[llvm-dev] Is -disable-llvm-passes and -disable-llvm-optzns different?

[toddy wang via llvm-dev]

clang -cc1as -help #Succeed
clang -cc1as --help #Succeed
clang -cc1as -help #Fail (may be no hidden option)
clang -cc1as --help #Fail

Also, options dumped by 'clang -help' is a subset of 'clang -cc1 -help'.

On Tue, Jan 9, 2018 at 2:34 AM, toddy wang <wenwangtoddy at gmail.com> wrote:

> Thanks for pointing this out.
>
> The following is a more extensive test.
>
> //succeed means dumping help info without Error message.
>
> clang -help #succeed
> 'clang -help-hidden' #Fail
> 'clang --help-hidden' #Succeed
>
> clang -mllvm -v -help #Succeed
> clang -mllvm -v -help-hidden #Fail
> clang -mllvm -v --help-hidden #Succeed
>
> 'clang -mllvm -help -c LULESH.cc' #Succeed
> 'clang -mllvm -help LULESH.cc' # Fail
>
> clang -cc1 -help #Succeed
> clang -cc1 -help-hidden #Fail . (may be no hidden option)
> clang -cc1 --help-hidden #Fail
>
> opt -help  #Succeed
> opt --help #Succeed
> opt -help-hidden #Succeed
> opt --help-hidden #Succeed
>
> llc -help  #Succeed
> llc --help #Succeed
> llc -help-hidden #Succeed
> llc --help-hidden #Succeed
>
> lld -help #Succeed
> lld --help #Succeed
> lld -help-hidden #Fail (may be no hidden option)
> lld --help-hidden # Fail
>
> On Tue, Jan 9, 2018 at 2:07 AM, toddy wang <wenwangtoddy at gmail.com> wrote:
>
>> clang -O3 -mllvm -help -c  LULESH.cc succeeds.
>>
>> On Tue, Jan 9, 2018 at 2:05 AM, toddy wang <wenwangtoddy at gmail.com>
>> wrote:
>>
>>> Quick results:
>>>
>>> [twang15 at c89 temp]$ clang -mllvm -help
>>> clang-5.0: error: no input files
>>> [twang15 at c89 temp]$ clang -mllvm -help-hidden
>>> clang-5.0: error: no input files
>>> [twang15 at c89 temp]$ clang -mllvm --help-hidden
>>> clang-5.0: error: no input files
>>> [twang15 at c89 temp]$ clang -mllvm --help
>>> clang-5.0: error: no input files
>>>
>>> Anything wrong?
>>>
>>> On Tue, Jan 9, 2018 at 1:56 AM, Craig Topper <craig.topper at gmail.com>
>>> wrote:
>>>
>>>> There's a hack in lib/Driver/ToolChains/Clang.cpp to accept "-mllvm
>>>> -disable-llvm-optzns" as a hack for legacy compatibility. It's deprecated
>>>> and the -Xclang spelling should be used.
>>>>
>>>> There does appear to be a bug with "-mllvm -disable-llvm-optzns" and
>>>> -save-temps. -save-temps causes clang to be invoked separately to text
>>>> assembly into binary code, and it looks like that call to clang gets -mllvm
>>>> -disable-llvm-optzns passed to it but it isn't capable of handling it.  You
>>>> can see this if you add "-v" to your command line so you can see all the
>>>> subprocesses that get invoked.
>>>>
>>>> For the -help question, when clang printed "Try: 'clang (LLVM option
>>>> parsing) -help'" it was trying and failing to tell you to type "clang
>>>> -mllvm -help" or "clang -mllvm -help-hidden". This will print the help from
>>>> the llvm components.
>>>>
>>>> ~Craig
>>>>
>>>> On Mon, Jan 8, 2018 at 10:40 PM, toddy wang via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Hi guys,
>>>>>
>>>>> According to this patch review:
>>>>> *Title: Remove the '-disable-llvm-passes' flag (which I didn't even
