[llvm-dwarfdump][Statistics] Distinguish functions/variables with same name across...

Different variables and functions might have the same name in different CU.
To calculate 'Availability' metric more accurate (i.e. to avoid getting
availability above 100%), we need to have some additional logic to
distinguish between them.

The patch introduces a DIE identifier that consists of a function/variable name
and declaration information: a filename and a line number. This allows
distinguishing different functions/variables (different means declared in
different files/lines) with the same name, keeping duplicates counted
as duplicates.

Reviewed by: aprantl, djtodoro

Differential Revision: https://reviews.llvm.org/D72797

diff --git a/llvm/test/tools/llvm-dwarfdump/X86/stats-multiple-cu-same-name.ll b/llvm/test/tools/llvm-dwarfdump/X86/stats-multiple-cu-same-name.ll
new file mode 100644 (file)
index 0000000..bfcc1b8
--- /dev/null
+++ b/llvm/test/tools/llvm-dwarfdump/X86/stats-multiple-cu-same-name.ll
@@ -0,0 +1,89 @@
+; RUN: llc -O0 %s -o - -filetype=obj \
+; RUN:   | llvm-dwarfdump -statistics - | FileCheck %s
+
+; Test that statistics distinguish functions with the same name.
+
+; CHECK:      "source functions":4,
+; CHECK-SAME: "unique source variables":2
+; CHECK-SAME: "source variables":2
+
+; $ cat test1.cpp
+; static int foo(int a) {
+;   return a;
+; }
+; int boo() { return foo(42); }
+;
+; $ cat test2.cpp
+; static int foo(int a) {
+;   return a;
+; }
+; int bar() { return foo(42); }
+
+source_filename = "llvm-link"
+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"
+
+; Function Attrs: noinline optnone uwtable
+define dso_local i32 @_Z3boov() !dbg !9 {
+entry:
+  %call = call i32 @_ZL3fooi(i32 42), !dbg !13
+  ret i32 %call
+}
+; Function Attrs: noinline nounwind optnone uwtable
+define internal i32 @_ZL3fooi(i32 %a) !dbg !15 {
+entry:
+  %a.addr = alloca i32, align 4
+  store i32 %a, i32* %a.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !18, metadata !DIExpression()), !dbg !19
+  %0 = load i32, i32* %a.addr, align 4, !dbg !20
+  ret i32 %0
+}
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+; Function Attrs: noinline optnone uwtable
+define dso_local i32 @_Z3barv() !dbg !22 {
+entry:
+  %call = call i32 @_ZL3fooi.1(i32 442), !dbg !23
+  ret i32 %call
+}
+; Function Attrs: noinline nounwind optnone uwtable
+define internal i32 @_ZL3fooi.1(i32 %a) !dbg !25 {
+entry:
+  %a.addr = alloca i32, align 4
+  store i32 %a, i32* %a.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !26, metadata !DIExpression()), !dbg !27
+  %0 = load i32, i32* %a.addr, align 4, !dbg !28
+  %mul = mul nsw i32 %0, 2
+  ret i32 %mul
+}
+
+!llvm.dbg.cu = !{!0, !3}
+!llvm.ident = !{!5, !5}
+!llvm.module.flags = !{!6, !7, !8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test1.cpp", directory: "/")
+!2 = !{}
+!3 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !4, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!4 = !DIFile(filename: "test2.cpp", directory: "/")
+!5 = !{!"clang version 10.0.0"}
+!6 = !{i32 7, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = distinct !DISubprogram(name: "boo", linkageName: "_Z3boov", scope: !1, file: !1, line: 5, type: !10, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !DILocation(line: 6, column: 10, scope: !9)
+!15 = distinct !DISubprogram(name: "foo", linkageName: "_ZL3fooi", scope: !1, file: !1, line: 1, type: !16, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!16 = !DISubroutineType(types: !17)
+!17 = !{!12, !12}
+!18 = !DILocalVariable(name: "a", arg: 1, scope: !15, file: !1, line: 1, type: !12)
+!19 = !DILocation(line: 1, column: 20, scope: !15)
+!20 = !DILocation(line: 2, column: 10, scope: !15)
+!22 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !4, file: !4, line: 5, type: !10, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !3, retainedNodes: !2)
+!23 = !DILocation(line: 6, column: 10, scope: !22)
+!25 = distinct !DISubprogram(name: "foo", linkageName: "_ZL3fooi", scope: !4, file: !4, line: 1, type: !16, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !3, retainedNodes: !2)
+!26 = !DILocalVariable(name: "a", arg: 1, scope: !25, file: !4, line: 1, type: !12)
+!27 = !DILocation(line: 1, column: 20, scope: !25)
+!28 = !DILocation(line: 2, column: 10, scope: !25)

