[PowerPC] Support @h modifier

This adds necessary infrastructure to support the @h modifier.
Note that all required relocation types were already present
(and unused).

This patch provides support for using @h in the assembler;
it would also be possible to now use this feature in code
generated by the compiler, but this is not done yet.

llvm-svn: 184548
diff --git a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index 752b6f7..964f272 100644
--- a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -546,7 +546,7 @@
 }
 
 /// Extract @l/@ha modifier from expression.  Recursively scan
-/// the expression and check for VK_PPC_LO / VK_PPC_HA
+/// the expression and check for VK_PPC_LO/HI/HA
 /// symbol variants.  If all symbols with modifier use the same
 /// variant, return the corresponding PPCMCExpr::VariantKind,
 /// and a modified expression using the default symbol variant.
@@ -569,6 +569,9 @@
     case MCSymbolRefExpr::VK_PPC_LO:
       Variant = PPCMCExpr::VK_PPC_LO;
       break;
+    case MCSymbolRefExpr::VK_PPC_HI:
+      Variant = PPCMCExpr::VK_PPC_HI;
+      break;
     case MCSymbolRefExpr::VK_PPC_HA:
       Variant = PPCMCExpr::VK_PPC_HA;
       break;