[DebugInfo] Remap extracted DIAssignIDs in hotcoldsplit (#91940)

Fix #91814

When instructions are extracted into a new function the `DIAssignID` metadata
uses and attachments need to be remapped so that the stores and assignment
markers don't link to stores and assignment markers in the original function.

This matches existing inlining behaviour for DIAssignIDs.

Author: OCHyams

llvm/include/llvm/IR/DebugInfo.h

@@ -268,6 +268,10 @@ bool calculateFragmentIntersect(
     uint64_t SliceSizeInBits, const DbgVariableRecord *DVRAssign,
     std::optional<DIExpression::FragmentInfo> &Result);
 
+/// Replace DIAssignID uses and attachments with IDs from \p Map.
+/// If an ID is unmapped a new ID is generated and added to \p Map.
+void remapAssignID(DenseMap<DIAssignID *, DIAssignID *> &Map, Instruction &I);
+
 /// Helper struct for trackAssignments, below. We don't use the similar
 /// DebugVariable class because trackAssignments doesn't (yet?) understand
 /// partial variables (fragment info) as input and want to make that clear and

llvm/lib/IR/DebugInfo.cpp

@@ -2130,6 +2130,30 @@ bool at::calculateFragmentIntersect(
                                         SliceSizeInBits, DVRAssign, Result);
 }
 
+/// Update inlined instructions' DIAssignID metadata. We need to do this
+/// otherwise a function inlined more than once into the same function
+/// will cause DIAssignID to be shared by many instructions.
+void at::remapAssignID(DenseMap<DIAssignID *, DIAssignID *> &Map,
+                       Instruction &I) {
+  auto GetNewID = [&Map](Metadata *Old) {
+    DIAssignID *OldID = cast<DIAssignID>(Old);
+    if (DIAssignID *NewID = Map.lookup(OldID))
+      return NewID;
+    DIAssignID *NewID = DIAssignID::getDistinct(OldID->getContext());
+    Map[OldID] = NewID;
+    return NewID;
+  };
+  // If we find a DIAssignID attachment or use, replace it with a new version.
+  for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
+    if (DVR.isDbgAssign())
+      DVR.setAssignId(GetNewID(DVR.getAssignID()));
+  }
+  if (auto *ID = I.getMetadata(LLVMContext::MD_DIAssignID))
+    I.setMetadata(LLVMContext::MD_DIAssignID, GetNewID(ID));
+  else if (auto *DAI = dyn_cast<DbgAssignIntrinsic>(&I))
+    DAI->setAssignId(GetNewID(DAI->getAssignID()));
+}
+
 /// Collect constant properies (base, size, offset) of \p StoreDest.
 /// Return std::nullopt if any properties are not constants or the
 /// offset from the base pointer is negative.

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -1678,8 +1678,9 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
     DVR->getMarker()->MarkedInstr->dropOneDbgRecord(DVR);
   DIB.finalizeSubprogram(NewSP);
 
-  // Fix up the scope information attached to the line locations in the new
-  // function.
+  // Fix up the scope information attached to the line locations and the
+  // debug assignment metadata in the new function.
+  DenseMap<DIAssignID *, DIAssignID *> AssignmentIDMap;
   for (Instruction &I : instructions(NewFunc)) {
     if (const DebugLoc &DL = I.getDebugLoc())
       I.setDebugLoc(
@@ -1695,6 +1696,7 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
       return MD;
     };
     updateLoopMetadataDebugLocations(I, updateLoopInfoLoc);
+    at::remapAssignID(AssignmentIDMap, I);
   }
   if (!TheCall.getDebugLoc())
     TheCall.setDebugLoc(DILocation::get(Ctx, 0, 0, OldSP));

