DebugInfo: Ensure that all debug location scope chains from instructions within a function, lead to the function itself.

Originally committed in r211723, reverted in r211724 due to failure
cases found and fixed (ArgumentPromotion: r211872, Inlining: r212065),
committed again in r212085 and reverted again in r212089 after fixing
some other cases, such as debug info subprogram lists not keeping track
of the function they represent (r212128) and then short-circuiting
things like LiveDebugVariables that build LexicalScopes for functions
that might not have full debug info.

And again, I believe the invariant actually holds for some reasonable
amount of code (but I'll keep an eye on the buildbots and see what
happens... ).

Original commit message:

PR20038: DebugInfo: Inlined call sites where the caller has debug info
but the call itself has no debug location.

This situation does bad things when inlined, so I've fixed Clang not to
produce inlinable call sites without locations when the caller has debug
info (in the one case where I could find that this occurred). This
updates the PR20038 test case to be what clang now produces, and readds
the assertion that had to be removed due to this bug.

I've also beefed up the debug info verifier to help diagnose these
issues in the future, and I hope to add checks to the inliner to just
assert-fail if it encounters this situation. If, in the future, we
decide we have to cope with this situation, the right thing to do is
probably to just remove all the DebugLocs from the inlined instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212205 91177308-0d34-0410-b5e6-96231b3b80d8

Author: dwblaikie

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -788,8 +788,7 @@ void DwarfDebug::finishVariableDefinitions() {
   for (const auto &Var : ConcreteVariables) {
     DIE *VariableDie = Var->getDIE();
     // FIXME: There shouldn't be any variables without DIEs.
-    if (!VariableDie)
-      continue;
+    assert(VariableDie);
     // FIXME: Consider the time-space tradeoff of just storing the unit pointer
     // in the ConcreteVariables list, rather than looking it up again here.
     // DIE::getUnit isn't simple - it walks parent pointers, etc.

lib/CodeGen/LexicalScopes.cpp

@@ -137,6 +137,8 @@ LexicalScope *LexicalScopes::findLexicalScope(DebugLoc DL) {
 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 /// not available then create new lexical scope.
 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
+  if (DL.isUnknown())
+    return nullptr;
   MDNode *Scope = nullptr;
   MDNode *InlinedAt = nullptr;
   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
@@ -172,9 +174,12 @@ LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
                               std::make_tuple(Parent, DIDescriptor(Scope),
                                               nullptr, false)).first;
 
-  if (!Parent && DIDescriptor(Scope).isSubprogram() &&
-      DISubprogram(Scope).describes(MF->getFunction()))
+  if (!Parent) {
+    assert(DIDescriptor(Scope).isSubprogram());
+    assert(DISubprogram(Scope).describes(MF->getFunction()));
+    assert(!CurrentFnLexicalScope);
     CurrentFnLexicalScope = &I->second;
+  }
 
   return &I->second;
 }

lib/IR/DebugInfo.cpp

@@ -538,6 +538,32 @@ bool DISubprogram::Verify() const {
   if (isLValueReference() && isRValueReference())
     return false;
 
+  if (auto *F = getFunction()) {
+    LLVMContext &Ctxt = F->getContext();
+    for (auto &BB : *F) {
+      for (auto &I : BB) {
+        DebugLoc DL = I.getDebugLoc();
+        if (DL.isUnknown())
+          continue;
+
+        MDNode *Scope = nullptr;
+        MDNode *IA = nullptr;
+        // walk the inlined-at scopes
+        while (DL.getScopeAndInlinedAt(Scope, IA, F->getContext()), IA)
+          DL = DebugLoc::getFromDILocation(IA);
+        DL.getScopeAndInlinedAt(Scope, IA, Ctxt);
+        assert(!IA);
+        while (!DIDescriptor(Scope).isSubprogram()) {
+          DILexicalBlockFile D(Scope);
+          Scope = D.isLexicalBlockFile()
+                      ? D.getScope()
+                      : DebugLoc::getFromDILexicalBlock(Scope).getScope(Ctxt);
+        }
+        if (!DISubprogram(Scope).describes(F))
+          return false;
+      }
+    }
+  }
   return DbgNode->getNumOperands() == 20;
 }
 

test/DebugInfo/PR20038.ll

@@ -18,26 +18,38 @@
 ; CHECK-NOT: DW_TAG
 ; CHECK:     DW_AT_name {{.*}} "~C"
 
-; CHECK: DW_TAG_subprogram
+; CHECK: [[D1_ABS:.*]]: DW_TAG_subprogram
 ; CHECK-NOT: DW_TAG
-; CHECK:   DW_AT_name {{.*}} "fun4"
-
-; FIXME: The dtor is inlined into fun4 and should have an inlined_subroutine
-; entry. (it may be necessary to put some non-trivial instruction, such as an
-; assignment to a global, in the dtor just to ensure its emission/inlining)
-
-; CHECK-NOT: DW_TAG_inlined_subroutine
+; CHECK:   DW_AT_MIPS_linkage_name {{.*}} "_ZN1CD1Ev"
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK: [[D1_THIS_ABS:.*]]:   DW_TAG_formal_parameter
+; CHECK-NOT: DW_TAG
+; CHECK:     DW_AT_name {{.*}} "this"
 
