[llvm] r369026 - [DebugInfo] Avoid crash from dropped fragments in LiveDebugValues

Tue Aug 20 02:40:05 PDT 2019

Merged to release_90 in r369354.

On Thu, Aug 15, 2019 at 7:48 PM Jeremy Morse via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
> Author: jmorse
> Date: Thu Aug 15 10:49:46 2019
> New Revision: 369026
>
> URL: http://llvm.org/viewvc/llvm-project?rev=369026&view=rev
> Log:
> [DebugInfo] Avoid crash from dropped fragments in LiveDebugValues
>
> This patch avoids a crash caused by DW_OP_LLVM_fragments being dropped
> from DIExpressions by LiveDebugValues spill-restore code. The appearance
> of a previously unseen fragment configuration confuses LDV, as documented
> in PR42773, and reproduced by the test function this patch adds (Crashes
> on a x86_64 debug build).
>
> To avoid this, on spill restore, we now use fragment information from the
> spilt-location-expression.
>
> In addition, when spilling, we now don't spill any DBG_VALUE with a complex
> expression, as it can't be safely restored and will definitely lead to an
> incorrect variable location. The discussion of this is in D65368.
>
> Differential Revision: https://reviews.llvm.org/D66284
>
> Modified:
>     llvm/trunk/lib/CodeGen/LiveDebugValues.cpp
>     llvm/trunk/test/DebugInfo/MIR/X86/live-debug-values-restore.mir
>
> Modified: llvm/trunk/lib/CodeGen/LiveDebugValues.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveDebugValues.cpp?rev=369026&r1=369025&r2=369026&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/LiveDebugValues.cpp (original)
> +++ llvm/trunk/lib/CodeGen/LiveDebugValues.cpp Thu Aug 15 10:49:46 2019
> @@ -691,9 +691,17 @@ void LiveDebugValues::insertTransferDebu
>             "No register supplied when handling a restore of a debug value");
>      MachineFunction *MF = MI.getMF();
>      DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
> +
> +    const DIExpression *NewExpr;
> +    if (auto Fragment = DebugInstr->getDebugExpression()->getFragmentInfo())
> +      NewExpr = *DIExpression::createFragmentExpression(DIB.createExpression(),
> +        Fragment->OffsetInBits, Fragment->SizeInBits);
> +    else
> +      NewExpr = DIB.createExpression();
> +
>      NewDebugInstr =
>          BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false,
> -                NewReg, DebugInstr->getDebugVariable(), DIB.createExpression());
> +                NewReg, DebugInstr->getDebugVariable(), NewExpr);
>      VarLoc VL(*NewDebugInstr, LS);
>      ProcessVarLoc(VL, NewDebugInstr);
>      LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
> @@ -848,9 +856,14 @@ void LiveDebugValues::transferSpillOrRes
>                        << "\n");
>    }
>    // Check if the register or spill location is the location of a debug value.
> +  // FIXME: Don't create a spill transfer if there is a complex expression,
> +  // because we currently cannot recover the original expression on restore.
>    for (unsigned ID : OpenRanges.getVarLocs()) {
> +    const MachineInstr *DebugInstr = &VarLocIDs[ID].MI;
> +
>      if (TKind == TransferKind::TransferSpill &&
> -        VarLocIDs[ID].isDescribedByReg() == Reg) {
> +        VarLocIDs[ID].isDescribedByReg() == Reg &&
> +        !DebugInstr->getDebugExpression()->isComplex()) {
>        LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
>                          << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
>      } else if (TKind == TransferKind::TransferRestore &&
>
> Modified: llvm/trunk/test/DebugInfo/MIR/X86/live-debug-values-restore.mir
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/MIR/X86/live-debug-values-restore.mir?rev=369026&r1=369025&r2=369026&view=diff
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/MIR/X86/live-debug-values-restore.mir (original)
> +++ llvm/trunk/test/DebugInfo/MIR/X86/live-debug-values-restore.mir Thu Aug 15 10:49:46 2019
> @@ -14,13 +14,17 @@
>  #   return *(p + 1);
>  # }
>
> +# Pick out DILocalVariable numbers for "p" and "q"
> +# CHECK: ![[PVAR:[0-9]+]] = !DILocalVariable(name: "p",
> +# CHECK: ![[QVAR:[0-9]+]] = !DILocalVariable(name: "q",
> +
>  # Ascertain that the spill has been recognized and manifested in a DBG_VALUE.
