[DebugInfo] Add calling conventions to DISubroutineType

[rnk]

Summary

This should have been a very simple change, but it was greatly
complicated by the construction of new Decls during IR generation.

In particular, we reconstruct the AST function type in order to get the
implicit 'this' parameter into C++ method types.

We also have to worry about FunctionDecls whose types are not
FunctionTypes because CGBlocks.cpp constructs some dummy FunctionDecls
with 'void' type.

Depends on D21114

[aprantl]

Assuming that we could usually get the calling convention from the Function — what's the motivation for emitting the calling convention of a subprogram that has been optimized away?

[rnk]

In D21141#452517, @aprantl wrote:

Assuming that we could usually get the calling convention from the Function — what's the motivation for emitting the calling convention of a subprogram that has been optimized away?

I don't have any motivation to emit DISubprograms for optimized away code, but Functions aren't always available. Function pointers can also have calling conventions, and they will only have a DISubroutineType.

[aprantl]

Function pointers make sense to me, thanks!
LGTM

lib/CodeGen/CGDebugInfo.cpp

834

I just wanted to say that it would be nice to have this function in DIBuilder, but then realized that CallingConv is defined in clang.

lib/CodeGen/CGDebugInfo.cpp

llvm::DIType *CGDebugInfo::CreateType(const TypedefType *Ty,
 
   // Typedefs are derived from some other type.
   return DBuilder.createTypedef(
       getOrCreateType(Ty->getDecl()->getUnderlyingType(), Unit),
       Ty->getDecl()->getName(), getOrCreateFile(Loc), getLineNumber(Loc),
       getDeclContextDescriptor(Ty->getDecl()));
 }
 
+static unsigned getDwarfCC(CallingConv CC) {
+  switch (CC) {
+  case CC_C:
+    // Avoid emitting DW_AT_calling_convention if the C convention was used.
+    return 0;
+
+  case CC_X86StdCall:
+    return llvm::dwarf::DW_CC_BORLAND_stdcall;
+  case CC_X86FastCall:
+    return llvm::dwarf::DW_CC_BORLAND_msfastcall;
+  case CC_X86ThisCall:
+    return llvm::dwarf::DW_CC_BORLAND_thiscall;
+  case CC_X86VectorCall:
+    return llvm::dwarf::DW_CC_LLVM_vectorcall;
+  case CC_X86Pascal:
+    return llvm::dwarf::DW_CC_BORLAND_pascal;
+
+  // FIXME: Create new DW_CC_ codes for these calling conventions.
+  case CC_X86_64Win64:
+  case CC_X86_64SysV:
+  case CC_AAPCS:
+  case CC_AAPCS_VFP:
+  case CC_IntelOclBicc:
+  case CC_SpirFunction:
+  case CC_SpirKernel:
+  case CC_Swift:
+  case CC_PreserveMost:
+  case CC_PreserveAll:
+    return 0;
+  }
+  return 0;
+}
+
 llvm::DIType *CGDebugInfo::CreateType(const FunctionType *Ty,
                                       llvm::DIFile *Unit) {
   SmallVector<llvm::Metadata *, 16> EltTys;
 
   // Add the result type at least.
   EltTys.push_back(getOrCreateType(Ty->getReturnType(), Unit));
 
   // Set up remainder of arguments if there is a prototype.
   // otherwise emit it as a variadic function.
   if (isa<FunctionNoProtoType>(Ty))
     EltTys.push_back(DBuilder.createUnspecifiedParameter());
   else if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(Ty)) {
     for (unsigned i = 0, e = FPT->getNumParams(); i != e; ++i)
       EltTys.push_back(getOrCreateType(FPT->getParamType(i), Unit));
     if (FPT->isVariadic())
       EltTys.push_back(DBuilder.createUnspecifiedParameter());
   }
 
   llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
-  return DBuilder.createSubroutineType(EltTypeArray);
+  return DBuilder.createSubroutineType(EltTypeArray, 0,
+                                       getDwarfCC(Ty->getCallConv()));
 }
 
 /// Convert an AccessSpecifier into the corresponding DINode flag.
 /// As an optimization, return 0 if the access specifier equals the
 /// default for the containing type.
 static unsigned getAccessFlag(AccessSpecifier Access, const RecordDecl *RD) {
   AccessSpecifier Default = clang::AS_none;
   if (RD && RD->isClass())
llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
   llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);
 
   unsigned Flags = 0;
   if (Func->getExtProtoInfo().RefQualifier == RQ_LValue)
     Flags |= llvm::DINode::FlagLValueReference;
   if (Func->getExtProtoInfo().RefQualifier == RQ_RValue)
     Flags |= llvm::DINode::FlagRValueReference;
 
