diff mbox series

[U-Boot,v2] x86: lib: Implement standalone __udivdi3 etc instead of libgcc ones

Message ID 20171117060228.23926-1-sr@denx.de
State Superseded
Delegated to: Bin Meng
Headers show
Series [U-Boot,v2] x86: lib: Implement standalone __udivdi3 etc instead of libgcc ones | expand

Commit Message

Stefan Roese Nov. 17, 2017, 6:02 a.m. UTC 
This patch removes the inclusion of the libgcc math functions and
replaces them by functions coded in C, taken from the coreboot
project. This makes U-Boot building more independent from the toolchain
installed / available on the build system.

The code taken from coreboot is authored from Vadim Bendebury
<vbendeb@chromium.org> on 2014-11-28 and committed with commit
ID e63990ef [libpayload: provide basic 64bit division implementation]
(coreboot git repository located here [1]).

I modified the code so that its checkpatch clean without any
functional changes.

[1] git://github.com/coreboot/coreboot.git

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
---
v2:
- Added coreboot git repository link to commit message

 arch/x86/config.mk    |   3 --
 arch/x86/lib/Makefile |   2 +-
 arch/x86/lib/div64.c  | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/lib/gcc.c    |  29 -------------
 4 files changed, 114 insertions(+), 33 deletions(-)
 create mode 100644 arch/x86/lib/div64.c
 delete mode 100644 arch/x86/lib/gcc.c

Comments

Bin Meng Nov. 20, 2017, 7:24 a.m. UTC | #1 
Hi Stefan,

On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
> This patch removes the inclusion of the libgcc math functions and
> replaces them by functions coded in C, taken from the coreboot
> project. This makes U-Boot building more independent from the toolchain
> installed / available on the build system.
>
> The code taken from coreboot is authored from Vadim Bendebury
> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
> ID e63990ef [libpayload: provide basic 64bit division implementation]
> (coreboot git repository located here [1]).
>
> I modified the code so that its checkpatch clean without any
> functional changes.
>
> [1] git://github.com/coreboot/coreboot.git
>
> Signed-off-by: Stefan Roese <sr@denx.de>
> Cc: Simon Glass <sjg@chromium.org>
> Cc: Bin Meng <bmeng.cn@gmail.com>
> ---
> v2:
> - Added coreboot git repository link to commit message
>
>  arch/x86/config.mk    |   3 --
>  arch/x86/lib/Makefile |   2 +-
>  arch/x86/lib/div64.c  | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  arch/x86/lib/gcc.c    |  29 -------------
>  4 files changed, 114 insertions(+), 33 deletions(-)
>  create mode 100644 arch/x86/lib/div64.c
>  delete mode 100644 arch/x86/lib/gcc.c
>
> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
> index 8835dcf36f..472ada5490 100644
> --- a/arch/x86/config.mk
> +++ b/arch/x86/config.mk
> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden
>  PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>  PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>
> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
> -
>  # This is used in the top-level Makefile which does not include
>  # PLATFORM_LDFLAGS
>  LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared --no-undefined
> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> index fe00d7573f..d9b23f5cc4 100644
> --- a/arch/x86/lib/Makefile
> +++ b/arch/x86/lib/Makefile
> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>  obj-y  += early_cmos.o
>  obj-$(CONFIG_EFI) += efi/
>  obj-y  += e820.o
> -obj-y  += gcc.o
> +obj-y  += div64.o
>  obj-y  += init_helpers.o
>  obj-y  += interrupts.o
>  obj-y  += lpc-uclass.o
> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
> new file mode 100644
> index 0000000000..4efed74037
> --- /dev/null
> +++ b/arch/x86/lib/div64.c
> @@ -0,0 +1,113 @@
> +/*
> + * This file is copied from the coreboot repository as part of
> + * the libpayload project:
> + *
> + * Copyright 2014 Google Inc.
> + *
> + * SPDX-License-Identifier:     BSD-3-Clause
> + */
> +
> +#include <common.h>
> +
> +union overlay64 {
> +       u64 longw;
> +       struct {
> +               u32 lower;
> +               u32 higher;
> +       } words;
> +};
> +
> +u64 __ashldi3(u64 num, unsigned int shift)
> +{
> +       union overlay64 output;
> +
> +       output.longw = num;
> +       if (shift >= 32) {
> +               output.words.higher = output.words.lower << (shift - 32);
> +               output.words.lower = 0;
> +       } else {
> +               if (!shift)
> +                       return num;
> +               output.words.higher = (output.words.higher << shift) |
> +                       (output.words.lower >> (32 - shift));
> +               output.words.lower = output.words.lower << shift;
> +       }
> +       return output.longw;
> +}
> +
> +u64 __lshrdi3(u64 num, unsigned int shift)
> +{
> +       union overlay64 output;
> +
> +       output.longw = num;
> +       if (shift >= 32) {
> +               output.words.lower = output.words.higher >> (shift - 32);
> +               output.words.higher = 0;
> +       } else {
> +               if (!shift)
> +                       return num;
> +               output.words.lower = output.words.lower >> shift |
> +                       (output.words.higher << (32 - shift));
> +               output.words.higher = output.words.higher >> shift;
> +       }
> +       return output.longw;
> +}
> +
> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
> +
> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
> +{
> +       u64 result = 0;
> +
> +       /*
> +        * If divider is zero - let the rest of the system care about the
> +        * exception.
> +        */
> +       if (!divider)
> +               return 1 / (u32)divider;
> +
> +       /* As an optimization, let's not use 64 bit division unless we must. */
> +       if (dividend <= MAX_32BIT_UINT) {
> +               if (divider > MAX_32BIT_UINT) {
> +                       result = 0;
> +                       if (rem_p)
> +                               *rem_p = divider;
> +               } else {
> +                       result = (u32)dividend / (u32)divider;
> +                       if (rem_p)
> +                               *rem_p = (u32)dividend % (u32)divider;
> +               }
> +               return result;
> +       }
> +
> +       while (divider <= dividend) {
> +               u64 locald = divider;
> +               u64 limit = __lshrdi3(dividend, 1);
> +               int shifts = 0;
> +
> +               while (locald <= limit) {
> +                       shifts++;
> +                       locald = locald + locald;
> +               }
> +               result |= __ashldi3(1, shifts);
> +               dividend -= locald;
> +       }
> +
> +       if (rem_p)
> +               *rem_p = dividend;
> +
> +       return result;
> +}
> +
> +u64 __udivdi3(u64 num, u64 den)
> +{
> +       return _64bit_divide(num, den, NULL);
> +}
> +
> +u64 __umoddi3(u64 num, u64 den)
> +{
> +       u64 v = 0;
> +
> +       _64bit_divide(num, den, &v);
> +       return v;
> +}
> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
> deleted file mode 100644
> index 3c70d790d4..0000000000
> --- a/arch/x86/lib/gcc.c
> +++ /dev/null
> @@ -1,29 +0,0 @@
> -/*
> - * This file is part of the coreboot project.
> - *
> - * Copyright (C) 2009 coresystems GmbH
> - *
> - * SPDX-License-Identifier:    GPL-2.0
> - */
> -
> -#ifdef __GNUC__
> -
> -/*
> - * GCC's libgcc handling is quite broken. While the libgcc functions
> - * are always regparm(0) the code that calls them uses whatever the
> - * compiler call specifies. Therefore we need a wrapper around those
> - * functions. See gcc bug PR41055 for more information.
> - */
> -#define WRAP_LIBGCC_CALL(type, name) \
> -       type __normal_##name(type a, type b) __attribute__((regparm(0))); \
> -       type __wrap_##name(type a, type b); \
> -       type __attribute__((no_instrument_function)) \
> -               __wrap_##name(type a, type b) \
> -                { return __normal_##name(a, b); }
> -
> -WRAP_LIBGCC_CALL(long long, __divdi3)
> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
> -WRAP_LIBGCC_CALL(long long, __moddi3)
> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
> -
> -#endif
> --

I don't see __divdi3 and __moddi3 in the new implementation. Are they
not needed?

