[PATCH 5/6] i386: use -mcpu, not -mtune, for GCCs older than 3.4

Paolo 'Blaisorblade' Giarrusso
2005-10-25T22:11:19Z

From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

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>
---

arch/i386/Makefile.cpu | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/i386/Makefile.cpu b/arch/i386/Makefile.cpu
--- 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)