[DebugInfo] getMergedLocation: match scopes based on their location

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"
@@ -125,6 +125,98 @@ DILocation *DILocation::getMergedLocations(ArrayRef<DILocation *> Locs) {
   return Merged;
 }
 
+static DILexicalBlockBase *cloneAndReplaceParentScope(DILexicalBlockBase *LBB,
+                                                      DIScope *NewParent) {
+  TempMDNode ClonedScope = LBB->clone();
+  cast<DILexicalBlockBase>(*ClonedScope).replaceScope(NewParent);
+  return cast<DILexicalBlockBase>(
+      MDNode::replaceWithUniqued(std::move(ClonedScope)));
+}
+
+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.");
+}
+
+// Returns the nearest matching scope inside a subprogram.
+template <typename MatcherT>
+static std::pair<DIScope *, LineColumn>
+getNearestMatchingScope(const DILocation *L1, const DILocation *L2) {
+  MatcherT Matcher;
+
+  DIScope *S1 = L1->getScope();
+  DIScope *S2 = L2->getScope();
+
+  LineColumn Loc1(L1->getLine(), L1->getColumn());
+  for (; S1; S1 = S1->getScope()) {
+    Loc1 = getLocalScopeLocationOr(S1, Loc1);
+    Matcher.insert(S1, Loc1);
+    if (isa<DISubprogram>(S1))
+      break;
+  }
+
+  LineColumn Loc2(L2->getLine(), L2->getColumn());
+  for (; S2; S2 = S2->getScope()) {
+    Loc2 = getLocalScopeLocationOr(S2, Loc2);
+
+    if (DIScope *S = Matcher.match(S2, Loc2))
+      return std::make_pair(S, Loc2);
+
+    if (isa<DISubprogram>(S2))
+      break;
+  }
+  return std::make_pair(nullptr, LineColumn(L2->getLine(), L2->getColumn()));
+}
+
+// Matches equal scopes.
+struct EqualScopesMatcher {
+  SmallPtrSet<DIScope *, 8> Scopes;
+
+  void insert(DIScope *S, LineColumn Loc) { Scopes.insert(S); }
+
+  DIScope *match(DIScope *S, LineColumn Loc) {
+    return Scopes.contains(S) ? S : nullptr;
+  }
+};
+
+// Matches scopes with the same location.
+struct ScopeLocationsMatcher {
+  SmallMapVector<std::pair<DIFile *, LineColumn>, SmallSetVector<DIScope *, 8>,
+                 8>
+      Scopes;
+
+  void insert(DIScope *S, LineColumn Loc) {
+    Scopes[{S->getFile(), Loc}].insert(S);
+  }
+
+  DIScope *match(DIScope *S, LineColumn Loc) {
+    auto ScopesAtLoc = Scopes.find({S->getFile(), Loc});
+    // No scope found with the given location.
+    if (ScopesAtLoc == Scopes.end())
+      return nullptr;
+
+    // Prefer S over other scopes with the same location.
+    if (ScopesAtLoc->second.contains(S))
+      return S;
+
+    if (!ScopesAtLoc->second.empty())
+      return *ScopesAtLoc->second.begin();
+
+    llvm_unreachable("Scopes must not have empty entries.");
+  }
+};
+
 DILocation *DILocation::getMergedLocation(DILocation *LocA, DILocation *LocB) {
   if (!LocA || !LocB)
     return nullptr;
@@ -208,28 +300,31 @@ DILocation *DILocation::getMergedLocation(DILocation *LocA, DILocation *LocB) {
     if (L1->getScope()->getSubprogram() != L2->getScope()->getSubprogram())
       return nullptr;
 
-    // Return the nearest common scope inside a subprogram.
-    auto GetNearestCommonScope = [](DIScope *S1, DIScope *S2) -> DIScope * {
-      SmallPtrSet<DIScope *, 8> Scopes;
-      for (; S1; S1 = S1->getScope()) {
-        Scopes.insert(S1);
-        if (isa<DISubprogram>(S1))
-          break;
-      }
-
-      for (; S2; S2 = S2->getScope()) {
-        if (Scopes.count(S2))
-          return S2;
-        if (isa<DISubprogram>(S2))
-          break;
-      }
-
-      return nullptr;
-    };
-
-    auto Scope = GetNearestCommonScope(L1->getScope(), L2->getScope());
+    // Find nearest common scope inside subprogram.
+    DIScope *Scope = getNearestMatchingScope<EqualScopesMatcher>(L1, L2).first;
     assert(Scope && "No common scope in the same subprogram?");
 
