Reland "[DebugInfo][CodeView] Use <lambda_n> as the display name for lambdas"

with fix to test case and stringrefs.

Currently (for codeview) lambdas have a string like `<lambda_0>` in
their mangled name, and don't have any display name. This change uses the
`<lambda_0>` as the display name, which helps distinguish between lambdas
in -gline-tables-only, since there are no linkage names there.
It also changes how we display lambda names; previously we used
`<unnamed-tag>`; now it will show `<lambda_0>`.

I added a function to the mangling context code to create this string;
for Itanium it just returns an empty string.

Bug: https://bugs.llvm.org/show_bug.cgi?id=48432

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D95187

This reverts 9b21d4b9434d2d4796b0d60d64f6ded9bac95441

clang/include/clang/AST/Mangle.h

@@ -89,6 +89,17 @@ public:
     return Result.first->second;
   }
 
+  uint64_t getAnonymousStructIdForDebugInfo(const NamedDecl *D) {
+    llvm::DenseMap<const NamedDecl *, uint64_t>::iterator Result =
+        AnonStructIds.find(D);
+    // The decl should already be inserted, but return 0 in case it is not.
+    if (Result == AnonStructIds.end())
+      return 0;
+    return Result->second;
+  }
+
+  virtual std::string getLambdaString(const CXXRecordDecl *Lambda) = 0;
+
   /// @name Mangler Entry Points
   /// @{
 

clang/lib/AST/ItaniumMangle.cpp

@@ -203,6 +203,36 @@ public:
     disc = discriminator-2;
     return true;
   }
+
+  std::string getLambdaString(const CXXRecordDecl *Lambda) override {
+    // This function matches the one in MicrosoftMangle, which returns
+    // the string that is used in lambda mangled names.
+    assert(Lambda->isLambda() && "RD must be a lambda!");
+    std::string Name("<lambda");
+    Decl *LambdaContextDecl = Lambda->getLambdaContextDecl();
+    unsigned LambdaManglingNumber = Lambda->getLambdaManglingNumber();
+    unsigned LambdaId;
+    const ParmVarDecl *Parm = dyn_cast_or_null<ParmVarDecl>(LambdaContextDecl);
+    const FunctionDecl *Func =
+        Parm ? dyn_cast<FunctionDecl>(Parm->getDeclContext()) : nullptr;
+
+    if (Func) {
+      unsigned DefaultArgNo =
+          Func->getNumParams() - Parm->getFunctionScopeIndex();
+      Name += llvm::utostr(DefaultArgNo);
+      Name += "_";
+    }
+
+    if (LambdaManglingNumber)
+      LambdaId = LambdaManglingNumber;
+    else
+      LambdaId = getAnonymousStructIdForDebugInfo(Lambda);
+
+    Name += llvm::utostr(LambdaId);
+    Name += '>';
+    return Name;
+  }
+
   /// @}
 };
 

clang/lib/AST/MicrosoftMangle.cpp

@@ -228,6 +228,34 @@ public:
     return true;
   }
 
+  std::string getLambdaString(const CXXRecordDecl *Lambda) override {
+    assert(Lambda->isLambda() && "RD must be a lambda!");
+    std::string Name("<lambda_");
+
+    Decl *LambdaContextDecl = Lambda->getLambdaContextDecl();
+    unsigned LambdaManglingNumber = Lambda->getLambdaManglingNumber();
+    unsigned LambdaId;
+    const ParmVarDecl *Parm = dyn_cast_or_null<ParmVarDecl>(LambdaContextDecl);
+    const FunctionDecl *Func =
+        Parm ? dyn_cast<FunctionDecl>(Parm->getDeclContext()) : nullptr;
+
+    if (Func) {
+      unsigned DefaultArgNo =
+          Func->getNumParams() - Parm->getFunctionScopeIndex();
+      Name += llvm::utostr(DefaultArgNo);
+      Name += "_";
+    }
+
+    if (LambdaManglingNumber)
+      LambdaId = LambdaManglingNumber;
+    else
+      LambdaId = getLambdaIdForDebugInfo(Lambda);
+
+    Name += llvm::utostr(LambdaId);
+    Name += ">";
+    return Name;
+  }
+
   unsigned getLambdaId(const CXXRecordDecl *RD) {
     assert(RD->isLambda() && "RD must be a lambda!");
     assert(!RD->isExternallyVisible() && "RD must not be visible!");
@@ -238,6 +266,19 @@ public:
     return Result.first->second;
   }
 
+  unsigned getLambdaIdForDebugInfo(const CXXRecordDecl *RD) {
+    assert(RD->isLambda() && "RD must be a lambda!");
+    assert(!RD->isExternallyVisible() && "RD must not be visible!");
+    assert(RD->getLambdaManglingNumber() == 0 &&
+           "RD must not have a mangling number!");
+    llvm::DenseMap<const CXXRecordDecl *, unsigned>::iterator Result =
+        LambdaIds.find(RD);
+    // The lambda should exist, but return 0 in case it doesn't.
+    if (Result == LambdaIds.end())
+      return 0;
+    return Result->second;
+  }
+
   /// Return a character sequence that is (somewhat) unique to the TU suitable
   /// for mangling anonymous namespaces.
   StringRef getAnonymousNamespaceHash() const {

