Initial TOC support for PowerPC64 object creation

This patch adds initial PPC64 TOC MC object creation using the small mcmodel
(a single 64K TOC) adding the some TOC relocations (R_PPC64_TOC,
R_PPC64_TOC16, and R_PPC64_TOC16DS).

The addition of 'undefinedExplicitRelSym' hook on 'MCELFObjectTargetWriter'
is meant to avoid the creation of an unreferenced ".TOC." symbol (used in
the .odp creation) as well to set the R_PPC64_TOC relocation target as the
temporary ".TOC." symbol. On PPC64 ABI, the R_PPC64_TOC relocation should
not point to any symbol.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166677 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index 1744738..87ecb13 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -29,9 +29,14 @@
   case FK_Data_1:
   case FK_Data_2:
   case FK_Data_4:
+  case FK_Data_8:
+  case PPC::fixup_ppc_toc:
     return Value;
+  case PPC::fixup_ppc_lo14:
+  case PPC::fixup_ppc_toc16_ds:
+    return (Value & 0xffff) << 2;
   case PPC::fixup_ppc_brcond14:
-    return Value & 0x3ffc;
+    return Value & 0xfffc;
   case PPC::fixup_ppc_br24:
     return Value & 0x3fffffc;
 #if 0
@@ -41,6 +46,7 @@
   case PPC::fixup_ppc_ha16:
     return ((Value >> 16) + ((Value & 0x8000) ? 1 : 0)) & 0xffff;
   case PPC::fixup_ppc_lo16:
+  case PPC::fixup_ppc_toc16:
     return Value & 0xffff;
   }
 }
@@ -72,7 +78,10 @@
       { "fixup_ppc_brcond14",    16,     14,   MCFixupKindInfo::FKF_IsPCRel },
       { "fixup_ppc_lo16",        16,     16,   0 },
       { "fixup_ppc_ha16",        16,     16,   0 },
-      { "fixup_ppc_lo14",        16,     14,   0 }
+      { "fixup_ppc_lo14",        16,     14,   0 },
+      { "fixup_ppc_toc",          0,     64,   0 },
+      { "fixup_ppc_toc16",       16,     16,   0 },
+      { "fixup_ppc_toc16_ds",    16,     14,   0 }
     };
 
     if (Kind < FirstTargetFixupKind)