>>>>> know existed, and I suspect many others aren't aware of either) and
>>>>> strength '-disable-llvm-optzns' to do the same thing*
>>>>> Link: https://reviews.llvm.org/D28047
>>>>>
>>>>> *-disable-llvm-optzns and -disable-llvm-passes are aliasing each
>>>>> other.*
>>>>>
>>>>> *1. Both  can be passed to cc1 w/ -Xclang when compilation is run to
>>>>> finish.*
>>>>> E.g
>>>>> [twang15 at c89 temp]$ clang++ -O2 -Xclang -disable-llvm-optzns
>>>>> -save-temps LULESH.cc
>>>>> [twang15 at c89 temp]$ cp a.out a.out.1
>>>>> [twang15 at c89 temp]$ clang++ -O2 -Xclang -disable-llvm-passes
>>>>> -save-temps LULESH.cc
>>>>> [twang15 at c89 temp]$ diff a.out a.out.1
>>>>> [twang15 at c89 temp]$
>>>>>
>>>>> *2. Both cannot be passed w/ -mllvm without -emit-llvm -c*
>>>>>
>>>>> [twang15 at c89 temp]$ clang++ -O2 -mllvm -disable-llvm-optzns
>>>>> -save-temps  LULESH.cc
>>>>> clang (LLVM option parsing): Unknown command line argument
>>>>> '-disable-llvm-optzns'.  Try: 'clang (LLVM option parsing) -help'
>>>>> clang (LLVM option parsing): Did you mean '-disable-cgp-gc-opts'?
>>>>>
>>>>> [twang15 at c89 temp]$ clang++ -O2 -mllvm -disable-llvm-passes
>>>>> -save-temps  LULESH.cc
>>>>> clang (LLVM option parsing): Unknown command line argument
>>>>> '-disable-llvm-passes'.  Try: 'clang (LLVM option parsing) -help'
>>>>> clang (LLVM option parsing): Did you mean '-disable-cleanups'?
>>>>>
>>>>> *3. However, -disable-llvm-optzns can be passed w/ -mllvm when
>>>>> -emit-llvm is also passed, but -disable-llvm-passes cannot *
>>>>>
>>>>> [twang15 at c89 temp]$ clang++ -O2 -mllvm -disable-llvm-optzns
>>>>> -save-temps -emit-llvm -c LULESH.cc
>>>>>
>>>>> [twang15 at c89 temp]$ clang++ -O2 -mllvm -disable-llvm-passes
>>>>> -save-temps -emit-llvm -c LULESH.cc
>>>>> clang (LLVM option parsing): Unknown command line argument
>>>>> '-disable-llvm-passes'.  Try: 'clang (LLVM option parsing) -help'
>>>>> clang (LLVM option parsing): Did you mean '-disable-cleanups'?
>>>>>
>>>>> *My questions: *
>>>>> 1. Is there a bug?
>>>>>
>>>>> 2. Lastly, try as clang instructs me: Try: 'clang (LLVM option
>>>>> parsing) -help'
>>>>>
>>>>> [twang15 at c89 temp]$ clang (LLVM option parsing) -help
>>>>> -bash: syntax error near unexpected token `LLVM'
>>>>>
>>>>> Can clang give me more helpful information on which flags can be
>>>>> passed with mllvm and which can be passed with -Xclang?
>>>>>
>>>>> 3. It seems to me clang cc1 has at least two major stages to handle
>>>>> *bc file.
>>>>> The first stage is to transform c/c++ to bc without any or w/ little
>>>>> optimizations, and -disable-llvm-passes is enabled by default.
>>>>>
>>>>> The second stage is to optimize bc files and output .s assembly. And
>>>>> by default, -disable-llvm-passes is disabled for this stage. -Xclang
>>>>> -disable-llvm-passes or -Xclang disable-llvm-optzns will affect this stage.
>>>>>
>>>>> Is this a correct understanding? or Partially correct? Where -mllvm
>>>>> options come into play?
>>>>>
>>>>> Thanks a lot!
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>>
>>>>
>>>
>>
>
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