[DebugInfo] getMergedLocation: match scopes based on their location

GetNearestCommonScope finds a common scope for two locations by finding
the common parent scope object.

With this commit, GetNearestCommonScope considers two scopes equal if
they have the same file, line and column values. Thus, it can find
the "nearest common included location" when merging locations from
different files. This may be useful for a case described here
llvm#125780 (comment).

DIScope's pointer equality isn't enough for scope equality check, since, for
example, two `#include "x.inc"` directives showing up on different lines
produce different DILocalScope objects representing the same file content.
Thus, two (even same) locations from "x.inc" may have different
parent scope objects representing the same source location.

If input DILocations are from different files, or common scope is in
another file than input locations, a textual inclusion case is assumed,
and the location of common scope ("nearest common included location") is
returned as a result of getMergedLocation.
It fixes llvm#122846.

Author: dzhidzhoev

llvm/lib/IR/DebugInfoMetadata.cpp

@@ -13,7 +13,7 @@
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "LLVMContextImpl.h"
 #include "MetadataImpl.h"
-#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/IR/DebugProgramInstruction.h"
@@ -118,6 +118,22 @@ DILocation *DILocation::getMergedLocations(ArrayRef<DILocation *> Locs) {
   return Merged;
 }
 
+using LineColumn = std::pair<unsigned /* Line */, unsigned /* Column */>;
+
+/// Returns the location of DILocalScope, if present, or a default value.
+static LineColumn getLocalScopeLocationOr(DIScope *S, LineColumn Default) {
+  assert(isa<DILocalScope>(S) && "Expected DILocalScope.");
+
+  if (isa<DILexicalBlockFile>(S))
+    return Default;
+  if (auto *LB = dyn_cast<DILexicalBlock>(S))
+    return {LB->getLine(), LB->getColumn()};
+  if (auto *SP = dyn_cast<DISubprogram>(S))
+    return {SP->getLine(), 0u};
+
+  llvm_unreachable("Unhandled type of DILocalScope.");
+}
+
 DILocation *DILocation::getMergedLocation(DILocation *LocA, DILocation *LocB) {
   if (!LocA || !LocB)
     return nullptr;
@@ -188,27 +204,67 @@ DILocation *DILocation::getMergedLocation(DILocation *LocA, DILocation *LocB) {
       return nullptr;
 
     // Return the nearest common scope inside a subprogram.
-    auto GetNearestCommonScope = [](DIScope *S1, DIScope *S2) -> DIScope * {
-      SmallPtrSet<DIScope *, 8> Scopes;
+    auto GetNearestCommonScope =
+        [](const DILocation *L1,
+           const DILocation *L2) -> std::pair<DIScope *, LineColumn> {
+      DIScope *S1 = L1->getScope();
+      DIScope *S2 = L2->getScope();
+
+      SmallMapVector<std::tuple<DIFile *, LineColumn>,
+                     SmallSetVector<DIScope *, 8>, 8>
+          Scopes;
+
+      // When matching DILexicalBlockFile's, ignore column numbers, so that
+      // DILocation's having different columns within the same
+      // DILexicalBlockFile will match.
+      auto getLocForBlockFile = [](LineColumn L) {
+        L.second = 0;
+        return L;
+      };
+
+      LineColumn Loc1(L1->getLine(), L1->getColumn());
       for (; S1; S1 = S1->getScope()) {
-        Scopes.insert(S1);
+        Loc1 = getLocalScopeLocationOr(S1, getLocForBlockFile(Loc1));
+        Scopes[{S1->getFile(), Loc1}].insert(S1);
+
         if (isa<DISubprogram>(S1))
           break;
       }
 
+      LineColumn Loc2(L2->getLine(), L2->getColumn());
       for (; S2; S2 = S2->getScope()) {
-        if (Scopes.count(S2))
-          return S2;
+        Loc2 = getLocalScopeLocationOr(S2, getLocForBlockFile(Loc2));
+
+        auto ScopesAtLoc = Scopes.find({S2->getFile(), Loc2});
+        // No scope found with the same file, line and column as S2.
+        if (ScopesAtLoc == Scopes.end())
+          continue;
+
+        // Return S2 if it is L1's parent.
+        if (ScopesAtLoc->second.contains(S2))
+          return std::make_pair(S2, Loc2);
+
+        // Return any L1's parent with the same file, line and column as S2.
+        if (!ScopesAtLoc->second.empty())
+          return std::make_pair(*ScopesAtLoc->second.begin(), Loc2);
+
         if (isa<DISubprogram>(S2))
           break;
       }
 
