linux-kernel - [PATCH 3.2 129/185] x86, build: Pass in additional -mno-mmx, -mno-sse options

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Date:	Sun, 29 Dec 2013 03:08:44 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Kevin B. Smith" <kevin.b.smith@...el.com>,
	"Sunil K. Pandey" <sunil.k.pandey@...el.com>,
	"H. J. Lu" <hjl.tools@...il.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: [PATCH 3.2 129/185] x86, build: Pass in additional -mno-mmx,
 -mno-sse options

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "H. Peter Anvin" <hpa@...ux.intel.com>

commit 8b3b005d675726e38bc504d2e35a991e55819155 upstream.

In checkin

    5551a34e5aea x86-64, build: Always pass in -mno-sse

we unconditionally added -mno-sse to the main build, to keep newer
compilers from generating SSE instructions from autovectorization.
However, this did not extend to the special environments
(arch/x86/boot, arch/x86/boot/compressed, and arch/x86/realmode/rm).
Add -mno-sse to the compiler command line for these environments, and
add -mno-mmx to all the environments as well, as we don't want a
compiler to generate MMX code either.

This patch also removes a $(cc-option) call for -m32, since we have
long since stopped supporting compilers too old for the -m32 option,
and in fact hardcode it in other places in the Makefiles.

Reported-by: Kevin B. Smith <kevin.b.smith@...el.com>
Cc: Sunil K. Pandey <sunil.k.pandey@...el.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Cc: H. J. Lu <hjl.tools@...il.com>
Link: http://lkml.kernel.org/n/tip-j21wzqv790q834n7yc6g80j1@git.kernel.org
[bwh: Backported to 3.2:
 - Drop changes to arch/x86/Makefile, which sets these flags earlier
 - Adjust context
 - Drop changes to arch/x86/realmode/rm/Makefile which doesn't exist]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -51,18 +51,18 @@ $(obj)/cpustr.h: $(obj)/mkcpustr FORCE
 
 # How to compile the 16-bit code.  Note we always compile for -march=i386,
 # that way we can complain to the user if the CPU is insufficient.
-KBUILD_CFLAGS	:= $(LINUXINCLUDE) -g -Os -D_SETUP -D__KERNEL__ \
+KBUILD_CFLAGS	:= $(LINUXINCLUDE) -m32 -g -Os -D_SETUP -D__KERNEL__ \
 		   -DDISABLE_BRANCH_PROFILING \
 		   -Wall -Wstrict-prototypes \
 		   -march=i386 -mregparm=3 \
 		   -include $(srctree)/$(src)/code16gcc.h \
 		   -fno-strict-aliasing -fomit-frame-pointer \
+		   -mno-mmx -mno-sse \
 		   $(call cc-option, -ffreestanding) \
 		   $(call cc-option, -fno-toplevel-reorder,\
-			$(call cc-option, -fno-unit-at-a-time)) \
+		   $(call cc-option, -fno-unit-at-a-time)) \
 		   $(call cc-option, -fno-stack-protector) \
 		   $(call cc-option, -mpreferred-stack-boundary=2)
-KBUILD_CFLAGS	+= $(call cc-option, -m32)
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
 
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -12,6 +12,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFIL
 cflags-$(CONFIG_X86_32) := -march=i386
 cflags-$(CONFIG_X86_64) := -mcmodel=small
 KBUILD_CFLAGS += $(cflags-y)
+KBUILD_CFLAGS += -mno-mmx -mno-sse
 KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
 KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
 

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