Regards,
Bin
Stefan Roese Nov. 20, 2017, 10:43 a.m. UTC | #2 
Hi Bin,

On 20.11.2017 08:24, Bin Meng wrote:
> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>> This patch removes the inclusion of the libgcc math functions and
>> replaces them by functions coded in C, taken from the coreboot
>> project. This makes U-Boot building more independent from the toolchain
>> installed / available on the build system.
>>
>> The code taken from coreboot is authored from Vadim Bendebury
>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>> (coreboot git repository located here [1]).
>>
>> I modified the code so that its checkpatch clean without any
>> functional changes.
>>
>> [1] git://github.com/coreboot/coreboot.git
>>
>> Signed-off-by: Stefan Roese <sr@denx.de>
>> Cc: Simon Glass <sjg@chromium.org>
>> Cc: Bin Meng <bmeng.cn@gmail.com>
>> ---
>> v2:
>> - Added coreboot git repository link to commit message
>>
>>   arch/x86/config.mk    |   3 --
>>   arch/x86/lib/Makefile |   2 +-
>>   arch/x86/lib/div64.c  | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>   arch/x86/lib/gcc.c    |  29 -------------
>>   4 files changed, 114 insertions(+), 33 deletions(-)
>>   create mode 100644 arch/x86/lib/div64.c
>>   delete mode 100644 arch/x86/lib/gcc.c
>>
>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>> index 8835dcf36f..472ada5490 100644
>> --- a/arch/x86/config.mk
>> +++ b/arch/x86/config.mk
>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden
>>   PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>   PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>
>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>> -
>>   # This is used in the top-level Makefile which does not include
>>   # PLATFORM_LDFLAGS
>>   LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared --no-undefined
>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>> index fe00d7573f..d9b23f5cc4 100644
>> --- a/arch/x86/lib/Makefile
>> +++ b/arch/x86/lib/Makefile
>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>   obj-y  += early_cmos.o
>>   obj-$(CONFIG_EFI) += efi/
>>   obj-y  += e820.o
>> -obj-y  += gcc.o
>> +obj-y  += div64.o
>>   obj-y  += init_helpers.o
>>   obj-y  += interrupts.o
>>   obj-y  += lpc-uclass.o
>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>> new file mode 100644
>> index 0000000000..4efed74037
>> --- /dev/null
>> +++ b/arch/x86/lib/div64.c
>> @@ -0,0 +1,113 @@
>> +/*
>> + * This file is copied from the coreboot repository as part of
>> + * the libpayload project:
>> + *
>> + * Copyright 2014 Google Inc.
>> + *
>> + * SPDX-License-Identifier:     BSD-3-Clause
>> + */
>> +
>> +#include <common.h>
>> +
>> +union overlay64 {
>> +       u64 longw;
>> +       struct {
>> +               u32 lower;
>> +               u32 higher;
>> +       } words;
>> +};
>> +
>> +u64 __ashldi3(u64 num, unsigned int shift)
>> +{
>> +       union overlay64 output;
>> +
>> +       output.longw = num;
>> +       if (shift >= 32) {
>> +               output.words.higher = output.words.lower << (shift - 32);
>> +               output.words.lower = 0;
>> +       } else {
>> +               if (!shift)
>> +                       return num;
>> +               output.words.higher = (output.words.higher << shift) |
>> +                       (output.words.lower >> (32 - shift));
>> +               output.words.lower = output.words.lower << shift;
>> +       }
>> +       return output.longw;
>> +}
>> +
>> +u64 __lshrdi3(u64 num, unsigned int shift)
>> +{
>> +       union overlay64 output;
>> +
>> +       output.longw = num;
>> +       if (shift >= 32) {
>> +               output.words.lower = output.words.higher >> (shift - 32);
>> +               output.words.higher = 0;
>> +       } else {
>> +               if (!shift)
>> +                       return num;
>> +               output.words.lower = output.words.lower >> shift |
>> +                       (output.words.higher << (32 - shift));
>> +               output.words.higher = output.words.higher >> shift;
>> +       }
>> +       return output.longw;
>> +}
>> +
>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>> +
>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>> +{
>> +       u64 result = 0;
>> +
>> +       /*
>> +        * If divider is zero - let the rest of the system care about the
>> +        * exception.
>> +        */
>> +       if (!divider)
>> +               return 1 / (u32)divider;
>> +
>> +       /* As an optimization, let's not use 64 bit division unless we must. */
>> +       if (dividend <= MAX_32BIT_UINT) {
>> +               if (divider > MAX_32BIT_UINT) {
>> +                       result = 0;
>> +                       if (rem_p)
>> +                               *rem_p = divider;
>> +               } else {
>> +                       result = (u32)dividend / (u32)divider;
>> +                       if (rem_p)
>> +                               *rem_p = (u32)dividend % (u32)divider;
>> +               }
>> +               return result;
>> +       }
>> +
>> +       while (divider <= dividend) {
>> +               u64 locald = divider;
>> +               u64 limit = __lshrdi3(dividend, 1);
>> +               int shifts = 0;
>> +
>> +               while (locald <= limit) {
>> +                       shifts++;
>> +                       locald = locald + locald;
>> +               }
>> +               result |= __ashldi3(1, shifts);
>> +               dividend -= locald;
>> +       }
>> +
>> +       if (rem_p)
>> +               *rem_p = dividend;
>> +
>> +       return result;
>> +}
>> +
>> +u64 __udivdi3(u64 num, u64 den)
>> +{
>> +       return _64bit_divide(num, den, NULL);
>> +}
>> +
>> +u64 __umoddi3(u64 num, u64 den)
>> +{
>> +       u64 v = 0;
>> +
>> +       _64bit_divide(num, den, &v);
>> +       return v;
>> +}
>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>> deleted file mode 100644
>> index 3c70d790d4..0000000000
>> --- a/arch/x86/lib/gcc.c
>> +++ /dev/null
>> @@ -1,29 +0,0 @@
>> -/*
>> - * This file is part of the coreboot project.
>> - *
>> - * Copyright (C) 2009 coresystems GmbH
>> - *
>> - * SPDX-License-Identifier:    GPL-2.0
>> - */
>> -
>> -#ifdef __GNUC__
>> -
>> -/*
>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>> - * are always regparm(0) the code that calls them uses whatever the
>> - * compiler call specifies. Therefore we need a wrapper around those
>> - * functions. See gcc bug PR41055 for more information.
>> - */
>> -#define WRAP_LIBGCC_CALL(type, name) \
>> -       type __normal_##name(type a, type b) __attribute__((regparm(0))); \
>> -       type __wrap_##name(type a, type b); \
>> -       type __attribute__((no_instrument_function)) \
>> -               __wrap_##name(type a, type b) \
>> -                { return __normal_##name(a, b); }
>> -
>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>> -
>> -#endif
>> --
> 
> I don't see __divdi3 and __moddi3 in the new implementation. Are they
> not needed?

Yes, at least I couldn't find any problems compiling U-Boot for x86 with
this patch.

BTW: The code size also did shrink a bit with this patch.

