[llvm] r343062 - [DebugInfo] Do not generate address info for removed debug labels.

[Hsiangkai Wang via llvm-commits]

Author: hsiangkai
Date: Tue Sep 25 21:19:23 2018
New Revision: 343062

URL: http://llvm.org/viewvc/llvm-project?rev=343062&view=rev
Log:
[DebugInfo] Do not generate address info for removed debug labels.

In some senario, LLVM will remove llvm.dbg.labels in IR. For example,
when the labels are in unreachable blocks, these labels will not
be generated in LLVM IR. In the case, these debug labels will have
address zero as their address. It is not legal address for debugger to
set breakpoints or query sources. So, the patch inhibits the address info
(DW_AT_low_pc) of removed labels.

Fix build failed in BuildBot, clang-stage1-cmake-RA-incremental, on macOS.

Differential Revision: https://reviews.llvm.org/D51908

Added:
    llvm/trunk/test/DebugInfo/X86/debug-label-unreached.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp?rev=343062&r1=343061&r2=343062&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp Tue Sep 25 21:19:23 2018
@@ -865,10 +865,9 @@ void DwarfCompileUnit::finishEntityDefin
       llvm_unreachable("DbgEntity must be DbgVariable or DbgLabel.");
   }
 
-  if (Label) {
-    const MCSymbol *Sym = Label->getSymbol();
-    addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
-  }
+  if (Label)
+    if (const auto *Sym = Label->getSymbol())
+      addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
 }
 
 DbgEntity *DwarfCompileUnit::getExistingAbstractEntity(const DINode *Node) {

Added: llvm/trunk/test/DebugInfo/X86/debug-label-unreached.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/debug-label-unreached.ll?rev=343062&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/debug-label-unreached.ll (added)
+++ llvm/trunk/test/DebugInfo/X86/debug-label-unreached.ll Tue Sep 25 21:19:23 2018
@@ -0,0 +1,39 @@
+; Test unreachable llvm.dbg.label
+;
+; RUN: llc -filetype=obj -split-dwarf-file debug.dwo -mtriple=x86_64-unknown-linux-gnu -o - %s | llvm-dwarfdump -v - | FileCheck %s
+;
+; CHECK: .debug_info.dwo contents:
+; CHECK: DW_TAG_label
+; CHECK-NEXT: DW_AT_name {{.*}}"done"
+; CHECK-NOT: {{DW_TAG|NULL}}
+; 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)