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[DebugInfo] Discard invalid DBG_VALUE instructions in LiveDebugVariables #77

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Mar 7, 2018
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[DebugInfo] Discard invalid DBG_VALUE instructions in LiveDebugVariables #77

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38 changes: 37 additions & 1 deletion lib/CodeGen/LiveDebugVariables.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -514,6 +514,39 @@ bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
return false;
}

// Detect invalid DBG_VALUE instructions, with a debug-use of a virtual
// register that hasn't been defined yet. If we do not remove those here, then
// the re-insertion of the DBG_VALUE instruction after register allocation
// will be incorrect.
// TODO: If earlier passes are corrected to generate sane debug information
// (and if the machine verifier is improved to catch this), then these checks
// could be removed or replaced by asserts.
bool Discard = false;
if (MI.getOperand(0).isReg() &&
TargetRegisterInfo::isVirtualRegister(MI.getOperand(0).getReg())) {
const unsigned Reg = MI.getOperand(0).getReg();
if (!LIS->hasInterval(Reg)) {
// The DBG_VALUE is described by a virtual register that does not have a
// live interval. Discard the DBG_VALUE.
Discard = true;
DEBUG(dbgs() << "Discarding debug info (no LIS interval): "
<< Idx << " " << MI);
} else {
// The DBG_VALUE is only valid if either Reg is live out from Idx, or Reg
// is defined dead at Idx (where Idx is the slot index for the instruction
// preceeding the DBG_VALUE).
const LiveInterval &LI = LIS->getInterval(Reg);
LiveQueryResult LRQ = LI.Query(Idx);
if (!LRQ.valueOutOrDead()) {
// We have found a DBG_VALUE with the value in a virtual register that
// is not live. Discard the DBG_VALUE.
Discard = true;
DEBUG(dbgs() << "Discarding debug info (reg not live): "
<< Idx << " " << MI);
}
}
}

// Get or create the UserValue for (variable,offset) here.
bool IsIndirect = MI.getOperand(1).isImm();
if (IsIndirect)
Expand All @@ -522,7 +555,10 @@ bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
const DIExpression *Expr = MI.getDebugExpression();
UserValue *UV =
getUserValue(Var, Expr, MI.getDebugLoc());
UV->addDef(Idx, MI.getOperand(0), IsIndirect);
if (!Discard)
UV->addDef(Idx, MI.getOperand(0), IsIndirect);
else
UV->addDef(Idx, MachineOperand::CreateReg(0U, RegState::Debug), false);
return true;
}

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6 changes: 3 additions & 3 deletions test/DebugInfo/X86/dbg-value-inlined-parameter.ll
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Expand Up @@ -32,10 +32,10 @@
;CHECK-NEXT: DW_AT_call_line

;CHECK: DW_TAG_formal_parameter
;FIXME: Linux shouldn't drop this parameter either...
;CHECK-NOT: DW_TAG
;DARWIN: DW_AT_abstract_origin {{.*}} "sp"
;DARWIN: DW_TAG_formal_parameter
;FIXME: Shouldn't drop this parameter...
;XCHECK: DW_AT_abstract_origin {{.*}} "sp"
;XCHECK: DW_TAG_formal_parameter
;CHECK: DW_AT_abstract_origin {{.*}} "nums"
;CHECK-NOT: DW_TAG_formal_parameter

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141 changes: 141 additions & 0 deletions test/DebugInfo/X86/live-debug-vars-discard-invalid.mir
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@@ -0,0 +1,141 @@
# RUN: llc -mtriple=x86_64-linux-gnu -start-before greedy -stop-after virtregrewriter -o - %s | FileCheck %s

--- |
; ModuleID = '<stdin>'
source_filename = "test/DebugInfo/X86/dbg-value-inlined-parameter.ll"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-darwin"