Thanks,
Stefan
Bin Meng Nov. 24, 2017, 8:29 a.m. UTC | #3 
Hi Stefan,

On Mon, Nov 20, 2017 at 6:43 PM, Stefan Roese <sr@denx.de> wrote:
> Hi Bin,
>
>
> On 20.11.2017 08:24, Bin Meng wrote:
>>
>> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>>>
>>> This patch removes the inclusion of the libgcc math functions and
>>> replaces them by functions coded in C, taken from the coreboot
>>> project. This makes U-Boot building more independent from the toolchain
>>> installed / available on the build system.
>>>
>>> The code taken from coreboot is authored from Vadim Bendebury
>>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>>> (coreboot git repository located here [1]).
>>>
>>> I modified the code so that its checkpatch clean without any
>>> functional changes.
>>>
>>> [1] git://github.com/coreboot/coreboot.git
>>>
>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>> Cc: Simon Glass <sjg@chromium.org>
>>> Cc: Bin Meng <bmeng.cn@gmail.com>
>>> ---
>>> v2:
>>> - Added coreboot git repository link to commit message
>>>
>>>   arch/x86/config.mk    |   3 --
>>>   arch/x86/lib/Makefile |   2 +-
>>>   arch/x86/lib/div64.c  | 113
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>   arch/x86/lib/gcc.c    |  29 -------------
>>>   4 files changed, 114 insertions(+), 33 deletions(-)
>>>   create mode 100644 arch/x86/lib/div64.c
>>>   delete mode 100644 arch/x86/lib/gcc.c
>>>
>>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>>> index 8835dcf36f..472ada5490 100644
>>> --- a/arch/x86/config.mk
>>> +++ b/arch/x86/config.mk
>>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections
>>> -fvisibility=hidden
>>>   PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>>   PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>>
>>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>>> -
>>>   # This is used in the top-level Makefile which does not include
>>>   # PLATFORM_LDFLAGS
>>>   LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared
>>> --no-undefined
>>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>>> index fe00d7573f..d9b23f5cc4 100644
>>> --- a/arch/x86/lib/Makefile
>>> +++ b/arch/x86/lib/Makefile
>>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>>   obj-y  += early_cmos.o
>>>   obj-$(CONFIG_EFI) += efi/
>>>   obj-y  += e820.o
>>> -obj-y  += gcc.o
>>> +obj-y  += div64.o
>>>   obj-y  += init_helpers.o
>>>   obj-y  += interrupts.o
>>>   obj-y  += lpc-uclass.o
>>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>>> new file mode 100644
>>> index 0000000000..4efed74037
>>> --- /dev/null
>>> +++ b/arch/x86/lib/div64.c
>>> @@ -0,0 +1,113 @@
>>> +/*
>>> + * This file is copied from the coreboot repository as part of
>>> + * the libpayload project:
>>> + *
>>> + * Copyright 2014 Google Inc.
>>> + *
>>> + * SPDX-License-Identifier:     BSD-3-Clause
>>> + */
>>> +
>>> +#include <common.h>
>>> +
>>> +union overlay64 {
>>> +       u64 longw;
>>> +       struct {
>>> +               u32 lower;
>>> +               u32 higher;
>>> +       } words;
>>> +};
>>> +
>>> +u64 __ashldi3(u64 num, unsigned int shift)
>>> +{
>>> +       union overlay64 output;
>>> +
>>> +       output.longw = num;
>>> +       if (shift >= 32) {
>>> +               output.words.higher = output.words.lower << (shift - 32);
>>> +               output.words.lower = 0;
>>> +       } else {
>>> +               if (!shift)
>>> +                       return num;
>>> +               output.words.higher = (output.words.higher << shift) |
>>> +                       (output.words.lower >> (32 - shift));
>>> +               output.words.lower = output.words.lower << shift;
>>> +       }
>>> +       return output.longw;
>>> +}
>>> +
>>> +u64 __lshrdi3(u64 num, unsigned int shift)
>>> +{
>>> +       union overlay64 output;
>>> +
>>> +       output.longw = num;
>>> +       if (shift >= 32) {
>>> +               output.words.lower = output.words.higher >> (shift - 32);
>>> +               output.words.higher = 0;
>>> +       } else {
>>> +               if (!shift)
>>> +                       return num;
>>> +               output.words.lower = output.words.lower >> shift |
>>> +                       (output.words.higher << (32 - shift));
>>> +               output.words.higher = output.words.higher >> shift;
>>> +       }
>>> +       return output.longw;
>>> +}
>>> +
>>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>>> +
>>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>>> +{
>>> +       u64 result = 0;
>>> +
>>> +       /*
>>> +        * If divider is zero - let the rest of the system care about the
>>> +        * exception.
>>> +        */
>>> +       if (!divider)
>>> +               return 1 / (u32)divider;
>>> +
>>> +       /* As an optimization, let's not use 64 bit division unless we
>>> must. */
>>> +       if (dividend <= MAX_32BIT_UINT) {
>>> +               if (divider > MAX_32BIT_UINT) {
>>> +                       result = 0;
>>> +                       if (rem_p)
>>> +                               *rem_p = divider;
>>> +               } else {
>>> +                       result = (u32)dividend / (u32)divider;
>>> +                       if (rem_p)
>>> +                               *rem_p = (u32)dividend % (u32)divider;
>>> +               }
>>> +               return result;
>>> +       }
>>> +
>>> +       while (divider <= dividend) {
>>> +               u64 locald = divider;
>>> +               u64 limit = __lshrdi3(dividend, 1);
>>> +               int shifts = 0;
>>> +
>>> +               while (locald <= limit) {
>>> +                       shifts++;
>>> +                       locald = locald + locald;
>>> +               }
>>> +               result |= __ashldi3(1, shifts);
>>> +               dividend -= locald;
>>> +       }
>>> +
>>> +       if (rem_p)
>>> +               *rem_p = dividend;
>>> +
>>> +       return result;
>>> +}
>>> +
>>> +u64 __udivdi3(u64 num, u64 den)
>>> +{
>>> +       return _64bit_divide(num, den, NULL);
>>> +}
>>> +
>>> +u64 __umoddi3(u64 num, u64 den)
>>> +{
>>> +       u64 v = 0;
>>> +
>>> +       _64bit_divide(num, den, &v);
>>> +       return v;
>>> +}
>>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>>> deleted file mode 100644
>>> index 3c70d790d4..0000000000
>>> --- a/arch/x86/lib/gcc.c
>>> +++ /dev/null
>>> @@ -1,29 +0,0 @@
>>> -/*
>>> - * This file is part of the coreboot project.
>>> - *
>>> - * Copyright (C) 2009 coresystems GmbH
>>> - *
>>> - * SPDX-License-Identifier:    GPL-2.0
>>> - */
>>> -
>>> -#ifdef __GNUC__
>>> -
>>> -/*
>>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>>> - * are always regparm(0) the code that calls them uses whatever the
>>> - * compiler call specifies. Therefore we need a wrapper around those
>>> - * functions. See gcc bug PR41055 for more information.
>>> - */
>>> -#define WRAP_LIBGCC_CALL(type, name) \
>>> -       type __normal_##name(type a, type b) __attribute__((regparm(0)));
>>> \
>>> -       type __wrap_##name(type a, type b); \
>>> -       type __attribute__((no_instrument_function)) \
>>> -               __wrap_##name(type a, type b) \
>>> -                { return __normal_##name(a, b); }
>>> -
>>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>>> -
>>> -#endif
>>> --
>>
>>
>> I don't see __divdi3 and __moddi3 in the new implementation. Are they
>> not needed?
>
>
> Yes, at least I couldn't find any problems compiling U-Boot for x86 with
> this patch.
>
> BTW: The code size also did shrink a bit with this patch.

