Using PGO and -O3

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Using PGO and -O3

Richard Smith via cfe-dev
Hello all,

clang-related PGO documentation recommends using PGO with -O2 (for
example:
https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization).
The question is: is there any reason why exactly -O2 is used in
examples? Are there any factors which can cause problems when using PGO
with -O3?

Thanks in advance for your advice!

--
Best Regards,

Victor Leschuk | Software Engineer | Access Softek

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Re: [llvm-dev] Using PGO and -O3

Richard Smith via cfe-dev
It means using PGO with -O2 and above (including -O3).

David

On Sun, Jan 28, 2018 at 6:48 PM, Victor Leschuk via llvm-dev <[hidden email]> wrote:
Hello all,

clang-related PGO documentation recommends using PGO with -O2 (for
example:
https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization).
The question is: is there any reason why exactly -O2 is used in
examples? Are there any factors which can cause problems when using PGO
with -O3?

Thanks in advance for your advice!

--
Best Regards,

Victor Leschuk | Software Engineer | Access Softek

_______________________________________________
LLVM Developers mailing list
[hidden email]
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


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Re: [llvm-dev] Using PGO and -O3

Richard Smith via cfe-dev

Maybe we should update the documentation to state this directly? Currently its a little bit confusing.


On 01/29/2018 05:51 AM, Xinliang David Li wrote:
It means using PGO with -O2 and above (including -O3).

David

On Sun, Jan 28, 2018 at 6:48 PM, Victor Leschuk via llvm-dev <[hidden email]> wrote:
Hello all,

clang-related PGO documentation recommends using PGO with -O2 (for
example:
https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization).
The question is: is there any reason why exactly -O2 is used in
examples? Are there any factors which can cause problems when using PGO
with -O3?

Thanks in advance for your advice!

--
Best Regards,

Victor Leschuk | Software Engineer | Access Softek

_______________________________________________
LLVM Developers mailing list
[hidden email]
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


-- 
Best Regards,

Victor Leschuk | Software Engineer | Access Softek

_______________________________________________
cfe-dev mailing list
[hidden email]
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Re: [llvm-dev] Using PGO and -O3

Richard Smith via cfe-dev
Sure:

echristo@jhereg ~/s/l/t/clang> git svn dcommit
M docs/UsersManual.rst
Committed r323902

-eric

On Wed, Jan 31, 2018 at 12:16 AM Victor Leschuk via llvm-dev <[hidden email]> wrote:

Maybe we should update the documentation to state this directly? Currently its a little bit confusing.


On 01/29/2018 05:51 AM, Xinliang David Li wrote:
It means using PGO with -O2 and above (including -O3).

David

On Sun, Jan 28, 2018 at 6:48 PM, Victor Leschuk via llvm-dev <[hidden email]> wrote:
Hello all,

clang-related PGO documentation recommends using PGO with -O2 (for
example:
https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization).
The question is: is there any reason why exactly -O2 is used in
examples? Are there any factors which can cause problems when using PGO
with -O3?

Thanks in advance for your advice!

--
Best Regards,

Victor Leschuk | Software Engineer | Access Softek

_______________________________________________
LLVM Developers mailing list
[hidden email]
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


-- 
Best Regards,

Victor Leschuk | Software Engineer | Access Softek
_______________________________________________
LLVM Developers mailing list
[hidden email]
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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