On Sat, 2009-05-02 at 21:48 +0200, Segher Boessenkool wrote: > > This patch introduces HAVE_NORMAL_FRAME_POINTER Kconfig symbol. When > > defined, the top level Makefile won't add -fno-omit-frame-pointer > > cflag (the flag is useless for PowerPC kernels, and also makes gcc > > generate wrong code). > > > +++ b/arch/powerpc/Kconfig > > > + select HAVE_NORMAL_FRAME_POINTER > > > +config HAVE_NORMAL_FRAME_POINTER > > + bool > > + help > > + Architectures should select this symbol if their ABI implies > > + having a frame pointer. > > I am totally confused what you call a frame pointer here. > None of the relevant PowerPC ABIs have a frame pointer > separate from the stack pointer; the compiler can create > one, of course. A better config symbol name and help text > would help understand this patch :-)
Yeah, I agree. This needs a better description. I only know what's going on because I was there for the start of the discussion. But just to be sure, this is what I think is happening. When we add "-pg" to gcc, it automatically causes frame pointers to be used. But with PPC, it always has frame pointers and there's no problem. But with Linux, when you add CONFIG_FRAME_POINTER, it automatically adds: -fno-omit-frame-pointer. Thus the config will add "-fomit-frame-pointer" when CONFIG_FRAME_POINTER is not set, or it will add "-fno-omit-frame-pointer" when it is set. The problem with PPC is that "-fno-omit-frame-pointer" is buggy and causes gcc to produce bad code. Perhaps a better name would be: HAVE_FRAME_POINTER_AS_DEFAULT ?? Or am I totally wrong in my analysis? -- Steve _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev