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

[Robinson, Paul]

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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