[llvm] r316481 - bpf: fix a bug in trunc-op optimization

[Evgenii Stepanov via llvm-commits]

Nope, for PODs default initialiization does nothing:
http://en.cppreference.com/w/cpp/language/default_initialization


On Tue, Oct 24, 2017 at 2:22 PM, Yonghong Song <yhs at fb.com> wrote:
>
> Yes. Previously, I do have this change. Later on, I checked some
> website (stackflow) which says, the constructor will assign NULL
> to a pointer value so that is why I did not initialize it in
> the constructor.
> Maybe my understanding is incorrect?
>
> On 10/24/17 2:19 PM, Evgenii Stepanov wrote:
>>
>> All stores to curr_func_ are dominated by loads, this can't be right.
>> You probably meant to initialize it to nullptr in the constructor?
>>
>> On Tue, Oct 24, 2017 at 2:17 PM, Evgenii Stepanov
>> <eugeni.stepanov at gmail.com> wrote:
>>>
>>> Hi,
>>>
>>> one of your changes broke the msan bot:
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lab.llvm.org-3A8011_builders_sanitizer-2Dx86-5F64-2Dlinux-2Dbootstrap-2Dmsan_builds_202_steps_check-2Dllvm-2520msan_logs_stdio&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=IkIAE-IfCDp2GWYOR5YHSXgGYE1V30dpyuL_J7-UFWg&s=huyyhqno9qhlXkirQWhS6bHMR6lgp_oWD_K7SZtkVQ4&e=
>>>
>>> On Tue, Oct 24, 2017 at 11:21 AM, Yonghong Song via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>>
>>>> Author: yhs
>>>> Date: Tue Oct 24 11:21:10 2017
>>>> New Revision: 316481
>>>>
>>>> URL:
>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D316481-26view-3Drev&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=IkIAE-IfCDp2GWYOR5YHSXgGYE1V30dpyuL_J7-UFWg&s=taKxbRkvdYyRFORIGxTNt44Z5yDJeNtIwPYGuGot5zk&e=
>>>> Log:
>>>> bpf: fix a bug in trunc-op optimization
>>>>
>>>> Previous implementation for per-function scope
>>>> is incorrect and too conservative.
>>>>
>>>> Signed-off-by: Yonghong Song <yhs at fb.com>
>>>>
>>>> Modified:
>>>>      llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp
>>>>
>>>> Modified: llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp
>>>> URL:
>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_lib_Target_BPF_BPFISelDAGToDAG.cpp-3Frev-3D316481-26r1-3D316480-26r2-3D316481-26view-3Ddiff&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=IkIAE-IfCDp2GWYOR5YHSXgGYE1V30dpyuL_J7-UFWg&s=9ml3oJPI84s7znc7K8tKbmG-kvwiOIJknrq06ZknAzU&e=
>>>>
>>>>
>>>> ==============================================================================
>>>> --- llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp (original)
>>>> +++ llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp Tue Oct 24 11:21:10
>>>> 2017
>>>> @@ -85,6 +85,8 @@ private:
>>>>     std::map<const void *, val_vec_type> cs_vals_;
>>>>     // Mapping from vreg to load memory opcode
>>>>     std::map<unsigned, unsigned> load_to_vreg_;
>>>> +  // Current function
>>>> +  const Function *curr_func_;
>>>>   };
>>>>   } // namespace
>>>>
>>>> @@ -332,7 +334,12 @@ void BPFDAGToDAGISel::PreprocessISelDAG(
>>>>
>>>>     // clear the load_to_vreg_ map so that we have a clean start
>>>>     // for this function.
>>>> -  load_to_vreg_.clear();
>>>> +  if (!curr_func_) {
>>>> +    curr_func_ = FuncInfo->Fn;
>>>> +  } else if (curr_func_ != FuncInfo->Fn) {
>>>> +    load_to_vreg_.clear();
>>>> +    curr_func_ = FuncInfo->Fn;
>>>> +  }
>>>>
>>>>     for (SelectionDAG::allnodes_iterator I = CurDAG->allnodes_begin(),
>>>>                                          E = CurDAG->allnodes_end();
>>>>
>>>>
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>>>>
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