[PATCH] x86: Drop cc-options call for all options supported in gcc
3.2+
The kernel only supports gcc 3.2+ now so it doesn't make sense
anymore to explicitely check for options this compiler version
already has.
This actually fixes a bug. The -mprefered-stack-boundary check
never worked because gcc rightly complains
CC arch/i386/kernel/asm-offsets.s
cc1: -mpreferred-stack-boundary=2 is not between 4 and 12
Hi
Your patch for stack alignment on i386 is wrong. -mprefered-stack-boundary
is log2 of the stack alignment (read gcc man page). On AMD64 16-byte
alignment is enforced because of SSE, on i386 minimal alignment is 4
bytes.
See the code in gcc that triggered your error:
i = atoi (ix86_preferred_stack_boundary_string);
if (i < (TARGET_64BIT ? 4 : 2) || i > 12)
error ("-mpreferred-stack-boundary=%d is not between %d and 12",
i,
TARGET_64BIT ? 4 : 2);
else
ix86_preferred_stack_boundary = (1 << i) * BITS_PER_UNIT;
You are actually dealing with gcc bug, not Linux bug --- when gcc is
compiled with AMD64 support it enforces 16-byte alignment even in 32-bit
mode.
Rather let it be as it was, adding -mpreferred-stack-boundary=4 doesn't
make sense, because it is default.
Mikulas
Signed-off-by: Mikulas Patocka <[email protected]>
--- linux-2.6.22-rc1/arch/i386/Makefile_ Thu May 17 23:47:31 2007
+++ linux-2.6.22-rc1/arch/i386/Makefile Thu May 17 23:47:45 2007
@@ -34,7 +34,9 @@
CFLAGS += -pipe -msoft-float -mregparm=3 -freg-struct-return
# prevent gcc from keeping the stack 16 byte aligned
-CFLAGS += -mpreferred-stack-boundary=4
+# gcc has a bug that it doesn't allow 4-byte alignment when compiled with
+# 64-bit support and producing 32-bit code, so this option must be tested
+CFLAGS += $(call cc-option,-mpreferred-stack-boundary=2)
# CPU-specific tuning. Anything which can be shared with UML should go here.
include $(srctree)/arch/i386/Makefile.cpu
-
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