But this is needed in fact. If you write some codes doing signed
64-bit integer division, you will get link errors.

 undefined reference to `__divdi3'

Regards,
Bin
Stefan Roese Nov. 24, 2017, 9:29 a.m. UTC | #4 
Hi Bin,

On 24.11.2017 09:29, Bin Meng wrote:
> On Mon, Nov 20, 2017 at 6:43 PM, Stefan Roese <sr@denx.de> wrote:
>> Hi Bin,
>>
>>
>> On 20.11.2017 08:24, Bin Meng wrote:
>>>
>>> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>>>>
>>>> This patch removes the inclusion of the libgcc math functions and
>>>> replaces them by functions coded in C, taken from the coreboot
>>>> project. This makes U-Boot building more independent from the toolchain
>>>> installed / available on the build system.
>>>>
>>>> The code taken from coreboot is authored from Vadim Bendebury
>>>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>>>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>>>> (coreboot git repository located here [1]).
>>>>
>>>> I modified the code so that its checkpatch clean without any
>>>> functional changes.
>>>>
>>>> [1] git://github.com/coreboot/coreboot.git
>>>>
>>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>>> Cc: Simon Glass <sjg@chromium.org>
>>>> Cc: Bin Meng <bmeng.cn@gmail.com>
>>>> ---
>>>> v2:
>>>> - Added coreboot git repository link to commit message
>>>>
>>>>    arch/x86/config.mk    |   3 --
>>>>    arch/x86/lib/Makefile |   2 +-
>>>>    arch/x86/lib/div64.c  | 113
>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>    arch/x86/lib/gcc.c    |  29 -------------
>>>>    4 files changed, 114 insertions(+), 33 deletions(-)
>>>>    create mode 100644 arch/x86/lib/div64.c
>>>>    delete mode 100644 arch/x86/lib/gcc.c
>>>>
>>>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>>>> index 8835dcf36f..472ada5490 100644
>>>> --- a/arch/x86/config.mk
>>>> +++ b/arch/x86/config.mk
>>>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections
>>>> -fvisibility=hidden
>>>>    PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>>>    PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>>>
>>>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>>>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>>>> -
>>>>    # This is used in the top-level Makefile which does not include
>>>>    # PLATFORM_LDFLAGS
>>>>    LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared
>>>> --no-undefined
>>>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>>>> index fe00d7573f..d9b23f5cc4 100644
>>>> --- a/arch/x86/lib/Makefile
>>>> +++ b/arch/x86/lib/Makefile
>>>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>>>    obj-y  += early_cmos.o
>>>>    obj-$(CONFIG_EFI) += efi/
>>>>    obj-y  += e820.o
>>>> -obj-y  += gcc.o
>>>> +obj-y  += div64.o
>>>>    obj-y  += init_helpers.o
>>>>    obj-y  += interrupts.o
>>>>    obj-y  += lpc-uclass.o
>>>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>>>> new file mode 100644
>>>> index 0000000000..4efed74037
>>>> --- /dev/null
>>>> +++ b/arch/x86/lib/div64.c
>>>> @@ -0,0 +1,113 @@
>>>> +/*
>>>> + * This file is copied from the coreboot repository as part of
>>>> + * the libpayload project:
>>>> + *
>>>> + * Copyright 2014 Google Inc.
>>>> + *
>>>> + * SPDX-License-Identifier:     BSD-3-Clause
>>>> + */
>>>> +
>>>> +#include <common.h>
>>>> +
>>>> +union overlay64 {
>>>> +       u64 longw;
>>>> +       struct {
>>>> +               u32 lower;
>>>> +               u32 higher;
>>>> +       } words;
>>>> +};
>>>> +
>>>> +u64 __ashldi3(u64 num, unsigned int shift)
>>>> +{
>>>> +       union overlay64 output;
>>>> +
>>>> +       output.longw = num;
>>>> +       if (shift >= 32) {
>>>> +               output.words.higher = output.words.lower << (shift - 32);
>>>> +               output.words.lower = 0;
>>>> +       } else {
>>>> +               if (!shift)
>>>> +                       return num;
>>>> +               output.words.higher = (output.words.higher << shift) |
>>>> +                       (output.words.lower >> (32 - shift));
>>>> +               output.words.lower = output.words.lower << shift;
>>>> +       }
>>>> +       return output.longw;
>>>> +}
>>>> +
>>>> +u64 __lshrdi3(u64 num, unsigned int shift)
>>>> +{
>>>> +       union overlay64 output;
>>>> +
>>>> +       output.longw = num;
>>>> +       if (shift >= 32) {
>>>> +               output.words.lower = output.words.higher >> (shift - 32);
>>>> +               output.words.higher = 0;
>>>> +       } else {
>>>> +               if (!shift)
>>>> +                       return num;
>>>> +               output.words.lower = output.words.lower >> shift |
>>>> +                       (output.words.higher << (32 - shift));
>>>> +               output.words.higher = output.words.higher >> shift;
>>>> +       }
>>>> +       return output.longw;
>>>> +}
>>>> +
>>>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>>>> +
>>>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>>>> +{
>>>> +       u64 result = 0;
>>>> +
>>>> +       /*
>>>> +        * If divider is zero - let the rest of the system care about the
>>>> +        * exception.
>>>> +        */
>>>> +       if (!divider)
>>>> +               return 1 / (u32)divider;
>>>> +
>>>> +       /* As an optimization, let's not use 64 bit division unless we
>>>> must. */
>>>> +       if (dividend <= MAX_32BIT_UINT) {
>>>> +               if (divider > MAX_32BIT_UINT) {
>>>> +                       result = 0;
>>>> +                       if (rem_p)
>>>> +                               *rem_p = divider;
>>>> +               } else {
>>>> +                       result = (u32)dividend / (u32)divider;
>>>> +                       if (rem_p)
>>>> +                               *rem_p = (u32)dividend % (u32)divider;
>>>> +               }
>>>> +               return result;
>>>> +       }
>>>> +
>>>> +       while (divider <= dividend) {
>>>> +               u64 locald = divider;
>>>> +               u64 limit = __lshrdi3(dividend, 1);
>>>> +               int shifts = 0;
>>>> +
>>>> +               while (locald <= limit) {
>>>> +                       shifts++;
>>>> +                       locald = locald + locald;
>>>> +               }
>>>> +               result |= __ashldi3(1, shifts);
>>>> +               dividend -= locald;
>>>> +       }
>>>> +
>>>> +       if (rem_p)
>>>> +               *rem_p = dividend;
>>>> +
>>>> +       return result;
>>>> +}
>>>> +
>>>> +u64 __udivdi3(u64 num, u64 den)
>>>> +{
>>>> +       return _64bit_divide(num, den, NULL);
>>>> +}
>>>> +
>>>> +u64 __umoddi3(u64 num, u64 den)
>>>> +{
>>>> +       u64 v = 0;
>>>> +
>>>> +       _64bit_divide(num, den, &v);
>>>> +       return v;
>>>> +}
>>>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>>>> deleted file mode 100644
>>>> index 3c70d790d4..0000000000
>>>> --- a/arch/x86/lib/gcc.c
>>>> +++ /dev/null
>>>> @@ -1,29 +0,0 @@
>>>> -/*
>>>> - * This file is part of the coreboot project.
>>>> - *
>>>> - * Copyright (C) 2009 coresystems GmbH
>>>> - *
>>>> - * SPDX-License-Identifier:    GPL-2.0
>>>> - */
>>>> -
>>>> -#ifdef __GNUC__
>>>> -
>>>> -/*
>>>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>>>> - * are always regparm(0) the code that calls them uses whatever the
>>>> - * compiler call specifies. Therefore we need a wrapper around those
>>>> - * functions. See gcc bug PR41055 for more information.
>>>> - */
>>>> -#define WRAP_LIBGCC_CALL(type, name) \
>>>> -       type __normal_##name(type a, type b) __attribute__((regparm(0)));
>>>> \
>>>> -       type __wrap_##name(type a, type b); \
>>>> -       type __attribute__((no_instrument_function)) \
>>>> -               __wrap_##name(type a, type b) \
>>>> -                { return __normal_##name(a, b); }
>>>> -
>>>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>>>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>>>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>>>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>>>> -
>>>> -#endif
>>>> --
>>>
>>>
>>> I don't see __divdi3 and __moddi3 in the new implementation. Are they
>>> not needed?
>>
>>
>> Yes, at least I couldn't find any problems compiling U-Boot for x86 with
>> this patch.
>>
>> BTW: The code size also did shrink a bit with this patch.
> 
> But this is needed in fact. If you write some codes doing signed
> 64-bit integer division, you will get link errors.
> 
>   undefined reference to `__divdi3'

You wrote some additional code to test this, that is currently not
in mainline, right? Writing code with divisions should be done very
carefully from my point of view. And as far as I know, using do_div()
and the functions from lib/div64 is preferred here.

