Re: [dpdk-dev] [PATCH v4 00/10] Add an option to use LTO for DPDK build

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Oct 22, 2019 at 01:54:02PM +0200, Andrzej Ostruszka wrote:
> This patch series adds an option to make use of link time optimization
> (if compiler has support for it).  It is split as follows:
> - 1st patch (build) is the enablement
> - remaining patches are fixes for the warnings produced by the compiler
>   and they are split by directory/subsystem so their maintainers can
>   easily find and verify the changes - please note that there are two
>   groups:
>   * errors (or possible errors) - with title "fix possible use ..."
>   * false positives - warnings that _I_ think are not valid and the
>     changes are made only to silence the compiler.
> 
> v4 Changes:
> -----------
> - merge nested conditionals in config/meson.build into one
> 
> v3 Changes:
> -----------
> - removed support for clang (only gcc and icc remain):
>   - it turned out that 'fat-lto-objects' is not really supported - it is
>     accepted as a flag but ignored e.g. clang v6.0:
>       clang: error: optimization flag '-ffat-lto-objects' is not supported
>       [-Werror,-Wignored-optimization-argument]
>     this was probably masked previously by playing around with meson and
>     testing for the availability of this flag and dropping LTO if not
>     supported.
> - improved commit messages:
>   - added 'Fixes' tags where appropriate
>   - included snippets of compiler warnings
> - changed commit names for the commits cleaning up 'false positive'
>   compiler warnings - these are not really 'fixes' for the code, just
>   workarounds for compiler shortcomings and check-git-log.sh was
>   complaining about missing 'Fixes' tag.
> 
> v2 Changes:
> -----------
> - fixed building of shared libraries:
>   - gcc does not scan top level assembler statements so it missed that
>     function implementations for specific versions were being used and
>     was removing them
> - fixed meson.build config files:
>   - moved from 'enable_lto' project option to built-in 'b_lto'
>   - documented that 'default_library' should be 'shared':
>     with 'default_library=static' (the default) the meson build with LTO
>     is broken - this is because, SHARED_LIB is fixed in rte_config.h
>     used by meson which leads to no alias for default version in
>     generated static libraries (MAP_STATIC_SYMBOL() is empty)
> - app/test: added log for failed bonding "config get"
> 
> Andrzej Ostruszka (10):
>   build: add an option to enable LTO build
>   eventdev: fix possible use of uninitialized var
>   app/eventdev: clean LTO build warnings (maybe-uninitialized)
>   event/octeontx2: clean LTO build warnings (maybe-uninitialized)
>   app/test: clean LTO build warnings (maybe-uninitialized)
>   net/dpaa2: fix possible use of uninitialized vars
>   net/e1000: clean LTO build warnings (maybe-uninitialized)
>   net/i40e: clean LTO build warnings (maybe-uninitialized)
>   net/ifc: clean LTO build warnings (maybe-uninitialized)
>   net/qede: clean LTO build warnings (maybe-uninitialized)
> 
Does this have a dependency on set 6726 [1] ?

Otherwise, this looks something useful to have support for in DPDK, so

Series-acked-by: Bruce Richardson <bruce.richardson@intel.com>

[1] http://patches.dpdk.org/project/dpdk/list/?series=6726