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invoke.texi (-flto): Expand section about using static libraries with LTO.

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2014-03-24  Tobias Burnus  <burnus@net-b.de>

        * doc/invoke.texi (-flto): Expand section about
        using static libraries with LTO.

From-SVN: r208798
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Tobias Burnus 2014-03-24 20:53:52 +01:00 committed by Tobias Burnus
parent 6f6c00f3a3
commit 09f15d1b52
2 changed files with 15 additions and 3 deletions
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@ -1,3 +1,8 @@
2014-03-24 Tobias Burnus <burnus@net-b.de>
* doc/invoke.texi (-flto): Expand section about
using static libraries with LTO.
2014-03-24 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
PR rtl-optimization/60501

13
gcc/doc/invoke.texi
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@ -8664,8 +8664,13 @@ regular (non-LTO) compilation.
If object files containing GIMPLE bytecode are stored in a library archive, say
@file{libfoo.a}, it is possible to extract and use them in an LTO link if you
are using a linker with plugin support. To enable this feature, use
the flag @option{-fuse-linker-plugin} at link time:
are using a linker with plugin support. To create static libraries suitable
for LTO, use @command{gcc-ar} and @command{gcc-ranlib} instead of @command{ar}
and @code{ranlib}; to show the symbols of object files with GIMPLE bytecode, use
@command{gcc-nm}. Those commands require that @command{ar}, @command{ranlib}
and @command{nm} have been compiled with plugin support. At link time, use the the
flag @option{-fuse-linker-plugin} to ensure that the library participates in
the LTO optimization process:
@smallexample
gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo
@ -8678,7 +8683,9 @@ to make them part of the aggregated GIMPLE image to be optimized.
If you are not using a linker with plugin support and/or do not
enable the linker plugin, then the objects inside @file{libfoo.a}
are extracted and linked as usual, but they do not participate
in the LTO optimization process.
in the LTO optimization process. In order to make a static library suitable
for both LTO optimization and usual linkage, compile its object files with
@option{-flto} @code{-ffat-lto-objects}.
Link-time optimizations do not require the presence of the whole program to
operate. If the program does not require any symbols to be exported, it is