From 33b192d72b2e0a65ecbaf2b2995a9e11fa795222 Mon Sep 17 00:00:00 2001 From: David Stenberg Date: Wed, 9 Jan 2019 09:58:59 +0000 Subject: [DebugInfo] Omit location list entries with empty ranges Summary: This fixes PR39710. In that case we emitted a location list looking like this: .Ldebug_loc0: .quad .Lfunc_begin0-.Lfunc_begin0 .quad .Lfunc_begin0-.Lfunc_begin0 .short 1 # Loc expr size .byte 85 # DW_OP_reg5 .quad .Lfunc_begin0-.Lfunc_begin0 .quad .Lfunc_end0-.Lfunc_begin0 .short 1 # Loc expr size .byte 85 # super-register DW_OP_reg5 .quad 0 .quad 0 As seen, the first entry's beginning and ending addresses evalute to 0, which meant that the entry inadvertently became an "end of list" entry, resulting in the location list ending sooner than expected. To fix this, omit all entries with empty ranges. Location list entries with empty ranges do not have any effect, as specified by DWARF, so we might as well drop them: "A location list entry (but not a base address selection or end of list entry) whose beginning and ending addresses are equal has no effect because the size of the range covered by such an entry is zero." Reviewers: davide, aprantl, dblaikie Reviewed By: aprantl Subscribers: javed.absar, JDevlieghere, llvm-commits Tags: #debug-info Differential Revision: https://reviews.llvm.org/D55919 llvm-svn: 350698 --- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'llvm/lib') diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp index 71fbfaa567c..151cf3c4247 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp @@ -1180,6 +1180,18 @@ DwarfDebug::buildLocationList(SmallVectorImpl &DebugLoc, LLVM_DEBUG(dbgs() << "DotDebugLoc: " << *Begin << "\n"); auto Value = getDebugLocValue(Begin); + + // Omit entries with empty ranges as they do not have any effect in DWARF. + if (StartLabel == EndLabel) { + // If this is a fragment, we must still add the value to the list of + // open ranges, since it may describe non-overlapping parts of the + // variable. + if (DIExpr->isFragment()) + OpenRanges.push_back(Value); + LLVM_DEBUG(dbgs() << "Omitting location list entry with empty range.\n"); + continue; + } + DebugLocEntry Loc(StartLabel, EndLabel, Value); bool couldMerge = false; @@ -1918,6 +1930,7 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT, void DebugLocEntry::finalize(const AsmPrinter &AP, DebugLocStream::ListBuilder &List, const DIBasicType *BT) { + assert(Begin != End && "unexpected location list entry with empty range"); DebugLocStream::EntryBuilder Entry(List, Begin, End); BufferByteStreamer Streamer = Entry.getStreamer(); DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer); -- cgit v1.2.3