Re: [dpdk-dev] [PATCH v4 01/10] build: add an option to enable LTO build

[Thomas Monjalon <thomas@monjalon.net>]

28/10/2019 11:47, Andrzej Ostruszka:
> On 10/27/19 12:47 PM, Thomas Monjalon wrote:
> >> +turned on.  This depends obviously on the capabilities of the compiler
> > 
> > Not sure what you are talking about.
> > If it is about fat objects, it is not obvious.
> > 
> >> +to do "whole program" optimization at link time and is available only
> 
> That was not a reference to some formally defined "capabilities" just an
> "obvious" statement that in order to benefit from LTO one needs a
> compiler "capable of" performing it.  I will rephrase this paragraph as:
> 
> -8<-------------
> The DPDK supports compilation with link time optimization turned on.
> This depends obviously on the ability of the compiler to do "whole
> program" optimization at link time and is available only for compilers
> that support that feature (gcc and icc).
> To be more specific, compiler (in addition to performing LTO) have to
> support creation of ELF objects containing both normal code and internal
> representation (fat-lto-objects).  This is required since during build
> some code is generated by parsing produced ELF objects (pmdinfogen).
> -8<-------------
> 
> Will it suffice?  If not, then please suggest wording to be used.

There is a confusion here:
"compilers that support that feature (gcc and icc)"
In my understanding, clang supports LTO but is not mentioned
because of the lack of fat object support.
I think you should mention gcc and icc only after explaining
the second constraint (fat objects).

> >> +for compilers that support that feature (gcc and icc).  To be more
> > 
> > Please start a new sentence at the beginning of a line in the RsT file.
> > It is easier to review and update.
> 
> OK

Please consider such comment to apply to the whole file :)


[...]
> OK.  I'll send the next version today.
> 
> Thank you again for the comments.

Thank you