Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when building .S file with -mfloat-abi=soft

[changyp]

I have a ASM file with extension .S
After I build this file with option
"-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"

And the output is
Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "4t"
  Tag_CPU_arch: v4T
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1
  Tag_FP_arch: VFPv3-D16

I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o from linking with other .o files.

However, when building .c or .cpp files, the generated .o files don't have " Tag_FP_arch: VFPv3-D16"

It seems that AS doen't respect option "-mfloat-abi=soft" and always add "Tag_FP_arch: VFPv3-D16" to the genrated .o files

[Zhenqiang Chen (zhenqiang-chen)]

Can you attach your .S file for us to reproduce the issue?

If your .S is writen with hard float ABI, I think there is no way for AS to change your code.

[changyp (changyp6)]

I checked, the .S file doesn't contain any hard float ABI.

You can test with the attached file, which is from bandwidth arm.

please compile with the following options:

arm-linux-gnueabihf-gcc -c -O3 -Wall -o routinesARM.o -marm -march=armv4t -mfloat-abi=soft routinesARM.S

you can check it with command:

arm-linux-gnueabihf-readelf -A routinesARM.o

The output is

Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "4T"
  Tag_CPU_arch: v4T
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1
  Tag_FP_arch: VFPv3-D16

[changyp (changyp6)]

I consider this behavior as a bug is based on the following facts.

When I try to build a multi-lib Linaro arm linux gcc, I always get error messages like this "libgcc_s.so.tmp uses VFP registers while xxxx.o does not", when building for armv6 soft float libgcc_s.so, even if I added -mfloat-abi=soft and -msoft-float and configured eglibc with option --without-fp

After some investigation, I found crti.o crtn.o and crt1.o are always tagged with Tag_FP_arch: VFPv3.
But when I build .c and .cpp files with -mfloat-abi=soft, this tag goes away.

So I did a test with Linaro-arm-linux-gcc 2014.03, and I found that when multi-lib gcc build .S files, the VFP tag is always added, but when building .c or .cpp files, gcc respect option -mfloat-abi=soft and remove Tag_FP_arch: XXXX

[changyp (changyp6)]

I found a solution, when build .S file using multi-lib gcc, -mfloat-api=soft is not enough, option -Wa,-mfpu=softvfp also needs to be added to the command line to make AS generate .o file without tagging Tag_FP_arch.

Is it possible to make gcc pass -mfpu=softvfp to AS when building .S file with option -mfloat-api=soft by default ?

[Zhenqiang Chen (zhenqiang-chen)]

"-mfpu=vfpv3-d16" is our default option. If you add "-v" when compiling the .S file, you can find the final options.

BTW:
What's the impact of "Tag_FP_arch: VFPv3-D16"? Link fail?

[changyp (changyp6)]

Yes，link fail.
The error would be xxx uses VFP register parameters，but xxx.o does not.
2014-4-9 上午11:55于 "Zhenqiang Chen" <email address hidden>写道：

> "-mfpu=vfpv3-d16" is our default option. If you add "-v" when compiling
> the .S file, you can find the final options.
>
> BTW:
> What's the impact of "Tag_FP_arch: VFPv3-D16"? Link fail?
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> New
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp files, the generated .o files don't
> have " Tag_FP_arch: VFPv3-D16"
>
> It seems that AS doen't respect option "-mfloat-abi=soft" and always
> add "Tag_FP_arch: VFPv3-D16" to the genrated .o files
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/gcc-linaro/+bug/1304267/+subscriptions
>

[Zhenqiang Chen (zhenqiang-chen)]

Then what's you link option? It seams you do not add the multilib options when linking the object files:

arm-linux-gnueabihf-gcc -marm -march=armv4t -mfloat-abi=soft ...

[changyp (changyp6)]

Thank you very much!
I forgot one option which led multilib link fail.
After I added that option, link works OK.

I still have one question.
I use crosstools-ng latest code to build multilib toolchain, I
modified t-mlibs to add arm mode softfp armv7-a support

the multilib options is "-marm -march=armv7-a -mtune=cortex-a9
-mfloat-abi=softfp -mfpu=vfpv3"
When building process goes to build libgcc stage 2, I always get the
following errors:

libgcc_s.so.1.tmp uses VFP registers, but xxx.o does not

I can't get any clue about this error.
Could you give me some suggestions about this error?

On Wed, Apr 9, 2014 at 1:44 PM, Zhenqiang Chen
<email address hidden> wrote:
> Then what's you link option? It seams you do not add the multilib
> options when linking the object files:
>
> arm-linux-gnueabihf-gcc -marm -march=armv4t -mfloat-abi=soft ...
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> New
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp files, the generated .o files don't
> have " Tag_FP_arch: VFPv3-D16"
>
> It seems that AS doen't respect option "-mfloat-abi=soft" and always
> add "Tag_FP_arch: VFPv3-D16" to the genrated .o files
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/gcc-linaro/+bug/1304267/+subscriptions

[Zhenqiang Chen (zhenqiang-chen)]

Please check your (e)glibc build whether it has all the multilib builds.

