[llvm] r240244 - AsmPrinter: Don't emit empty .debug_loc entries
Duncan P. N. Exon Smith
dexonsmith at apple.com
Sun Jun 21 09:54:56 PDT 2015
Author: dexonsmith
Date: Sun Jun 21 11:54:56 2015
New Revision: 240244
URL: http://llvm.org/viewvc/llvm-project?rev=240244&view=rev
Log:
AsmPrinter: Don't emit empty .debug_loc entries
If we don't know how to represent a .debug_loc entry, skip the entry
entirely rather than emitting an empty one. Similarly, if a .debug_loc
list has no entries, don't create the list.
We still want to create the variables, just in an optimized-out form
that doesn't have a DW_AT_location.
Added:
llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.cpp
llvm/trunk/test/DebugInfo/X86/debug-loc-empty-entries.ll
Modified:
llvm/trunk/lib/CodeGen/AsmPrinter/CMakeLists.txt
llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h
llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.h
llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/CMakeLists.txt?rev=240244&r1=240243&r2=240244&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/CMakeLists.txt (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/CMakeLists.txt Sun Jun 21 11:54:56 2015
@@ -5,6 +5,7 @@ add_llvm_library(LLVMAsmPrinter
AsmPrinterDwarf.cpp
AsmPrinterInlineAsm.cpp
DbgValueHistoryCalculator.cpp
+ DebugLocStream.cpp
DIE.cpp
DIEHash.cpp
DwarfAccelTable.cpp
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h?rev=240244&r1=240243&r2=240244&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocEntry.h Sun Jun 21 11:54:56 2015
@@ -142,7 +142,7 @@ public:
}
/// \brief Lower this entry into a DWARF expression.
- void finalize(const AsmPrinter &AP, DebugLocStream &Locs,
+ void finalize(const AsmPrinter &AP, DebugLocStream::ListBuilder &List,
const DIBasicType *BT);
};
Added: llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.cpp?rev=240244&view=auto
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.cpp (added)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.cpp Sun Jun 21 11:54:56 2015
@@ -0,0 +1,46 @@
+//===- DebugLocStream.cpp - DWARF debug_loc stream --------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DebugLocStream.h"
+#include "DwarfDebug.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+
+using namespace llvm;
+
+bool DebugLocStream::finalizeList(AsmPrinter &Asm) {
+ if (Lists.back().EntryOffset == Entries.size()) {
+ // Empty list. Delete it.
+ Lists.pop_back();
+ return false;
+ }
+
+ // Real list. Generate a label for it.
+ Lists.back().Label = Asm.createTempSymbol("debug_loc");
+ return true;
+}
+
+void DebugLocStream::finalizeEntry() {
+ if (Entries.back().ByteOffset != DWARFBytes.size())
+ return;
+
+ // The last entry was empty. Delete it.
+ Comments.erase(Comments.begin() + Entries.back().CommentOffset,
+ Comments.end());
+ Entries.pop_back();
+
+ assert(Lists.back().EntryOffset <= Entries.size() &&
+ "Popped off more entries than are in the list");
+}
+
+DebugLocStream::ListBuilder::~ListBuilder() {
+ if (!Locs.finalizeList(Asm))
+ return;
+ V.initializeDbgValue(&MI);
+ V.setDebugLocListIndex(ListIndex);
+}
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.h?rev=240244&r1=240243&r2=240244&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.h (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugLocStream.h Sun Jun 21 11:54:56 2015
@@ -15,7 +15,11 @@
#include "ByteStreamer.h"
namespace llvm {
+
+class AsmPrinter;
+class DbgVariable;
class DwarfCompileUnit;
+class MachineInstr;
class MCSymbol;
/// \brief Byte stream of .debug_loc entries.
@@ -29,10 +33,10 @@ class DebugLocStream {
public:
struct List {
DwarfCompileUnit *CU;
- MCSymbol *Label;
+ MCSymbol *Label = nullptr;
size_t EntryOffset;
- List(DwarfCompileUnit *CU, MCSymbol *Label, size_t EntryOffset)
- : CU(CU), Label(Label), EntryOffset(EntryOffset) {}
+ List(DwarfCompileUnit *CU, size_t EntryOffset)
+ : CU(CU), EntryOffset(EntryOffset) {}
};
struct Entry {
const MCSymbol *BeginSym;
@@ -61,18 +65,30 @@ public:
const List &getList(size_t LI) const { return Lists[LI]; }
ArrayRef<List> getLists() const { return Lists; }
+ class ListBuilder;
+ class EntryBuilder;
+
+private:
/// \brief Start a new .debug_loc entry list.
