFCLASS64
+  Data:                ELFDATA2LSB
+  Type:                ET_REL
+  Machine:             EM_X86_64
+Sections:
+  - Name:              .group
+    Type:              SHT_GROUP
+    Link:              .symtab
+    Info:              foo
+    Members:
+      - SectionOrType: 0xFF
+      - SectionOrType: 3
+Symbols:
+  Global:
+    - Name:            foo
+
+## Check we are able to produce SHT_GROUP section with a custom Type (0xFF).
+# CHECK:       Groups {
+# CHECK-NEXT:   Group {
+# CHECK-NEXT:     Name: .group
+# CHECK-NEXT:     Index: 1
+# CHECK-NEXT:     Link: 2
+# CHECK-NEXT:     Info: 1
+# CHECK-NEXT:     Type: COMDAT (0xFF)
+# CHECK-NEXT:     Signature: foo
+# CHECK-NEXT:     Section(s) in group [
+# CHECK-NEXT:       .strtab (3)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:   }

tools/yaml2obj/yaml2elf.cpp

@@ -537,7 +537,8 @@ bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
     unsigned int sectionIndex = 0;
     if (member.sectionNameOrType == "GRP_COMDAT")
       sectionIndex = llvm::ELF::GRP_COMDAT;
-    else if (SN2I.lookup(member.sectionNameOrType, sectionIndex)) {
+    else if (SN2I.lookup(member.sectionNameOrType, sectionIndex) &&
+             !to_integer(member.sectionNameOrType, sectionIndex)) {
       WithColor::error() << "Unknown section referenced: '"
                          << member.sectionNameOrType << "' at YAML section' "
                          << Section.Name << "\n";