 ; CHECK: DW_TAG_subprogram
 ; CHECK-NOT: DW_TAG
-; CHECK: DW_AT_MIPS_linkage_name {{.*}} "_ZN1CD1Ev"
+; CHECK:   DW_AT_name {{.*}} "fun4"
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:   DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:     DW_TAG_inlined_subroutine
+; CHECK-NOT: DW_TAG
+; CHECK:       DW_AT_abstract_origin {{.*}} {[[D1_ABS]]}
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:       DW_TAG_formal_parameter
+; CHECK-NOT: DW_TAG
+; CHECK:         DW_AT_abstract_origin {{.*}} {[[D1_THIS_ABS]]}
 
-; FIXME: But I think where the real issue is for PR20038 is that the D1 ctor, ;
-; calling and inlining D2, doesn't end up with an inlined_subroutine. Though this
-; might be more the result of a lack of any actual work in D2 (again, could use
-; an assignment to global, etc)
+; FIXME: D2 is actually inlined into D1 but doesn't show up here, possibly due
+; to there being no work in D2 (calling another member function from the dtor
+; causes D2 to show up, calling a free function doesn't).
 
-; CHECK-NOT: DW_TAG_inlined_subroutine
+; CHECK-NOT: DW_TAG
+; CHECK:       NULL
+; CHECK-NOT: DW_TAG
+; CHECK:     NULL
+; CHECK-NOT: DW_TAG
+; CHECK:   NULL
 
 %struct.C = type { i8 }
 
@@ -47,58 +59,58 @@
 define void @_Z4fun4v() #0 {
 entry:
   %this.addr.i.i = alloca %struct.C*, align 8, !dbg !21
-  %this.addr.i = alloca %struct.C*, align 8
+  %this.addr.i = alloca %struct.C*, align 8, !dbg !22
   %agg.tmp.ensured = alloca %struct.C, align 1
   %cleanup.cond = alloca i1
-  %0 = load i8* @b, align 1, !dbg !22
-  %tobool = trunc i8 %0 to i1, !dbg !22
+  %0 = load i8* @b, align 1, !dbg !24
+  %tobool = trunc i8 %0 to i1, !dbg !24
   store i1 false, i1* %cleanup.cond
-  br i1 %tobool, label %land.rhs, label %land.end, !dbg !22
+  br i1 %tobool, label %land.rhs, label %land.end, !dbg !24
 
 land.rhs:                                         ; preds = %entry
-  store i1 true, i1* %cleanup.cond, !dbg !23
+  store i1 true, i1* %cleanup.cond, !dbg !25
   br label %land.end
 
 land.end:                                         ; preds = %land.rhs, %entry
   %1 = phi i1 [ false, %entry ], [ true, %land.rhs ]
-  %cleanup.is_active = load i1* %cleanup.cond
-  br i1 %cleanup.is_active, label %cleanup.action, label %cleanup.done
+  %cleanup.is_active = load i1* %cleanup.cond, !dbg !27
+  br i1 %cleanup.is_active, label %cleanup.action, label %cleanup.done, !dbg !27
 
 cleanup.action:                                   ; preds = %land.end
-  store %struct.C* %agg.tmp.ensured, %struct.C** %this.addr.i, align 8
-  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i}, metadata !25), !dbg !27
-  %this1.i = load %struct.C** %this.addr.i
+  store %struct.C* %agg.tmp.ensured, %struct.C** %this.addr.i, align 8, !dbg !22
+  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i}, metadata !29), !dbg !31
+  %this1.i = load %struct.C** %this.addr.i, !dbg !22
   store %struct.C* %this1.i, %struct.C** %this.addr.i.i, align 8, !dbg !21
-  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i.i}, metadata !28), !dbg !29
+  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i.i}, metadata !32), !dbg !33
   %this1.i.i = load %struct.C** %this.addr.i.i, !dbg !21
-  br label %cleanup.done
+  br label %cleanup.done, !dbg !22
 
 cleanup.done:                                     ; preds = %cleanup.action, %land.end
-  ret void, !dbg !22
+  ret void, !dbg !34
 }
 
