llvm dev - Jan 2018 - Is -disable-llvm-passes and -disable-llvm-optzns different?

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!
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180109/a212f6c0/attachment.html>

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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180108/a1004359/attachment.html>

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
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180109/0904aa8b/attachment-0001.html>