[PATCH 4/5] gcov: disable tree-loop-im to reduce stack usage
From: arnd@arndb.de (Arnd Bergmann)
Date: 2016-02-12 16:07:51
Also in:
linux-kbuild, lkml
Subsystem:
kernel build + files below scripts/ (unless maintained elsewhere), the rest · Maintainers:
Nathan Chancellor, Nicolas Schier, Linus Torvalds
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. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 352f55ccc54e..6bb89728a9d1 100644
--- a/Makefile
+++ b/Makefile@@ -364,7 +364,7 @@ AFLAGS_MODULE = LDFLAGS_MODULE = CFLAGS_KERNEL = AFLAGS_KERNEL = -CFLAGS_GCOV = -fprofile-arcs -ftest-coverage +CFLAGS_GCOV = -fprofile-arcs -ftest-coverage -fno-tree-loop-im CFLAGS_KCOV = -fsanitize-coverage=trace-pc
--
2.7.0