I would prefer to add this patch and once compile breakage occur because
of such "undefined reference" error from above, we should investigate
the root cause of fix it by replacing division operation by one of
the provided helper functions.

Thanks,
Stefan
Bin Meng Nov. 27, 2017, 9:46 a.m. UTC | #5 
Hi Stefan,

On Fri, Nov 24, 2017 at 5:29 PM, Stefan Roese <sr@denx.de> wrote:
> Hi Bin,
>
>
> On 24.11.2017 09:29, Bin Meng wrote:
>>
>> On Mon, Nov 20, 2017 at 6:43 PM, Stefan Roese <sr@denx.de> wrote:
>>>
>>> Hi Bin,
>>>
>>>
>>> On 20.11.2017 08:24, Bin Meng wrote:
>>>>
>>>>
>>>> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>>>>>
>>>>>
>>>>> This patch removes the inclusion of the libgcc math functions and
>>>>> replaces them by functions coded in C, taken from the coreboot
>>>>> project. This makes U-Boot building more independent from the toolchain
>>>>> installed / available on the build system.
>>>>>
>>>>> The code taken from coreboot is authored from Vadim Bendebury
>>>>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>>>>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>>>>> (coreboot git repository located here [1]).
>>>>>
>>>>> I modified the code so that its checkpatch clean without any
>>>>> functional changes.
>>>>>
>>>>> [1] git://github.com/coreboot/coreboot.git
>>>>>
>>>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>>>> Cc: Simon Glass <sjg@chromium.org>
>>>>> Cc: Bin Meng <bmeng.cn@gmail.com>
>>>>> ---
>>>>> v2:
>>>>> - Added coreboot git repository link to commit message
>>>>>
>>>>>    arch/x86/config.mk    |   3 --
>>>>>    arch/x86/lib/Makefile |   2 +-
>>>>>    arch/x86/lib/div64.c  | 113
>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>>    arch/x86/lib/gcc.c    |  29 -------------
>>>>>    4 files changed, 114 insertions(+), 33 deletions(-)
>>>>>    create mode 100644 arch/x86/lib/div64.c
>>>>>    delete mode 100644 arch/x86/lib/gcc.c
>>>>>
>>>>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>>>>> index 8835dcf36f..472ada5490 100644
>>>>> --- a/arch/x86/config.mk
>>>>> +++ b/arch/x86/config.mk
>>>>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections
>>>>> -fvisibility=hidden
>>>>>    PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>>>>    PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>>>>
>>>>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>>>>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>>>>> -
>>>>>    # This is used in the top-level Makefile which does not include
>>>>>    # PLATFORM_LDFLAGS
>>>>>    LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared
>>>>> --no-undefined
>>>>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>>>>> index fe00d7573f..d9b23f5cc4 100644
>>>>> --- a/arch/x86/lib/Makefile
>>>>> +++ b/arch/x86/lib/Makefile
>>>>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>>>>    obj-y  += early_cmos.o
>>>>>    obj-$(CONFIG_EFI) += efi/
>>>>>    obj-y  += e820.o
>>>>> -obj-y  += gcc.o
>>>>> +obj-y  += div64.o
>>>>>    obj-y  += init_helpers.o
>>>>>    obj-y  += interrupts.o
>>>>>    obj-y  += lpc-uclass.o
>>>>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>>>>> new file mode 100644
>>>>> index 0000000000..4efed74037
>>>>> --- /dev/null
>>>>> +++ b/arch/x86/lib/div64.c
>>>>> @@ -0,0 +1,113 @@
>>>>> +/*
>>>>> + * This file is copied from the coreboot repository as part of
>>>>> + * the libpayload project:
>>>>> + *
>>>>> + * Copyright 2014 Google Inc.
>>>>> + *
>>>>> + * SPDX-License-Identifier:     BSD-3-Clause
>>>>> + */
>>>>> +
>>>>> +#include <common.h>
>>>>> +
>>>>> +union overlay64 {
>>>>> +       u64 longw;
>>>>> +       struct {
>>>>> +               u32 lower;
>>>>> +               u32 higher;
>>>>> +       } words;
>>>>> +};
>>>>> +
>>>>> +u64 __ashldi3(u64 num, unsigned int shift)
>>>>> +{
>>>>> +       union overlay64 output;
>>>>> +
>>>>> +       output.longw = num;
>>>>> +       if (shift >= 32) {
>>>>> +               output.words.higher = output.words.lower << (shift -
>>>>> 32);
>>>>> +               output.words.lower = 0;
>>>>> +       } else {
>>>>> +               if (!shift)
>>>>> +                       return num;
>>>>> +               output.words.higher = (output.words.higher << shift) |
>>>>> +                       (output.words.lower >> (32 - shift));
>>>>> +               output.words.lower = output.words.lower << shift;
>>>>> +       }
>>>>> +       return output.longw;
>>>>> +}
>>>>> +
>>>>> +u64 __lshrdi3(u64 num, unsigned int shift)
>>>>> +{
>>>>> +       union overlay64 output;
>>>>> +
>>>>> +       output.longw = num;
>>>>> +       if (shift >= 32) {
>>>>> +               output.words.lower = output.words.higher >> (shift -
>>>>> 32);
>>>>> +               output.words.higher = 0;
>>>>> +       } else {
>>>>> +               if (!shift)
>>>>> +                       return num;
>>>>> +               output.words.lower = output.words.lower >> shift |
>>>>> +                       (output.words.higher << (32 - shift));
>>>>> +               output.words.higher = output.words.higher >> shift;
>>>>> +       }
>>>>> +       return output.longw;
>>>>> +}
>>>>> +
>>>>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>>>>> +
>>>>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>>>>> +{
>>>>> +       u64 result = 0;
>>>>> +
>>>>> +       /*
>>>>> +        * If divider is zero - let the rest of the system care about
>>>>> the
>>>>> +        * exception.
>>>>> +        */
>>>>> +       if (!divider)
>>>>> +               return 1 / (u32)divider;
>>>>> +
>>>>> +       /* As an optimization, let's not use 64 bit division unless we
>>>>> must. */
>>>>> +       if (dividend <= MAX_32BIT_UINT) {
>>>>> +               if (divider > MAX_32BIT_UINT) {
>>>>> +                       result = 0;
>>>>> +                       if (rem_p)
>>>>> +                               *rem_p = divider;
>>>>> +               } else {
>>>>> +                       result = (u32)dividend / (u32)divider;
>>>>> +                       if (rem_p)
>>>>> +                               *rem_p = (u32)dividend % (u32)divider;
>>>>> +               }
>>>>> +               return result;
>>>>> +       }
>>>>> +
>>>>> +       while (divider <= dividend) {
>>>>> +               u64 locald = divider;
>>>>> +               u64 limit = __lshrdi3(dividend, 1);
>>>>> +               int shifts = 0;
>>>>> +
>>>>> +               while (locald <= limit) {
>>>>> +                       shifts++;
>>>>> +                       locald = locald + locald;
>>>>> +               }
>>>>> +               result |= __ashldi3(1, shifts);
>>>>> +               dividend -= locald;
>>>>> +       }
>>>>> +
>>>>> +       if (rem_p)
>>>>> +               *rem_p = dividend;
>>>>> +
>>>>> +       return result;
>>>>> +}
>>>>> +
>>>>> +u64 __udivdi3(u64 num, u64 den)
>>>>> +{
>>>>> +       return _64bit_divide(num, den, NULL);
>>>>> +}
>>>>> +
>>>>> +u64 __umoddi3(u64 num, u64 den)
>>>>> +{
>>>>> +       u64 v = 0;
>>>>> +
>>>>> +       _64bit_divide(num, den, &v);
>>>>> +       return v;
>>>>> +}
>>>>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>>>>> deleted file mode 100644
>>>>> index 3c70d790d4..0000000000
>>>>> --- a/arch/x86/lib/gcc.c
>>>>> +++ /dev/null
>>>>> @@ -1,29 +0,0 @@
>>>>> -/*
>>>>> - * This file is part of the coreboot project.
>>>>> - *
>>>>> - * Copyright (C) 2009 coresystems GmbH
>>>>> - *
>>>>> - * SPDX-License-Identifier:    GPL-2.0
>>>>> - */
>>>>> -
>>>>> -#ifdef __GNUC__
>>>>> -
>>>>> -/*
>>>>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>>>>> - * are always regparm(0) the code that calls them uses whatever the
>>>>> - * compiler call specifies. Therefore we need a wrapper around those
>>>>> - * functions. See gcc bug PR41055 for more information.
>>>>> - */
>>>>> -#define WRAP_LIBGCC_CALL(type, name) \
>>>>> -       type __normal_##name(type a, type b)
>>>>> __attribute__((regparm(0)));
>>>>> \
>>>>> -       type __wrap_##name(type a, type b); \
>>>>> -       type __attribute__((no_instrument_function)) \
>>>>> -               __wrap_##name(type a, type b) \
>>>>> -                { return __normal_##name(a, b); }
>>>>> -
>>>>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>>>>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>>>>> -
>>>>> -#endif
>>>>> --
>>>>
>>>>
>>>>
>>>> I don't see __divdi3 and __moddi3 in the new implementation. Are they
>>>> not needed?
>>>
>>>
>>>
>>> Yes, at least I couldn't find any problems compiling U-Boot for x86 with
>>> this patch.
>>>
>>> BTW: The code size also did shrink a bit with this patch.
>>
>>
>> But this is needed in fact. If you write some codes doing signed
>> 64-bit integer division, you will get link errors.
>>
>>   undefined reference to `__divdi3'
>
>
> You wrote some additional code to test this, that is currently not
> in mainline, right? Writing code with divisions should be done very
> carefully from my point of view. And as far as I know, using do_div()
> and the functions from lib/div64 is preferred here.
>

