[llvm] [DebugInfo][DWARF] Add heapallocsite information (PR #132073)
via llvm-commits
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Wed Mar 19 11:10:40 PDT 2025
https://github.com/thejh created https://github.com/llvm/llvm-project/pull/132073
LLVM currently stores heapallocsite information in CodeView debuginfo, but not in DWARF debuginfo. Plumb it into DWARF as an LLVM-specific extension.
heapallocsite debug information is useful when it is combined with allocator instrumentation that stores caller addresses; I've used a previous version of this patch for:
- analyzing memory usage by object type
- analyzing the distributions of values of class members
Other possible uses might be:
- attributing memory access profiles (for example, on Intel CPUs, from PEBS records with Linear Data Address) to object types or specific object members
- adding type information to crash/ASAN reports
>From 775c75a3723227a9618237c3fbf507ad26496b34 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh at google.com>
Date: Thu, 14 Oct 2021 13:46:30 +0200
Subject: [PATCH] [DebugInfo][DWARF] Add heapallocsite information
LLVM currently stores heapallocsite information in CodeView debuginfo, but
not in DWARF debuginfo. heapallocsite information is useful for profiling
and memory analysis; plumb it into DWARF as an LLVM-specific extension.
---
llvm/include/llvm/BinaryFormat/Dwarf.def | 1 +
.../CodeGen/AsmPrinter/DwarfCompileUnit.cpp | 16 +++++----
.../lib/CodeGen/AsmPrinter/DwarfCompileUnit.h | 3 +-
llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 25 +++++++-------
llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp | 1 +
.../DebugInfo/X86/DW_AT_LLVM_heapallocsite.ll | 33 +++++++++++++++++++
6 files changed, 59 insertions(+), 20 deletions(-)
create mode 100644 llvm/test/DebugInfo/X86/DW_AT_LLVM_heapallocsite.ll
diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.def b/llvm/include/llvm/BinaryFormat/Dwarf.def
index e52324a8ebc12..51660b30568a5 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.def
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -624,6 +624,7 @@ HANDLE_DW_AT(0x3e09, LLVM_ptrauth_authenticates_null_values, 0, LLVM)
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_heapallocsite, 0, LLVM)
// Apple extensions.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index dad14b98d2c3d..f14742d048c39 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1289,12 +1289,10 @@ 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);
@@ -1303,7 +1301,7 @@ 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) &&
@@ -1348,6 +1346,10 @@ DIE &DwarfCompileUnit::constructCallSiteEntryDIE(DIE &ScopeDIE,
getDwarf5OrGNUAttr(dwarf::DW_AT_call_return_pc), PCAddr);
}
+ if (AllocSiteTy) {
+ addType(CallSiteDIE, AllocSiteTy, dwarf::DW_AT_LLVM_heapallocsite);
+ }
+
return CallSiteDIE;
}
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 104039db03c7c..52186d29c8272 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -285,7 +285,8 @@ 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
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index b7b083028ef65..62ffe6e6e6c38 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -930,28 +930,29 @@ void DwarfDebug::constructCallSiteEntryDIEs(const DISubprogram &SP,
if (MI.hasDelaySlot() && !delaySlotSupported(*&MI))
return;
+ DIType *AllocSiteTy = 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);
@@ -986,7 +987,7 @@ 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()) {
diff --git a/llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp b/llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp
index f66773ad2e694..586d1c2abd5e0 100644
--- a/llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp
+++ b/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_heapallocsite:
return true;
}
llvm_unreachable("Improper attribute.");
diff --git a/llvm/test/DebugInfo/X86/DW_AT_LLVM_heapallocsite.ll b/llvm/test/DebugInfo/X86/DW_AT_LLVM_heapallocsite.ll
new file mode 100644
index 0000000000000..53975e02acbc3
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/DW_AT_LLVM_heapallocsite.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_heapallocsite ([[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)
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