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[DWARF] Don't leak line numbers onto frame-setup instructions #161845

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[DWARF] Don't leak line numbers onto frame-setup instructions #161845

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46 changes: 28 additions & 18 deletions llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2053,11 +2053,36 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
if (NoDebug)
return;

auto RecordLineZero = [&]() {
// Preserve the file and column numbers, if we can, to save space in
// the encoded line table.
// Do not update PrevInstLoc, it remembers the last non-0 line.
const MDNode *Scope = nullptr;
unsigned Column = 0;
if (PrevInstLoc) {
Scope = PrevInstLoc.getScope();
Column = PrevInstLoc.getCol();
}
recordSourceLine(/*Line=*/0, Column, Scope, /*Flags=*/0);
};

// When we emit a line-0 record, we don't update PrevInstLoc; so look at
// the last line number actually emitted, to see if it was line 0.
unsigned LastAsmLine =
Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();

// Check if source location changes, but ignore DBG_VALUE and CFI locations.
// If the instruction is part of the function frame setup code, do not emit
// any line record, as there is no correspondence with any user code.
if (MI->isMetaInstruction() || MI->getFlag(MachineInstr::FrameSetup))
if (MI->isMetaInstruction())
return;
if (MI->getFlag(MachineInstr::FrameSetup)) {
// Prevent a loc from the previous block leaking into frame setup instrs.
if (LastAsmLine && PrevInstBB && PrevInstBB != MI->getParent())
RecordLineZero();
return;
}

const DebugLoc &DL = MI->getDebugLoc();
unsigned Flags = 0;

Expand All @@ -2080,11 +2105,6 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
LocationString);
};

// When we emit a line-0 record, we don't update PrevInstLoc; so look at
// the last line number actually emitted, to see if it was line 0.
unsigned LastAsmLine =
Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();

// There may be a mixture of scopes using and not using Key Instructions.
// Not-Key-Instructions functions inlined into Key Instructions functions
// should use not-key is_stmt handling. Key Instructions functions inlined
Expand Down Expand Up @@ -2150,18 +2170,8 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
// - Instruction is at the top of a block; we don't want to inherit the
// location from the physically previous (maybe unrelated) block.
if (UnknownLocations == Enable || PrevLabel ||
(PrevInstBB && PrevInstBB != MI->getParent())) {
// Preserve the file and column numbers, if we can, to save space in
// the encoded line table.
// Do not update PrevInstLoc, it remembers the last non-0 line.
const MDNode *Scope = nullptr;
unsigned Column = 0;
if (PrevInstLoc) {
Scope = PrevInstLoc.getScope();
Column = PrevInstLoc.getCol();
}
recordSourceLine(/*Line=*/0, Column, Scope, /*Flags=*/0);
}
(PrevInstBB && PrevInstBB != MI->getParent()))
RecordLineZero();
return;
}

Expand Down
139 changes: 139 additions & 0 deletions llvm/test/DebugInfo/X86/shrink-wrap-frame-setup-no-loc.mir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,139 @@
# RUN: %llc_dwarf %s -o - -mtriple=x86_64-unknown-unknown | FileCheck %s

## Check the line number from the ret above `.LBB0_1` doesn't leak onto the
## frame setup instructions in the `.LBB0_1` block; `pushq %rax` should
## explicitly get set to line zero.

