[PATCH] i386: use -mcpu, not -mtune, for GCCs older than 3.4

I just noted that -mtune is used, which is only supported on recent GCCs; by
reading http://gcc.gnu.org/gcc-3.4/changes.html, you see "-mcpu has been
renamed to -mtune.", so for GCC < 3.4 we're not using any specific tuning in
the appropriate cases.  However -mcpu is deprecated, so use -mtune when
possible.

This was introduced by commit e9d4dce954a60dc23dd1d967766ca2347b780e54 of the
old tree (between 2.6.10-rc3 and 2.6.10) by Linus Torvalds, to remove the use
of -march, since that could trigger gcc using SSE on its own.  But no
attention was used about using -mcpu vs.  -mtune.

And btw, the old 2.6.4 code (for instance) was:
cflags-$(CONFIG_MPENTIUMII)     += $(call check_gcc,-march=pentium2,-march=i686)
cflags-$(CONFIG_MPENTIUMIII)    += $(call check_gcc,-march=pentium3,-march=i686)
cflags-$(CONFIG_MPENTIUMM)      += $(call check_gcc,-march=pentium3,-march=i686)
cflags-$(CONFIG_MPENTIUM4)      += $(call check_gcc,-march=pentium4,-march=i686)

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/Makefile.cpu b/arch/i386/Makefile.cpu
index 86c7bb1..8e51456 100644 (file)
--- a/arch/i386/Makefile.cpu
+++ b/arch/i386/Makefile.cpu
@@ -1,6 +1,14 @@
 # CPU tuning section - shared with UML.
 # Must change only cflags-y (or [yn]), not CFLAGS! That makes a difference for UML.
 
+#-mtune exists since gcc 3.4, and some -mcpu flavors didn't exist in gcc 2.95.
+HAS_MTUNE      := $(call cc-option-yn, -mtune=i386)
+ifeq ($(HAS_MTUNE),y)
+tune           = $(call cc-option,-mtune=$(1),)
+else
+tune           = $(call cc-option,-mcpu=$(1),)
+endif
+
 align := $(cc-option-align)
 cflags-$(CONFIG_M386)          += -march=i386
 cflags-$(CONFIG_M486)          += -march=i486
@@ -8,17 +16,17 @@ cflags-$(CONFIG_M586)                += -march=i586
 cflags-$(CONFIG_M586TSC)       += -march=i586
 cflags-$(CONFIG_M586MMX)       += $(call cc-option,-march=pentium-mmx,-march=i586)
 cflags-$(CONFIG_M686)          += -march=i686
-cflags-$(CONFIG_MPENTIUMII)    += -march=i686 $(call cc-option,-mtune=pentium2)
-cflags-$(CONFIG_MPENTIUMIII)   += -march=i686 $(call cc-option,-mtune=pentium3)
-cflags-$(CONFIG_MPENTIUMM)     += -march=i686 $(call cc-option,-mtune=pentium3)
-cflags-$(CONFIG_MPENTIUM4)     += -march=i686 $(call cc-option,-mtune=pentium4)
+cflags-$(CONFIG_MPENTIUMII)    += -march=i686 $(call tune,pentium2)
+cflags-$(CONFIG_MPENTIUMIII)   += -march=i686 $(call tune,pentium3)
+cflags-$(CONFIG_MPENTIUMM)     += -march=i686 $(call tune,pentium3)
+cflags-$(CONFIG_MPENTIUM4)     += -march=i686 $(call tune,pentium4)
 cflags-$(CONFIG_MK6)           += -march=k6
 # Please note, that patches that add -march=athlon-xp and friends are pointless.
 # They make zero difference whatsosever to performance at this time.
 cflags-$(CONFIG_MK7)           += $(call cc-option,-march=athlon,-march=i686 $(align)-functions=4)
 cflags-$(CONFIG_MK8)           += $(call cc-option,-march=k8,$(call cc-option,-march=athlon,-march=i686 $(align)-functions=4))
 cflags-$(CONFIG_MCRUSOE)       += -march=i686 $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
-cflags-$(CONFIG_MEFFICEON)     += -march=i686 $(call cc-option,-mtune=pentium3) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
+cflags-$(CONFIG_MEFFICEON)     += -march=i686 $(call tune,pentium3) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
 cflags-$(CONFIG_MWINCHIPC6)    += $(call cc-option,-march=winchip-c6,-march=i586)
 cflags-$(CONFIG_MWINCHIP2)     += $(call cc-option,-march=winchip2,-march=i586)
 cflags-$(CONFIG_MWINCHIP3D)    += $(call cc-option,-march=winchip2,-march=i586)