I wrote some codes soemthing like:

s64 a, b, c;
c = a/b;

The compiler will generate codes to call __divdi3. This works before your patch.

> I would prefer to add this patch and once compile breakage occur because
> of such "undefined reference" error from above, we should investigate
> the root cause of fix it by replacing division operation by one of
> the provided helper functions.
>

Regards,
Bin
Stefan Roese Nov. 27, 2017, 4:34 p.m. UTC | #6 
Hi Bin,

On 27.11.2017 10:46, Bin Meng wrote:
> On Fri, Nov 24, 2017 at 5:29 PM, Stefan Roese <sr@denx.de> wrote:
>> Hi Bin,
>>
>>
>> On 24.11.2017 09:29, Bin Meng wrote:
>>>
>>> On Mon, Nov 20, 2017 at 6:43 PM, Stefan Roese <sr@denx.de> wrote:
>>>>
>>>> Hi Bin,
>>>>
>>>>
>>>> On 20.11.2017 08:24, Bin Meng wrote:
>>>>>
>>>>>
>>>>> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>>>>>>
>>>>>>
>>>>>> This patch removes the inclusion of the libgcc math functions and
>>>>>> replaces them by functions coded in C, taken from the coreboot
>>>>>> project. This makes U-Boot building more independent from the toolchain
>>>>>> installed / available on the build system.
>>>>>>
>>>>>> The code taken from coreboot is authored from Vadim Bendebury
>>>>>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>>>>>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>>>>>> (coreboot git repository located here [1]).
>>>>>>
>>>>>> I modified the code so that its checkpatch clean without any
>>>>>> functional changes.
>>>>>>
>>>>>> [1] git://github.com/coreboot/coreboot.git
>>>>>>
>>>>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>>>>> Cc: Simon Glass <sjg@chromium.org>
>>>>>> Cc: Bin Meng <bmeng.cn@gmail.com>
>>>>>> ---
>>>>>> v2:
>>>>>> - Added coreboot git repository link to commit message
>>>>>>
>>>>>>     arch/x86/config.mk    |   3 --
>>>>>>     arch/x86/lib/Makefile |   2 +-
>>>>>>     arch/x86/lib/div64.c  | 113
>>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>>>     arch/x86/lib/gcc.c    |  29 -------------
>>>>>>     4 files changed, 114 insertions(+), 33 deletions(-)
>>>>>>     create mode 100644 arch/x86/lib/div64.c
>>>>>>     delete mode 100644 arch/x86/lib/gcc.c
>>>>>>
>>>>>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>>>>>> index 8835dcf36f..472ada5490 100644
>>>>>> --- a/arch/x86/config.mk
>>>>>> +++ b/arch/x86/config.mk
>>>>>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections
>>>>>> -fvisibility=hidden
>>>>>>     PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>>>>>     PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>>>>>
>>>>>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>>>>>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>>>>>> -
>>>>>>     # This is used in the top-level Makefile which does not include
>>>>>>     # PLATFORM_LDFLAGS
>>>>>>     LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared
>>>>>> --no-undefined
>>>>>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>>>>>> index fe00d7573f..d9b23f5cc4 100644
>>>>>> --- a/arch/x86/lib/Makefile
>>>>>> +++ b/arch/x86/lib/Makefile
>>>>>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>>>>>     obj-y  += early_cmos.o
>>>>>>     obj-$(CONFIG_EFI) += efi/
>>>>>>     obj-y  += e820.o
>>>>>> -obj-y  += gcc.o
>>>>>> +obj-y  += div64.o
>>>>>>     obj-y  += init_helpers.o
>>>>>>     obj-y  += interrupts.o
>>>>>>     obj-y  += lpc-uclass.o
>>>>>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>>>>>> new file mode 100644
>>>>>> index 0000000000..4efed74037
>>>>>> --- /dev/null
>>>>>> +++ b/arch/x86/lib/div64.c
>>>>>> @@ -0,0 +1,113 @@
>>>>>> +/*
>>>>>> + * This file is copied from the coreboot repository as part of
>>>>>> + * the libpayload project:
>>>>>> + *
>>>>>> + * Copyright 2014 Google Inc.
>>>>>> + *
>>>>>> + * SPDX-License-Identifier:     BSD-3-Clause
>>>>>> + */
>>>>>> +
>>>>>> +#include <common.h>
>>>>>> +
>>>>>> +union overlay64 {
>>>>>> +       u64 longw;
>>>>>> +       struct {
>>>>>> +               u32 lower;
>>>>>> +               u32 higher;
>>>>>> +       } words;
>>>>>> +};
>>>>>> +
>>>>>> +u64 __ashldi3(u64 num, unsigned int shift)
>>>>>> +{
>>>>>> +       union overlay64 output;
>>>>>> +
>>>>>> +       output.longw = num;
>>>>>> +       if (shift >= 32) {
>>>>>> +               output.words.higher = output.words.lower << (shift -
>>>>>> 32);
>>>>>> +               output.words.lower = 0;
>>>>>> +       } else {
>>>>>> +               if (!shift)
>>>>>> +                       return num;
>>>>>> +               output.words.higher = (output.words.higher << shift) |
>>>>>> +                       (output.words.lower >> (32 - shift));
>>>>>> +               output.words.lower = output.words.lower << shift;
>>>>>> +       }
>>>>>> +       return output.longw;
>>>>>> +}
>>>>>> +
>>>>>> +u64 __lshrdi3(u64 num, unsigned int shift)
>>>>>> +{
>>>>>> +       union overlay64 output;
>>>>>> +
>>>>>> +       output.longw = num;
>>>>>> +       if (shift >= 32) {
>>>>>> +               output.words.lower = output.words.higher >> (shift -
>>>>>> 32);
>>>>>> +               output.words.higher = 0;
>>>>>> +       } else {
>>>>>> +               if (!shift)
>>>>>> +                       return num;
