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Re: [llvm-dev] [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event

From Alexei Starovoitov <alexei.starovoitov@gmail.com>
Newsgroups linux.kernel
Subject Re: [llvm-dev] [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event
Date 2015-08-06 05:30 +0200
Message-ID <pUk2t-4Ik-5@gated-at.bofh.it> (permalink)
References (5 earlier) <pTW9P-3AW-1@gated-at.bofh.it> <pTWjx-41F-43@gated-at.bofh.it> <pU0Qa-22l-17@gated-at.bofh.it> <pU19w-2FR-1@gated-at.bofh.it> <pU2oV-4nL-1@gated-at.bofh.it>
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On Wed, Aug 05, 2015 at 04:28:13PM +0800, Wangnan (F) wrote:
> 
> It doesn't work for me at first since in my llvm there's only
> llvm.bpf.load.*.
> 
> I think llvm.bpf.store.* belone to some patches you haven't posted yet?

nope. only loads have special instructions ld_abs/ld_ind
which are represented by these intrinsics.
stores, so far, are done via single bpf_store_bytes() helper function.

> >the typeid changing ids with order is surprising.
> >I think the assertion in ExtractTypeInfo() is not hard.
> >Just there were no such use cases. May be we can do something
> >similar to what LowerIntrinsicCall() does and lower it differently
> >in the backend.
> >
> But in backend can we still get type information? I thought type is
> meaningful in frontend only, and backend behaviors is unable to affect
> DWARF generation, right?

why do we need to affect type generation? we just need to know dwarf
type id in the backend, so we can emit it as a constant.
I still think lowering eh_typeid_for differently may work.
Like instead of doing
GV = ExtractTypeInfo(I.getArgOperand(0)) followed by
getMachineFunction().getMMI().getTypeIDFor(GV)
we can get dwarf type id from I.getArgOperand(0) if it's
any pointer to struct type.
I'm not familiar with dwarf handling part of llvm, but feels possible.

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Re: Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH v4 3/3] bpf:  Introduce function for outputing data to perf event "Wangnan (F)" <wangnan0@huawei.com> - 2015-08-05 04:00 +0200
  Re: Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH v4 3/3] bpf:  Introduce function for outputing data to perf event "Wangnan (F)" <wangnan0@huawei.com> - 2015-08-05 04:10 +0200
    Re: [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH  v4 3/3] bpf: Introduce function for outputing data to perf event "Wangnan (F)" <wangnan0@huawei.com> - 2015-08-05 09:00 +0200
      Re: [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH v4  3/3] bpf: Introduce function for outputing data to perf event Alexei Starovoitov <ast@plumgrid.com> - 2015-08-05 09:20 +0200
        Re: [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re: [RFC PATCH  v4 3/3] bpf: Introduce function for outputing data to perf event "Wangnan (F)" <wangnan0@huawei.com> - 2015-08-05 10:40 +0200
          Re: [llvm-dev] [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re:  [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-08-06 05:30 +0200
            Re: [llvm-dev] [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re:  [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event "Wangnan (F)" <wangnan0@huawei.com> - 2015-08-06 06:40 +0200
              Re: [llvm-dev] [LLVMdev] Cc llvmdev: Re: llvm bpf debug info. Re:  [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-08-06 09:00 +0200

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