[llvm] r360678 - DWARF v5: emit DW_AT_addr_base if DW_AT_low_pc references .debug_addr

[Fangrui Song via llvm-commits]

Author: maskray
Date: Tue May 14 07:37:26 2019
New Revision: 360678

URL: http://llvm.org/viewvc/llvm-project?rev=360678&view=rev
Log:
DWARF v5: emit DW_AT_addr_base if DW_AT_low_pc references .debug_addr

The condition !AddrPool.empty() is tested before attachRangesOrLowHighPC(), which may add an entry to AddrPool. We emit DW_AT_low_pc (DW_FORM_addrx) but may incorrectly omit DW_AT_addr_base for LineTablesOnly. This can be easily reproduced:

clang -gdwarf-5 -gmlt -c a.cc

Fix this by moving !AddrPool.empty() below.

This was discovered while investigating an lld crash (fixed by D61889) on such object files: ld.lld --gdb-index a.o

Reviewed By: probinson

Differential Revision: https://reviews.llvm.org/D61891

Added:
    llvm/trunk/test/DebugInfo/Generic/line-table-addrx.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
    llvm/trunk/test/DebugInfo/X86/convert-debugloc.ll
    llvm/trunk/test/DebugInfo/X86/fission-ranges.ll

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=360678&r1=360677&r2=360678&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Tue May 14 07:37:26 2019
@@ -901,13 +901,6 @@ void DwarfDebug::finalizeModuleInfo() {
     // ranges for all subprogram DIEs for mach-o.
     DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;
 
-    // We don't keep track of which addresses are used in which CU so this
-    // is a bit pessimistic under LTO.
-    if (!AddrPool.isEmpty() &&
-        (getDwarfVersion() >= 5 ||
-         (SkCU && !empty(TheCU.getUnitDie().children()))))
-      U.addAddrTableBase();
-
     if (unsigned NumRanges = TheCU.getRanges().size()) {
       if (NumRanges > 1 && useRangesSection())
         // A DW_AT_low_pc attribute may also be specified in combination with
@@ -920,6 +913,13 @@ void DwarfDebug::finalizeModuleInfo() {
       U.attachRangesOrLowHighPC(U.getUnitDie(), TheCU.takeRanges());
     }
 
+    // We don't keep track of which addresses are used in which CU so this
+    // is a bit pessimistic under LTO.
+    if (!AddrPool.isEmpty() &&
+        (getDwarfVersion() >= 5 ||
+         (SkCU && !empty(TheCU.getUnitDie().children()))))
+      U.addAddrTableBase();
+
     if (getDwarfVersion() >= 5) {
       if (U.hasRangeLists())
         U.addRnglistsBase();

Added: llvm/trunk/test/DebugInfo/Generic/line-table-addrx.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/line-table-addrx.ll?rev=360678&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/Generic/line-table-addrx.ll (added)
+++ llvm/trunk/test/DebugInfo/Generic/line-table-addrx.ll Tue May 14 07:37:26 2019
@@ -0,0 +1,21 @@
+; RUN: %llc_dwarf -filetype=obj %s -o - | llvm-dwarfdump -v -debug-info - | FileCheck %s
+
+;; In DWARF v5, emit DW_AT_addr_base as DW_AT_addr_base is used for DW_AT_low_pc.
+; CHECK: DW_AT_low_pc [DW_FORM_addrx]
+; CHECK: DW_AT_addr_base
+
+define i64 @foo() !dbg !7 {
+entry:
+  ret i64 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, emissionKind: LineTablesOnly, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "a.cc", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!7 = distinct !DISubprogram(name: "a", scope: !1, file: !1, line: 22, type: !8, scopeLine: 22, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !2)

Modified: llvm/trunk/test/DebugInfo/X86/convert-debugloc.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/convert-debugloc.ll?rev=360678&r1=360677&r2=360678&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/convert-debugloc.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/convert-debugloc.ll Tue May 14 07:37:26 2019
@@ -11,9 +11,9 @@
 ; DW5-CHECK-NEXT:               DW_AT_str_offsets_base	(0x00000008)
 ; DW5-CHECK-NEXT:               DW_AT_stmt_list	(0x00000000)
 ; DW5-CHECK-NEXT:               DW_AT_comp_dir {{.*}}
-; DW5-CHECK-NEXT:               DW_AT_addr_base	(0x00000008)
 ; DW5-CHECK-NEXT:               DW_AT_low_pc	(0x0000000000000000)
 ; DW5-CHECK-NEXT:               DW_AT_high_pc	(0x0000000000000007)
+; DW5-CHECK-NEXT:               DW_AT_addr_base	(0x00000008)
 ; DW5-CHECK-NEXT:               DW_AT_loclists_base	(0x0000000c)
 ; DW5-CHECK-EMPTY:
 ; DW5-CHECK-NEXT: 0x00000027:   DW_TAG_base_type

Modified: llvm/trunk/test/DebugInfo/X86/fission-ranges.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/fission-ranges.ll?rev=360678&r1=360677&r2=360678&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/fission-ranges.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/fission-ranges.ll Tue May 14 07:37:26 2019
@@ -12,6 +12,8 @@
 ; CHECK-NEXT: DW_AT_GNU_dwo_name
 ; CHECK-NEXT: DW_AT_GNU_dwo_id
 ; CHECK-NEXT: DW_AT_GNU_ranges_base
+; CHECK-NEXT: DW_AT_low_pc
+; CHECK-NEXT: DW_AT_high_pc
 ; CHECK-NEXT: DW_AT_GNU_addr_base [DW_FORM_sec_offset]                   (0x00000000)
 
 ; CHECK: .debug_info.dwo contents: