[DebugInfo] Skip implicit_const attributes when dumping .debug_info. NFC.

When dumping .debug_info section we loop through all attributes mentioned in
.debug_abbrev section and dump values using DWARFFormValue::extractValue().
We need to skip implicit_const attributes here as their values are not
really located in .debug_info but directly in .debug_abbrev. This patch fixes
triggered assert() in DWARFFormValue::extractValue() caused by trying to
access implicit_const values from .debug_info.

llvm-svn: 296253
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 6949366..bdeff7b 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -329,6 +329,12 @@
         
         // Dump all data in the DIE for the attributes.
         for (const auto &AttrSpec : AbbrevDecl->attributes()) {
+          if (AttrSpec.Form == DW_FORM_implicit_const) {
+            // We are dumping .debug_info section ,
+            // implicit_const attribute values are not really stored here,
+            // but in .debug_abbrev section. So we just skip such attrs.
+            continue;
+          }
           dumpAttribute(OS, *this, &offset, AttrSpec.Attr, AttrSpec.Form,
                         Indent);
         }