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -1888,29 +1888,12 @@ static void trackInlinedStores(Function::iterator Start, Function::iterator End,
 /// otherwise a function inlined more than once into the same function
 /// will cause DIAssignID to be shared by many instructions.
 static void fixupAssignments(Function::iterator Start, Function::iterator End) {
-  // Map {Old, New} metadata. Not used directly - use GetNewID.
   DenseMap<DIAssignID *, DIAssignID *> Map;
-  auto GetNewID = [&Map](Metadata *Old) {
-    DIAssignID *OldID = cast<DIAssignID>(Old);
-    if (DIAssignID *NewID = Map.lookup(OldID))
-      return NewID;
-    DIAssignID *NewID = DIAssignID::getDistinct(OldID->getContext());
-    Map[OldID] = NewID;
-    return NewID;
-  };
   // Loop over all the inlined instructions. If we find a DIAssignID
   // attachment or use, replace it with a new version.
   for (auto BBI = Start; BBI != End; ++BBI) {
-    for (Instruction &I : *BBI) {
-      for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
-        if (DVR.isDbgAssign())
-          DVR.setAssignId(GetNewID(DVR.getAssignID()));
-      }
-      if (auto *ID = I.getMetadata(LLVMContext::MD_DIAssignID))
-        I.setMetadata(LLVMContext::MD_DIAssignID, GetNewID(ID));
-      else if (auto *DAI = dyn_cast<DbgAssignIntrinsic>(&I))
-        DAI->setAssignId(GetNewID(DAI->getAssignID()));
-    }
+    for (Instruction &I : *BBI)
+      at::remapAssignID(Map, I);
   }
 }
 #undef DEBUG_TYPE

llvm/test/DebugInfo/assignment-tracking/X86/hotcoldsplit.ll

@@ -0,0 +1,50 @@
+; RUN: opt %s -passes=hotcoldsplit -S | FileCheck %s
+
+;; Check the extracted DIAssignID gets remapped.
+
+; CHECK-LABEL: define void @_foo()
+; CHECK: common.ret:
+; CHECK-NEXT: dbg.assign(metadata i64 0, metadata ![[#]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 64), metadata ![[ID1:[0-9]+]], {{.*}}, metadata !DIExpression())
+
+; CHECK-LABEL: define internal void @_foo.cold.1()
+; CHECK: store i64 0, ptr null, align 8, !DIAssignID ![[ID2:[0-9]+]]
+
+; CHECK-DAG: ![[ID1]] = distinct !DIAssignID()
+; CHECK-DAG: ![[ID2]] = distinct !DIAssignID()
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @_foo() !dbg !4 {
+entry:
+  br i1 false, label %if.then7, label %common.ret
+
+common.ret:                                       ; preds = %entry
+  call void @llvm.dbg.assign(metadata i64 0, metadata !7, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 64), metadata !12, metadata ptr null, metadata !DIExpression()), !dbg !13
+  ret void
+
+if.then7:                                         ; preds = %entry
+  %call21 = load i1, ptr null, align 4294967296
+  store i64 0, ptr null, align 8, !DIAssignID !12
+  unreachable
+}
+
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "file.cpp", directory: "foo")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "foo", linkageName: "_foo", scope: !5, file: !1, line: 425, type: !6, scopeLine: 425, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!5 = !DINamespace(name: "llvm", scope: null)
+!6 = distinct !DISubroutineType(types: !2)
+!7 = !DILocalVariable(name: "Path", scope: !4, file: !1, line: 436, type: !8)
+!8 = !DIDerivedType(tag: DW_TAG_typedef, name: "string", scope: !9, file: !1, line: 79, baseType: !10)
+!9 = !DINamespace(name: "std", scope: null)
+!10 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "basic_string<char, std::char_traits<char>, std::allocator<char> >", scope: !11, file: !1, line: 85, size: 256, flags: DIFlagTypePassByReference | DIFlagNonTrivial, elements: !2, templateParams: !2, identifier: "_ZTSNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE")
+!11 = !DINamespace(name: "__cxx11", scope: !9, exportSymbols: true)
+!12 = distinct !DIAssignID()
+!13 = !DILocation(line: 0, scope: !4)