 ; Function Attrs: alwaysinline nounwind
 define void @_ZN1CD1Ev(%struct.C* %this) unnamed_addr #1 align 2 {
 entry:
-  %this.addr.i = alloca %struct.C*, align 8, !dbg !21
+  %this.addr.i = alloca %struct.C*, align 8, !dbg !37
   %this.addr = alloca %struct.C*, align 8
   store %struct.C* %this, %struct.C** %this.addr, align 8
-  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr}, metadata !25), !dbg !27
+  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr}, metadata !29), !dbg !38
   %this1 = load %struct.C** %this.addr
-  store %struct.C* %this1, %struct.C** %this.addr.i, align 8, !dbg !21
-  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i}, metadata !28), !dbg !29
-  %this1.i = load %struct.C** %this.addr.i, !dbg !21
-  ret void, !dbg !21
+  store %struct.C* %this1, %struct.C** %this.addr.i, align 8, !dbg !37
+  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr.i}, metadata !32), !dbg !39
+  %this1.i = load %struct.C** %this.addr.i, !dbg !37
+  ret void, !dbg !37
 }
 
 ; Function Attrs: alwaysinline nounwind
 define void @_ZN1CD2Ev(%struct.C* %this) unnamed_addr #1 align 2 {
 entry:
   %this.addr = alloca %struct.C*, align 8
   store %struct.C* %this, %struct.C** %this.addr, align 8
-  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr}, metadata !28), !dbg !30
+  call void @llvm.dbg.declare(metadata !{%struct.C** %this.addr}, metadata !32), !dbg !40
   %this1 = load %struct.C** %this.addr
-  ret void, !dbg !31
+  ret void, !dbg !41
 }
 
 ; Function Attrs: nounwind readnone
@@ -133,14 +145,24 @@ attributes #2 = { nounwind readnone }
 !18 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
 !19 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
 !20 = metadata !{metadata !"clang version 3.5.0 "}
-!21 = metadata !{i32 6, i32 0, metadata !17, null}
-!22 = metadata !{i32 5, i32 0, metadata !12, null}
-!23 = metadata !{i32 5, i32 0, metadata !24, null}
-!24 = metadata !{i32 786443, metadata !5, metadata !12, i32 5, i32 0, i32 1, i32 1} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
-!25 = metadata !{i32 786689, metadata !17, metadata !"this", null, i32 16777216, metadata !26, i32 1088, i32 0} ; [ DW_TAG_arg_variable ] [this] [line 0]
-!26 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, metadata !"_ZTS1C"} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from _ZTS1C]
-!27 = metadata !{i32 0, i32 0, metadata !17, null}
-!28 = metadata !{i32 786689, metadata !16, metadata !"this", null, i32 16777216, metadata !26, i32 1088, i32 0} ; [ DW_TAG_arg_variable ] [this] [line 0]
-!29 = metadata !{i32 0, i32 0, metadata !16, metadata !21}
-!30 = metadata !{i32 0, i32 0, metadata !16, null}
-!31 = metadata !{i32 6, i32 0, metadata !16, null}
+!21 = metadata !{i32 6, i32 0, metadata !17, metadata !22}
+!22 = metadata !{i32 5, i32 0, metadata !23, null}
+!23 = metadata !{i32 786443, metadata !5, metadata !12, i32 5, i32 0, i32 3, i32 3} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
+!24 = metadata !{i32 5, i32 0, metadata !12, null}
+!25 = metadata !{i32 5, i32 0, metadata !26, null}
+!26 = metadata !{i32 786443, metadata !5, metadata !12, i32 5, i32 0, i32 1, i32 1} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
+!27 = metadata !{i32 5, i32 0, metadata !28, null}
+!28 = metadata !{i32 786443, metadata !5, metadata !12, i32 5, i32 0, i32 2, i32 2} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
+!29 = metadata !{i32 786689, metadata !17, metadata !"this", null, i32 16777216, metadata !30, i32 1088, i32 0} ; [ DW_TAG_arg_variable ] [this] [line 0]
+!30 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, metadata !"_ZTS1C"} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from _ZTS1C]
+!31 = metadata !{i32 0, i32 0, metadata !17, metadata !22}
+!32 = metadata !{i32 786689, metadata !16, metadata !"this", null, i32 16777216, metadata !30, i32 1088, i32 0} ; [ DW_TAG_arg_variable ] [this] [line 0]
+!33 = metadata !{i32 0, i32 0, metadata !16, metadata !21}
+!34 = metadata !{i32 5, i32 0, metadata !35, null}
+!35 = metadata !{i32 786443, metadata !5, metadata !36, i32 5, i32 0, i32 5, i32 5} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
+!36 = metadata !{i32 786443, metadata !5, metadata !12, i32 5, i32 0, i32 4, i32 4} ; [ DW_TAG_lexical_block ] [/tmp/dbginfo/PR20038.cpp]
+!37 = metadata !{i32 6, i32 0, metadata !17, null}
+!38 = metadata !{i32 0, i32 0, metadata !17, null}
+!39 = metadata !{i32 0, i32 0, metadata !16, metadata !37}
+!40 = metadata !{i32 0, i32 0, metadata !16, null}
+!41 = metadata !{i32 6, i32 0, metadata !16, null}