[CodeExtractor] Preserve entire scope of labels when moving them

[fdeazeve]

Summary

When a dbg.label is moved into a new function, its corresponding scope
should be preserved, with the exception of the subprogram at the end of
the scope chain, which should now be the subprogram of the destination
function. See D139671.

Depends on D139848

llvm/lib/Transforms/Utils/CodeExtractor.cpp

for (Instruction &I : instructions(NewFunc)) {
 
     // Point the intrinsic to a fresh label within the new function if the
     // intrinsic was not inlined from some other function.
     if (auto *DLI = dyn_cast<DbgLabelInst>(&I)) {
       if (DLI->getDebugLoc().getInlinedAt())
         continue;
       DILabel *OldLabel = DLI->getLabel();
       DINode *&NewLabel = RemappedMetadata[OldLabel];
-      if (!NewLabel)
-        NewLabel = DILabel::get(Ctx, NewSP, OldLabel->getName(),
+      if (!NewLabel) {
+        DILocalScope *NewScope = DILocalScope::cloneScopeForSubprogram(
+            *OldLabel->getScope(), *NewSP, Ctx, Cache);
+        NewLabel = DILabel::get(Ctx, NewScope, OldLabel->getName(),
                                 OldLabel->getFile(), OldLabel->getLine());
+      }
       DLI->setArgOperand(0, MetadataAsValue::get(Ctx, NewLabel));
       continue;
     }
 
     auto IsInvalidLocation = [&NewFunc](Value *Location) {
       // Location is invalid if it isn't a constant or an instruction, or is an
       // instruction but isn't in the new function.
       if (!Location ||

llvm/test/Transforms/HotColdSplit/split-out-dbg-label.ll

 ; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s
 
 ; When an llvm.dbg.label intrinsic is extracted into a new function, make sure
 ; that its metadata argument is a DILabel that points to a scope within the new
 ; function.
 ;
 ; In this example, the label "bye" points to the scope for @foo before
 ; splitting, and should point to the scope for @foo.cold.1 after splitting.
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.14.0"
 
 ; CHECK-LABEL: define {{.*}}@foo.cold.1
 ; CHECK: llvm.dbg.label(metadata [[LABEL:![0-9]+]]), !dbg [[LINE:![0-9]+]]
 ; CHECK: llvm.dbg.label(metadata [[LABEL_IN_INLINE_ME:![0-9]+]]), !dbg [[LINE2:![0-9]+]]
+; CHECK: llvm.dbg.label(metadata [[SCOPED_LABEL:![0-9]+]]), !dbg [[LINE]]
 
 ; CHECK: [[FILE:![0-9]+]] = !DIFile
 ; CHECK: [[INLINE_ME_SCOPE:![0-9]+]] = distinct !DISubprogram(name: "inline_me"
 ; CHECK: [[SCOPE:![0-9]+]] = distinct !DISubprogram(name: "foo.cold.1"
 ; CHECK: [[LINE]] = !DILocation(line: 1, column: 1, scope: [[SCOPE]]
 ; CHECK: [[LABEL]] = !DILabel(scope: [[SCOPE]], name: "bye", file: [[FILE]], line: 28
 ; CHECK: [[LABEL_IN_INLINE_ME]] = !DILabel(scope: [[INLINE_ME_SCOPE]], name: "label_in_@inline_me", file: [[FILE]], line: 29
 ; CHECK: [[LINE2]] = !DILocation(line: 2, column: 2, scope: [[INLINE_ME_SCOPE]], inlinedAt: [[LINE]]
+; CHECK: [[SCOPED_LABEL]] = !DILabel(scope: [[SCOPE_IN_FOO:![0-9]+]], name: "scoped_label_in_foo", file: [[FILE]], line: 30
+; CHECK: [[SCOPE_IN_FOO]] = !DILexicalBlock(scope: [[SCOPE]], file: [[FILE]], line: 31, column: 31)
 
 define void @foo(i32 %arg1) !dbg !6 {
 entry:
   %var = add i32 0, 0, !dbg !11
   br i1 undef, label %if.then, label %if.end
 
 if.then:                                          ; preds = %entry
   ret void
 
 if.end:                                           ; preds = %entry
   call void @llvm.dbg.label(metadata !12), !dbg !11
   call void @llvm.dbg.label(metadata !14), !dbg !15
+  call void @llvm.dbg.label(metadata !16), !dbg !11
   call void @sink()
   ret void
 }
 
 declare void @llvm.dbg.label(metadata)
 
 declare void @sink() cold
 

 !8 = !{!9}
 !9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
 !10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
 !11 = !DILocation(line: 1, column: 1, scope: !6)
 !12 = !DILabel(scope: !6, name: "bye", file: !1, line: 28)
 !13 = distinct !DISubprogram(name: "inline_me", linkageName: "inline_me", scope: null, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, retainedNodes: !8)
 !14 = !DILabel(scope: !13, name: "label_in_@inline_me", file: !1, line: 29)
 !15 = !DILocation(line: 2, column: 2, scope: !13, inlinedAt: !11)
+!16 = !DILabel(scope: !17, name: "scoped_label_in_foo", file: !1, line: 30)
+!17 = distinct !DILexicalBlock(scope: !6, file: !1, line: 31, column: 31)