[DebugInfo][DWARF] Add DW_AT_alloc_type support (in LLVM ID space)

LLVM currently stores heapallocsite information in CodeView debuginfo, but
not in DWARF debuginfo. heapallocsite information is useful for profiling
and memory analysis.

The DWARF v6 working draft includes this feature as DW_AT_alloc_type; but
since that is not yet an official standard, use LLVM-private ID space for
now.

Author: thejh

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -625,6 +625,9 @@ HANDLE_DW_AT(0x3e0a, LLVM_ptrauth_authentication_mode, 0, LLVM)
 HANDLE_DW_AT(0x3e0b, LLVM_num_extra_inhabitants, 0, LLVM)
 HANDLE_DW_AT(0x3e0c, LLVM_stmt_sequence, 0, LLVM)
 HANDLE_DW_AT(0x3e0d, LLVM_coro_suspend_idx, 0, LLVM)
+// The DWARF v6 working draft defines DW_AT_alloc_type; use this LLVM-private ID
+// until that is released as an official standard.
+HANDLE_DW_AT(0x3e0e, LLVM_alloc_type, 0, LLVM)
 
 // Apple extensions.
 

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -1291,12 +1291,10 @@ DwarfCompileUnit::getDwarf5OrGNULocationAtom(dwarf::LocationAtom Loc) const {
   }
 }
 
-DIE &DwarfCompileUnit::constructCallSiteEntryDIE(DIE &ScopeDIE,
-                                                 const DISubprogram *CalleeSP,
-                                                 bool IsTail,
-                                                 const MCSymbol *PCAddr,
-                                                 const MCSymbol *CallAddr,
-                                                 unsigned CallReg) {
+DIE &DwarfCompileUnit::constructCallSiteEntryDIE(
+    DIE &ScopeDIE, const DISubprogram *CalleeSP, bool IsTail,
+    const MCSymbol *PCAddr, const MCSymbol *CallAddr, unsigned CallReg,
+    DIType *AllocSiteTy) {
   // Insert a call site entry DIE within ScopeDIE.
   DIE &CallSiteDIE = createAndAddDIE(getDwarf5OrGNUTag(dwarf::DW_TAG_call_site),
                                      ScopeDIE, nullptr);
@@ -1305,7 +1303,7 @@ DIE &DwarfCompileUnit::constructCallSiteEntryDIE(DIE &ScopeDIE,
     // Indirect call.
     addAddress(CallSiteDIE, getDwarf5OrGNUAttr(dwarf::DW_AT_call_target),
                MachineLocation(CallReg));
-  } else {
+  } else if (CalleeSP) {
     DIE *CalleeDIE = getOrCreateSubprogramDIE(CalleeSP);
     assert(CalleeDIE && "Could not create DIE for call site entry origin");
     if (AddLinkageNamesToDeclCallOriginsForTuning(DD) &&
@@ -1350,6 +1348,10 @@ DIE &DwarfCompileUnit::constructCallSiteEntryDIE(DIE &ScopeDIE,
                     getDwarf5OrGNUAttr(dwarf::DW_AT_call_return_pc), PCAddr);
   }
 
+  if (AllocSiteTy) {
+    addType(CallSiteDIE, AllocSiteTy, dwarf::DW_AT_LLVM_alloc_type);
+  }
+
   return CallSiteDIE;
 }
 

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

@@ -289,7 +289,8 @@ class DwarfCompileUnit final : public DwarfUnit {
   /// the \p CallReg is set to 0.
   DIE &constructCallSiteEntryDIE(DIE &ScopeDIE, const DISubprogram *CalleeSP,
                                  bool IsTail, const MCSymbol *PCAddr,
-                                 const MCSymbol *CallAddr, unsigned CallReg);
+                                 const MCSymbol *CallAddr, unsigned CallReg,
+                                 DIType *AllocSiteTy);
   /// Construct call site parameter DIEs for the \p CallSiteDIE. The \p Params
   /// were collected by the \ref collectCallSiteParameters.
   /// Note: The order of parameters does not matter, since debuggers recognize

