[llvm] r243057 - fix crash in machine trace metrics due to processing dbg_value instructions (PR24199)

[Hans Wennborg]

Ping?

On Fri, Jul 24, 2015 at 9:28 AM, Hans Wennborg <hans at chromium.org> wrote:
> Seems reasonable.
>
> Evan, I believe you're the code owner here. OK to merge to 3.7?
>
> On Fri, Jul 24, 2015 at 8:57 AM, Robinson, Paul
> <Paul_Robinson at playstation.sony.com> wrote:
>> Can we please have this merged to the 3.7 branch?
>> Thanks,
>> --paulr
>>
>>> -----Original Message-----
>>> From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-
>>> bounces at cs.uiuc.edu] On Behalf Of Sanjay Patel
>>> Sent: Thursday, July 23, 2015 3:57 PM
>>> To: llvm-commits at cs.uiuc.edu
>>> Subject: [llvm] r243057 - fix crash in machine trace metrics due to
>>> processing dbg_value instructions (PR24199)
>>>
>>> Author: spatel
>>> Date: Thu Jul 23 17:56:53 2015
>>> New Revision: 243057
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=243057&view=rev
>>> Log:
>>> fix crash in machine trace metrics due to processing dbg_value
>>> instructions (PR24199)
>>>
>>> The test in PR24199 ( https://llvm.org/bugs/show_bug.cgi?id=24199 )
>>> crashes because machine
>>> trace metrics was not ignoring dbg_value instructions when calculating
>>> data dependencies.
>>>
>>> The machine-combiner pass asks machine trace metrics to calculate an
>>> instruction trace,
>>> does some reassociations, and calls
>>> MachineInstr::eraseFromParentAndMarkDBGValuesForRemoval()
>>> along with MachineTraceMetrics::invalidate(). The dbg_value instructions
>>> have their operands
>>> invalidated, but the instructions are not expected to be deleted.
>>>
>>> On a subsequent loop iteration of the machine-combiner pass, machine trace
>>> metrics would be
>>> called again and die while accessing the invalid debug instructions.
>>>
>>> Differential Revision: http://reviews.llvm.org/D11423
>>>
>>>
>>> Added:
>>>     llvm/trunk/test/CodeGen/X86/machine-trace-metrics-crash.ll
>>> Modified:
>>>     llvm/trunk/lib/CodeGen/MachineTraceMetrics.cpp
>>>
>>> Modified: llvm/trunk/lib/CodeGen/MachineTraceMetrics.cpp
>>> URL: http://llvm.org/viewvc/llvm-
>>> project/llvm/trunk/lib/CodeGen/MachineTraceMetrics.cpp?rev=243057&r1=24305
>>> 6&r2=243057&view=diff
>>> ==========================================================================
>>> ====
>>> --- llvm/trunk/lib/CodeGen/MachineTraceMetrics.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/MachineTraceMetrics.cpp Thu Jul 23 17:56:53
>>> 2015
>>> @@ -624,6 +624,10 @@ struct DataDep {
>>>  static bool getDataDeps(const MachineInstr *UseMI,
>>>                          SmallVectorImpl<DataDep> &Deps,
>>>                          const MachineRegisterInfo *MRI) {
>>> +  // Debug values should not be included in any calculations.
>>> +  if (UseMI->isDebugValue())
>>> +    return false;
>>> +
>>>    bool HasPhysRegs = false;
>>>    for (MachineInstr::const_mop_iterator I = UseMI->operands_begin(),
>>>         E = UseMI->operands_end(); I != E; ++I) {
>>>
>>> Added: llvm/trunk/test/CodeGen/X86/machine-trace-metrics-crash.ll
>>> URL: http://llvm.org/viewvc/llvm-
>>> project/llvm/trunk/test/CodeGen/X86/machine-trace-metrics-
