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    Subject[PATCH 3.12 01/84] gcov: disable tree-loop-im to reduce stack usage
    Date
    From: Arnd Bergmann <arnd@arndb.de>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit c87bf431448b404a6ef5fbabd74c0e3e42157a7f upstream.

    Enabling CONFIG_GCOV_PROFILE_ALL produces us a lot of warnings like

    lib/lz4/lz4hc_compress.c: In function 'lz4_compresshcctx':
    lib/lz4/lz4hc_compress.c:514:1: warning: the frame size of 1504 bytes is larger than 1024 bytes [-Wframe-larger-than=]

    After some investigation, I found that this behavior started with gcc-4.9,
    and opened https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69702.
    A suggested workaround for it is to use the -fno-tree-loop-im
    flag that turns off one of the optimization stages in gcc, so the
    code runs a little slower but does not use excessive amounts
    of stack.

    We could make this conditional on the gcc version, but I could not
    find an easy way to do this in Kbuild and the benefit would be
    fairly small, given that most of the gcc version in production are
    affected now.

    I'm marking this for 'stable' backports because it addresses a bug
    with code generation in gcc that exists in all kernel versions
    with the affected gcc releases.

    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
    Signed-off-by: Michal Marek <mmarek@suse.com>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    Makefile | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/Makefile b/Makefile
    index a90b363b3493..4c1baa9b6bae 100644
    --- a/Makefile
    +++ b/Makefile
    @@ -347,7 +347,7 @@ AFLAGS_MODULE =
    LDFLAGS_MODULE =
    CFLAGS_KERNEL =
    AFLAGS_KERNEL =
    -CFLAGS_GCOV = -fprofile-arcs -ftest-coverage
    +CFLAGS_GCOV = -fprofile-arcs -ftest-coverage -fno-tree-loop-im


    # Use USERINCLUDE when you must reference the UAPI directories only.
    --
    2.10.1
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