And please try to add "--disable-multiarch" for your gcc config.

Finally, please goto the build-cc dir and run the final failed cmdline with additional option "-v" to check which libc is linked.

[changyp (changyp6)]

Hi Zhengqiang,

Thank you for your instruction.
I have found the root cause.
The problem causing this issue is that the link search path for
libgcc_s.so.1.tmp is wrong, it is set to the default path instead of
the multilib path.

Is this a bug in libgcc configure or somewhere else? How can I fix this issue?

Thanks again for your instruction!

On Wed, Apr 9, 2014 at 3:02 PM, Zhenqiang Chen
<email address hidden> wrote:
> Please check your (e)glibc build whether it has all the multilib builds.
>
> And please try to add "--disable-multiarch" for your gcc config.
>
> Finally, please goto the build-cc dir and run the final failed cmdline
> with additional option "-v" to check which libc is linked.
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> New
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp files, the generated .o files don't
> have " Tag_FP_arch: VFPv3-D16"
>
> It seems that AS doen't respect option "-mfloat-abi=soft" and always
> add "Tag_FP_arch: VFPv3-D16" to the genrated .o files
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/gcc-linaro/+bug/1304267/+subscriptions

[Zhenqiang Chen (zhenqiang-chen)]

I do not think it is a libgcc bug. If your multilib option is correct, libgcc should find the correct path.

Can you show me the multilib options?

./gcc/xgcc --print-multi-lib

And all your libc layout in your install dir?

[changyp (changyp6)]

I changed t-mlibs to support armv6k and armv7-a without fpu and with
vfpv3 respectively.
Here is the output
./gcc/xgcc -print-multi-lib
.;
armv7a-linux-gnueabi;@marm@march=armv7-a@mtune=cortex-a9@mfloat-abi=softfp@mfpu=vfpv3
armv6k-linux-gnueabi;@marm@march=armv6k@mtune=arm1136j-s@mfloat-abi=soft@Wa,-mfpu=softvfp

libc layout in install_root/arm-linux-gnueabihf/libc/usr/lib is

usr/lib
├── arm-linux-gnueabihf
│ ├── crt1.o
│ ├── crti.o
│ ├── crtn.o
│ └── libc.so
├── armv6k-linux-gnueabi
│ ├── crt1.o
│ ├── crti.o
│ ├── crtn.o
│ └── libc.so
└── armv7a-linux-gnueabi
    ├── crt1.o
    ├── crti.o
    ├── crtn.o
    └── libc.so

The final link commands of
armv6k-linux-gnueabi/libgcc/libgcc_s.so.1.tmp show that xgcc is
looking for ./gcc/crtendS.o instead of
./gcc/armv6k-linux-gnueabi/crtendS.o

However, libgcc_s.so.1 for armv7a-linux-gnueabi is compiled
successfully, the link command is correct,
armv7a-linux-gnueabi/libgcc/libgcc_s.so.1.tmp is linking
./gcc/armv7a-linux-gnueabi/crtendS.o

I don't understand why one multilib directory is correct, the other is wrong.

On Wed, Apr 9, 2014 at 5:29 PM, Zhenqiang Chen
<email address hidden> wrote:
> I do not think it is a libgcc bug. If your multilib option is correct,
> libgcc should find the correct path.
>
> Can you show me the multilib options?
>
> ./gcc/xgcc --print-multi-lib
>
> And all your libc layout in your install dir?
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> Invalid
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp files, the generated .o files don't
> have " Tag_FP_arch: VFPv3-D16"
>
> It seems that AS doen't respect option "-mfloat-abi=soft" and always
> add "Tag_FP_arch: VFPv3-D16" to the genrated .o files
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/gcc-linaro/+bug/1304267/+subscriptions

[changyp (changyp6)]

Hi Zhengqiang,
I have found the root cause.

The following command can get correct results
./gcc/xgcc -print-multi-lib
.;
armv7a-linux-gnueabi;@marm@march=armv7-a@mtune=cortex-a9@mfloat-abi=softfp@mfpu=vfpv3
armv6k-linux-gnueabi;@marm@march=armv6k@mtune=arm1136j-s@mfloat-abi=soft@Wa,-mfpu=softvfp

./gcc/xgcc -print-multi-directory -marm -march=armv7-a
-mtune=cortex-a9 -mfloat-abi=softfp -mfpu=vfpv3
armv7a-linux-gnueabi

But this command can't get the correct multi-directory
./gcc/xgcc -print-multi-directory -marm -march=armv6k
-mtune=arm1136j-s -mfloat-abi=soft -Wa,-mfpu=softvfp
.
The result is .(dot), instead of armv6k-linux-gnueabi

I don't know if there's something wrong with my t-mlibs file, here is
my t-mlibs file, could you please help check and give me some
suggestions:

# A set of predefined MULTILIB for different ARM targets.
# Through the configure option --with-multilib-list, user can customize the
# final MULTILIB implementation.

