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authorIngo Molnar <mingo@elte.hu>2006-01-14 13:21:29 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-14 18:27:15 -0800
commit9ab34fe76114b9538bfcaf3a9d112dee0feb5f17 (patch)
tree3bd494625e6bef27f876d37f39fe537d554af571 /arch
parent40fc55cb69c0386504ab5184e9bea0a7aecb2bd3 (diff)
downloadop-kernel-dev-9ab34fe76114b9538bfcaf3a9d112dee0feb5f17.zip
op-kernel-dev-9ab34fe76114b9538bfcaf3a9d112dee0feb5f17.tar.gz
[PATCH] enable unit-at-a-time optimisations for gcc4
Allow gcc4 compilers to optimize unit-at-a-time. This flag enables gcc to "see" the entire C file before making optimisation decisions such as inline, which results in gcc making better decisions. One of the immediate effects of this is that static functions that are used only once now get inlined. gcc 3.4 has this flag as well, however gcc 3.x have a problem with inlining and stacks and as a result, enabling this flag there would cause excessive and unacceptable stack use. This problem is fixed in the gcc 4.x series. The x86-64 architecture already enables this feature so it's well tested already. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Acked-by: Jeff Garzik <jgarzik@pobox.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/Makefile6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/i386/Makefile b/arch/i386/Makefile
index d3c0409..bd2d53a 100644
--- a/arch/i386/Makefile
+++ b/arch/i386/Makefile
@@ -42,9 +42,9 @@ include $(srctree)/arch/i386/Makefile.cpu
cflags-$(CONFIG_REGPARM) += $(shell if [ $(call cc-version) -ge 0300 ] ; then \
echo "-mregparm=3"; fi ;)
-# Disable unit-at-a-time mode, it makes gcc use a lot more stack
-# due to the lack of sharing of stacklots.
-CFLAGS += $(call cc-option,-fno-unit-at-a-time)
+# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
+# a lot more stack due to the lack of sharing of stacklots:
+CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then echo $(call cc-option,-fno-unit-at-a-time); fi ;)
CFLAGS += $(cflags-y)
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