-  return DBuilder.createSubroutineType(EltTypeArray, Flags);
+  return DBuilder.createSubroutineType(EltTypeArray, Flags,
+                                       getDwarfCC(Func->getCallConv()));
 }
 
 /// isFunctionLocalClass - Return true if CXXRecordDecl is defined
 /// inside a function.
 static bool isFunctionLocalClass(const CXXRecordDecl *RD) {
   if (const CXXRecordDecl *NRD = dyn_cast<CXXRecordDecl>(RD->getDeclContext()))
     return isFunctionLocalClass(NRD);
   if (isa<FunctionDecl>(RD->getDeclContext()))
CGDebugInfo::getFunctionForwardDeclaration(const FunctionDecl *FD) {
   unsigned Line = getLineNumber(Loc);
 
   collectFunctionDeclProps(FD, Unit, Name, LinkageName, DContext,
                            TParamsArray, Flags);
   // Build function type.
   SmallVector<QualType, 16> ArgTypes;
   for (const ParmVarDecl *Parm: FD->parameters())
     ArgTypes.push_back(Parm->getType());
-  QualType FnType =
-    CGM.getContext().getFunctionType(FD->getReturnType(), ArgTypes,
-                                     FunctionProtoType::ExtProtoInfo());
+  CallingConv CC = FD->getType()->castAs<FunctionType>()->getCallConv();
+  QualType FnType = CGM.getContext().getFunctionType(
+      FD->getReturnType(), ArgTypes, FunctionProtoType::ExtProtoInfo(CC));
   llvm::DISubprogram *SP = DBuilder.createTempFunctionFwdDecl(
       DContext, Name, LinkageName, Unit, Line,
       getOrCreateFunctionType(FD, FnType, Unit), !FD->isExternallyVisible(),
       /* isDefinition = */ false, 0, Flags, CGM.getLangOpts().Optimize,
       TParamsArray.get(), getFunctionDeclaration(FD));
   const FunctionDecl *CanonDecl = cast<FunctionDecl>(FD->getCanonicalDecl());
   FwdDeclReplaceMap.emplace_back(std::piecewise_construct,
                                  std::make_tuple(CanonDecl),
llvm::DISubroutineType *CGDebugInfo::getOrCreateFunctionType(const Decl *D,
                                                              llvm::DIFile *F) {
   if (!D || DebugKind <= codegenoptions::DebugLineTablesOnly)
     // Create fake but valid subroutine type. Otherwise -verify would fail, and
     // subprogram DIE will miss DW_AT_decl_file and DW_AT_decl_line fields.
     return DBuilder.createSubroutineType(DBuilder.getOrCreateTypeArray(None));
 
   if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D))
     return getOrCreateMethodType(Method, F);
+
+  const auto *FTy = FnType->getAs<FunctionType>();
+  CallingConv CC = FTy ? FTy->getCallConv() : CallingConv::CC_C;
+
   if (const ObjCMethodDecl *OMethod = dyn_cast<ObjCMethodDecl>(D)) {
     // Add "self" and "_cmd"
     SmallVector<llvm::Metadata *, 16> Elts;
 
     // First element is always return type. For 'void' functions it is NULL.
     QualType ResultTy = OMethod->getReturnType();
 
     // Replace the instancetype keyword with the actual type.
if (const ObjCMethodDecl *OMethod = dyn_cast<ObjCMethodDecl>(D)) {
     // Get rest of the arguments.
     for (const auto *PI : OMethod->params())
       Elts.push_back(getOrCreateType(PI->getType(), F));
     // Variadic methods need a special marker at the end of the type list.
     if (OMethod->isVariadic())
       Elts.push_back(DBuilder.createUnspecifiedParameter());
 
     llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);
-    return DBuilder.createSubroutineType(EltTypeArray);
+    return DBuilder.createSubroutineType(EltTypeArray, 0, getDwarfCC(CC));
   }
 