%struct.S1 = type { float*, i32 }

@p = common global %struct.S1 zeroinitializer, align 8, !dbg !0

; Function Attrs: nounwind optsize ssp
define void @foobar() !dbg !15 {
entry:
tail call void @llvm.dbg.value(metadata %struct.S1* @p, metadata !18, metadata !DIExpression()) , !dbg !25
ret void, !dbg !32
}

; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #2

!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!14}

!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = !DIGlobalVariable(name: "p", scope: !2, file: !3, line: 14, type: !6, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 2.9 (trunk 125693)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, retainedTypes: !4, globals: !5, imports: !4)
!3 = !DIFile(filename: "nm2.c", directory: "/private/tmp")
!4 = !{}
!5 = !{!0}
!6 = !DIDerivedType(tag: DW_TAG_typedef, name: "S1", scope: !2, file: !3, line: 4, baseType: !7)
!7 = !DICompositeType(tag: DW_TAG_structure_type, name: "S1", scope: !2, file: !3, line: 1, size: 128, align: 64, elements: !8)
!8 = !{!9, !12}
!9 = !DIDerivedType(tag: DW_TAG_member, name: "m", scope: !3, file: !3, line: 2, baseType: !10, size: 64, align: 64)
!10 = !DIDerivedType(tag: DW_TAG_pointer_type, scope: !2, baseType: !11, size: 64, align: 64)
!11 = !DIBasicType(name: "float", size: 32, align: 32, encoding: DW_ATE_float)
!12 = !DIDerivedType(tag: DW_TAG_member, name: "nums", scope: !3, file: !3, line: 3, baseType: !13, size: 32, align: 32, offset: 64)
!13 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
!14 = !{i32 1, !"Debug Info Version", i32 3}
!15 = distinct !DISubprogram(name: "foobar", scope: !3, file: !3, line: 15, type: !16, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !2)
!16 = !DISubroutineType(types: !17)
!17 = !{null}
!18 = !DILocalVariable(name: "sp", arg: 1, scope: !19, file: !3, line: 7, type: !24)
!19 = distinct !DISubprogram(name: "foo", scope: !3, file: !3, line: 8, type: !20, isLocal: false, isDefinition: true, scopeLine: 8, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !2, variables: !22)
!20 = !DISubroutineType(types: !21)
!21 = !{!13}
!22 = !{!18, !23}
!23 = !DILocalVariable(name: "nums", arg: 2, scope: !19, file: !3, line: 7, type: !13)
!24 = !DIDerivedType(tag: DW_TAG_pointer_type, scope: !2, baseType: !6, size: 64, align: 64)
!25 = !DILocation(line: 7, column: 13, scope: !19, inlinedAt: !26)
!26 = !DILocation(line: 16, column: 3, scope: !27)
!27 = distinct !DILexicalBlock(scope: !15, file: !3, line: 15, column: 15)
!32 = !DILocation(line: 17, column: 1, scope: !27)

...
---
name: foobar
tracksRegLiveness: true
body: |
bb.0:
%1:gr64 = IMPLICIT_DEF
%2:gr64 = IMPLICIT_DEF

bb.1:
; This DBG_VALUE will be discarded (use before def of %0).
DBG_VALUE debug-use %0, debug-use $noreg, !18, !DIExpression(), debug-location !25
%0:gr64 = IMPLICIT_DEF
%0:gr64 = IMPLICIT_DEF
%0:gr64 = IMPLICIT_DEF
%0:gr64 = IMPLICIT_DEF

bb.2:
; This DBG_VALUE will be discarded (%1 is defined earlier, but it is not live in, so we do not know where %1 is stored).
DBG_VALUE debug-use %1, debug-use $noreg, !18, !DIExpression(), debug-location !25
%1:gr64 = IMPLICIT_DEF
%1:gr64 = IMPLICIT_DEF
%1:gr64 = IMPLICIT_DEF
%1:gr64 = IMPLICIT_DEF
; This DBG_VALUE is kept, even if %1 is dead, it was defined in the prev instruction,
; so the value should be available for as long as the register allocated to %1 is live.
DBG_VALUE debug-use %1, debug-use $noreg, !18, !DIExpression(), debug-location !25