+    // Try using the nearest scope with common location if files are different.
+    if (Scope->getFile() != L1->getFile() || L1->getFile() != L2->getFile()) {
+      auto [CommonLocScope, CommonLoc] =
+          getNearestMatchingScope<ScopeLocationsMatcher>(L1, L2);
+
+      // If CommonLocScope is a DILexicalBlockBase, clone it and locate
+      // a new scope inside the nearest common scope to preserve
+      // lexical blocks structure.
+      if (auto *LBB = dyn_cast<DILexicalBlockBase>(CommonLocScope);
+          LBB && LBB != Scope)
+        CommonLocScope = cloneAndReplaceParentScope(LBB, Scope);
+
+      Scope = CommonLocScope;
+
+      // If files are still different, assume that L1 and L2 were "included"
+      // from CommonLoc. Use it as merged location.
+      if (Scope->getFile() != L1->getFile() || L1->getFile() != L2->getFile())
+        return DILocation::get(C, CommonLoc.first, CommonLoc.second,
+                               CommonLocScope, InlinedAt);
+    }
+
     bool SameLine = L1->getLine() == L2->getLine();
     bool SameCol = L1->getColumn() == L2->getColumn();
     unsigned Line = SameLine ? L1->getLine() : 0;
@@ -1187,10 +1282,8 @@ DILocalScope *DILocalScope::cloneScopeForSubprogram(
   // cached result).
   DIScope *UpdatedScope = CachedResult ? CachedResult : &NewSP;
   for (DIScope *ScopeToUpdate : reverse(ScopeChain)) {
-    TempMDNode ClonedScope = ScopeToUpdate->clone();
-    cast<DILexicalBlockBase>(*ClonedScope).replaceScope(UpdatedScope);
-    UpdatedScope =
-        cast<DIScope>(MDNode::replaceWithUniqued(std::move(ClonedScope)));
+    UpdatedScope = cloneAndReplaceParentScope(
+        cast<DILexicalBlockBase>(ScopeToUpdate), UpdatedScope);
     Cache[ScopeToUpdate] = UpdatedScope;
   }
 

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

@@ -0,0 +1,79 @@
+; RUN: opt -mtriple=aarch64-unknown-linux-gnu -S %s -passes=sroa -o - | FileCheck %s
+
+; In this test we want to ensure that the merged location of phi instruction
+; 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;
+; }
+
+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"
+
+define i32 @foo() !dbg !3 {
+; CHECK:    phi i32 {{.*}}, !dbg [[PHILOC:![0-9]+]]
+;
+entry:
+  %i = alloca i32, align 4
+  br i1 false, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  store i32 1, ptr %i, align 4, !dbg !7
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  store i32 0, ptr %i, align 4, !dbg !12
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %0 = load i32, ptr %i, align 4
+  ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!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 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "foo", scope: !4, file: !4, line: 1, type: !5, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !6)
+!4 = !DIFile(filename: "1.c", directory: "")
+!5 = !DISubroutineType(types: !6)
+!6 = !{}
+!7 = !DILocation(line: 42, column: 3, scope: !8)
+!8 = !DILexicalBlockFile(scope: !10, file: !9, discriminator: 0)
+!9 = !DIFile(filename: "m.c", directory: "")
+!10 = distinct !DILexicalBlock(scope: !11, file: !4, line: 3, column: 21)
+!11 = distinct !DILexicalBlock(scope: !3, file: !4, line: 3, column: 7)
+!12 = !DILocation(line: 42, column: 3, scope: !13)
+!13 = !DILexicalBlockFile(scope: !14, file: !9, discriminator: 0)
+!14 = distinct !DILexicalBlock(scope: !11, file: !4, line: 6, column: 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: [[PHILOC]] = !DILocation(line: 42, column: 3, scope: [[LBF:![0-9]+]])
+; CHECK: [[LBF]] = !DILexicalBlockFile(scope: [[LB:![0-9]+]], file: [[FILE2:![0-9]+]], discriminator: 0)
+; CHECK: [[FILE2]] = !DIFile(filename: "m.c", directory: "")
+; CHECK: [[LB]] = distinct !DILexicalBlock(scope: [[SP]], file: [[FILE1]], line: 3, column: 7)