   // Handle variadic function types; they need an additional
   // unspecified parameter.
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
     if (FD->isVariadic()) {
       SmallVector<llvm::Metadata *, 16> EltTys;
       EltTys.push_back(getOrCreateType(FD->getReturnType(), F));
       if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FnType))
         for (unsigned i = 0, e = FPT->getNumParams(); i != e; ++i)
           EltTys.push_back(getOrCreateType(FPT->getParamType(i), F));
       EltTys.push_back(DBuilder.createUnspecifiedParameter());
       llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
-      return DBuilder.createSubroutineType(EltTypeArray);
+      return DBuilder.createSubroutineType(EltTypeArray, 0, getDwarfCC(CC));
     }
 
   return cast<llvm::DISubroutineType>(getOrCreateType(FnType, F));
 }
 
 void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, SourceLocation Loc,
                                     SourceLocation ScopeLoc, QualType FnType,
                                     llvm::Function *Fn, CGBuilderTy &Builder) {

lib/CodeGen/CodeGenFunction.cpp

void CodeGenFunction::StartFunction(GlobalDecl GD,
   AllocaInsertPt = new llvm::BitCastInst(Undef, Int32Ty, "allocapt", EntryBB);
 
   ReturnBlock = getJumpDestInCurrentScope("return");
 
   Builder.SetInsertPoint(EntryBB);
 
   // Emit subprogram debug descriptor.
   if (CGDebugInfo *DI = getDebugInfo()) {
+    // Reconstruct the type from the argument list so that implicit parameters,
+    // such as 'this' and 'vtt', show up in the debug info. Preserve the calling
+    // convention.
+    CallingConv CC = CallingConv::CC_C;
+    if (auto *FD = dyn_cast_or_null<FunctionDecl>(D))
+      if (const auto *SrcFnTy = FD->getType()->getAs<FunctionType>())
+        CC = SrcFnTy->getCallConv();
     SmallVector<QualType, 16> ArgTypes;
-    for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
-   i != e; ++i) {
-      ArgTypes.push_back((*i)->getType());
-    }
-
-    QualType FnType =
-      getContext().getFunctionType(RetTy, ArgTypes,
-                                   FunctionProtoType::ExtProtoInfo());
+    for (const VarDecl *VD : Args)
+      ArgTypes.push_back(VD->getType());
+    QualType FnType = getContext().getFunctionType(
+        RetTy, ArgTypes, FunctionProtoType::ExtProtoInfo(CC));
     DI->EmitFunctionStart(GD, Loc, StartLoc, FnType, CurFn, Builder);
   }
 
   if (ShouldInstrumentFunction())
     EmitFunctionInstrumentation("__cyg_profile_func_enter");
 
   if (CGM.getCodeGenOpts().InstrumentForProfiling)
     EmitMCountInstrumentation();

test/CodeGenCXX/debug-info-calling-conventions.cpp

+// RUN: %clang_cc1 %s -triple=i686-pc-windows-msvc -debug-info-kind=limited -emit-llvm -o - | FileCheck %s
+
+struct A {
+  void thiscallcc();
+};
+void A::thiscallcc() {}
+
+// CHECK: !DISubprogram(name: "thiscallcc", {{.*}} type: ![[thiscallty:[^,]*]], {{.*}})
+// CHECK: ![[thiscallty]] = !DISubroutineType(cc: DW_CC_BORLAND_thiscall, types: ![[thisargs:[^,)]*]])
+// CHECK: ![[thisargs]] = !{null, ![[thisptrty:[^,}]*]]}
+// CHECK: ![[thisptrty]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !{{.*}}, size: 32, align: 32, flags: DIFlagArtificial | DIFlagObjectPointer)
+
+void cdeclcc() {}
+void __fastcall fastcallcc() {}
+void __stdcall stdcallcc() {}
+void __vectorcall vectorcallcc() {}
+
+// CHECK: !DISubprogram(name: "cdeclcc", {{.*}} type: ![[cdeclty:[^,]*]], {{.*}})
+// CHECK: ![[cdeclty]] = !DISubroutineType(types: ![[noargs:[^,)]*]])
+// CHECK: ![[noargs]] = !{null}
+// CHECK: !DISubprogram(name: "fastcallcc", {{.*}} type: ![[fastcallty:[^,]*]], {{.*}})
+// CHECK: ![[fastcallty]] = !DISubroutineType(cc: DW_CC_BORLAND_msfastcall, types: ![[noargs]])
+// CHECK: !DISubprogram(name: "stdcallcc", {{.*}} type: ![[stdcallty:[^,]*]], {{.*}})
+// CHECK: ![[stdcallty]] = !DISubroutineType(cc: DW_CC_BORLAND_stdcall, types: ![[noargs]])
+// CHECK: !DISubprogram(name: "vectorcallcc", {{.*}} type: ![[vectorcallty:[^,]*]], {{.*}})
+// CHECK: ![[vectorcallty]] = !DISubroutineType(cc: DW_CC_LLVM_vectorcall, types: ![[noargs]])