[DebugInfo] Improvements to representation of enumeration types (PR36168)

This patch is the LLVM part of fixing the issues, described in
https://bugs.llvm.org/show_bug.cgi?id=36168

* The representation of enumerator values in the debug info metadata now
  contains a boolean flag isUnsigned, which determines how the bits of
  the value are interpreted.
* The DW_TAG_enumeration type DIE now always (for DWARF version >= 3)
  includes a DW_AT_type attribute, which refers to the underlying
  integer type, as suggested in DWARFv4 (5.7 Enumeration Type Entries).
* The debug info metadata for enumeration type contains (in flags)
  indication whether this is a C++11 "fixed enum".
* For C++11 enumeration with a fixed underlying type, the DIE also
  includes the DW_AT_enum_class attribute (for DWARF version >= 4).
* Encoding of enumerator constants uses DW_FORM_sdata for signed values
  and DW_FORM_udata for unsigned values, as suggested by DWARFv4 (7.5.4
  Attribute Encodings).

The changes should be backwards compatible:

* the isUnsigned attribute is optional and defaults to false.
* if the underlying type for the enumeration is not available, the
  enumerator values are considered signed.
* the FixedEnum flag defaults to clear.
* the bitcode format for DIEnumerator stores the unsigned flag bit #1 of
  the first record element, so the format does not change and the zero
  previously stored there is consistent with the false default for
  IsUnsigned.

Differential Revision: https://reviews.llvm.org/D42734

llvm-svn: 324489

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index ed3e28144d1..f9aca8afec9 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -233,9 +233,10 @@ DIMacroFile *DIBuilder::createTempMacroFile(DIMacroFile *Parent,
   return MF;
 }
 
-DIEnumerator *DIBuilder::createEnumerator(StringRef Name, int64_t Val) {
+DIEnumerator *DIBuilder::createEnumerator(StringRef Name, int64_t Val,
+                                          bool IsUnsigned) {
   assert(!Name.empty() && "Unable to create enumerator without name");
-  return DIEnumerator::get(VMContext, Val, Name);
+  return DIEnumerator::get(VMContext, Val, IsUnsigned, Name);
 }
 
 DIBasicType *DIBuilder::createUnspecifiedType(StringRef Name) {
@@ -492,11 +493,12 @@ DISubroutineType *DIBuilder::createSubroutineType(DITypeRefArray ParameterTypes,
 DICompositeType *DIBuilder::createEnumerationType(
     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
     uint64_t SizeInBits, uint32_t AlignInBits, DINodeArray Elements,
-    DIType *UnderlyingType, StringRef UniqueIdentifier) {
+    DIType *UnderlyingType, StringRef UniqueIdentifier, bool IsFixed) {
   auto *CTy = DICompositeType::get(
       VMContext, dwarf::DW_TAG_enumeration_type, Name, File, LineNumber,
       getNonCompileUnitScope(Scope), UnderlyingType, SizeInBits, AlignInBits, 0,
-      DINode::FlagZero, Elements, 0, nullptr, nullptr, UniqueIdentifier);
+      IsFixed ? DINode::FlagFixedEnum : DINode::FlagZero, Elements, 0, nullptr,
+      nullptr, UniqueIdentifier);
   AllEnumTypes.push_back(CTy);
   trackIfUnresolved(CTy);
   return CTy;