///
/// Start a new .debug_loc entry list. Return the new list's index so it can
/// be retrieved later via \a getList().
///
/// Until the next call, \a startEntry() will add entries to this list.
- size_t startList(DwarfCompileUnit *CU, MCSymbol *Label) {
+ size_t startList(DwarfCompileUnit *CU) {
size_t LI = Lists.size();
- Lists.emplace_back(CU, Label, Entries.size());
+ Lists.emplace_back(CU, Entries.size());
return LI;
}
+ /// Finalize a .debug_loc entry list.
+ ///
+ /// If there are no entries in this list, delete it outright. Otherwise,
+ /// create a label with \a Asm.
+ ///
+ /// \return false iff the list is deleted.
+ bool finalizeList(AsmPrinter &Asm);
+
/// \brief Start a new .debug_loc entry.
///
/// Until the next call, bytes added to the stream will be added to this
@@ -81,6 +97,10 @@ public:
Entries.emplace_back(BeginSym, EndSym, DWARFBytes.size(), Comments.size());
}
+ /// Finalize a .debug_loc entry, deleting if it's empty.
+ void finalizeEntry();
+
+public:
BufferByteStreamer getStreamer() {
return BufferByteStreamer(DWARFBytes, Comments, GenerateComments);
}
@@ -129,5 +149,45 @@ private:
return Entries[EI + 1].CommentOffset - Entries[EI].CommentOffset;
}
};
+
+/// Builder for DebugLocStream lists.
+class DebugLocStream::ListBuilder {
+ DebugLocStream &Locs;
+ AsmPrinter &Asm;
+ DbgVariable &V;
+ const MachineInstr &MI;
+ size_t ListIndex;
+
+public:
+ ListBuilder(DebugLocStream &Locs, DwarfCompileUnit &CU, AsmPrinter &Asm,
+ DbgVariable &V, const MachineInstr &MI)
+ : Locs(Locs), Asm(Asm), V(V), MI(MI), ListIndex(Locs.startList(&CU)) {}
+
+ /// Finalize the list.
+ ///
+ /// If the list is empty, delete it. Otherwise, finalize it by creating a
+ /// temp symbol in \a Asm and setting up the \a DbgVariable.
+ ~ListBuilder();
+
+ DebugLocStream &getLocs() { return Locs; }
+};
+
+/// Builder for DebugLocStream entries.
+class DebugLocStream::EntryBuilder {
+ DebugLocStream &Locs;
+
+public:
+ EntryBuilder(ListBuilder &List, const MCSymbol *Begin, const MCSymbol *End)
+ : Locs(List.getLocs()) {
+ Locs.startEntry(Begin, End);
+ }
+
+ /// Finalize the entry, deleting it if it's empty.
+ ~EntryBuilder() { Locs.finalizeEntry(); }
+
+ BufferByteStreamer getStreamer() { return Locs.getStreamer(); }
+};
+
} // namespace llvm
+
#endif
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=240244&r1=240243&r2=240244&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Sun Jun 21 11:54:56 2015
@@ -908,15 +908,15 @@ void DwarfDebug::collectVariableInfo(Dwa
const MachineInstr *MInsn = Ranges.front().first;
assert(MInsn->isDebugValue() && "History must begin with debug value");
- RegVar->initializeDbgValue(MInsn);
// Check if the first DBG_VALUE is valid for the rest of the function.
- if (Ranges.size() == 1 && Ranges.front().second == nullptr)
+ if (Ranges.size() == 1 && Ranges.front().second == nullptr) {
+ RegVar->initializeDbgValue(MInsn);
continue;
+ }
// Handle multiple DBG_VALUE instructions describing one variable.
- RegVar->setDebugLocListIndex(
- DebugLocs.startList(&TheCU, Asm->createTempSymbol("debug_loc")));
+ DebugLocStream::ListBuilder List(DebugLocs, TheCU, *Asm, *RegVar, *MInsn);
// Build the location list for this variable.
SmallVector<DebugLocEntry, 8> Entries;
@@ -930,7 +930,7 @@ void DwarfDebug::collectVariableInfo(Dwa
// Finalize the entry by lowering it into a DWARF bytestream.
for (auto &Entry : Entries)
- Entry.finalize(*Asm, DebugLocs, BT);
+ Entry.finalize(*Asm, List, BT);
}
// Collect info for variables that were optimized out.