# CHECK: loop:
# CHECK-NEXT: .Lfunc_begin0:
# CHECK-NEXT: .cfi_startproc
# CHECK-NEXT: # %bb.0:
# CHECK-NEXT: .file 1 "/" "test.c"
# CHECK-NEXT: .loc 1 5 16 prologue_end # test.c:5:16
# CHECK-NEXT: testq %rax, %rax
# CHECK-NEXT: je .LBB0_1
# CHECK-NEXT: # %bb.2:
# CHECK-NEXT: .loc 1 5 16 # test.c:5:16
# CHECK-NEXT: retq
# CHECK-NEXT: .LBB0_1:
# -- Check the .loc below sets the current location to line 0.
# CHECK-NEXT: .loc 1 0 16 is_stmt 0 # test.c:0:16
# CHECK-NEXT: pushq %rax
# CHECK-NEXT: .cfi_def_cfa_offset 16
# CHECK-NEXT: addq $8, %rsp
# CHECK-NEXT: .cfi_def_cfa_offset 8
# CHECK-NEXT: .loc 1 5 16 is_stmt 1 # test.c:5:16
# CHECK-NEXT: retq

--- |
source_filename = "reduced.ll"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-unknown"

define void @loop(i64 %i) !dbg !4 {
entry:
%cmp.not = icmp eq i64 %i, 0, !dbg !7
br i1 %cmp.not, label %for.body, label %for.end

for.body: ; preds = %entry
%puts10 = tail call i32 null(ptr null)
%inc = add i64 0, 0
br label %for.end

for.end: ; preds = %for.body, %entry
ret void
}

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3}

!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 22.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.c", directory: "/")
!2 = !{}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = distinct !DISubprogram(name: "loop", scope: !1, file: !1, line: 4, type: !5, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2, keyInstructions: true)
!5 = !DISubroutineType(types: !6)
!6 = !{null}
!7 = !DILocation(line: 5, column: 16, scope: !8, atomGroup: 720, atomRank: 2)
!8 = distinct !DILexicalBlock(scope: !4, file: !1, line: 5, column: 9)
...
---
name: loop
alignment: 16
exposesReturnsTwice: false
legalized: false
regBankSelected: false
selected: false
failedISel: false
tracksRegLiveness: true
hasWinCFI: false
noPhis: false
isSSA: true
noVRegs: false
hasFakeUses: false
callsEHReturn: false
callsUnwindInit: false
hasEHContTarget: false
hasEHScopes: false
hasEHFunclets: false
isOutlined: false
debugInstrRef: false
failsVerification: false
tracksDebugUserValues: false
registers:
- { id: 0, class: gr64, preferred-register: '', flags: [ ] }
- { id: 1, class: gr32, preferred-register: '', flags: [ ] }
- { id: 2, class: gr64, preferred-register: '', flags: [ ] }
- { id: 3, class: gr32, preferred-register: '', flags: [ ] }
- { id: 4, class: gr64, preferred-register: '', flags: [ ] }
- { id: 5, class: gr32, preferred-register: '', flags: [ ] }
- { id: 6, class: gr32, preferred-register: '', flags: [ ] }
- { id: 7, class: gr64, preferred-register: '', flags: [ ] }
liveins: []
frameInfo:
isFrameAddressTaken: false
isReturnAddressTaken: false
hasStackMap: false
hasPatchPoint: false
stackSize: 0
offsetAdjustment: 0
maxAlignment: 1
adjustsStack: false
hasCalls: true
stackProtector: ''
functionContext: ''
maxCallFrameSize: 4294967295
cvBytesOfCalleeSavedRegisters: 0
hasOpaqueSPAdjustment: false
hasVAStart: false
hasMustTailInVarArgFunc: false
hasTailCall: false
isCalleeSavedInfoValid: false
localFrameSize: 0
fixedStack: []
stack: []
entry_values: []
callSites: []
debugValueSubstitutions: []
constants: []
machineFunctionInfo:
amxProgModel: None
body: |
bb.0:
successors: %bb.1(0x30000000), %bb.2(0x50000000)
liveins: $rdi

%7:gr64 = IMPLICIT_DEF
TEST64rr undef %7, undef %7, implicit-def $eflags, debug-location !7
JCC_1 %bb.2, 5, implicit $eflags
JMP_1 %bb.1

bb.1:
successors: %bb.2(0x80000000)

ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp

bb.2:
RET 0, debug-location !7
...
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