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -936,28 +936,29 @@ void DwarfDebug::constructCallSiteEntryDIEs(const DISubprogram &SP,
       if (MI.hasDelaySlot() && !delaySlotSupported(*&MI))
         return;
 
+      DIType *AllocSiteTy = dyn_cast_or_null<DIType>(MI.getHeapAllocMarker());
+
       // If this is a direct call, find the callee's subprogram.
       // In the case of an indirect call find the register that holds
       // the callee.
       const MachineOperand &CalleeOp = TII->getCalleeOperand(MI);
-      if (!CalleeOp.isGlobal() &&
-          (!CalleeOp.isReg() || !CalleeOp.getReg().isPhysical()))
-        continue;
 
       unsigned CallReg = 0;
       const DISubprogram *CalleeSP = nullptr;
       const Function *CalleeDecl = nullptr;
-      if (CalleeOp.isReg()) {
-        CallReg = CalleeOp.getReg();
-        if (!CallReg)
-          continue;
-      } else {
+      if (CalleeOp.isReg() && CalleeOp.getReg().isPhysical()) {
+        CallReg = CalleeOp.getReg(); // might be zero
+      } else if (CalleeOp.isGlobal()) {
         CalleeDecl = dyn_cast<Function>(CalleeOp.getGlobal());
-        if (!CalleeDecl || !CalleeDecl->getSubprogram())
-          continue;
-        CalleeSP = CalleeDecl->getSubprogram();
+        if (CalleeDecl)
+          CalleeSP = CalleeDecl->getSubprogram(); // might be nullptr
       }
 
+      // Omit DIE if we can't tell where the call goes *and* we don't want to
+      // add metadata to it.
+      if (CalleeSP == nullptr && CallReg == 0 && AllocSiteTy == nullptr)
+        continue;
+
       // TODO: Omit call site entries for runtime calls (objc_msgSend, etc).
 
       bool IsTail = TII->isTailCall(MI);
@@ -991,7 +992,7 @@ void DwarfDebug::constructCallSiteEntryDIEs(const DISubprogram &SP,
                         << (IsTail ? " [IsTail]" : "") << "\n");
 
       DIE &CallSiteDIE = CU.constructCallSiteEntryDIE(
-          ScopeDIE, CalleeSP, IsTail, PCAddr, CallAddr, CallReg);
+          ScopeDIE, CalleeSP, IsTail, PCAddr, CallAddr, CallReg, AllocSiteTy);
 
       // Optionally emit call-site-param debug info.
       if (emitDebugEntryValues()) {

llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp

@@ -109,6 +109,7 @@ static bool isODRAttribute(uint16_t Attr) {
   case dwarf::DW_AT_specification:
   case dwarf::DW_AT_abstract_origin:
   case dwarf::DW_AT_import:
+  case dwarf::DW_AT_LLVM_alloc_type:
     return true;
   }
   llvm_unreachable("Improper attribute.");

llvm/test/DebugInfo/X86/DW_AT_alloc_type.ll

@@ -0,0 +1,33 @@
+; RUN: llc -O3 -o %t -filetype=obj %s
+; RUN: llvm-dwarfdump %t | FileCheck %s
+
+; based on clang++ output for `int *alloc_int() { return new int; }`
+
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local ptr @alloc_int() !dbg !3 {
+; CHECK: DW_TAG_subprogram
+entry:
+  %call = call ptr @alloc(i64 noundef 4), !heapallocsite !7
+; CHECK: DW_TAG_GNU_call_site
+; CHECK: DW_AT_LLVM_alloc_type ([[ALLOCSITE:.*]])
+  ret ptr %call
+}
+
+; CHECK: {{.*}}[[ALLOCSITE]]: DW_TAG_base_type
+; CHECK: DW_AT_name ("int")
+
+declare dso_local ptr @alloc(i64 noundef)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, emissionKind: FullDebug)
+!1 = !DIFile(filename: "a.cpp", directory: "/")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "alloc_int", scope: !1, file: !1, line: 1, type: !4, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition, unit: !0)
+!4 = !DISubroutineType(types: !5)
+!5 = !{!6}
+!6 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)