Hi, On 29 June 2015 at 22:18, Kushwaha Prabhakar <[email protected]> wrote: > Hi Simon, Tom, > > -fdelete-null-pointer-checks flag controls global dataflow analyses and > eliminate useless checks for null pointers; It assume that if a pointer is > checked after it has already been dereferenced, it cannot be null. This flag > is enabled by default. > gcc v4.9 has more optimizations added to this option. Hence it is very > aggressive with GCC v4.9 series. It is also well documented in the GCC v4.9 > release notes: > https://gcc.gnu.org/gcc-4.9/porting_to.html > > There is possibility after moving to gcc-4.9 some platform may/may not work > properly. > I tested this patch for freescale powerpc platforms. > But It may needs be taken care by all architecture like ARM, powerpc. If this > is the case; this flag should be in top level Makefile (not sure) >
I suspect a top-level option would be best, perhaps near this one in Makefile: KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector) Regards, Simon > Regards, > Prabhakar > >> -----Original Message----- >> From: Wood Scott-B07421 >> Sent: Wednesday, May 20, 2015 11:04 PM >> To: Sun York-R58495 >> Cc: Kushwaha Prabhakar-B32579; [email protected]; Dharmakan Rohit- >> B30502 >> Subject: Re: [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null- >> pointer-checks >> >> On Wed, 2015-05-20 at 10:10 -0700, York Sun wrote: >> > Scott, >> > >> > Please comment on this patch. >> > >> > York >> >> I think this should be set treewide (as Linux does), not just for mpc85xx. >> But >> use cc-option to make sure that the compiler supports the option. >> >> -Scott >> >> > >> > On 05/06/2015 11:07 PM, Prabhakar Kushwaha wrote: >> > > -fdelete-null-pointer-checks flag controls global dataflow analyses >> > > and eliminate useless checks for null pointers; It assume that if a >> > > pointer is checked after it has already been dereferenced, it cannot be >> null. >> > > This flag is enabled by default. >> > > >> > > gcc v4.9 has more optimizations added to this option. Hence it is >> > > very aggressive with GCC v4.9 series. Add >> > > -fno-delete-null-pointer-checks to disable the optimization >> > > >> > > Signed-off-by: Rohit Dharmakan <[email protected]> >> > > Signed-off-by: Prabhakar Kushwaha <[email protected]> >> > > --- >> > > arch/powerpc/cpu/mpc85xx/config.mk | 3 ++- >> > > 1 file changed, 2 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/arch/powerpc/cpu/mpc85xx/config.mk >> > > b/arch/powerpc/cpu/mpc85xx/config.mk >> > > index 72c964c..2aedd24 100644 >> > > --- a/arch/powerpc/cpu/mpc85xx/config.mk >> > > +++ b/arch/powerpc/cpu/mpc85xx/config.mk >> > > @@ -5,7 +5,8 @@ >> > > # SPDX-License-Identifier: GPL-2.0+ >> > > # >> > > >> > > -PLATFORM_CPPFLAGS += -Wa,-me500 -msoft-float -mno-string >> > > +PLATFORM_CPPFLAGS += -Wa,-me500 -msoft-float -mno-string \ >> > > + -fno-delete-null-pointer-checks >> > > >> > > # -mspe=yes is needed to have -mno-spe accepted by a buggy GCC; # >> > > see "[PATCH,rs6000] make -mno-spe work as expected" on >> > > >> > _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