-      return nullptr;
+      return std::make_pair(nullptr,
+                            LineColumn(L2->getLine(), L2->getColumn()));
     };
 
-    auto Scope = GetNearestCommonScope(L1->getScope(), L2->getScope());
+    auto [Scope, ScopeLoc] = GetNearestCommonScope(L1, L2);
     assert(Scope && "No common scope in the same subprogram?");
 
+    // Use inclusion location if files are different.
+    if (Scope->getFile() != L1->getFile() || L1->getFile() != L2->getFile()) {
+      return DILocation::get(C, ScopeLoc.first, ScopeLoc.second, Scope,
+                             InlinedAt);
+    }
+
     bool SameLine = L1->getLine() == L2->getLine();
     bool SameCol = L1->getColumn() == L2->getColumn();
     unsigned Line = SameLine ? L1->getLine() : 0;

llvm/test/DebugInfo/AArch64/merge-nested-block-loc.ll

@@ -0,0 +1,194 @@
+; RUN: opt -mtriple=aarch64-unknown-linux-gnu -S %s -passes=sroa -o - | FileCheck %s
+
+; In this test we want to ensure that the location of phi instruction merged from locations
+; of %mul3 and %mul9 belongs to the correct scope (DILexicalBlockFile), so that line
+; number of that location belongs to the corresponding file.
+
+; Generated with clang from
+; # 1 "1.c" 1
+; # 1 "1.c" 2
+; int foo(int a) {
+;   int i = 0;
+;   if ((a & 1) == 1) {
+;     a -= 1;
+; # 1 "m.c" 1
+; # 40 "m.c"
+; i += a;
+; i -= 10*a;
+; i *= a*a;
+; # 6 "1.c" 2
+;  } else {
+;     a += 3;
+; # 1 "m.c" 1
+; # 40 "m.c"
+; i += a;
+; i -= 10*a;
+; i *= a*a;
+; # 9 "1.c" 2
+;  }
+;   return i;
+; }
+
+source_filename = "repro.c"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "aarch64-unknown-linux-gnu"
+
+; Function Attrs: nounwind uwtable
+define dso_local i32 @foo(i32 noundef %a) !dbg !9 {
+; CHECK:    phi i32 {{.*}}, !dbg [[PHILOC:![0-9]+]]
+;
+entry:
+  %a.addr = alloca i32, align 4, !DIAssignID !17
+  #dbg_assign(i1 undef, !15, !DIExpression(), !17, ptr %a.addr, !DIExpression(), !18)
+  %i = alloca i32, align 4, !DIAssignID !19
+  #dbg_assign(i1 undef, !16, !DIExpression(), !19, ptr %i, !DIExpression(), !18)
+  store i32 %a, ptr %a.addr, align 4, !tbaa !20, !DIAssignID !24
+  #dbg_assign(i32 %a, !15, !DIExpression(), !24, ptr %a.addr, !DIExpression(), !18)
+  call void @llvm.lifetime.start.p0(i64 4, ptr %i), !dbg !25
+  store i32 0, ptr %i, align 4, !dbg !26, !tbaa !20, !DIAssignID !27
+  #dbg_assign(i32 0, !16, !DIExpression(), !27, ptr %i, !DIExpression(), !18)
+  %0 = load i32, ptr %a.addr, align 4, !dbg !28, !tbaa !20
+  %and = and i32 %0, 1, !dbg !30
+  %cmp = icmp eq i32 %and, 1, !dbg !31
+  br i1 %cmp, label %if.then, label %if.else, !dbg !31
+
+if.then:                                          ; preds = %entry
+  %1 = load i32, ptr %a.addr, align 4, !dbg !32, !tbaa !20
+  %sub = sub nsw i32 %1, 1, !dbg !32
+  store i32 %sub, ptr %a.addr, align 4, !dbg !32, !tbaa !20, !DIAssignID !34
+  #dbg_assign(i32 %sub, !15, !DIExpression(), !34, ptr %a.addr, !DIExpression(), !18)
+  %2 = load i32, ptr %a.addr, align 4, !dbg !35, !tbaa !20
+  %3 = load i32, ptr %i, align 4, !dbg !38, !tbaa !20
+  %add = add nsw i32 %3, %2, !dbg !38
+  store i32 %add, ptr %i, align 4, !dbg !38, !tbaa !20, !DIAssignID !39