>  # CHECK: MOV64mr $rsp,{{.*-8.*}}killed{{.*}}$rdi :: (store 8 into %stack.0)
> -# CHECK-NEXT: DBG_VALUE $rsp,{{.*}}![[MDIX:[0-9]+]],{{.*}}!DIExpression(DW_OP_constu, 8, DW_OP_minus)
> +# CHECK-NEXT: DBG_VALUE $rsp,{{.*}}![[PVAR]],{{.*}}!DIExpression(DW_OP_constu, 8, DW_OP_minus)
>
>  # Check for the restore.
>  # CHECK: $rdi = MOV64rm $rsp,{{.*-8.*}}:: (load 8 from %stack.0)
> -# CHECK-NEXT: DBG_VALUE $rdi,{{.*}}![[MDIX]], !DIExpression()
> +# CHECK-NEXT: DBG_VALUE $rdi,{{.*}}![[PVAR]], !DIExpression()
>
>  --- |
>    define dso_local i32 @f(i32* readonly %p) local_unnamed_addr !dbg !7 {
> @@ -39,6 +43,22 @@
>      ret i32 %0, !dbg !28
>    }
>
> +  define dso_local i32 @g(i32* readonly %p) local_unnamed_addr !dbg !107 {
> +  entry:
> +    call void @llvm.dbg.value(metadata i32* %p, metadata !113, metadata !DIExpression()), !dbg !114
> +    %tobool = icmp eq i32* %p, null, !dbg !115
> +    br i1 %tobool, label %if.end, label %if.then, !dbg !117
> +
> +  if.then:                                          ; preds = %entry
> +    tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"(), !dbg !118, !srcloc !120
> +    br label %if.end, !dbg !121
> +
> +  if.end:                                           ; preds = %entry, %if.then
> +    %add.ptr = getelementptr inbounds i32, i32* %p, i64 1, !dbg !122
> +    %0 = load i32, i32* %add.ptr, align 4, !dbg !123, !tbaa !24
> +    ret i32 %0, !dbg !128
> +  }
> +
>    declare void @llvm.dbg.value(metadata, metadata, metadata)
>
>    !llvm.dbg.cu = !{!0}
> @@ -74,6 +94,22 @@
>    !26 = !{!"omnipotent char", !27, i64 0}
>    !27 = !{!"Simple C/C++ TBAA"}
>    !28 = !DILocation(line: 9, column: 3, scope: !7)
> +  !101 = !DIBasicType(name: "looong int", size: 64, encoding: DW_ATE_signed)
> +  !107 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 105, type: !8, scopeLine: 105, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !112)
> +  !112 = !{!113}
> +  !113 = !DILocalVariable(name: "q", arg: 1, scope: !107, file: !1, line: 105, type: !101)
> +  !114 = !DILocation(line: 105, column: 12, scope: !107)
> +  !115 = !DILocation(line: 106, column: 7, scope: !116)
> +  !116 = distinct !DILexicalBlock(scope: !107, file: !1, line: 106, column: 7)
> +  !117 = !DILocation(line: 106, column: 7, scope: !107)
> +  !118 = !DILocation(line: 107, column: 5, scope: !119)
> +  !119 = distinct !DILexicalBlock(scope: !116, file: !1, line: 106, column: 10)
> +  !120 = !{i32 -2147471544}
> +  !121 = !DILocation(line: 108, column: 3, scope: !119)
> +  !122 = !DILocation(line: 109, column: 14, scope: !107)
> +  !123 = !DILocation(line: 109, column: 10, scope: !107)
> +  !128 = !DILocation(line: 109, column: 3, scope: !107)
> +
>
>  ...
>  ---
> @@ -187,3 +223,78 @@ body:             |
>      RETQ $eax, debug-location !28
>
>  ...
