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llvm-project/llvm/test/DebugInfo/MIR/X86/prolog-epilog-indirection.mir

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[DebugInfo] Avoid adding too much indirection to pointer-valued variables This patch addresses PR41675, where a stack-pointer variable is dereferenced too many times by its location expression, presenting a value on the stack as the pointer to the stack. The difference between a stack *pointer* DBG_VALUE and one that refers to a value on the stack, is currently the indirect flag. However the DWARF backend will also try to guess whether something is a memory location or not, based on whether there is any computation in the location expression. By simply prepending the stack offset to existing expressions, we can accidentally convert a register location into a memory location, which introduces a suprise (and unintended) dereference. The solution is to add DW_OP_stack_value whenever we add a DIExpression computation to a stack *pointer*. It's an implicit location computed on the expression stack, thus needs to be flagged as a stack_value. For the edge case where the offset is zero and the location could be a register location, DIExpression::prepend will still generate opcodes, and thus DW_OP_stack_value must still be added. Differential Revision: https://reviews.llvm.org/D63429 llvm-svn: 364736
2019-07-01 17:38:23 +08:00
# RUN: llc %s -x mir -o - -mtriple=x86_64-unknown-unknown -run-pass=prologepilog | FileCheck %s
#
# Check when the DBG_VALUE on a stack slot below (for var "c") has its stack
# slot replaced with $rsp and a complex expression, it has DW_OP_stack_value
# added. A direct reference to the stack slot is considered to be the _address_
# of that stack slot, wheras its contents would be an indirect DBG_VALUE.
#
# Check too that for the same DBG_VALUE inst, with an indirect reference to
# the stack slot, we do _not_ get DW_OP_plus_uconst added. This expression
# should remain indirect, referring to the contents of the stack slot.
#
# CHECK: ![[VAR:[0-9]+]] = !DILocalVariable(name: "c"
# CHECK: ![[VAR2:[0-9]+]] = !DILocalVariable(name: "asdf"
# CHECK: ![[VAR3:[0-9]+]] = !DILocalVariable(name: "bees"
#
# CHECK: LEA64r $rsp
# CHECK-NEXT: DBG_VALUE $rsp, $noreg, ![[VAR]], !DIExpression(DW_OP_plus_uconst, {{[0-9]+}}, DW_OP_stack_value)
# CHECK-NEXT: DBG_VALUE $rsp, $noreg, ![[VAR2]], !DIExpression(DW_OP_plus_uconst, {{[0-9]+}}, DW_OP_stack_value, DW_OP_LLVM_fragment, 1, 2)
# CHECK-NEXT: DBG_VALUE $rsp, $noreg, ![[VAR3]], !DIExpression(DW_OP_plus_uconst, {{[0-9]+}}, DW_OP_LLVM_tag_offset, 0, DW_OP_stack_value)
# CHECK-NEXT: DBG_VALUE 1834104526
# CHECK-NEXT: MOV64mr
# CHECK-NEXT: DBG_VALUE $rsp, 0, ![[VAR]], !DIExpression(DW_OP_plus_uconst, {{[0-9]+}})
--- |
; ModuleID = 'out.ll'
source_filename = "abc.c"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@b = common dso_local local_unnamed_addr global i32* null, align 8, !dbg !0
@a = common dso_local local_unnamed_addr global i32 0, align 4, !dbg !6
; Function Attrs: nounwind uwtable
define dso_local i32 @main() local_unnamed_addr !dbg !14 {
entry:
%l_1081 = alloca i32, align 4
%0 = bitcast i32* %l_1081 to i8*, !dbg !20
call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0), !dbg !20
call void @llvm.dbg.value(metadata i32 1834104526, metadata !18, metadata !DIExpression()), !dbg !21
call void @llvm.dbg.value(metadata i32* %l_1081, metadata !19, metadata !DIExpression()), !dbg !21
store i32* %l_1081, i32** @b, align 8, !dbg !22, !tbaa !23
store i32 9, i32* @a, align 4, !dbg !27, !tbaa !28
store i32 9, i32* %l_1081, align 4, !dbg !30, !tbaa !28
%call = call i32 (...) @optimize_me_not(), !dbg !31
call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %0), !dbg !32
ret i32 0, !dbg !32
}
; Function Attrs: argmemonly nounwind
declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
declare dso_local i32 @optimize_me_not(...) local_unnamed_addr
; Function Attrs: argmemonly nounwind
declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!10, !11, !12}
!llvm.ident = !{!13}
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !9, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
!3 = !DIFile(filename: "abc.c", directory: ".")
