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![Josh Poimboeuf](/assets/img/avatar_default.png)
The GCC '-maccumulate-outgoing-args' flag is enabled for most configs, mostly because of issues which are no longer relevant. For most configs, and with most recent versions of GCC, it's no longer needed. Clarify which cases need it, and only enable it for those cases. Also produce a compile-time error for the ftrace graph + mcount + '-Os' case, which will otherwise cause runtime failures. The main benefit of '-maccumulate-outgoing-args' is that it prevents an ugly prologue for functions which have aligned stacks. But removing the option also has some benefits: more readable argument saves, smaller text size, and (presumably) slightly improved performance. Here are the object size savings for 32-bit and 64-bit defconfig kernels: text data bss dec hex filename 10006710 3543328 1773568 15323606 e9d1d6 vmlinux.x86-32.before 9706358 3547424 1773568 15027350 e54c96 vmlinux.x86-32.after text data bss dec hex filename 10652105 4537576 843776 16033457 f4a6b1 vmlinux.x86-64.before 10639629 4537576 843776 16020981 f475f5 vmlinux.x86-64.after That comes out to a 3% text size improvement on x86-32 and a 0.1% text size improvement on x86-64. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrew Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Pavel Machek <pavel@ucw.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170316193133.zrj6gug53766m6nn@treble Signed-off-by: Ingo Molnar <mingo@kernel.org>
52 lines
2.5 KiB
Text
52 lines
2.5 KiB
Text
# CPU tuning section - shared with UML.
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# Must change only cflags-y (or [yn]), not CFLAGS! That makes a difference for UML.
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#-mtune exists since gcc 3.4
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HAS_MTUNE := $(call cc-option-yn, -mtune=i386)
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ifeq ($(HAS_MTUNE),y)
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tune = $(call cc-option,-mtune=$(1),$(2))
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else
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tune = $(call cc-option,-mcpu=$(1),$(2))
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endif
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align := $(cc-option-align)
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cflags-$(CONFIG_M486) += -march=i486
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cflags-$(CONFIG_M586) += -march=i586
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cflags-$(CONFIG_M586TSC) += -march=i586
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cflags-$(CONFIG_M586MMX) += -march=pentium-mmx
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cflags-$(CONFIG_M686) += -march=i686
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cflags-$(CONFIG_MPENTIUMII) += -march=i686 $(call tune,pentium2)
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cflags-$(CONFIG_MPENTIUMIII) += -march=i686 $(call tune,pentium3)
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cflags-$(CONFIG_MPENTIUMM) += -march=i686 $(call tune,pentium3)
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cflags-$(CONFIG_MPENTIUM4) += -march=i686 $(call tune,pentium4)
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cflags-$(CONFIG_MK6) += -march=k6
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# Please note, that patches that add -march=athlon-xp and friends are pointless.
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# They make zero difference whatsosever to performance at this time.
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cflags-$(CONFIG_MK7) += -march=athlon
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cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8,-march=athlon)
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cflags-$(CONFIG_MCRUSOE) += -march=i686 $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
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cflags-$(CONFIG_MEFFICEON) += -march=i686 $(call tune,pentium3) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
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cflags-$(CONFIG_MWINCHIPC6) += $(call cc-option,-march=winchip-c6,-march=i586)
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cflags-$(CONFIG_MWINCHIP3D) += $(call cc-option,-march=winchip2,-march=i586)
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cflags-$(CONFIG_MCYRIXIII) += $(call cc-option,-march=c3,-march=i486) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0
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cflags-$(CONFIG_MVIAC3_2) += $(call cc-option,-march=c3-2,-march=i686)
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cflags-$(CONFIG_MVIAC7) += -march=i686
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cflags-$(CONFIG_MCORE2) += -march=i686 $(call tune,core2)
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cflags-$(CONFIG_MATOM) += $(call cc-option,-march=atom,$(call cc-option,-march=core2,-march=i686)) \
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$(call cc-option,-mtune=atom,$(call cc-option,-mtune=generic))
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# AMD Elan support
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cflags-$(CONFIG_MELAN) += -march=i486
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# Geode GX1 support
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cflags-$(CONFIG_MGEODEGX1) += -march=pentium-mmx
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cflags-$(CONFIG_MGEODE_LX) += $(call cc-option,-march=geode,-march=pentium-mmx)
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# add at the end to overwrite eventual tuning options from earlier
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# cpu entries
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cflags-$(CONFIG_X86_GENERIC) += $(call tune,generic,$(call tune,i686))
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# Bug fix for binutils: this option is required in order to keep
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# binutils from generating NOPL instructions against our will.
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ifneq ($(CONFIG_X86_P6_NOP),y)
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cflags-y += $(call cc-option,-Wa$(comma)-mtune=generic32,)
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endif
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