> +---
> +# This second function has been appended as a regression test against a
> +# crash, caused by expressions being created from spill restores that did
> +# not preserve fragment information. Test that no empty expressions are
> +# created at all, and the last block describes both variable fragments.
> +
> +# CHECK-LABEL: name: g
> +# CHECK-NOT: !DIExpression()
> +# CHECK-LABEL: bb.2.if.end:
> +# CHECK:       DBG_VALUE $rdi, $noreg, ![[QVAR]], !DIExpression(DW_OP_LLVM_fragment, 0, 32)
> +# CHECK-NEXT:  DBG_VALUE $rbx, $noreg, ![[QVAR]], !DIExpression(DW_OP_LLVM_fragment, 32, 32)
> +
> +name:            g
> +alignment:       4
> +tracksRegLiveness: true
> +liveins:
> +  - { reg: '$rdi', virtual-reg: '' }
> +frameInfo:
> +  stackSize:       48
> +  offsetAdjustment: -48
> +  maxAlignment:    8
> +  cvBytesOfCalleeSavedRegisters: 48
> +  localFrameSize:  0
> +fixedStack:
> +  - { id: 0, type: spill-slot, offset: -56, size: 8, alignment: 8, stack-id: default,
> +      callee-saved-register: '$rbx', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +  - { id: 1, type: spill-slot, offset: -48, size: 8, alignment: 16, stack-id: default,
> +      callee-saved-register: '$r12', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +  - { id: 2, type: spill-slot, offset: -40, size: 8, alignment: 8, stack-id: default,
> +      callee-saved-register: '$r13', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +  - { id: 3, type: spill-slot, offset: -32, size: 8, alignment: 16, stack-id: default,
> +      callee-saved-register: '$r14', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +  - { id: 4, type: spill-slot, offset: -24, size: 8, alignment: 8, stack-id: default,
> +      callee-saved-register: '$r15', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +  - { id: 5, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: default,
> +      callee-saved-register: '$rbp', callee-saved-restored: true, debug-info-variable: '',
> +      debug-info-expression: '', debug-info-location: '' }
> +stack:
> +  - { id: 0, name: '', type: spill-slot, offset: -64, size: 8, alignment: 8,
> +      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
> +      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
> +constants:       []
> +body:             |
> +  bb.0.entry:
> +    successors: %bb.1(0x50000000)
> +    liveins: $rdi, $rbx, $r12, $r13, $r14, $r15, $rbp
> +
> +    DBG_VALUE $rdi, $noreg, !113, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !114
> +    TEST64rr renamable $rdi, renamable $rdi, implicit-def $eflags, debug-location !115
> +    JMP_1 %bb.1, implicit $eflags, debug-location !117
> +
> +  bb.1.if.then:
> +    successors: %bb.2(0x80000000)
> +    liveins: $rdi, $rbp, $r15, $r14, $r13, $r12, $rbx
> +
> +    MOV64mr $rsp, 1, $noreg, -8, $noreg, killed renamable $rdi :: (store 8 into %stack.0)
> +    renamable $rdi = MOV64rm $rsp, 1, $noreg, -8, $noreg :: (load 8 from %stack.0)
> +
> +  bb.2.if.end:
> +    liveins: $rdi, $rbx, $r12, $r13, $r14, $r15, $rbp
> +
> +    DBG_VALUE $rbx, $noreg, !113, !DIExpression(DW_OP_LLVM_fragment, 32, 32), debug-location !114
> +    MOV64mr $rsp, 1, $noreg, -8, $noreg, killed renamable $rbx :: (store 8 into %stack.0)
> +    renamable $rsi = MOV64rm $rsp, 1, $noreg, -8, $noreg :: (load 8 from %stack.0)
> +
> +    renamable $eax = MOV32rm killed renamable $rsi, 1, $noreg, 4, $noreg, debug-location !123 :: (load 4 from %ir.add.ptr, !tbaa !24)
> +    $rdi = MOV64ri 0
> +    RETQ $eax, debug-location !128
> +
> +...
>
>
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