[DebugInfo]Generate call-site information in swift

This patch adds support for emitting the flag
llvm::DINode::FlagAllCallsDescribed when generating LLVM IR from the
Swift compiler to get call-site information for swift source code.

Author: rastogishubham

include/swift/AST/IRGenOptions.h

@@ -296,6 +296,10 @@ class IRGenOptions {
   /// indexing info.
   PathRemapper FilePrefixMap;
 
+  /// Indicates whether or not the frontend should generate callsite information
+  /// in the debug info.
+  bool DebugCallsiteInfo = false;
+
   /// What level of debug info to generate.
   IRGenDebugInfoLevel DebugInfoLevel : 2;
 

include/swift/Option/Options.td

@@ -2191,6 +2191,10 @@ def cas_backend: Flag<["-"], "cas-backend">,
   Flags<[FrontendOption, NoDriverOption]>,
   HelpText<"Enable using CASBackend for object file output">;
 
+def debug_callsite_info: Flag<["-"], "debug-callsite-info">,
+  Flags<[FrontendOption, NoDriverOption]>,
+  HelpText<"Generate callsite information in debug info">;
+
 def cas_backend_mode: Joined<["-"], "cas-backend-mode=">,
   Flags<[FrontendOption, NoDriverOption]>,
   HelpText<"CASBackendMode for output kind">,

lib/Frontend/CompilerInvocation.cpp

@@ -3681,6 +3681,8 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
   Opts.UseCASBackend |= Args.hasArg(OPT_cas_backend);
   Opts.EmitCASIDFile |= Args.hasArg(OPT_cas_emit_casid_file);
 
+  Opts.DebugCallsiteInfo |= Args.hasArg(OPT_debug_callsite_info);
+
   return false;
 }
 

lib/IRGen/IRGenDebugInfo.cpp

@@ -284,6 +284,10 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
   void emitPackCountParameter(IRGenFunction &IGF, llvm::Value *Metadata,
                               SILDebugVariable VarInfo);
 
+  /// Return flags which enable debug info emission for call sites, provided
+  /// that it is supported and enabled.
+  llvm::DINode::DIFlags getCallSiteRelatedAttrs() const;
+
   /// Return the DIBuilder.
   llvm::DIBuilder &getBuilder() { return DBuilder; }
 
@@ -3042,6 +3046,33 @@ void IRGenDebugInfoImpl::emitImport(ImportDecl *D) {
   ImportedModules.insert(Imported.importedModule);
 }
 
+/// This is effectively \p clang::CGDebugInfo::getCallSiteRelatedAttrs().
+llvm::DINode::DIFlags IRGenDebugInfoImpl::getCallSiteRelatedAttrs() const {
+
+  // Do not generate callsite attributes if unless the -gen-callsite-info flag
+  // is passed.
+  if (!Opts.DebugCallsiteInfo)
+    return llvm::DINode::FlagZero;
+
+  auto SwiftLangOpts = IGM.Context.LangOpts;
+  auto Loader = IGM.getSILModule().getASTContext().getClangModuleLoader();
+  auto *Importer = static_cast<ClangImporter *>(&*Loader);
+  auto &CGO = Importer->getCodeGenOpts();
+
+  // Do not generate callsite attributes if there is no debug info to be
+  // emitted.
+  if (CGO.getDebugInfo() == llvm::codegenoptions::NoDebugInfo ||
+      CGO.getDebugInfo() == llvm::codegenoptions::LocTrackingOnly)
+    return llvm::DINode::FlagZero;
+
+  // Callsite attributes are available in DWARFv5. However, for swift, lldb can
+  // accept these attributes as if they were part of DWARFv4.
+  if (Opts.DWARFVersion < 4)
+    return llvm::DINode::FlagZero;
+
+  return llvm::DINode::FlagAllCallsDescribed;
+}
+
 llvm::DISubprogram *IRGenDebugInfoImpl::emitFunction(SILFunction &SILFn,
                                                      llvm::Function *Fn) {
   auto *DS = SILFn.getDebugScope();
@@ -3193,9 +3224,10 @@ IRGenDebugInfoImpl::emitFunction(const SILDebugScope *DS, llvm::Function *Fn,
   }
 
   // Construct the DISubprogram.
-  llvm::DISubprogram *SP = DBuilder.createFunction(
-      Scope, Name, LinkageName, File, Line, DIFnTy, ScopeLine, Flags, SPFlags,
-      TemplateParameters, Decl, Error);
+  llvm::DISubprogram *SP =
+      DBuilder.createFunction(Scope, Name, LinkageName, File, Line, DIFnTy,
+                              ScopeLine, Flags | getCallSiteRelatedAttrs(),
+                              SPFlags, TemplateParameters, Decl, Error);
 
   if (Fn && !Fn->isDeclaration())
     Fn->setSubprogram(SP);

test/DebugInfo/call-site-info.swift

@@ -0,0 +1,7 @@
+// RUN: %target-swift-frontend -debug-callsite-info -emit-ir -parse-as-library -g -O -module-name S %s -o - | %FileCheck %s
+// CHECK: {{[0-9]+}} = distinct !DISubprogram(name: "f", linkageName: {{.*}}, scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, type: !{{[0-9]+}}, scopeLine: {{[0-9]+}}, flags: DIFlagAllCallsDescribed
+// CHECK: {{[0-9]+}} = distinct !DISubprogram(linkageName: {{.*}}, scope: !{{[0-9]+}}, file: !{{[0-9]+}}, type: !{{[0-9]+}}, flags: {{.*}} DIFlagAllCallsDescribed
+
+public struct S {
+  public func f() {}
+}