+  #dbg_assign(i32 %add, !16, !DIExpression(), !39, ptr %i, !DIExpression(), !18)
+  %4 = load i32, ptr %a.addr, align 4, !dbg !40, !tbaa !20
+  %mul = mul nsw i32 10, %4, !dbg !41
+  %5 = load i32, ptr %i, align 4, !dbg !42, !tbaa !20
+  %sub1 = sub nsw i32 %5, %mul, !dbg !42
+  store i32 %sub1, ptr %i, align 4, !dbg !42, !tbaa !20, !DIAssignID !43
+  #dbg_assign(i32 %sub1, !16, !DIExpression(), !43, ptr %i, !DIExpression(), !18)
+  %6 = load i32, ptr %a.addr, align 4, !dbg !44, !tbaa !20
+  %7 = load i32, ptr %a.addr, align 4, !dbg !45, !tbaa !20
+  %mul2 = mul nsw i32 %6, %7, !dbg !46
+  %8 = load i32, ptr %i, align 4, !dbg !47, !tbaa !20
+  %mul3 = mul nsw i32 %8, %mul2, !dbg !47
+  store i32 %mul3, ptr %i, align 4, !dbg !47, !tbaa !20, !DIAssignID !48
+  #dbg_assign(i32 %mul3, !16, !DIExpression(), !48, ptr %i, !DIExpression(), !18)
+  br label %if.end, !dbg !49
+
+if.else:                                          ; preds = %entry
+  %9 = load i32, ptr %a.addr, align 4, !dbg !51, !tbaa !20
+  %add4 = add nsw i32 %9, 3, !dbg !51
+  store i32 %add4, ptr %a.addr, align 4, !dbg !51, !tbaa !20, !DIAssignID !53
+  #dbg_assign(i32 %add4, !15, !DIExpression(), !53, ptr %a.addr, !DIExpression(), !18)
+  %10 = load i32, ptr %a.addr, align 4, !dbg !54, !tbaa !20
+  %11 = load i32, ptr %i, align 4, !dbg !56, !tbaa !20
+  %add5 = add nsw i32 %11, %10, !dbg !56
+  store i32 %add5, ptr %i, align 4, !dbg !56, !tbaa !20, !DIAssignID !57
+  #dbg_assign(i32 %add5, !16, !DIExpression(), !57, ptr %i, !DIExpression(), !18)
+  %12 = load i32, ptr %a.addr, align 4, !dbg !58, !tbaa !20
+  %mul6 = mul nsw i32 10, %12, !dbg !59
+  %13 = load i32, ptr %i, align 4, !dbg !60, !tbaa !20
+  %sub7 = sub nsw i32 %13, %mul6, !dbg !60
+  store i32 %sub7, ptr %i, align 4, !dbg !60, !tbaa !20, !DIAssignID !61
+  #dbg_assign(i32 %sub7, !16, !DIExpression(), !61, ptr %i, !DIExpression(), !18)
+  %14 = load i32, ptr %a.addr, align 4, !dbg !62, !tbaa !20
+  %15 = load i32, ptr %a.addr, align 4, !dbg !63, !tbaa !20
+  %mul8 = mul nsw i32 %14, %15, !dbg !64
+  %16 = load i32, ptr %i, align 4, !dbg !65, !tbaa !20
+  %mul9 = mul nsw i32 %16, %mul8, !dbg !65
+  store i32 %mul9, ptr %i, align 4, !dbg !65, !tbaa !20, !DIAssignID !66
+  #dbg_assign(i32 %mul9, !16, !DIExpression(), !66, ptr %i, !DIExpression(), !18)
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %17 = load i32, ptr %i, align 4, !dbg !67, !tbaa !20
+  call void @llvm.lifetime.end.p0(i64 4, ptr %i), !dbg !68
+  ret i32 %17, !dbg !69
+}
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture)
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 21.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "repro.c", directory: "")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{!"clang version 21.0.0git"}
+!9 = distinct !DISubprogram(name: "foo", scope: !10, file: !10, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !14)
+!10 = !DIFile(filename: "1.c", directory: "")
+!11 = !DISubroutineType(types: !12)
+!12 = !{!13, !13}
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !{!15, !16}
+!15 = !DILocalVariable(name: "a", arg: 1, scope: !9, file: !10, line: 1, type: !13)