>>> crash.ll?rev=243057&view=auto
>>> ==========================================================================
>>> ====
>>> --- llvm/trunk/test/CodeGen/X86/machine-trace-metrics-crash.ll (added)
>>> +++ llvm/trunk/test/CodeGen/X86/machine-trace-metrics-crash.ll Thu Jul 23
>>> 17:56:53 2015
>>> @@ -0,0 +1,62 @@
>>> +; RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mattr=sse -
>>> enable-unsafe-fp-math < %s | FileCheck %s
>>> +
>>> +; The debug info in this test case was causing a crash because machine
>>> trace metrics
>>> +; did not correctly ignore debug instructions. The check lines ensure
>>> that the
>>> +; machine-combiner pass has run, reassociated the add operands, and
>>> therefore
>>> +; used machine trace metrics.
>>> +
>>> +define void @PR24199() {
>>> +; CHECK-LABEL:       PR24199:
>>> +; CHECK:     addss   %xmm1, %xmm0
>>> +; CHECK:     addss   %xmm2, %xmm0
>>> +
>>> +entry:
>>> +  %i = alloca %struct.A, align 8
>>> +  %tobool = icmp ne i32 undef, 0
>>> +  br i1 undef, label %if.end, label %if.then
>>> +
>>> +if.then:
>>> +  br label %if.end
>>> +
>>> +if.end:
>>> +  %h = phi float [ 0.0, %if.then ], [ 4.0, %entry ]
>>> +  call void @foo(%struct.A* nonnull undef)
>>> +  tail call void @llvm.dbg.value(metadata %struct.A* undef, i64 0,
>>> metadata !5, metadata !4), !dbg !6
>>> +  tail call void @llvm.dbg.value(metadata float %h, i64 0, metadata !5,
>>> metadata !4), !dbg !6
>>> +  %n0 = load float, float* undef, align 4
>>> +  %mul = fmul fast float %n0, %h
>>> +  %add = fadd fast float %mul, 1.0
>>> +  tail call void @llvm.dbg.value(metadata %struct.A* undef, i64 0,
>>> metadata !5, metadata !4), !dbg !6
>>> +  tail call void @llvm.dbg.value(metadata float %add, i64 0, metadata !5,
>>> metadata !4), !dbg !6
>>> +  %add.i = fadd fast float %add, %n0
>>> +  store float %add.i, float* undef, align 4
>>> +  %n1 = bitcast %struct.A* %i to i8*
>>> +  call void @llvm.lifetime.start(i64 16, i8* %n1)
>>> +  %n2 = load <2 x float>, <2 x float>* undef, align 8
>>> +  %conv = uitofp i1 %tobool to float
>>> +  %bitcast = extractelement <2 x float> %n2, i32 0
>>> +  %factor = fmul fast float %bitcast, 2.0
>>> +  %add3 = fadd fast float %factor, %conv
>>> +  call void @bar(float %add3)
>>> +  ret void
>>> +}
>>> +
>>> +%struct.A = type { float, float }
>>> +
>>> +declare void @bar(float)
>>> +declare void @foo(%struct.A*)
>>> +declare void @llvm.lifetime.start(i64, i8* nocapture)
>>> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
>>> +
>>> +!llvm.dbg.cu = !{!0}
>>> +!llvm.module.flags = !{!2}
>>> +
>>> +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1,
>>> isOptimized: true, runtimeVersion: 0, emissionKind: 1)
>>> +!1 = !DIFile(filename: "24199.cpp", directory: "/bin")
>>> +!2 = !{i32 2, !"Debug Info Version", i32 3}
>>> +!3 = !DISubprogram(linkageName: "foo", file: !1, line: 18, isLocal:
>>> false, isDefinition: true, scopeLine: 18, function: void (%struct.A*)*
>>> @foo)
>>> +!4 = !DIExpression()
>>> +!5 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1,
>>> scope: !3, flags: DIFlagArtificial | DIFlagObjectPointer)
>>> +!6 = !DILocation(line: 0, scope: !3)
>>> +
>>> +
>>>
>>>
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