llvm/test/DebugInfo/AArch64/merge-nested-block-loc2.ll

@@ -0,0 +1,130 @@
+; RUN: opt -mtriple=aarch64-unknown-linux-gnu -S %s -passes=sroa -o - | FileCheck %s
+
+; In this test we want to ensure that getMergedLocations uses common include
+; location if incoming locations belong to different files.
+; The location of phi instruction merged from locations of %mul3 and %mul10
+; should be the location of do-loop lexical block from y.c.
+
+; Generated with clang from
+;
+; main.c:
+;   int foo(int a) {
+;     int i = 0;
+;     if ((a & 1) == 1) {
+;       a -= 1;
+;   #define A
+;   #include "y.c"
+;    } else {
+;       a += 3;
+;   #undef A
+;   #include "y.c"
+;    }
+;     return i;
+;   }
+;
+; y.c:
+;   # 300 "y.c" 1
+;   do {
+;   #ifdef A
+;   #include "z1.c"
+;   #else
+;   #include "z2.c"
+;   #endif
+;   } while (0);
+;
+; z1.c:
+;   # 100 "z1.c" 1
+;   i += a;
+;   i -= 10*a;
+;   i *= a*a;
+;
+; z2.c:
+;   # 200 "z1.c" 1
+;   i += a;
+;   i -= 10*a;
+;   i *= a*a;
+;
+; Preprocessed source:
+;
+; # 1 "main.c"
+; int foo(int a) {
+;   int i = 0;
+;   if ((a & 1) == 1) {
+;     a -= 1;
+; # 300 "y.c" 1
+; do {
+; # 100 "z1.c" 1
+; i += a;
+; i -= 10*a;
+; i *= a*a;
+; # 303 "y.c" 2
+; } while (0);
+; # 7 "main.c" 2
+;  } else {
+;     a += 3;
+; # 300 "y.c" 1
+; do {
+; # 200 "z2.c" 1
+; i += a;
+; i -= 10*a;
+; i *= a*a;
+; # 305 "y.c" 2
+; } while (0);
+; # 11 "main.c" 2
+;  }
+;   return i;
+; }
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "arm64-apple-macosx15.0.0"
+
+define i32 @foo() !dbg !3 {
+; CHECK:    phi i32 {{.*}}, !dbg [[PHILOC:![0-9]+]]
+;
+entry:
+  %i = alloca i32, align 4
+  br i1 false, label %do.body, label %if.else
+
+do.body:                                          ; preds = %entry
+  store i32 1, ptr %i, align 4, !dbg !6
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  store i32 0, ptr %i, align 4, !dbg !14
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %do.body
+  %0 = load i32, ptr %i, align 4
+  ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: Apple, sysroot: "/")
+!1 = !DIFile(filename: "main.c", directory: "")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !4, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !5)
+!4 = !DISubroutineType(types: !5)
+!5 = !{}
+!6 = !DILocation(line: 102, column: 3, scope: !7)
+!7 = !DILexicalBlockFile(scope: !9, file: !8, discriminator: 0)
+!8 = !DIFile(filename: "z1.c", directory: "")
+!9 = distinct !DILexicalBlock(scope: !11, file: !10, line: 300, column: 4)
+!10 = !DIFile(filename: "y.c", directory: "")
+!11 = !DILexicalBlockFile(scope: !12, file: !10, discriminator: 0)
+!12 = distinct !DILexicalBlock(scope: !13, file: !1, line: 3, column: 21)
+!13 = distinct !DILexicalBlock(scope: !3, file: !1, line: 3, column: 7)
+!14 = !DILocation(line: 202, column: 3, scope: !15)
+!15 = !DILexicalBlockFile(scope: !17, file: !16, discriminator: 0)
+!16 = !DIFile(filename: "z2.c", directory: "")
+!17 = distinct !DILexicalBlock(scope: !18, file: !10, line: 300, column: 4)
+!18 = !DILexicalBlockFile(scope: !19, file: !10, discriminator: 0)
+!19 = distinct !DILexicalBlock(scope: !13, file: !1, line: 7, column: 9)
+
+; CHECK: [[FILE_MAIN:![0-9]+]] = !DIFile(filename: "main.c"
+; CHECK: [[SP:![0-9]+]] = distinct !DISubprogram(name: "foo", scope: [[FILE_MAIN]], file: [[FILE_MAIN]], line: 1
+; CHECK: [[PHILOC]] = !DILocation(line: 300, column: 4, scope: [[BLOCK_Y:![0-9]+]])
+; CHECK-NEXT: [[BLOCK_Y]] = !DILexicalBlock(scope: [[BLOCK_MAIN:![0-9]+]], file: [[FILE_Y:![0-9]+]], line: 300, column: 4)
+; CHECK-NEXT: [[FILE_Y]] = !DIFile(filename: "y.c"
+; CHECK: [[BLOCK_MAIN]] = distinct !DILexicalBlock(scope: [[SP]], file: [[FILE_MAIN]], line: 3, column: 7)