Add the ability to get a signed integer attribute from a DWARFDebugInfoEntry.

[clayborg]

Summary

Trying to keep things smaller. This will be needed by an upcoming DWARF generator patch, but this is small and self contained.

[dblaikie]

Trying to keep things smaller. This will be needed by an upcoming DWARF generator patch, but this is small and self contained.

I /really/ appreciate the effort to keep patches small - it helps everyone (faster to review (good for you and reviewers), easier to revert or investigate when looking for regressions, etc). But the converse of that - is that we don't generally commit dead code (that's why it's great to find an existing use case that could be improved by a refactoring/introduction of a new piece of functionality, etc).

If there's an existing piece of the codebase that could benefit from this API (reduce code duplication, etc) that you could add such a use to this patch, it'd be great to review/commit it separately like this, otherwise it may have to be grouped with anotehr commit - or at least a unit test?

[clayborg]

Yeah, can't do a unit test until I get the DWARF generator in. I will bundle it with that then.

include/llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h

public:
   const char *getAttributeValueAsString(const DWARFUnit *U, 
                                         dwarf::Attribute Attr,
                                         const char *FailValue) const;
 
   uint64_t getAttributeValueAsAddress(const DWARFUnit *U, 
                                       dwarf::Attribute Attr,
                                       uint64_t FailValue) const;
 
+  int64_t getAttributeValueAsSignedConstant(const DWARFUnit *U,
+                                            dwarf::Attribute Attr,
+                                            int64_t FailValue) const;
+
   uint64_t getAttributeValueAsUnsignedConstant(const DWARFUnit *U,
                                                dwarf::Attribute Attr,
                                                uint64_t FailValue) const;
 
   uint64_t getAttributeValueAsReference(const DWARFUnit *U, 
                                         dwarf::Attribute Attr,
                                         uint64_t FailValue) const;
 

lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp

uint64_t DWARFDebugInfoEntryMinimal::getAttributeValueAsAddress(
     uint64_t FailValue) const {
   DWARFFormValue FormValue;
   if (!getAttributeValue(U, Attr, FormValue))
     return FailValue;
   Optional<uint64_t> Result = FormValue.getAsAddress();
   return Result.hasValue() ? Result.getValue() : FailValue;
 }
 
+int64_t DWARFDebugInfoEntryMinimal::getAttributeValueAsSignedConstant(
+    const DWARFUnit *U, dwarf::Attribute Attr, int64_t FailValue) const {
+  DWARFFormValue FormValue;
+  if (!getAttributeValue(U, Attr, FormValue))
+    return FailValue;
+  Optional<int64_t> Result = FormValue.getAsSignedConstant();
+  return Result.hasValue() ? Result.getValue() : FailValue;
+}
+
 uint64_t DWARFDebugInfoEntryMinimal::getAttributeValueAsUnsignedConstant(
     const DWARFUnit *U, dwarf::Attribute Attr, 
     uint64_t FailValue) const {
   DWARFFormValue FormValue;
   if (!getAttributeValue(U, Attr, FormValue))
     return FailValue;
   Optional<uint64_t> Result = FormValue.getAsUnsignedConstant();
   return Result.hasValue() ? Result.getValue() : FailValue;