Debug Info: Support address space attributes on rvalue references.

[aprantl]

Summary

DWARF5, 2.12 20ff says that

Any debugging information entry representing a pointer or reference type [may have a DW_AT_address_class attribute]

The existing code (https://reviews.llvm.org/D29670) seems to take a quite literal interpretation of that wording. I don't see a reason why an rvalue reference isn't a reference type in the spirit of that paragraph. This patch allows rvalue references to also have address spaces.

Let me know if I'm missing something.

rdar://problem/50511483

[bjope]

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

799 ↗

(On Diff #198379)

nit: I figure the comment can be updated to say something like this:

"If DWARF address space value is other than None, add it. The IR verifier checks that DWARF address space only exists for pointer or reference types."

[probinson]

+1 to Bjorn's comment.
The DWARF spec says address class is also allowed on a "subroutine or subroutine type" do we allow generating code into nonzero address spaces?

[aprantl]

In D61625#1493532, @probinson wrote:

+1 to Bjorn's comment.
The DWARF spec says address class is also allowed on a "subroutine or subroutine type" do we allow generating code into nonzero address spaces?

I don't know, but I wouldn't be surprised if we didn't. IIUC address spaces are used for heterogeneous computing to identify, e.g., which memory lives on a GPU vs the main memory, and in that case the code for the GPU would be generated by a different backend anyway, so the distinction is probably less useful?

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

void DwarfUnit::constructTypeDIE(DIE &Buffer, const DIDerivedType *DTy) {
 
   if (Tag == dwarf::DW_TAG_ptr_to_member_type)
     addDIEEntry(Buffer, dwarf::DW_AT_containing_type,
                 *getOrCreateTypeDIE(cast<DIDerivedType>(DTy)->getClassType()));
   // Add source line info if available and TyDesc is not a forward declaration.
   if (!DTy->isForwardDecl())
     addSourceLine(Buffer, DTy);
 
-  // If DWARF address space value is other than None, add it for pointer and
-  // reference types as DW_AT_address_class.
-  if (DTy->getDWARFAddressSpace() && (Tag == dwarf::DW_TAG_pointer_type ||
-                                      Tag == dwarf::DW_TAG_reference_type))
+  // If DWARF address space value is other than None, add it.  The IR
+  // verifier checks that DWARF address space only exists for pointer
+  // or reference types.
+  if (DTy->getDWARFAddressSpace())
     addUInt(Buffer, dwarf::DW_AT_address_class, dwarf::DW_FORM_data4,
             DTy->getDWARFAddressSpace().getValue());
 }
 
 void DwarfUnit::constructSubprogramArguments(DIE &Buffer, DITypeRefArray Args) {
   for (unsigned i = 1, N = Args.size(); i < N; ++i) {
     const DIType *Ty = Args[i];
     if (!Ty) {

llvm/trunk/lib/IR/Verifier.cpp

void Verifier::visitDIDerivedType(const DIDerivedType &N) {
   }
 
   AssertDI(isScope(N.getRawScope()), "invalid scope", &N, N.getRawScope());
   AssertDI(isType(N.getRawBaseType()), "invalid base type", &N,
            N.getRawBaseType());
 
   if (N.getDWARFAddressSpace()) {
     AssertDI(N.getTag() == dwarf::DW_TAG_pointer_type ||
-                 N.getTag() == dwarf::DW_TAG_reference_type,
+                 N.getTag() == dwarf::DW_TAG_reference_type ||
+                 N.getTag() == dwarf::DW_TAG_rvalue_reference_type,
              "DWARF address space only applies to pointer or reference types",
              &N);
   }
 }
 
 /// Detect mutually exclusive flags.
 static bool hasConflictingReferenceFlags(unsigned Flags) {
   return ((Flags & DINode::FlagLValueReference) &&

llvm/trunk/test/DebugInfo/Generic/address_space_rvalue.ll

+; REQUIRES: object-emission
+
+; RUN: %llc_dwarf -O0 -filetype=obj < %s | llvm-dwarfdump -debug-info - | FileCheck %s
+
+; This nonsensical example tests that address spaces for rvalue
+; references are produced.
+
+; CHECK: DW_TAG_rvalue_reference_type
+; CHECK-NOT: DW_TAG
+; CHECK: DW_AT_address_class  (0x00000001)
+
+@y = global i8* null, align 8, !dbg !0
+
+!llvm.dbg.cu = !{!5}
+!llvm.module.flags = !{!8, !9}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = !DIGlobalVariable(name: "x", scope: null, file: !2, line: 2, type: !3, isLocal: false, isDefinition: true)
+!2 = !DIFile(filename: "test.cpp", directory: "/")
+!3 = !DIDerivedType(tag: DW_TAG_rvalue_reference_type, baseType: !4, size: 64, align: 64, dwarfAddressSpace: 1)
+!4 = !DIBasicType(name: "long long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!5 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !2, producer: "clang version 3.5.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !6, retainedTypes: !6, globals: !7, imports: !6)
+!6 = !{}
+!7 = !{!0}
+!8 = !{i32 2, !"Dwarf Version", i32 5}
+!9 = !{i32 1, !"Debug Info Version", i32 3}

llvm/trunk/test/Verifier/diderivedtype-address-space-rvalue-reference-type.ll

-; RUN: not opt -S < %s 2>&1 | FileCheck %s
+; RUN: opt -S < %s 2>&1 | FileCheck %s
 
 !named = !{!0, !1}
 !0 = !DIBasicType(tag: DW_TAG_base_type, name: "name", size: 1, align: 2, encoding: DW_ATE_unsigned_char)
-; CHECK: DWARF address space only applies to pointer or reference types
+; CHECK: !DIDerivedType(tag: DW_TAG_rvalue_reference_type, {{.*}}, dwarfAddressSpace: 1)
 !1 = !DIDerivedType(tag: DW_TAG_rvalue_reference_type, baseType: !0, size: 32, align: 32, dwarfAddressSpace: 1)