[yaml2obj] - Allow producing ELFDATANONE ELFs

I need this to remove a binary from LLD test suite.
The patch also simplifies the code a bit.

Differential revision: https://reviews.llvm.org/D59082

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355591 91177308-0d34-0410-b5e6-96231b3b80d8

Author: George Rimar

lib/ObjectYAML/ELFYAML.cpp

@@ -232,8 +232,9 @@ void ScalarEnumerationTraits<ELFYAML::ELF_ELFCLASS>::enumeration(
 void ScalarEnumerationTraits<ELFYAML::ELF_ELFDATA>::enumeration(
     IO &IO, ELFYAML::ELF_ELFDATA &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X)
-  // Since the semantics of ELFDATANONE is "invalid", just don't accept it
-  // here.
+  // ELFDATANONE is an invalid data encoding, but we accept it because
+  // we want to be able to produce invalid binaries for the tests.
+  ECase(ELFDATANONE);
   ECase(ELFDATA2LSB);
   ECase(ELFDATA2MSB);
 #undef ECase

test/tools/yaml2obj/elf-header-elfdatanone.yaml

@@ -0,0 +1,15 @@
+## We have a YAML file describing an invalid data type.
+## Check we are able to produce the invalid binary.
+
+# RUN: yaml2obj %s -o %t.o
+
+## Check that EI_DATA field is ELFDATANONE(0)
+# RUN:   od -b %t.o +5 | FileCheck %s
+# CHECK: 0000005 000
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATANONE
+  Type:            ET_REL
+  Machine:         EM_X86_64

tools/yaml2obj/yaml2elf.cpp

@@ -207,8 +207,7 @@ void ELFState<ELFT>::initELFHeader(Elf_Ehdr &Header) {
   Header.e_ident[EI_MAG2] = 'L';
   Header.e_ident[EI_MAG3] = 'F';
   Header.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
-  bool IsLittleEndian = ELFT::TargetEndianness == support::little;
-  Header.e_ident[EI_DATA] = IsLittleEndian ? ELFDATA2LSB : ELFDATA2MSB;
+  Header.e_ident[EI_DATA] = Doc.Header.Data;
   Header.e_ident[EI_VERSION] = EV_CURRENT;
   Header.e_ident[EI_OSABI] = Doc.Header.OSABI;
   Header.e_ident[EI_ABIVERSION] = Doc.Header.ABIVersion;