@@ -1504,10 +1504,11 @@ static void emitDebugLocValue(const AsmP
// FIXME: ^
}
-void DebugLocEntry::finalize(const AsmPrinter &AP, DebugLocStream &Locs,
+void DebugLocEntry::finalize(const AsmPrinter &AP,
+ DebugLocStream::ListBuilder &List,
const DIBasicType *BT) {
- Locs.startEntry(Begin, End);
- BufferByteStreamer Streamer = Locs.getStreamer();
+ DebugLocStream::EntryBuilder Entry(List, Begin, End);
+ BufferByteStreamer Streamer = Entry.getStreamer();
const DebugLocEntry::Value &Value = Values[0];
if (Value.isBitPiece()) {
// Emit all pieces that belong to the same variable and range.
Added: llvm/trunk/test/DebugInfo/X86/debug-loc-empty-entries.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/debug-loc-empty-entries.ll?rev=240244&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/debug-loc-empty-entries.ll (added)
+++ llvm/trunk/test/DebugInfo/X86/debug-loc-empty-entries.ll Sun Jun 21 11:54:56 2015
@@ -0,0 +1,66 @@
+; RUN: llc -mtriple=x86_64-apple-macosx <%s | FileCheck %s
+; Test that we don't generate empty .debug_loc entries. Originally, there were
+; two empty .debug_loc entries for 'a' in an otherwise empty .debug_loc list.
+;
+; CHECK: .section __DWARF,__debug_loc,regular,debug
+; CHECK-NEXT: Lsection_debug_loc:
+; CHECK-NEXT: .section __DWARF,__debug_abbrev,regular,debug
+;
+; Test that the variable stuck around.
+; CHECK: .section __DWARF,__debug_info,regular,debug
+; CHECK: DW_TAG_variable
+; CHECK-NOT: DW_AT_location
+
+; Generated using clang -cc1 with the following args:
+;
+; -triple x86_64-apple-macosx -emit-llvm -gdwarf-4 -O1
+;
+; From this testcase:
+;
+;; void fn1() {
+;; float a = 1;
+;; for (;;)
+;; a = 0;
+;; }
+
+; Function Attrs: noreturn nounwind readnone
+define void @_Z3fn1v() #0 {
+entry:
+ tail call void @llvm.dbg.value(metadata float 1.000000e+00, i64 0, metadata !9, metadata !14), !dbg !15
+ br label %for.cond, !dbg !16
+
+for.cond: ; preds = %for.cond, %entry
+ tail call void @llvm.dbg.value(metadata float 0.000000e+00, i64 0, metadata !9, metadata !14), !dbg !15
+ br label %for.cond, !dbg !17
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { noreturn nounwind readnone "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-realign-stack" "stack-protector-buffer-size"="8" "target-features"="+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!11, !12}
+!llvm.ident = !{!13}
+
+!0 = !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.7.0 (trunk 238517) (llvm/trunk 238524)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !DIFile(filename: "<stdin>", directory: "/Users/dexonsmith/data/llvm/bootstrap/play/delta2/testcase")
+!2 = !{}
+!3 = !{!4}
+!4 = !DISubprogram(name: "fn1", linkageName: "_Z3fn1v", scope: !5, file: !5, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, function: void ()* @_Z3fn1v, variables: !8)
+!5 = !DIFile(filename: "t.cpp", directory: "/Users/dexonsmith/data/llvm/bootstrap/play/delta2/testcase")
+!6 = !DISubroutineType(types: !7)
+!7 = !{null}
+!8 = !{!9}
+!9 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "a", scope: !4, file: !5, line: 2, type: !10)
+!10 = !DIBasicType(name: "float", size: 32, align: 32, encoding: DW_ATE_float)
+!11 = !{i32 2, !"Dwarf Version", i32 4}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = !{!"clang version 3.7.0 (trunk 238517) (llvm/trunk 238524)"}
+!14 = !DIExpression()
+!15 = !DILocation(line: 2, scope: !4)
+!16 = !DILocation(line: 3, scope: !4)
+!17 = !DILocation(line: 3, scope: !18)
+!18 = distinct !DILexicalBlock(scope: !19, file: !5, line: 3)
+!19 = distinct !DILexicalBlock(scope: !4, file: !5, line: 3)
More information about the llvm-commits
mailing list