[U-Boot] [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks
-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 rohitarulraj@freescale.com Signed-off-by: Prabhakar Kushwaha prabhakar@freescale.com --- 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
Scott,
Please comment on this patch.
York
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 rohitarulraj@freescale.com Signed-off-by: Prabhakar Kushwaha prabhakar@freescale.com
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
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 rohitarulraj@freescale.com Signed-off-by: Prabhakar Kushwaha prabhakar@freescale.com
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
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)
Regards, Prabhakar
-----Original Message----- From: Wood Scott-B07421 Sent: Wednesday, May 20, 2015 11:04 PM To: Sun York-R58495 Cc: Kushwaha Prabhakar-B32579; u-boot@lists.denx.de; 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 rohitarulraj@freescale.com Signed-off-by: Prabhakar Kushwaha prabhakar@freescale.com
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
Hi,
On 29 June 2015 at 22:18, Kushwaha Prabhakar prabhakar@freescale.com 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; u-boot@lists.denx.de; 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 rohitarulraj@freescale.com Signed-off-by: Prabhakar Kushwaha prabhakar@freescale.com
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
On Tue, Jun 30, 2015 at 08:58:26AM -0600, Simon Glass wrote:
Hi,
On 29 June 2015 at 22:18, Kushwaha Prabhakar prabhakar@freescale.com 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)
I also agree with Scott and Simon, default, top level, using cc-option just like the Linux kernel please, thanks!
-----Original Message----- From: sjg@google.com [mailto:sjg@google.com] On Behalf Of Simon Glass Sent: Tuesday, June 30, 2015 8:28 PM To: Kushwaha Prabhakar-B32579 Cc: Wood Scott-B07421; Sun York-R58495; trini@konsulko.com; u- boot@lists.denx.de; Dharmakan Rohit-B30502 Subject: Re: [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null- pointer-checks
Hi,
On 29 June 2015 at 22:18, Kushwaha Prabhakar prabhakar@freescale.com 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)
I agree to put it here.
But how to test it against different platform supported by u-boot.
--prabhakar
participants (6)
-
Kushwaha Prabhakar -
Prabhakar Kushwaha
-
Scott Wood -
Simon Glass -
Tom Rini -
York Sun