>>>>>> +               output.words.lower = output.words.lower >> shift |
>>>>>> +                       (output.words.higher << (32 - shift));
>>>>>> +               output.words.higher = output.words.higher >> shift;
>>>>>> +       }
>>>>>> +       return output.longw;
>>>>>> +}
>>>>>> +
>>>>>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>>>>>> +
>>>>>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>>>>>> +{
>>>>>> +       u64 result = 0;
>>>>>> +
>>>>>> +       /*
>>>>>> +        * If divider is zero - let the rest of the system care about
>>>>>> the
>>>>>> +        * exception.
>>>>>> +        */
>>>>>> +       if (!divider)
>>>>>> +               return 1 / (u32)divider;
>>>>>> +
>>>>>> +       /* As an optimization, let's not use 64 bit division unless we
>>>>>> must. */
>>>>>> +       if (dividend <= MAX_32BIT_UINT) {
>>>>>> +               if (divider > MAX_32BIT_UINT) {
>>>>>> +                       result = 0;
>>>>>> +                       if (rem_p)
>>>>>> +                               *rem_p = divider;
>>>>>> +               } else {
>>>>>> +                       result = (u32)dividend / (u32)divider;
>>>>>> +                       if (rem_p)
>>>>>> +                               *rem_p = (u32)dividend % (u32)divider;
>>>>>> +               }
>>>>>> +               return result;
>>>>>> +       }
>>>>>> +
>>>>>> +       while (divider <= dividend) {
>>>>>> +               u64 locald = divider;
>>>>>> +               u64 limit = __lshrdi3(dividend, 1);
>>>>>> +               int shifts = 0;
>>>>>> +
>>>>>> +               while (locald <= limit) {
>>>>>> +                       shifts++;
>>>>>> +                       locald = locald + locald;
>>>>>> +               }
>>>>>> +               result |= __ashldi3(1, shifts);
>>>>>> +               dividend -= locald;
>>>>>> +       }
>>>>>> +
>>>>>> +       if (rem_p)
>>>>>> +               *rem_p = dividend;
>>>>>> +
>>>>>> +       return result;
>>>>>> +}
>>>>>> +
>>>>>> +u64 __udivdi3(u64 num, u64 den)
>>>>>> +{
>>>>>> +       return _64bit_divide(num, den, NULL);
>>>>>> +}
>>>>>> +
>>>>>> +u64 __umoddi3(u64 num, u64 den)
>>>>>> +{
>>>>>> +       u64 v = 0;
>>>>>> +
>>>>>> +       _64bit_divide(num, den, &v);
>>>>>> +       return v;
>>>>>> +}
>>>>>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>>>>>> deleted file mode 100644
>>>>>> index 3c70d790d4..0000000000
>>>>>> --- a/arch/x86/lib/gcc.c
>>>>>> +++ /dev/null
>>>>>> @@ -1,29 +0,0 @@
>>>>>> -/*
>>>>>> - * This file is part of the coreboot project.
>>>>>> - *
>>>>>> - * Copyright (C) 2009 coresystems GmbH
>>>>>> - *
>>>>>> - * SPDX-License-Identifier:    GPL-2.0
>>>>>> - */
>>>>>> -
>>>>>> -#ifdef __GNUC__
>>>>>> -
>>>>>> -/*
>>>>>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>>>>>> - * are always regparm(0) the code that calls them uses whatever the
>>>>>> - * compiler call specifies. Therefore we need a wrapper around those
>>>>>> - * functions. See gcc bug PR41055 for more information.
>>>>>> - */
>>>>>> -#define WRAP_LIBGCC_CALL(type, name) \
>>>>>> -       type __normal_##name(type a, type b)
>>>>>> __attribute__((regparm(0)));
>>>>>> \
>>>>>> -       type __wrap_##name(type a, type b); \
>>>>>> -       type __attribute__((no_instrument_function)) \
>>>>>> -               __wrap_##name(type a, type b) \
>>>>>> -                { return __normal_##name(a, b); }
>>>>>> -
>>>>>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>>>>>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>>>>>> -
>>>>>> -#endif
>>>>>> --
>>>>>
>>>>>
>>>>>
>>>>> I don't see __divdi3 and __moddi3 in the new implementation. Are they
>>>>> not needed?
>>>>
>>>>
>>>>
>>>> Yes, at least I couldn't find any problems compiling U-Boot for x86 with
>>>> this patch.
>>>>
>>>> BTW: The code size also did shrink a bit with this patch.
>>>
>>>
>>> But this is needed in fact. If you write some codes doing signed
>>> 64-bit integer division, you will get link errors.
>>>
>>>    undefined reference to `__divdi3'
>>
>>
>> You wrote some additional code to test this, that is currently not
>> in mainline, right? Writing code with divisions should be done very
>> carefully from my point of view. And as far as I know, using do_div()
>> and the functions from lib/div64 is preferred here.
>>
> 
> I wrote some codes soemthing like:
> 
> s64 a, b, c;
> c = a/b;
> 
> The compiler will generate codes to call __divdi3. This works before your patch.

Yes, I understand this. But right now, we don't have any code
generating this error. And if this will happen at some time, I would
prefer to investigate this code sequence introducing this division, to
use the division functions / macros available in U-Boot (as mentioned
above) and in the kernel instead.

Here a short explanation, why this new version is preferred to the
currently available functions pulled from libgcc: We are fixing an
"ugly" Yocto build problem with this patch, related to 32bit binaries
with 64bit toolchains (multilib) building by not relying on anything
from libgcc. Please see this thread for some more details:

https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html

I hope this helps a bit to understand the motivation behind this patch.