!4 = !{}
!5 = !{!6, !0}
!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
!7 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !8, isLocal: false, isDefinition: true)
!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !8, size: 64)
!10 = !{i32 2, !"Dwarf Version", i32 4}
!11 = !{i32 2, !"Debug Info Version", i32 3}
!12 = !{i32 1, !"wchar_size", i32 4}
!13 = !{!"clang"}
!14 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 3, type: !15, scopeLine: 3, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !17)
!15 = !DISubroutineType(types: !16)
!16 = !{!8}
!17 = !{!18, !19, !33, !34}
!18 = !DILocalVariable(name: "l_1081", scope: !14, file: !3, line: 4, type: !8)
!19 = !DILocalVariable(name: "c", scope: !14, file: !3, line: 5, type: !9)
!20 = !DILocation(line: 4, column: 3, scope: !14)
!21 = !DILocation(line: 0, scope: !14)
!22 = !DILocation(line: 6, column: 5, scope: !14)
!23 = !{!24, !24, i64 0}
!24 = !{!"any pointer", !25, i64 0}
!25 = !{!"omnipotent char", !26, i64 0}
!26 = !{!"Simple C/C++ TBAA"}
!27 = !DILocation(line: 7, column: 10, scope: !14)
!28 = !{!29, !29, i64 0}
!29 = !{!"int", !25, i64 0}
!30 = !DILocation(line: 7, column: 6, scope: !14)
!31 = !DILocation(line: 8, column: 3, scope: !14)
!32 = !DILocation(line: 9, column: 1, scope: !14)
!33 = !DILocalVariable(name: "asdf", scope: !14, file: !3, line: 4, type: !8)
!34 = !DILocalVariable(name: "bees", scope: !14, file: !3, line: 4, type: !8)
...
---
name: main
[Alignment] Use llvm::Align in MachineFunction and TargetLowering - fixes mir parsing Summary: This catches malformed mir files which specify alignment as log2 instead of pow2. See https://reviews.llvm.org/D65945 for reference, This is patch is part of a series to introduce an Alignment type. See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html See this patch for the introduction of the type: https://reviews.llvm.org/D64790 Reviewers: courbet Subscribers: MatzeB, qcolombet, dschuff, arsenm, sdardis, nemanjai, jvesely, nhaehnle, hiraditya, kbarton, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, jsji, Petar.Avramovic, asbirlea, s.egerton, pzheng, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D67433 llvm-svn: 371608
2019-09-11 19:16:48 +08:00
alignment: 16
[DebugInfo] Avoid adding too much indirection to pointer-valued variables This patch addresses PR41675, where a stack-pointer variable is dereferenced too many times by its location expression, presenting a value on the stack as the pointer to the stack. The difference between a stack *pointer* DBG_VALUE and one that refers to a value on the stack, is currently the indirect flag. However the DWARF backend will also try to guess whether something is a memory location or not, based on whether there is any computation in the location expression. By simply prepending the stack offset to existing expressions, we can accidentally convert a register location into a memory location, which introduces a suprise (and unintended) dereference. The solution is to add DW_OP_stack_value whenever we add a DIExpression computation to a stack *pointer*. It's an implicit location computed on the expression stack, thus needs to be flagged as a stack_value. For the edge case where the offset is zero and the location could be a register location, DIExpression::prepend will still generate opcodes, and thus DW_OP_stack_value must still be added. Differential Revision: https://reviews.llvm.org/D63429 llvm-svn: 364736
2019-07-01 17:38:23 +08:00
tracksRegLiveness: true
frameInfo:
maxAlignment: 4
hasCalls: true
stack:
- { id: 0, name: l_1081, type: default, offset: 0, size: 4, alignment: 4,
callee-saved-register: '', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
body: |
bb.0.entry:
renamable $rax = LEA64r %stack.0.l_1081, 1, $noreg, 0, $noreg
DBG_VALUE %stack.0.l_1081, $noreg, !19, !DIExpression(), debug-location !21
DBG_VALUE %stack.0.l_1081, $noreg, !33, !DIExpression(DW_OP_LLVM_fragment, 1, 2), debug-location !21
DBG_VALUE %stack.0.l_1081, $noreg, !34, !DIExpression(DW_OP_LLVM_tag_offset, 0), debug-location !21
DBG_VALUE 1834104526, $noreg, !18, !DIExpression(), debug-location !21
MOV64mr $rip, 1, $noreg, @b, $noreg, killed renamable $rax, debug-location !22 :: (store 8 into @b, !tbaa !23)
DBG_VALUE %stack.0.l_1081, 0, !19, !DIExpression(), debug-location !21
MOV32mi $rip, 1, $noreg, @a, $noreg, 9, debug-location !27 :: (store 4 into @a, !tbaa !28)
MOV32mi %stack.0.l_1081, 1, $noreg, 0, $noreg, 9, debug-location !30 :: (store 4 into %ir.l_1081, !tbaa !28)
ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !31
dead $eax = MOV32r0 implicit-def dead $eflags, implicit-def $al, debug-location !31
CALL64pcrel32 @optimize_me_not, csr_64, implicit $rsp, implicit $ssp, implicit $al, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax, debug-location !31
ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !31
$eax = MOV32r0 implicit-def dead $eflags, debug-location !32
RET 0, $eax, debug-location !32
...