[CodeExtractor] Preserve entire scope of !DIVariables when moving them

When a dbg.value is moved into a new function, the corresponding
variable should have its entire scope chain reparented with the new
function. The current implementation drops the scope chain and replaces
it with a subprogram for the new function.

Differential Revision: https://reviews.llvm.org/D139671

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -1556,6 +1556,7 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
   //     point to a variable in the wrong scope.
   SmallDenseMap<DINode *, DINode *> RemappedMetadata;
   SmallVector<Instruction *, 4> DebugIntrinsicsToDelete;
+  DenseMap<const MDNode *, MDNode *> Cache;
   for (Instruction &I : instructions(NewFunc)) {
     auto *DII = dyn_cast<DbgInfoIntrinsic>(&I);
     if (!DII)
@@ -1593,11 +1594,14 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
     if (!DVI->getDebugLoc().getInlinedAt()) {
       DILocalVariable *OldVar = DVI->getVariable();
       DINode *&NewVar = RemappedMetadata[OldVar];
-      if (!NewVar)
+      if (!NewVar) {
+        DILocalScope *NewScope = DILocalScope::cloneScopeForSubprogram(
+            *OldVar->getScope(), *NewSP, Ctx, Cache);
         NewVar = DIB.createAutoVariable(
-            NewSP, OldVar->getName(), OldVar->getFile(), OldVar->getLine(),
+            NewScope, OldVar->getName(), OldVar->getFile(), OldVar->getLine(),
             OldVar->getType(), /*AlwaysPreserve=*/false, DINode::FlagZero,
             OldVar->getAlignInBits());
+      }
       DVI->setVariable(cast<DILocalVariable>(NewVar));
     }
   }
@@ -1608,7 +1612,6 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
 
   // Fix up the scope information attached to the line locations in the new
   // function.
-  DenseMap<const MDNode *, MDNode *> Cache;
   for (Instruction &I : instructions(NewFunc)) {
     if (const DebugLoc &DL = I.getDebugLoc())
       I.setDebugLoc(

llvm/test/Transforms/HotColdSplit/transfer-debug-info.ll

@@ -35,6 +35,11 @@ target triple = "x86_64-apple-macosx10.14.0"
 ; CHECK-SAME:      metadata [[VAR_FROM_INLINE_ME:![0-9]+]]
 ; CHECK-SAME:      !dbg [[LINE2]]
 
+; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[ADD1]]
+; CHECK-SAME:      metadata [[VAR2:![0-9]+]]
+; CHECK-SAME:     !dbg [[LINE4:![0-9]+]]
+
+
 ; - The DISubprogram for @foo.cold.1 has an empty DISubroutineType
 ; CHECK: [[FILE:![0-9]+]] = !DIFile(filename: "<stdin>"
 ; CHECK: [[EMPTY_MD:![0-9]+]] = !{}
@@ -54,6 +59,11 @@ target triple = "x86_64-apple-macosx10.14.0"
 ; CHECK: [[VAR_FROM_INLINE_ME]] = !DILocalVariable(name: "var_from_inline_me",
 ; CHECK-SAME:                                      scope: [[INLINE_ME_SCOPE]]
 
+; CHECK: [[VAR2]] = !DILocalVariable(name: "var_from_scope_in_foo",
+; CHECK-SAME:                        scope: [[NEWSCOPE2:![0-9]+]]
+; CHECK: [[NEWSCOPE2]] = !DILexicalBlock(scope: [[NEWSCOPE]], file: [[FILE]], line: 7, column: 7)
+; CHECK: [[LINE4]] =     !DILocation(line: 6, column: 6, scope: [[NEWSCOPE2]]
+
 define void @foo(i32 %arg1) !dbg !6 {
 entry:
   %var = add i32 0, 0, !dbg !11
@@ -72,6 +82,7 @@ if.end:                                           ; preds = %entry
   call void @sink(i32 %add1), !dbg !13 ; inlined from @inline_me
   call void @sink(i32 %add1), !dbg !14 ; not inlined, but inside some scope of foo
   call void @llvm.dbg.value(metadata i32 %add1, metadata !17, metadata !DIExpression()), !dbg !13 ; variable from @inline_me, should preserve scope in !17.
+  call void @llvm.dbg.value(metadata i32 %add1, metadata !18, metadata !DIExpression()), !dbg !19 ; variable not inlined, but inside some scope of foo
   ret void
 }
 
@@ -105,3 +116,6 @@ define void @inline_me() !dbg !12{
 !15 = distinct !DILexicalBlock(scope: !16, file: !1, line: 4, column: 4)
 !16 = distinct !DILexicalBlock(scope: !6, file: !1, line: 5, column: 5)
 !17 = !DILocalVariable(name: "var_from_inline_me", scope: !12, file: !1, line: 1, type: !10)
+!18 = !DILocalVariable(name: "var_from_scope_in_foo", scope: !20, file: !1, line: 1, type: !10)
+!19 = !DILocation(line: 6, column: 6, scope: !20)
+!20 = distinct !DILexicalBlock(scope: !6, file: !1, line: 7, column: 7)