[clang][DebugInfo] Attach DISubprogram to additional call variants (#166202)

`DISubprogram`s are attached to call sites to support various debug info
features, including entry values and tail calls. Clang 9.0
(0f65168) was the first version to
include this kind of call site `DISubprogram` attachment.

This earlier work appears to visit only some call site variants,
however. The call site attachment was added to a higher-level `EmitCall`
path in Clang's code gen that is only used by some call variants. In
particular, some C++ member calls use a different code gen path, which
did not include this call site attachment step, and thus the debug info
it triggers (e.g. call site entries) was not emitted for such calls.

This moves `DISubprogram` attachment to a lower-level call emission path
that is used by all call variants.

Fixes #161962

Author: jryans

clang/lib/CodeGen/CGCall.cpp

@@ -38,6 +38,7 @@
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
@@ -6277,6 +6278,24 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
     pushDestroy(QualType::DK_nontrivial_c_struct, Ret.getAggregateAddress(),
                 RetTy);
 
+  // Generate function declaration DISuprogram in order to be used
+  // in debug info about call sites.
+  if (CGDebugInfo *DI = getDebugInfo()) {
+    // Ensure call site info would actually be emitted before collecting
+    // further callee info.
+    if (CalleeDecl && !CalleeDecl->hasAttr<NoDebugAttr>() &&
+        DI->getCallSiteRelatedAttrs() != llvm::DINode::FlagZero) {
+      CodeGenFunction CalleeCGF(CGM);
+      const GlobalDecl &CalleeGlobalDecl =
+          Callee.getAbstractInfo().getCalleeDecl();
+      CalleeCGF.CurGD = CalleeGlobalDecl;
+      FunctionArgList Args;
+      QualType ResTy = CalleeCGF.BuildFunctionArgList(CalleeGlobalDecl, Args);
+      DI->EmitFuncDeclForCallSite(
+          CI, DI->getFunctionType(CalleeDecl, ResTy, Args), CalleeGlobalDecl);
+    }
+  }
+
   return Ret;
 }
 

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -4957,7 +4957,7 @@ void CGDebugInfo::EmitFunctionDecl(GlobalDecl GD, SourceLocation Loc,
 
 void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
                                           QualType CalleeType,
-                                          const FunctionDecl *CalleeDecl) {
+                                          GlobalDecl CalleeGlobalDecl) {
   if (!CallOrInvoke)
     return;
   auto *Func = dyn_cast<llvm::Function>(CallOrInvoke->getCalledOperand());
@@ -4966,6 +4966,9 @@ void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
   if (Func->getSubprogram())
     return;
 
+  const FunctionDecl *CalleeDecl =
+      cast<FunctionDecl>(CalleeGlobalDecl.getDecl());
+
   // Do not emit a declaration subprogram for a function with nodebug
   // attribute, or if call site info isn't required.
   if (CalleeDecl->hasAttr<NoDebugAttr>() ||
@@ -4976,7 +4979,8 @@ void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
   // create the one describing the function in order to have complete
   // call site debug info.
   if (!CalleeDecl->isStatic() && !CalleeDecl->isInlined())
-    EmitFunctionDecl(CalleeDecl, CalleeDecl->getLocation(), CalleeType, Func);
+    EmitFunctionDecl(CalleeGlobalDecl, CalleeDecl->getLocation(), CalleeType,
+                     Func);
 }
 
 void CGDebugInfo::EmitInlineFunctionStart(CGBuilderTy &Builder, GlobalDecl GD) {

clang/lib/CodeGen/CGDebugInfo.h

@@ -511,7 +511,7 @@ class CGDebugInfo {
   /// This is needed for call site debug info.
   void EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
                                QualType CalleeType,
-                               const FunctionDecl *CalleeDecl);
+                               GlobalDecl CalleeGlobalDecl);
 
   /// Constructs the debug code for exiting a function.
   void EmitFunctionEnd(CGBuilderTy &Builder, llvm::Function *Fn);
@@ -678,6 +678,10 @@ class CGDebugInfo {
   /// Emit symbol for debugger that holds the pointer to the vtable.
   void emitVTableSymbol(llvm::GlobalVariable *VTable, const CXXRecordDecl *RD);
 
+  /// Return flags which enable debug info emission for call sites, provided
+  /// that it is supported and enabled.
+  llvm::DINode::DIFlags getCallSiteRelatedAttrs() const;
+
 private:
   /// Amend \p I's DebugLoc with \p Group (its source atom group) and \p
   /// Rank (lower nonzero rank is higher precedence). Does nothing if \p I
@@ -827,11 +831,6 @@ class CGDebugInfo {
                          unsigned LineNo, StringRef LinkageName,
                          llvm::GlobalVariable *Var, llvm::DIScope *DContext);
 
-
-  /// Return flags which enable debug info emission for call sites, provided
-  /// that it is supported and enabled.
-  llvm::DINode::DIFlags getCallSiteRelatedAttrs() const;
-
   /// Get the printing policy for producing names for debug info.
   PrintingPolicy getPrintingPolicy() const;
 

clang/lib/CodeGen/CGExpr.cpp

@@ -6632,15 +6632,6 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType,
                          E == MustTailCall, E->getExprLoc());
 
   if (auto *CalleeDecl = dyn_cast_or_null<FunctionDecl>(TargetDecl)) {
-    // Generate function declaration DISuprogram in order to be used
-    // in debug info about call sites.
-    if (CGDebugInfo *DI = getDebugInfo()) {
-      FunctionArgList Args;
-      QualType ResTy = BuildFunctionArgList(CalleeDecl, Args);
-      DI->EmitFuncDeclForCallSite(LocalCallOrInvoke,
-                                  DI->getFunctionType(CalleeDecl, ResTy, Args),
-                                  CalleeDecl);
-    }
     if (CalleeDecl->hasAttr<RestrictAttr>() ||
         CalleeDecl->hasAttr<AllocSizeAttr>()) {
       // Function has 'malloc' (aka. 'restrict') or 'alloc_size' attribute.

clang/test/DebugInfo/CXX/decl-member-call.cpp

@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -O1 -triple x86_64-unknown_unknown -emit-llvm \
+// RUN:   -debug-info-kind=standalone -dwarf-version=5 %s -o - | FileCheck %s
+
+// Ensure both nonmember and member calls to declared function
+// have attached `DISubprogram`s.
+
+int nonmember(int n);
+
+struct S {
+  int x;
+  int member(int n);
+};
+
+int main(int argc, char** argv) {
+  struct S s = {};
+  int a = s.member(argc);
+  int b = nonmember(argc);
+  return a + b;
+}
+
+// CHECK: declare !dbg ![[SP1:[0-9]+]] noundef i32 @_ZN1S6memberEi(
+// CHECK: declare !dbg ![[SP2:[0-9]+]] noundef i32 @_Z9nonmemberi(
+
+// CHECK: ![[SP1]] = !DISubprogram(name: "member", linkageName: "_ZN1S6memberEi"
+// CHECK: ![[SP2]] = !DISubprogram(name: "nonmember", linkageName: "_Z9nonmemberi"