bb.3:
%1:gr64 = IMPLICIT_DEF
DBG_VALUE 0, debug-use $noreg, !23, !DIExpression(), debug-location !25
; This DBG_VALUE is kept, even if %1 is dead, it was defined in the prev non-dbg instruction,
; so the value should be available for as long as the register allocated to %1 is live.
DBG_VALUE debug-use %1, debug-use $noreg, !18, !DIExpression(), debug-location !25

bb.4:
; All DBG_VALUEs here should survive. %2 is livein as it was defined in bb.0, and it has use/def in the BTS64rr instruction.
DBG_VALUE debug-use %2, debug-use $noreg, !18, !DIExpression(), debug-location !25
%2:gr64 = BTS64rr %2, 0, implicit-def $eflags
DBG_VALUE 0, debug-use $noreg, !23, !DIExpression(), debug-location !25
DBG_VALUE debug-use %2, debug-use $noreg, !18, !DIExpression(), debug-location !25
%2:gr64 = BTS64rr %2, 0, implicit-def $eflags
DBG_VALUE debug-use %2, debug-use $noreg, !18, !DIExpression(), debug-location !25
%2:gr64 = BTS64rr %2, 0, implicit-def $eflags
DBG_VALUE debug-use %2, debug-use $noreg, !18, !DIExpression(), debug-location !25

bb.5:
RET 0, debug-location !32
...

# CHECK-LABEL: name: foobar

# CHECK-LABEL: bb.1:
## After solving https://bugs.llvm.org/show_bug.cgi?id=36579 we expect to get a
## DBG_VALUE debug-use $noreg
## here.
# CHECK-NOT: DBG_VALUE

# CHECK-LABEL: bb.2:
## After solving https://bugs.llvm.org/show_bug.cgi?id=36579 we expect to get a
## DBG_VALUE debug-use $noreg
## here.
# CHECK-NOT: DBG_VALUE
# CHECK: dead renamable $rcx = IMPLICIT_DEF
# CHECK-NEXT: dead renamable $rcx = IMPLICIT_DEF
# CHECK-NEXT: dead renamable $rcx = IMPLICIT_DEF
# CHECK-NEXT: dead renamable $rcx = IMPLICIT_DEF
# CHECK-NEXT: DBG_VALUE debug-use $rcx, debug-use $noreg, !18, !DIExpression()

# CHECK-LABEL: bb.3:
# CHECK: dead renamable $rcx = IMPLICIT_DEF
# CHECK-NEXT: DBG_VALUE 0, debug-use $noreg, !23, !DIExpression()
# CHECK-NEXT: DBG_VALUE debug-use $rcx, debug-use $noreg, !18, !DIExpression()

# CHECK-LABEL: bb.4:
# CHECK: liveins: $rax
# CHECK: DBG_VALUE debug-use $rax, debug-use $noreg, !18, !DIExpression()
# CHECK-NEXT: renamable $rax = BTS64rr killed renamable $rax, 0, implicit-def $eflags
# CHECK-NEXT: DBG_VALUE 0, debug-use $noreg, !23, !DIExpression()
# CHECK-NEXT: DBG_VALUE debug-use $rax, debug-use $noreg, !18, !DIExpression()
# CHECK-NEXT: renamable $rax = BTS64rr killed renamable $rax, 0, implicit-def $eflags
# CHECK-NEXT: DBG_VALUE debug-use $rax, debug-use $noreg, !18, !DIExpression()
# CHECK-NEXT: dead renamable $rax = BTS64rr killed renamable $rax, 0, implicit-def $eflags

# CHECK-LABEL: bb.5:
# CHECK-NEXT: RET 0