On Tue, Feb 03, 2009 at 05:06:45PM +0100, Ingo Molnar wrote: > > * Anton Vorontsov <avoront...@ru.mvista.com> wrote: > > > According to this discussion: > > > > http://lkml.org/lkml/2008/7/25/338 > > http://lkml.org/lkml/2008/7/26/72 > > > > Frame pointers do nothing useful on PowerPC, so lib/Kconfig.debug > > makes CONFIG_FRAME_POINTER unselectable on PPC targets. But ftrace.h > > requires CONFIG_FRAME_POINTER for CALLER_ADDR macros. [...] > > hm, why not add PPC to FRAME_POINTERS list of architectures, and select it > from the powerpc arch Kconfig? Does that cause complications somewhere?
-fno-omit-frame-pointers makes the code worse w/o any actual benefit that we would use. Plus, there is a long standing bug in gcc that makes -fno-omit-frame-pointer generate wrong code for PPC targets: http://lkml.org/lkml/2008/9/2/25 That is, the only tracer that needs[1] -fno-omit-frame-pointer is "FUNCTION_TRCER", but we workaround the issue via -mno-sched-epilog, quoting arch/powerpc/Makefile: # Work around a gcc code-gen bug with -fno-omit-frame-pointer. ifeq ($(CONFIG_FUNCTION_TRACER),y) KBUILD_CFLAGS += -mno-sched-epilog endif [1] Btw, why exactly do we need the -fno-omit-frame-pointer for "FUNCTION_TRCER" tracer? Why just -pg isn't sufficient?.. -- Anton Vorontsov email: cbouatmai...@gmail.com irc://irc.freenode.net/bd2 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev