[PATCH] D51908: [DebugInfo] Do not generate address info for removed labels.

[Hsiangkai Wang via Phabricator via llvm-commits]

HsiangKai updated this revision to Diff 165952.
HsiangKai retitled this revision from "[DebugInfo] Do not generate debug info for removed labels." to "[DebugInfo] Do not generate address info for removed labels.".
HsiangKai edited the summary of this revision.
HsiangKai added a comment.

I think that all of us agreed that it is a bug in GDB to crash when setting breakpoints on labels without address information. So, I updated the patch to generate label debug information without address even when the labels are removed after optimizations.


Repository:
  rL LLVM

https://reviews.llvm.org/D51908

Files:
  lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
  test/DebugInfo/Generic/debug-label-unreached.ll


Index: test/DebugInfo/Generic/debug-label-unreached.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/Generic/debug-label-unreached.ll
@@ -0,0 +1,38 @@
+; Test unreachable llvm.dbg.label
+;
+; RUN: llc -filetype=obj -split-dwarf-file debug.dwo -o - %s | llvm-dwarfdump -v - | FileCheck %s
+;
+; CHECK: .debug_info.dwo contents:
+; CHECK: DW_TAG_label
+; CHECK-NEXT: DW_AT_name {{.*}}"done"
+; CHECK: DW_AT_low_pc
+; CHECK: DW_TAG_label
+; CHECK-NEXT: DW_AT_name {{.*}}"removed"
+; CHECK-NOT: DW_AT_low_pc
+source_filename = "debug-label-unreached.c"
+
+define dso_local i32 @foo(i32 %a, i32 %b) !dbg !8 {
+entry:
+  %sum = add nsw i32 %a, %b, !dbg !12
+  call void @llvm.dbg.label(metadata !11), !dbg !12
+  ret i32 %sum, !dbg !13
+}
+
+declare void @llvm.dbg.label(metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "debug-label-unreached.c", directory: "./")
+!2 = !{}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7}
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 8, type: !5, isLocal: false, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !9)
+!9 = !{!10, !11}
+!10 = !DILabel(scope: !8, name: "removed", file: !1, line: 11)
+!11 = !DILabel(scope: !8, name: "done", file: !1, line: 13)
+!12 = !DILocation(line: 13, column: 1, scope: !8)
+!13 = !DILocation(line: 14, column: 5, scope: !8)
Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -867,7 +867,8 @@
 
   if (Label) {
     const MCSymbol *Sym = Label->getSymbol();
-    addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
+    if (Sym)
+      addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
   }
 }
 


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