+!16 = !DILocalVariable(name: "i", scope: !9, file: !10, line: 2, type: !13)
+!17 = distinct !DIAssignID()
+!18 = !DILocation(line: 0, scope: !9)
+!19 = distinct !DIAssignID()
+!20 = !{!21, !21, i64 0}
+!21 = !{!"int", !22, i64 0}
+!22 = !{!"omnipotent char", !23, i64 0}
+!23 = !{!"Simple C/C++ TBAA"}
+!24 = distinct !DIAssignID()
+!25 = !DILocation(line: 2, column: 3, scope: !9)
+!26 = !DILocation(line: 2, column: 7, scope: !9)
+!27 = distinct !DIAssignID()
+!28 = !DILocation(line: 3, column: 8, scope: !29)
+!29 = distinct !DILexicalBlock(scope: !9, file: !10, line: 3, column: 7)
+!30 = !DILocation(line: 3, column: 10, scope: !29)
+!31 = !DILocation(line: 3, column: 15, scope: !29)
+!32 = !DILocation(line: 4, column: 7, scope: !33)
+!33 = distinct !DILexicalBlock(scope: !29, file: !10, line: 3, column: 21)
+!34 = distinct !DIAssignID()
+!35 = !DILocation(line: 40, column: 6, scope: !36)
+!36 = !DILexicalBlockFile(scope: !33, file: !37, discriminator: 0)
+!37 = !DIFile(filename: "m.c", directory: "")
+!38 = !DILocation(line: 40, column: 3, scope: !36)
+!39 = distinct !DIAssignID()
+!40 = !DILocation(line: 41, column: 9, scope: !36)
+!41 = !DILocation(line: 41, column: 8, scope: !36)
+!42 = !DILocation(line: 41, column: 3, scope: !36)
+!43 = distinct !DIAssignID()
+!44 = !DILocation(line: 42, column: 6, scope: !36)
+!45 = !DILocation(line: 42, column: 8, scope: !36)
+!46 = !DILocation(line: 42, column: 7, scope: !36)
+!47 = !DILocation(line: 42, column: 3, scope: !36)
+!48 = distinct !DIAssignID()
+!49 = !DILocation(line: 6, column: 2, scope: !50)
+!50 = !DILexicalBlockFile(scope: !33, file: !10, discriminator: 0)
+!51 = !DILocation(line: 7, column: 7, scope: !52)
+!52 = distinct !DILexicalBlock(scope: !29, file: !10, line: 6, column: 9)
+!53 = distinct !DIAssignID()
+!54 = !DILocation(line: 40, column: 6, scope: !55)
+!55 = !DILexicalBlockFile(scope: !52, file: !37, discriminator: 0)
+!56 = !DILocation(line: 40, column: 3, scope: !55)
+!57 = distinct !DIAssignID()
+!58 = !DILocation(line: 41, column: 9, scope: !55)
+!59 = !DILocation(line: 41, column: 8, scope: !55)
+!60 = !DILocation(line: 41, column: 3, scope: !55)
+!61 = distinct !DIAssignID()
+!62 = !DILocation(line: 42, column: 6, scope: !55)
+!63 = !DILocation(line: 42, column: 8, scope: !55)
+!64 = !DILocation(line: 42, column: 7, scope: !55)
+!65 = !DILocation(line: 42, column: 3, scope: !55)
+!66 = distinct !DIAssignID()
+!67 = !DILocation(line: 10, column: 10, scope: !9)
+!68 = !DILocation(line: 11, column: 1, scope: !9)
+!69 = !DILocation(line: 10, column: 3, scope: !9)
+
+; CHECK: [[SP:![0-9]+]] = distinct !DISubprogram(name: "foo", scope: [[FILE1:![0-9]+]], file: [[FILE1]], line: 1
+; CHECK: [[FILE1]] = !DIFile(filename: "1.c", directory: "")
+; CHECK: [[LB1:![0-9]+]] = distinct !DILexicalBlock(scope: [[SP]], file: [[FILE1]], line: 3, column: 7)
+; CHECK: [[LB2:![0-9]+]] = distinct !DILexicalBlock(scope: [[LB1]], file: [[FILE1]], line: 3, column: 21)
+; CHECK: [[LBF:![0-9]+]] = !DILexicalBlockFile(scope: [[LB2]], file: [[FILE2:![0-9]+]], discriminator: 0)
+; CHECK: [[FILE2]] = !DIFile(filename: "m.c", directory: "")
+; CHECK: [[PHILOC]] = !DILocation(line: 42, column: 3, scope: [[LBF]])