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -317,8 +317,9 @@ StringRef CGDebugInfo::getClassName(const RecordDecl *RD) {
   if (const IdentifierInfo *II = RD->getIdentifier())
     return II->getName();
 
-  // The CodeView printer in LLVM wants to see the names of unnamed types: it is
-  // used to reconstruct the fully qualified type names.
+  // The CodeView printer in LLVM wants to see the names of unnamed types
+  // because they need to have a unique identifier.
+  // These names are used to reconstruct the fully qualified type names.
   if (CGM.getCodeGenOpts().EmitCodeView) {
     if (const TypedefNameDecl *D = RD->getTypedefNameForAnonDecl()) {
       assert(RD->getDeclContext() == D->getDeclContext() &&
@@ -342,6 +343,12 @@ StringRef CGDebugInfo::getClassName(const RecordDecl *RD) {
         // associate typedef mangled in if they have one.
         Name = TND->getName();
 
+      // Give lambdas a display name based on their name mangling.
+      if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
+        if (CXXRD->isLambda())
+          return internString(
+              CGM.getCXXABI().getMangleContext().getLambdaString(CXXRD));
+
       if (!Name.empty()) {
         SmallString<256> UnnamedType("<unnamed-type-");
         UnnamedType += Name;

clang/test/CodeGenCXX/debug-info-codeview-unnamed.cpp

@@ -100,7 +100,7 @@ int main(int argc, char* argv[], char* arge[]) {
   // MSVC-SAME:      )
   // MSVC:       [[TYPE_OF_FOUR]] = distinct !DICompositeType
   // MSVC-SAME:      tag: DW_TAG_class_type
-  // MSVC-NOT:       name:
+  // MSVC-SAME:      name: "<lambda_0>"
   // MSVC-SAME:      identifier: ".?AV<lambda_0>@?0??main@@9@"
   // MSVC-SAME:      )
 

clang/test/CodeGenCXX/debug-info-gline-tables-only-codeview.cpp

@@ -1,17 +1,26 @@
-// RUN: %clang_cc1 %s -gcodeview -debug-info-kind=line-tables-only -S \
-// RUN:   -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -triple x86_64-windows-msvc -gcodeview
+// RUN: -debug-info-kind=line-tables-only -emit-llvm -o - | FileCheck %s
 // Checks that clang with "-gline-tables-only" with CodeView emits some debug
 // info for variables and types when they appear in function scopes.
 
 namespace NS {
 struct C {
   void m() {}
+  // Test externally visible lambda.
+  void lambda2() { []() {}(); }
+ 
+  // Test naming for function parameters.
+  void lambda_params(int x = [](){ return 0; }(), int y = [](){ return 1; }()) {}
 };
 void f() {}
 }
 
+// Test non- externally visible lambda.
+auto lambda1 = []() { return 1; };
+
 NS::C c;
 
+
 void test() {
   // CHECK: !DISubprogram(name: "f", scope: ![[NS:[0-9]+]],
   // CHECK-SAME:          type: ![[F:[0-9]+]]
@@ -21,10 +30,30 @@ void test() {
   NS::f();
 
   // CHECK: ![[M:[0-9]+]] = distinct !DISubprogram(name: "m", scope: ![[C:[0-9]+]],
-  // CHECK-SAME:                                   type: ![[MTYPE:[0-9]+]]
+  // CHECK-SAME:                                   type: ![[MTYPE:[0-9]+]],
   // CHECK: ![[C]] = !DICompositeType(tag: DW_TAG_structure_type, name: "C",
   // CHECK-SAME:                      flags: DIFlagFwdDecl
   // CHECK-NOT: identifier
   // CHECK: ![[MTYPE]] = !DISubroutineType({{.*}}types: !{{.*}})
   c.m();
+
+  // CHECK: !DISubprogram(name: "operator()", scope: ![[LAMBDA0:[0-9]+]],
+  // CHECK: ![[LAMBDA0]] = !DICompositeType(tag: DW_TAG_class_type,
+  // CHECK-SAME:                            name: "<lambda_0>",
+  // CHECK-SAME:                            flags: DIFlagFwdDecl
+  lambda1();
+
+  // CHECK: !DISubprogram(name: "operator()", scope: ![[LAMBDA1_1:[0-9]+]],
+  // CHECK: ![[LAMBDA1_1]] = !DICompositeType(tag: DW_TAG_class_type,
+  // CHECK-SAME:                              name: "<lambda_1_1>",
+  // CHECK: !DISubprogram(name: "operator()", scope: ![[LAMBDA2_1:[0-9]+]],
+  // CHECK: ![[LAMBDA2_1]] = !DICompositeType(tag: DW_TAG_class_type,
+  // CHECK-SAME:                              name: "<lambda_2_1>",
+  c.lambda_params();
+
+  // CHECK: !DISubprogram(name: "operator()", scope: ![[LAMBDA1:[0-9]+]],
+  // CHECK: ![[LAMBDA1]] = !DICompositeType(tag: DW_TAG_class_type,
+  // CHECK-SAME:                            name: "<lambda_1>",
+  // CHECK-SAME:                            flags: DIFlagFwdDecl
+  c.lambda2();
 }