diff --git a/llvm/tools/llvm-dwarfdump/Statistics.cpp b/llvm/tools/llvm-dwarfdump/Statistics.cpp
index a183501..c77e9e4 100644 (file)
--- a/llvm/tools/llvm-dwarfdump/Statistics.cpp
+++ b/llvm/tools/llvm-dwarfdump/Statistics.cpp
@@ -157,6 +157,35 @@ static void collectLocStats(uint64_t BytesCovered, uint64_t BytesInScope,
   else if (IsLocalVar)
     VarLocStats[CoverageBucket]++;
 }
+/// Construct an identifier for a given DIE from its Prefix, Name, DeclFileName
+/// and DeclLine. The identifier aims to be unique for any unique entities,
+/// but keeping the same among different instances of the same entity.
+static std::string constructDieID(DWARFDie Die,
+                                  StringRef Prefix = StringRef()) {
+  std::string IDStr;
+  llvm::raw_string_ostream ID(IDStr);
+  ID << Prefix
+     << Die.getName(DINameKind::LinkageName);
+
+  // Prefix + Name is enough for local variables and parameters.
+  if (!Prefix.empty() && !Prefix.equals("g"))
+    return ID.str();
+
+  auto DeclFile = Die.findRecursively(dwarf::DW_AT_decl_file);
+  std::string File;
+  if (DeclFile) {
+    DWARFUnit *U = Die.getDwarfUnit();
+    if (const auto *LT = U->getContext().getLineTableForUnit(U))
+      if (LT->getFileNameByIndex(
+              dwarf::toUnsigned(DeclFile, 0), U->getCompilationDir(),
+              DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, File))
+        File = sys::path::filename(File);
+  }
+  ID << ":" << (File.empty() ? "/" : File);
+  ID << ":"
+     << dwarf::toUnsigned(Die.findRecursively(dwarf::DW_AT_decl_line), 0);
+  return ID.str();
+}
 
 /// Collect debug info quality metrics for one DIE.
 static void collectStatsForDie(DWARFDie Die, std::string FnPrefix,
@@ -270,10 +299,10 @@ static void collectStatsForDie(DWARFDie Die, std::string FnPrefix,
   if (DWARFDie D =
           Die.getAttributeValueAsReferencedDie(dwarf::DW_AT_abstract_origin))
     Die = D;
-  // By using the variable name + the path through the lexical block tree, the
-  // keys are consistent across duplicate abstract origins in different CUs.
-  std::string VarName = StringRef(Die.getName(DINameKind::ShortName));
-  FnStats.VarsInFunction.insert(VarPrefix + VarName);
+
+  std::string VarID = constructDieID(Die, VarPrefix);
+  FnStats.VarsInFunction.insert(VarID);
+
   if (BytesInScope) {
     FnStats.TotalVarWithLoc += (unsigned)HasLoc;
     // Turns out we have a lot of ranges that extend past the lexical scope.
@@ -358,27 +387,25 @@ static void collectStatsRecursive(DWARFDie Die, std::string FnPrefix,
 
     // Count the function.
     if (!IsBlock) {
-      StringRef Name = Die.getName(DINameKind::LinkageName);
-      if (Name.empty())
-        Name = Die.getName(DINameKind::ShortName);
-      FnPrefix = Name;
       // Skip over abstract origins.
       if (Die.find(dwarf::DW_AT_inline))
         return;
+      std::string FnID = constructDieID(Die);
       // We've seen an (inlined) instance of this function.
-      auto &FnStats = FnStatMap[Name];
+      auto &FnStats = FnStatMap[FnID];
+      FnStats.IsFunction = true;
       if (IsInlinedFunction) {
         FnStats.NumFnInlined++;
         if (Die.findRecursively(dwarf::DW_AT_abstract_origin))
           FnStats.NumAbstractOrigins++;
       }
-      FnStats.IsFunction = true;
       if (BytesInThisScope && !IsInlinedFunction)
         FnStats.HasPCAddresses = true;
-      std::string FnName = StringRef(Die.getName(DINameKind::ShortName));
       if (Die.findRecursively(dwarf::DW_AT_decl_file) &&
           Die.findRecursively(dwarf::DW_AT_decl_line))
         FnStats.HasSourceLocation = true;
+      // Update function prefix.
+      FnPrefix = FnID;
     }
 
     if (BytesInThisScope) {