[DebugInfo] Bug 41152 - Improve dumping of empty location expressions

Fixes PR41152 (https://bugs.llvm.org/show_bug.cgi?id=41152).

Reviewed by: jhenderson, dblaikie, SouraVX

Differential Revision: https://reviews.llvm.org/D103502

llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp

@@ -326,6 +326,9 @@ void DWARFExpression::print(raw_ostream &OS, DIDumpOptions DumpOpts,
                             bool IsEH) const {
   uint32_t EntryValExprSize = 0;
   uint64_t EntryValStartOffset = 0;
+  if (Data.getData().empty())
+    OS << "<empty>";
+
   for (auto &Op : *this) {
     if (!Op.print(OS, DumpOpts, this, RegInfo, U, IsEH)) {
       uint64_t FailOffset = Op.getEndOffset();

llvm/test/DebugInfo/X86/dwarf-empty-expression.s

@@ -0,0 +1,23 @@
+# RUN: llvm-mc -triple x86_64-unknown-linux -filetype=obj %s -o %t.o
+# RUN: llvm-dwarfdump %t.o --debug-loclists | FileCheck %s
+
+# CHECK: DW_LLE_offset_pair     (0x0000000000000000, 0x0000000000000000): <empty>
+
+.Lfunc_begin0:
+.Ltmp1:
+.section .debug_loclists, "",@progbits
+        .long   .Ldebug_list_header_end0-.Ldebug_list_header_start0 # Length
+.Ldebug_list_header_start0:
+        .short  5                               # Version
+        .byte   8                               # Address size
+        .byte   0                               # Segment selector size
+        .long   1                               # Offset entry count
+.Lloclists_table_base0:
+        .long   .Ldebug_loc0-.Lloclists_table_base0
+.Ldebug_loc0:
+        .byte   4                               # DW_LLE_offset_pair
+        .uleb128 .Lfunc_begin0-.Lfunc_begin0    #   starting offset
+        .uleb128 .Ltmp1-.Lfunc_begin0           #   ending offset
+        .byte   0                               ### empty
+        .byte   0                               # DW_LLE_end_of_list
+.Ldebug_list_header_end0:

llvm/test/MC/X86/dwarf-size-field-overflow.test

@@ -6,7 +6,7 @@
 #
 # CHECK:       0x0000004d:       DW_TAG_formal_parameter
 # CHECK-NEXT:      DW_AT_location   (0x00000000
-# CHECK-NEXT:           [0x0000000000000000,  0x0000000000000008): )
+# CHECK-NEXT:           [0x0000000000000000,  0x0000000000000008): <empty>)
 # CHECK-NEXT:      DW_AT_name   ("self")
 
 import sys