powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

PATCH New Prabhakar Kushwaha 5 participants 7 messages May 7, 2015 – Jul 1, 2015 PowerPC

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Prabhakar Kushwaha

author

2015-05-07 06:07 UTC #0 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

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(-)

arch/powerpc/cpu/mpc85xx/config.mk +2 -1

index 72c964c..2aedd24 100644
@@ -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

Signature · 1 line

1.9.1

York Sun

2015-05-20 17:10 UTC #1 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

Scott,

Please comment on this patch.

York

Quoted 30 lines · Prabhakar Kushwaha

-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(-)
arch/powerpc/cpu/mpc85xx/config.mk +2 -1
index 72c964c..2aedd24 100644
@@ -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 Wood

2015-05-20 17:33 UTC #2 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

Quoted 5 lines · York Sun

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

Quoted 32 lines · Prabhakar Kushwaha

Quoted 30 lines
-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(-)
arch/powerpc/cpu/mpc85xx/config.mk +2 -1
index 72c964c..2aedd24 100644
@@ -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

Kushwaha Prabhakar

author

2015-06-30 04:18 UTC #3 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

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

Quoted 56 lines

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, May 20, 2015 11:04 PM
To: Sun York-R58495
Cc: Kushwaha Prabhakar-B32579; u-boot at lists.denx.de; Dharmakan Rohit- B30502
Subject: Re: [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null- pointer-checks
Quoted 5 lines · York Sun
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
Quoted 5 lines · Prabhakar Kushwaha
Quoted 3 lines
-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.
Quoted 28 lines
Quoted 28 lines
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(-)
arch/powerpc/cpu/mpc85xx/config.mk +2 -1
index 72c964c..2aedd24 100644
@@ -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

Simon Glass

2015-06-30 14:58 UTC #4 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

Hi,

Quoted 10 lines · Kushwaha Prabhakar

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

Quoted 60 lines

Regards,
Prabhakar
Quoted 56 lines
-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, May 20, 2015 11:04 PM
To: Sun York-R58495
Cc: Kushwaha Prabhakar-B32579; u-boot at lists.denx.de; Dharmakan Rohit- B30502
Subject: Re: [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null- pointer-checks
Quoted 5 lines · York Sun
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
Quoted 5 lines · Prabhakar Kushwaha
Quoted 3 lines
-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.
Quoted 28 lines
Quoted 28 lines
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(-)
arch/powerpc/cpu/mpc85xx/config.mk +2 -1
index 72c964c..2aedd24 100644
@@ -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

Tom Rini

2015-06-30 18:22 UTC #5 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

Quoted 9 lines · Simon Glass

Hi,
Quoted 6 lines · Kushwaha Prabhakar
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

Quoted 8 lines

Quoted 4 lines
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!

Signature · 8 lines

Tom
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Kushwaha Prabhakar

author

2015-07-01 03:10 UTC #6 lore raw

PATCH 1/1 powerpc/mpc85xx:Add GCC flag -fno-delete-null-pointer-checks

In reply to Simon Glass

Quoted 33 lines

-----Original Message-----
From: sjg at google.com [mailto:sjg at 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 at konsulko.com; u- boot at lists.denx.de; Dharmakan Rohit-B30502
Subject: Re: [PATCH] powerpc/mpc85xx:Add GCC flag -fno-delete-null- pointer-checks
Hi,
Quoted 3 lines · Kushwaha Prabhakar
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.
Quoted 1 line
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:
Quoted 3 lines
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.
Quoted 5 lines
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)

Quoted 4 lines

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