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

[fdeazeve]

Summary

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.

[fdeazeve]

Err, ignore this. I meant to create a series of patches

[fdeazeve]

Trying to create a sequence of patches

[aprantl]

llvm/include/llvm/IR/DebugInfoMetadata.h

1588 ↗

(On Diff #481399)

Might want to add a unit test for this.

[fdeazeve]

Remove other commits

[fdeazeve]

I'll resubmit this properly.

[aprantl]

llvm/lib/Transforms/Utils/CodeExtractor.cpp

1593

if (!)

llvm/lib/Transforms/Utils/CodeExtractor.cpp

for (Instruction &I : instructions(NewFunc)) {
     };
 
     auto *DVI = cast<DbgVariableIntrinsic>(DII);
     // If any of the used locations are invalid, delete the intrinsic.
     if (any_of(DVI->location_ops(), IsInvalidLocation)) {
       DebugIntrinsicsToDelete.push_back(DVI);
       continue;
     }
-
-    // Point the intrinsic to a fresh variable within the new function.
+    // If the variable was in the scope of the old function, i.e. it was not
+    // inlined, point the intrinsic to a fresh variable within the new function.
+    if (DVI->getDebugLoc().getInlinedAt() == nullptr) {
       DILocalVariable *OldVar = DVI->getVariable();
       DINode *&NewVar = RemappedMetadata[OldVar];
-    if (!NewVar)
+      if (!NewVar) {
         NewVar = DIB.createAutoVariable(
             NewSP, OldVar->getName(), OldVar->getFile(), OldVar->getLine(),
             OldVar->getType(), /*AlwaysPreserve=*/false, DINode::FlagZero,
             OldVar->getAlignInBits());
+      }
       DVI->setVariable(cast<DILocalVariable>(NewVar));
     }
+  }
+
   for (auto *DII : DebugIntrinsicsToDelete)
     DII->eraseFromParent();
   DIB.finalizeSubprogram(NewSP);
 
   // Fix up the scope information attached to the line locations in the new
   // function.
   DenseMap<const MDNode *, MDNode *> Cache;
   for (Instruction &I : instructions(NewFunc)) {

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

 ; CHECK-NEXT: llvm.dbg.value(metadata i32 [[ADD1]], metadata [[VAR1:![0-9]+]], metadata !DIExpression()), !dbg [[LINE1]]
 
 ; - Expressions inside of dbg.value intrinsics are preserved
 ; CHECK-NEXT: llvm.dbg.value(metadata i32 [[ADD1]], metadata [[VAR1]], metadata !DIExpression(DW_OP_constu, 1, DW_OP_plus, DW_OP_stack_value)
 
 ; CHECK-NEXT: call void @sink(i32 [[ADD1]]), !dbg [[LINE2:![0-9]+]]
 ; CHECK-NEXT: call void @sink(i32 [[ADD1]]), !dbg [[LINE3:![0-9]+]]
 
+; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[ADD1]]
+; CHECK-SAME:      metadata [[VAR_FROM_INLINE_ME:![0-9]+]]
+; CHECK-SAME:      !dbg [[LINE2]]
+
 ; - The DISubprogram for @foo.cold.1 has an empty DISubroutineType
 ; CHECK: [[FILE:![0-9]+]] = !DIFile(filename: "<stdin>"
 ; CHECK: [[EMPTY_MD:![0-9]+]] = !{}
 ; CHECK: [[EMPTY_TYPE:![0-9]+]] = !DISubroutineType(types: [[EMPTY_MD]])
 ; CHECK: [[INLINE_ME_SCOPE:![0-9]+]] = distinct !DISubprogram(name: "inline_me"
 ; CHECK: [[NEWSCOPE:![0-9]+]] = distinct !DISubprogram(name: "foo.cold.1", linkageName: "foo.cold.1", scope: null, file: [[FILE]], type: [[EMPTY_TYPE]], spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized
 
 ; - Line locations in @foo.cold.1 point to the new scope for @foo.cold.1
 ; CHECK: [[LINE1]] = !DILocation(line: 1, column: 1, scope: [[NEWSCOPE]])
 
 ; CHECK: [[LINE2]] =          !DILocation(line: 2, column: 2, scope: [[INLINE_ME_SCOPE]]
 ; CHECK-SAME:                            inlinedAt: [[LINE3]]
 ; CHECK: [[LINE3]] =          !DILocation(line: 3, column: 3, scope: [[INLINED_SCOPE1:![0-9]*]]
 ; CHECK: [[INLINED_SCOPE1]] = !DILexicalBlock(scope: [[INLINED_SCOPE2:![0-9]*]], file: [[FILE]], line: 4, column: 4)
 ; CHECK: [[INLINED_SCOPE2]] = !DILexicalBlock(scope: [[NEWSCOPE]], file: [[FILE]], line: 5, column: 5)
 
+; CHECK: [[VAR_FROM_INLINE_ME]] = !DILocalVariable(name: "var_from_inline_me",
+; CHECK-SAME:                                      scope: [[INLINE_ME_SCOPE]]
+
 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.value(metadata i32 %arg1, metadata !9, metadata !DIExpression()), !dbg !11
   %add1 = add i32 %arg1, 1
   call void @sink(i32 %add1)
   call void @sink(i32 %add1), !dbg !11
   call void @llvm.dbg.value(metadata i32 %add1, metadata !9, metadata !DIExpression()), !dbg !11
   call void @llvm.dbg.value(metadata i32 %add1, metadata !9, metadata !DIExpression(DW_OP_constu, 1, DW_OP_plus, DW_OP_stack_value)), !dbg !11
   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.
   ret void
 }
 
 declare void @llvm.dbg.value(metadata, metadata, metadata)
 
 declare void @sink(i32) cold
 
 define void @inline_me() !dbg !12{

 !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 = 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)
 !13 = !DILocation(line: 2, column: 2, scope: !12, inlinedAt: !14)
 !14 = !DILocation(line: 3, column: 3, scope: !15)
 !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)