From: David Stenberg Date: Wed, 9 Jan 2019 09:58:59 +0000 (+0000) Subject: [DebugInfo] Omit location list entries with empty ranges X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e81d719f146775ce33c976dadb60096d576cac80;p=llvm [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 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350698 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp index 71fbfaa567c..151cf3c4247 100644 --- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp +++ b/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); diff --git a/test/DebugInfo/ARM/PR26163.ll b/test/DebugInfo/ARM/PR26163.ll index 3b3ec9c3f4f..f341a83cbc3 100644 --- a/test/DebugInfo/ARM/PR26163.ll +++ b/test/DebugInfo/ARM/PR26163.ll @@ -1,16 +1,17 @@ ; RUN: llc -filetype=obj -o - < %s | llvm-dwarfdump -v -debug-info - | FileCheck %s ; -; Checks that we're creating two ranges, one that terminates immediately -; and one that spans the rest of the function. This isn't necessarily the -; best thing to do here (and also not necessarily correct, since the first -; one has a bit_piece), but it is what is currently being emitted, any -; change here needs to be intentional, so the test is very specific. +; Checks that we're omitting the first range, as it is empty, and that we're +; emitting one that spans the rest of the function. In this case, the first +; range, which we omit, describes 8 bytes of the variable using DW_OP_litX, +; whereas the second one only describes 4 bytes, so clobbering the whole 8 byte +; fragment with the 4 bytes fragment isn't necessarily best thing to do here, +; but it is what is currently being emitted. Any change here needs to be +; intentional, so the test is very specific. ; ; CHECK: DW_TAG_inlined_subroutine ; CHECK: DW_TAG_variable ; CHECK: DW_AT_location [DW_FORM_sec_offset] ({{.*}} -; CHECK: [0x00000004, 0x00000004): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x8 -; CHECK: [0x00000004, 0x00000014): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x4) +; CHECK-NEXT: [0x00000004, 0x00000014): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x4) ; Created form the following test case (PR26163) with ; clang -cc1 -triple armv4t--freebsd11.0-gnueabi -emit-obj -debug-info-kind=standalone -O2 -x c test.c diff --git a/test/DebugInfo/X86/PR26148.ll b/test/DebugInfo/X86/PR26148.ll index 685f2d50371..d5ae2dc2ab2 100644 --- a/test/DebugInfo/X86/PR26148.ll +++ b/test/DebugInfo/X86/PR26148.ll @@ -16,11 +16,10 @@ ; This is similar to the bug in test/DebugInfo/ARM/PR26163.ll, except that there is an ; extra non-overlapping range first. Thus, we make sure that the backend actually looks ; at all expressions when determining whether to merge ranges, not just the first one. -; AS in 26163, we expect two ranges (as opposed to one), the first one being zero sized +; AS in 26163, we only expect one range as the first one is zero sized. ; ; -; CHECK: [0x0000000000000004, 0x0000000000000004): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_reg5 RDI, DW_OP_piece 0x2 -; CHECK: [0x0000000000000004, 0x0000000000000014): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_lit0, DW_OP_piece 0x4 +; CHECK: [0x0000000000000000, 0x000000000000000f): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_lit0, DW_OP_piece 0x4 source_filename = "test/DebugInfo/X86/PR26148.ll" target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" @@ -35,11 +34,8 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) #0 ; Function Attrs: nounwind readnone declare void @llvm.dbg.value(metadata, metadata, metadata) #0 -; The attributes are here to force the zero-sized range not to be at the start of -; the function, which has special interpretation in DWARF. The fact that this happens -; at all is probably an LLVM bug. -define void @fn1(i16 signext %p1) #1 !dbg !16 { +define void @fn1(i16 signext %p1) !dbg !16 { entry: tail call void @llvm.dbg.value(metadata i16 %p1, metadata !20, metadata !23), !dbg !24 tail call void @llvm.dbg.declare(metadata %struct.S0* undef, metadata !21, metadata !23), !dbg !25 @@ -60,7 +56,6 @@ entry: } attributes #0 = { nounwind readnone } -attributes #1 = { "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" } !llvm.dbg.cu = !{!2} !llvm.module.flags = !{!12, !13, !14} diff --git a/test/DebugInfo/X86/pieces-3.ll b/test/DebugInfo/X86/pieces-3.ll index 0f705f14f8f..e91bd262e79 100644 --- a/test/DebugInfo/X86/pieces-3.ll +++ b/test/DebugInfo/X86/pieces-3.ll @@ -18,12 +18,10 @@ ; CHECK: DW_TAG_formal_parameter [3] ; CHECK-NEXT: DW_AT_location [DW_FORM_data4] ( ; CHECK-NEXT: [0x0000000000000000, 0x0000000000000007): DW_OP_reg5 RDI, DW_OP_piece 0x8, DW_OP_piece 0x4, DW_OP_reg4 RSI, DW_OP_piece 0x4 -; CHECK-NEXT: [0x0000000000000007, 0x0000000000000007): DW_OP_reg5 RDI, DW_OP_piece 0x8, DW_OP_piece 0x4, DW_OP_reg0 RAX, DW_OP_piece 0x4) ; CHECK-NEXT: DW_AT_name {{.*}}"outer" ; CHECK: DW_TAG_variable -; CHECK-NEXT: DW_AT_location [DW_FORM_data4] (0x00000044 -; CHECK-NEXT: [0x0000000000000007, 0x0000000000000007): DW_OP_reg0 RAX, DW_OP_piece 0x4) -; CHECK-NEXT: "i1" +; CHECK-NEXT: DW_AT_name {{.*}}"i1" +; CHECK-NOT: DW_AT_location ; ModuleID = '/Volumes/Data/llvm/test/DebugInfo/X86/sroasplit-2.ll' target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"