comma := ,
space :=
space +=

MULTILIB_OPTIONS = marm
MULTILIB_DIRNAMES = arm
MULTILIB_OPTIONS += march=armv6k
MULTILIB_DIRNAMES += armv6k
MULTILIB_OPTIONS += march=armv7-a
MULTILIB_DIRNAMES += armv7-a
MULTILIB_OPTIONS += mtune=arm1136j-s
MULTILIB_DIRNAMES += arm1136j-s
MULTILIB_OPTIONS += mtune=cortex-a9
MULTILIB_DIRNAMES += cortex-a9
MULTILIB_OPTIONS += mfloat-abi=soft
MULTILIB_DIRNAMES += soft
MULTILIB_OPTIONS += mfloat-abi=softfp
MULTILIB_DIRNAMES += softfp
MULTILIB_OPTIONS += mfpu=vfpv3
MULTILIB_DIRNAMES += vfpv3
MULTILIB_OPTIONS += Wa,-mfpu=softvfp
MULTILIB_DIRNAMES += softvfp

MULTILIB_EXCEPTIONS =

MULTILIB_REQUIRED =
marm/march=armv7-a/mtune=cortex-a9/mfloat-abi=softfp/mfpu=vfpv3
MULTILIB_OSDIRNAMES =
marm/march.armv7-a/mtune.cortex-a9/mfloat-abi.softfp/mfpu.vfpv3=!armv7a-linux-gnueabi

MULTILIB_REQUIRED +=
marm/march=armv6k/mtune=arm1136j-s/mfloat-abi=soft/Wa,-mfpu=softvfp
MULTILIB_OSDIRNAMES +=
marm/march.armv6k/mtune.arm1136j-s/mfloat-abi.soft/Wa,-mfpu.softvfp=!armv6k-linux-gnueabi

On Wed, Apr 9, 2014 at 5:29 PM, Zhenqiang Chen
<email address hidden> wrote:
> I do not think it is a libgcc bug. If your multilib option is correct,
> libgcc should find the correct path.
>
> Can you show me the multilib options?
>
> ./gcc/xgcc --print-multi-lib
>
> And all your libc layout in your install dir?
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> Invalid
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp...

[Zhenqiang Chen (zhenqiang-chen)]

Please try to remove " -Wa,-mfpu=softvfp".

[changyp (changyp6)]

Hi Zhengqiang,

Thanks for your reply!

I removed "-Wa,-mfpu=softvfp", but result is the same.
But, if I also remove "-mfpu=vfpv3", xgcc -print-multi-directory can
work correctly, both armv6k-linux-gnueabi and armv7a-linux-gnueabi can
be printed.

Are there any constrains on MULTILIB_OPTIONS ? Or is this a bug
related to gcc multilib option parsing?

On Fri, Apr 11, 2014 at 9:21 AM, Zhenqiang Chen
<email address hidden> wrote:
> Please try to remove " -Wa,-mfpu=softvfp".
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304267
>
> Title:
> Linaro arm linux gnueabihf gcc always add Tag_FP_arch: VFPv3-D16 when
> building .S file with -mfloat-abi=soft
>
> Status in Linaro GCC:
> Invalid
>
> Bug description:
> I have a ASM file with extension .S
> After I build this file with option
> "-marm -march=armv4t -mfloat-abi=soft -c xxx.S -o xxx.o"
> I checked xxx.o with command "arm-linux-gnueabihf-readelf -A xxx.o"
>
> And the output is
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "4t"
> Tag_CPU_arch: v4T
> Tag_ARM_ISA_use: Yes
> Tag_THUMB_ISA_use: Thumb-1
> Tag_FP_arch: VFPv3-D16
>
> I noticed tag " Tag_FP_arch: VFPv3-D16", this tag prevents this xxx.o
> from linking with other .o files.
>
> However, when building .c or .cpp files, the generated .o files don't
> have " Tag_FP_arch: VFPv3-D16"
>
> It seems that AS doen't respect option "-mfloat-abi=soft" and always
> add "Tag_FP_arch: VFPv3-D16" to the genrated .o files
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/gcc-linaro/+bug/1304267/+subscriptions

[Zhenqiang Chen (zhenqiang-chen)]

On 11 April 2014 16:25, changyp <email address hidden> wrote:
> Hi Zhengqiang,
>
> Thanks for your reply!
>
> I removed "-Wa,-mfpu=softvfp", but result is the same.
> But, if I also remove "-mfpu=vfpv3", xgcc -print-multi-directory can
> work correctly, both armv6k-linux-gnueabi and armv7a-linux-gnueabi can
> be printed.
>
> Are there any constrains on MULTILIB_OPTIONS ? Or is this a bug
> related to gcc multilib option parsing?

I do not know. Multilib is always mess. If you think it it a bug,
please reproduce the issue based on a clean gcc trunk and raise to gcc
upstream.

Thanks!
-Zhenqiang