Prevent DW_AT_abstract_origin from being emitted twice for the same subprogram

[aprantl]

Summary

This fixes a bug where DW_AT_abstract_origin is being emitted twice for the same subprogram if a function is both inlined and emitted in the same translation unit, by restoring the pre-r266446 behavior.

[dblaikie]

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

525

Do we need the extra data structure? How did this code work before the CU<>Subprogram inversion?

test/DebugInfo/X86/abstract_origin.ll

3

Simplify the test case - remove the parameters and return value and use attribute((alwaysinline)) (I never remember how to spell that attribute name..)

Should be simple enough to just use:

void f1();
__attribute__((alwaysinline)) void f2() {
  f1();
}
void f3() {
  f2();
}

Even at -O0 it should produce the same/desired code (an inlined function and a non-inline version).

5

Unintentional blank line here?

[aprantl]

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

525

Ok, this is a really good question. There is no evidence for this code existing prior to the CU<>Subprogram inversion and the test suite still passes after removing it.

[aaboud]

LGTM.
You may commit once you fix the test as David suggested and use the attribute((always_inline)).

Regards,
Amjad

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

525

This change seems to be correct.
Inline (DW_TAG_inlined_subroutine) and abstract (DW_TAG_subprogram) entries are filled once they are created.
The only entry that is filled when it is finalizing (finishing) subprograms is the concrete (DW_TAG_subprogram) entry, and this entry exists only if there is code generated for it.
So, the first loop is enough to handle this entry.

[aprantl]

thanks! r269103.

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

if (AbsVar && AbsVar->getDIE()) {
       Unit->addDIEEntry(*VariableDie, dwarf::DW_AT_abstract_origin,
                         *AbsVar->getDIE());
     } else
       Unit->applyVariableAttributes(*Var, *VariableDie);
   }
 }
 
 void DwarfDebug::finishSubprogramDefinitions() {
   for (auto &F : MMI->getModule()->functions())
     if (auto *SP = F.getSubprogram())
       if (ProcessedSPNodes.count(SP) &&
           SP->getUnit()->getEmissionKind() != DICompileUnit::NoDebug)
         forBothCUs(*CUMap.lookup(SP->getUnit()), [&](DwarfCompileUnit &CU) {
           CU.finishSubprogramDefinition(SP);
         });
-  for (auto *AbsScope : LScopes.getAbstractScopesList())
-    if (auto *SP = dyn_cast<DISubprogram>(AbsScope->getScopeNode()))
-      if (ProcessedSPNodes.count(SP) &&
-          SP->getUnit()->getEmissionKind() != DICompileUnit::NoDebug)
-        forBothCUs(*CUMap.lookup(SP->getUnit()), [&](DwarfCompileUnit &CU) {
-          CU.finishSubprogramDefinition(SP);
-        });
 }
 
 void DwarfDebug::finalizeModuleInfo() {
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
 
   finishSubprogramDefinitions();
 
   finishVariableDefinitions();

test/DebugInfo/X86/abstract_origin.ll

+; RUN: %llc_dwarf -filetype=obj %s -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+; Generated at -O2 from:
+;   void f();
+;   __attribute__((always_inline)) void g() {
+;     f();
+;   }
+;   void h() {
+;     g();
+;   };
+; CHECK: DW_TAG_subprogram
+; CHECK:  DW_AT_abstract_origin {{.*}}"g"
+; CHECK-NOT:  DW_AT_abstract_origin {{.*}}"g"
+; CHECK: DW_TAG
+source_filename = "test.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+; Function Attrs: alwaysinline nounwind ssp uwtable
+define void @g() #0 !dbg !7 {
+entry:
+  tail call void (...) @f() #3, !dbg !10
+  ret void, !dbg !11
+}
+
+declare void @f(...)
+
+; Function Attrs: nounwind ssp uwtable
+define void @h() #2 !dbg !12 {
+entry:
+  tail call void (...) @f() #3, !dbg !13
+  ret void, !dbg !15
+}
+
+attributes #0 = { alwaysinline nounwind ssp uwtable }
+attributes #2 = { nounwind ssp uwtable }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "/Volumes/Data/llvm")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 2}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"PIC Level", i32 2}
+!6 = !{!"clang version 3.9.0 "}
+!7 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: true, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocation(line: 3, column: 3, scope: !7)
+!11 = !DILocation(line: 4, column: 1, scope: !7)
+!12 = distinct !DISubprogram(name: "h", scope: !1, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true, scopeLine: 5, isOptimized: true, unit: !0, variables: !2)
+!13 = !DILocation(line: 3, column: 3, scope: !7, inlinedAt: !14)
+!14 = distinct !DILocation(line: 6, column: 3, scope: !12)
+!15 = !DILocation(line: 7, column: 1, scope: !12)