[ObjectYAML] Support for DW_FORM_implicit_const DWARF5 form

This patch adds support to the DWARF YAML reader and writer for the new DWARF5 abbreviation form, DW_FORM_implicit_const.

The attribute was added in r291599.

llvm-svn: 297091
diff --git a/llvm/lib/ObjectYAML/DWARFYAML.cpp b/llvm/lib/ObjectYAML/DWARFYAML.cpp
index f55d59a..2a8cdd5 100644
--- a/llvm/lib/ObjectYAML/DWARFYAML.cpp
+++ b/llvm/lib/ObjectYAML/DWARFYAML.cpp
@@ -54,6 +54,8 @@
     IO &IO, DWARFYAML::AttributeAbbrev &AttAbbrev) {
   IO.mapRequired("Attribute", AttAbbrev.Attribute);
   IO.mapRequired("Form", AttAbbrev.Form);
+  if(AttAbbrev.Form == dwarf::DW_FORM_implicit_const)
+    IO.mapRequired("Value", AttAbbrev.Value);
 }
 
 void MappingTraits<DWARFYAML::ARangeDescriptor>::mapping(