[llvm][dsymutil] Add DW_TAG_imported_declaration to accelerator table

**Summary**

After this patch, `dsymutil` will preserve `DW_TAG_imported_declarations`
entries in accelerator tables.

This allows consumers to resolve imported declarations even on
executables processsed through dsymutil.

This helps consumers, particularly LLDB's expression evaluator,
to resolve imported declarations (i.e., useful for namespace aliases
in C++) more efficiently.

**Testing**

* Added unit-test

Differential Revision: https://reviews.llvm.org/D143458

diff --git a/llvm/lib/DWARFLinker/DWARFLinker.cpp b/llvm/lib/DWARFLinker/DWARFLinker.cpp
index d302d61..6d6bd33 100644 (file)
--- a/llvm/lib/DWARFLinker/DWARFLinker.cpp
+++ b/llvm/lib/DWARFLinker/DWARFLinker.cpp
@@ -1589,6 +1589,8 @@ DIE *DWARFLinker::DIECloner::cloneDIE(const DWARFDie &InputDIE,
     if (!AttrInfo.Name)
       AttrInfo.Name = StringPool.getEntry("(anonymous namespace)");
     Unit.addNamespaceAccelerator(Die, AttrInfo.Name);
+  } else if (Tag == dwarf::DW_TAG_imported_declaration && AttrInfo.Name) {
+    Unit.addNamespaceAccelerator(Die, AttrInfo.Name);
   } else if (isTypeTag(Tag) && !AttrInfo.IsDeclaration &&
              getDIENames(InputDIE, AttrInfo, StringPool) && AttrInfo.Name &&
              AttrInfo.Name.getString()[0]) {

diff --git a/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test b/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test
new file mode 100644 (file)
index 0000000..1c59167
--- /dev/null
+++ b/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test
@@ -0,0 +1,47 @@
+RUN: dsymutil -accelerator=Dwarf %p/../Inputs/accel-imported-declaration.macho-arm64 -o %t.dwarf.dSYM
+RUN: dsymutil -accelerator=Apple %p/../Inputs/accel-imported-declaration.macho-arm64 -o %t.apple.dSYM
+
+RUN: llvm-dwarfdump -v %t.dwarf.dSYM | FileCheck %s -check-prefixes=DWARF,COMMON
+RUN: llvm-dwarfdump -v %t.apple.dSYM | FileCheck %s -check-prefixes=APPLE,COMMON
+
+COMMON: .debug_info contents
+COMMON: {{.*}}DW_TAG_namespace
+COMMON:   DW_AT_name{{.*}}"A"
+COMMON: {{.*}}DW_TAG_namespace
+COMMON:   DW_AT_name{{.*}}"B"
+COMMON: [[NAMESPACE:0x[0-9a-f]*]]:{{.*}}DW_TAG_namespace
+COMMON:   DW_AT_name{{.*}}"C"
+COMMON: [[IMPORTED:0x[0-9a-f]*]]:{{.*}}DW_TAG_imported_declaration
+COMMON:   DW_AT_name{{.*}}"C"
+
+DWARF:      .debug_names contents:
+DWARF:      Bucket 0 [
+DWARF-NEXT:   Name {{.*}} {
+DWARF-NEXT:     Hash: {{.*}}
+DWARF-NEXT:     String: {{.*}} "C"
+DWARF-NEXT:     Entry {{.*}} {
+DWARF-NEXT:       Abbrev: {{.*}}
+DWARF-NEXT:       Tag: DW_TAG_namespace
+DWARF-NEXT:       DW_IDX_die_offset: [[NAMESPACE]]
+DWARF-NEXT:     }
+DWARF-NEXT:     Entry {{.*}} {
+DWARF-NEXT:       Abbrev: {{.*}}
+DWARF-NEXT:       Tag: DW_TAG_imported_declaration
+DWARF-NEXT:       DW_IDX_die_offset: [[IMPORTED]]
+DWARF-NEXT:     }
+DWARF-NEXT:   }
+
+APPLE:      .apple_namespaces contents:
+APPLE:      Bucket 1 [
+APPLE-NEXT:   Hash {{.*}} [
+APPLE-NEXT:     Name@{{.*}} {
+APPLE-NEXT:       String: {{.*}} "C"
+APPLE-NEXT:       Data 0 [
+APPLE-NEXT:         Atom[0]: [[NAMESPACE]]
+APPLE-NEXT:       ]
+APPLE-NEXT:       Data 1 [
+APPLE-NEXT:         Atom[0]: [[IMPORTED]]
+APPLE-NEXT:       ]
+APPLE-NEXT:     }
+APPLE-NEXT:   ]
+APPLE-NEXT: ]

diff --git a/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.cpp b/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.cpp
new file mode 100644 (file)
index 0000000..2ee98ce
--- /dev/null
+++ b/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.cpp
@@ -0,0 +1,17 @@
+// Compiled on macOS using:
+// clang++ -c -std=c++2a -gdwarf-4 -O0 -o accel-imported-declaration.macho-arm64.o
+
+namespace A {
+namespace B {
+namespace C {
+int a = -1;
+} // namespace C
+} // namespace B
+
+namespace C = B::C;
+
+using namespace B::C;
+using B::C::a;
+} // namespace A
+
+int main() { return A::a; }

diff --git a/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.macho-arm64 b/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.macho-arm64
new file mode 100755 (executable)
index 0000000..691d553
Binary files /dev/null and b/llvm/test/tools/dsymutil/Inputs/accel-imported-declaration.macho-arm64 differ