[llvm] r350698 - [DebugInfo] Omit location list entries with empty ranges
David Stenberg via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 9 01:58:59 PST 2019
Author: dstenb
Date: Wed Jan 9 01:58:59 2019
New Revision: 350698
URL: http://llvm.org/viewvc/llvm-project?rev=350698&view=rev
Log:
[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
Modified:
llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
llvm/trunk/test/DebugInfo/ARM/PR26163.ll
llvm/trunk/test/DebugInfo/X86/PR26148.ll
llvm/trunk/test/DebugInfo/X86/pieces-3.ll
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=350698&r1=350697&r2=350698&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Wed Jan 9 01:58:59 2019
@@ -1180,6 +1180,18 @@ DwarfDebug::buildLocationList(SmallVecto
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 AsmP
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);
Modified: llvm/trunk/test/DebugInfo/ARM/PR26163.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/ARM/PR26163.ll?rev=350698&r1=350697&r2=350698&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/ARM/PR26163.ll (original)
+++ llvm/trunk/test/DebugInfo/ARM/PR26163.ll Wed Jan 9 01:58:59 2019
@@ -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
Modified: llvm/trunk/test/DebugInfo/X86/PR26148.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/PR26148.ll?rev=350698&r1=350697&r2=350698&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/PR26148.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/PR26148.ll Wed Jan 9 01:58:59 2019
@@ -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,
; 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}
Modified: llvm/trunk/test/DebugInfo/X86/pieces-3.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/pieces-3.ll?rev=350698&r1=350697&r2=350698&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/pieces-3.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/pieces-3.ll Wed Jan 9 01:58:59 2019
@@ -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"
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