PATCH: Don't use -mtune=merced for gcc 3.4

PATCH: Don't use -mtune=merced for gcc 3.4

[H. J. Lu]

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Gcc 3.4 has a new DFA scheduler for ia64. Unfortunately, it is not
well tested for Itanium 1. When I tried to use gcc 3.4 to compile
2.6 kernel configured for Merced, gcc failed in many places:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15598
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15653
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15655
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16130
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16142
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16143

Some of them have been fixed. But I am afraid many more remain. I don't
know how many Itanium 1 machines left in production use. If people want
to optimize kernel for Itanium 1, they can stick with the older gccs.
Or they should upgrade their machines. I think the gcc developer's time
should be better spent on somewhere else. I have been using this patch
for a while, kernel seems to work OK.


H.J.

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--- linux-2.6.7/arch/ia64/Makefile.merced	2004-06-22 09:09:50.000000000 -0700
+++ linux-2.6.7/arch/ia64/Makefile	2004-06-22 09:12:03.000000000 -0700
@@ -43,7 +43,8 @@ endif
 
 ifeq ($(GCC_VERSION),3)
  ifeq ($(GCC_MINOR_VERSION),4)
-	cflags-$(CONFIG_ITANIUM)	+= -mtune=merced
+# Workaround Itanium 1 bugs in gcc 3.4.
+#	cflags-$(CONFIG_ITANIUM)	+= -mtune=merced
 	cflags-$(CONFIG_MCKINLEY)	+= -mtune=mckinley
  endif
 endif

Re: PATCH: Don't use -mtune=merced for gcc 3.4

[David Mosberger]

>>>>> On Mon, 28 Jun 2004 11:40:40 -0700, "H. J. Lu" <hjl@lucon.org> said:

  HJ> If people want to optimize kernel for Itanium 1, they can stick
  HJ> with the older gccs.  Or they should upgrade their machines. I
  HJ> think the gcc developer's time should be better spent on
  HJ> somewhere else.

I agree, but I do worry a bit whether this isn't an indication of a
deeper problem.  Let's hope not.  (I did apply the patch, thanks.)

	--david