[PowerPC][AIX] Adds support for writing the data section in object files

Adds support for generating the XCOFF data section in object files for global variables with initialization.

Merged aix-xcoff-common.ll into aix-xcoff-data.ll.

Changed variable name charr to chrarray in the test case to test if readobj works with 8-character names.

Authored by: xingxue

Reviewers: hubert.reinterptrtcast, sfertile, jasonliu, daltenty, Xiangling_L.

Reviewed by: hubert.reinterpretcast, sfertile, daltenty.

Subscribers: DiggerLin, Wuzish, nemanjai, hiraditya, MaskRay, jsji, shchenz, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67125

Author: jasonliudev

llvm/lib/MC/XCOFFObjectWriter.cpp

@@ -158,15 +158,17 @@ class XCOFFObjectWriter : public MCObjectWriter {
   // the sections. Should have one for each set of csects that get mapped into
   // the same section and get handled in a 'similar' way.
   CsectGroup ProgramCodeCsects{CsectGroup::LabelDefSupported, {}};
+  CsectGroup DataCsects{CsectGroup::LabelDefSupported, {}};
   CsectGroup BSSCsects{CsectGroup::LabelDefUnsupported, {}};
 
   // The Predefined sections.
   Section Text;
+  Section Data;
   Section BSS;
 
   // All the XCOFF sections, in the order they will appear in the section header
   // table.
-  std::array<Section *const, 2> Sections{{&Text, &BSS}};
+  std::array<Section *const, 3> Sections{{&Text, &Data, &BSS}};
 
   CsectGroup &getCsectGroup(const MCSectionXCOFF *MCSec);
 
@@ -224,6 +226,8 @@ XCOFFObjectWriter::XCOFFObjectWriter(
       Strings(StringTableBuilder::XCOFF),
       Text(".text", XCOFF::STYP_TEXT, /* IsVirtual */ false,
            CsectGroups{&ProgramCodeCsects}),
+      Data(".data", XCOFF::STYP_DATA, /* IsVirtual */ false,
+           CsectGroups{&DataCsects}),
       BSS(".bss", XCOFF::STYP_BSS, /* IsVirtual */ true,
           CsectGroups{&BSSCsects}) {}
 
@@ -251,6 +255,9 @@ CsectGroup &XCOFFObjectWriter::getCsectGroup(const MCSectionXCOFF *MCSec) {
     if (XCOFF::XTY_CM == MCSec->getCSectType())
       return BSSCsects;
 
+    if (XCOFF::XTY_SD == MCSec->getCSectType())
+      return DataCsects;
+
     report_fatal_error("Unhandled mapping of read-write csect to section.");
   case XCOFF::XMC_BS:
     assert(XCOFF::XTY_CM == MCSec->getCSectType() &&