Thanks,
Stefan
Bin Meng Nov. 29, 2017, 8:30 a.m. UTC | #7 
Hi Stefan,

On Tue, Nov 28, 2017 at 12:34 AM, Stefan Roese <sr@denx.de> wrote:
> Hi Bin,
>
>
> On 27.11.2017 10:46, Bin Meng wrote:
>>
>> On Fri, Nov 24, 2017 at 5:29 PM, Stefan Roese <sr@denx.de> wrote:
>>>
>>> Hi Bin,
>>>
>>>
>>> On 24.11.2017 09:29, Bin Meng wrote:
>>>>
>>>>
>>>> On Mon, Nov 20, 2017 at 6:43 PM, Stefan Roese <sr@denx.de> wrote:
>>>>>
>>>>>
>>>>> Hi Bin,
>>>>>
>>>>>
>>>>> On 20.11.2017 08:24, Bin Meng wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Fri, Nov 17, 2017 at 2:02 PM, Stefan Roese <sr@denx.de> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> This patch removes the inclusion of the libgcc math functions and
>>>>>>> replaces them by functions coded in C, taken from the coreboot
>>>>>>> project. This makes U-Boot building more independent from the
>>>>>>> toolchain
>>>>>>> installed / available on the build system.
>>>>>>>
>>>>>>> The code taken from coreboot is authored from Vadim Bendebury
>>>>>>> <vbendeb@chromium.org> on 2014-11-28 and committed with commit
>>>>>>> ID e63990ef [libpayload: provide basic 64bit division implementation]
>>>>>>> (coreboot git repository located here [1]).
>>>>>>>
>>>>>>> I modified the code so that its checkpatch clean without any
>>>>>>> functional changes.
>>>>>>>
>>>>>>> [1] git://github.com/coreboot/coreboot.git
>>>>>>>
>>>>>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>>>>>> Cc: Simon Glass <sjg@chromium.org>
>>>>>>> Cc: Bin Meng <bmeng.cn@gmail.com>
>>>>>>> ---
>>>>>>> v2:
>>>>>>> - Added coreboot git repository link to commit message
>>>>>>>
>>>>>>>     arch/x86/config.mk    |   3 --
>>>>>>>     arch/x86/lib/Makefile |   2 +-
>>>>>>>     arch/x86/lib/div64.c  | 113
>>>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>     arch/x86/lib/gcc.c    |  29 -------------
>>>>>>>     4 files changed, 114 insertions(+), 33 deletions(-)
>>>>>>>     create mode 100644 arch/x86/lib/div64.c
>>>>>>>     delete mode 100644 arch/x86/lib/gcc.c
>>>>>>>
>>>>>>> diff --git a/arch/x86/config.mk b/arch/x86/config.mk
>>>>>>> index 8835dcf36f..472ada5490 100644
>>>>>>> --- a/arch/x86/config.mk
>>>>>>> +++ b/arch/x86/config.mk
>>>>>>> @@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections
>>>>>>> -fvisibility=hidden
>>>>>>>     PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
>>>>>>>     PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
>>>>>>>
>>>>>>> -LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
>>>>>>> -LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
>>>>>>> -
>>>>>>>     # This is used in the top-level Makefile which does not include
>>>>>>>     # PLATFORM_LDFLAGS
>>>>>>>     LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared
>>>>>>> --no-undefined
>>>>>>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>>>>>>> index fe00d7573f..d9b23f5cc4 100644
>>>>>>> --- a/arch/x86/lib/Makefile
>>>>>>> +++ b/arch/x86/lib/Makefile
>>>>>>> @@ -18,7 +18,7 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
>>>>>>>     obj-y  += early_cmos.o
>>>>>>>     obj-$(CONFIG_EFI) += efi/
>>>>>>>     obj-y  += e820.o
>>>>>>> -obj-y  += gcc.o
>>>>>>> +obj-y  += div64.o
>>>>>>>     obj-y  += init_helpers.o
>>>>>>>     obj-y  += interrupts.o
>>>>>>>     obj-y  += lpc-uclass.o
>>>>>>> diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
>>>>>>> new file mode 100644
>>>>>>> index 0000000000..4efed74037
>>>>>>> --- /dev/null
>>>>>>> +++ b/arch/x86/lib/div64.c
>>>>>>> @@ -0,0 +1,113 @@
>>>>>>> +/*
>>>>>>> + * This file is copied from the coreboot repository as part of
>>>>>>> + * the libpayload project:
>>>>>>> + *
>>>>>>> + * Copyright 2014 Google Inc.
>>>>>>> + *
>>>>>>> + * SPDX-License-Identifier:     BSD-3-Clause
>>>>>>> + */
>>>>>>> +
>>>>>>> +#include <common.h>
>>>>>>> +
>>>>>>> +union overlay64 {
>>>>>>> +       u64 longw;
>>>>>>> +       struct {
>>>>>>> +               u32 lower;
>>>>>>> +               u32 higher;
>>>>>>> +       } words;
>>>>>>> +};
>>>>>>> +
>>>>>>> +u64 __ashldi3(u64 num, unsigned int shift)
>>>>>>> +{
>>>>>>> +       union overlay64 output;
>>>>>>> +
>>>>>>> +       output.longw = num;
>>>>>>> +       if (shift >= 32) {
>>>>>>> +               output.words.higher = output.words.lower << (shift -
>>>>>>> 32);
>>>>>>> +               output.words.lower = 0;
>>>>>>> +       } else {
>>>>>>> +               if (!shift)
>>>>>>> +                       return num;
>>>>>>> +               output.words.higher = (output.words.higher << shift)
>>>>>>> |
>>>>>>> +                       (output.words.lower >> (32 - shift));
>>>>>>> +               output.words.lower = output.words.lower << shift;
>>>>>>> +       }
>>>>>>> +       return output.longw;
>>>>>>> +}
>>>>>>> +
>>>>>>> +u64 __lshrdi3(u64 num, unsigned int shift)
>>>>>>> +{
>>>>>>> +       union overlay64 output;
>>>>>>> +
>>>>>>> +       output.longw = num;
>>>>>>> +       if (shift >= 32) {
>>>>>>> +               output.words.lower = output.words.higher >> (shift -
>>>>>>> 32);
>>>>>>> +               output.words.higher = 0;
>>>>>>> +       } else {
>>>>>>> +               if (!shift)
>>>>>>> +                       return num;
>>>>>>> +               output.words.lower = output.words.lower >> shift |
>>>>>>> +                       (output.words.higher << (32 - shift));
>>>>>>> +               output.words.higher = output.words.higher >> shift;
>>>>>>> +       }
>>>>>>> +       return output.longw;
>>>>>>> +}
>>>>>>> +
>>>>>>> +#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
>>>>>>> +
>>>>>>> +static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
>>>>>>> +{
>>>>>>> +       u64 result = 0;
>>>>>>> +
>>>>>>> +       /*
>>>>>>> +        * If divider is zero - let the rest of the system care about
>>>>>>> the
>>>>>>> +        * exception.
>>>>>>> +        */
>>>>>>> +       if (!divider)
>>>>>>> +               return 1 / (u32)divider;
>>>>>>> +
>>>>>>> +       /* As an optimization, let's not use 64 bit division unless
>>>>>>> we
>>>>>>> must. */
>>>>>>> +       if (dividend <= MAX_32BIT_UINT) {
>>>>>>> +               if (divider > MAX_32BIT_UINT) {
>>>>>>> +                       result = 0;
>>>>>>> +                       if (rem_p)
>>>>>>> +                               *rem_p = divider;
>>>>>>> +               } else {
>>>>>>> +                       result = (u32)dividend / (u32)divider;
>>>>>>> +                       if (rem_p)
>>>>>>> +                               *rem_p = (u32)dividend %
>>>>>>> (u32)divider;
>>>>>>> +               }
>>>>>>> +               return result;
>>>>>>> +       }
>>>>>>> +
>>>>>>> +       while (divider <= dividend) {
>>>>>>> +               u64 locald = divider;
>>>>>>> +               u64 limit = __lshrdi3(dividend, 1);
>>>>>>> +               int shifts = 0;
>>>>>>> +
>>>>>>> +               while (locald <= limit) {
>>>>>>> +                       shifts++;
>>>>>>> +                       locald = locald + locald;
>>>>>>> +               }
>>>>>>> +               result |= __ashldi3(1, shifts);
>>>>>>> +               dividend -= locald;
>>>>>>> +       }
>>>>>>> +
>>>>>>> +       if (rem_p)
>>>>>>> +               *rem_p = dividend;
>>>>>>> +
>>>>>>> +       return result;
>>>>>>> +}
>>>>>>> +
>>>>>>> +u64 __udivdi3(u64 num, u64 den)
>>>>>>> +{
>>>>>>> +       return _64bit_divide(num, den, NULL);
>>>>>>> +}
>>>>>>> +
>>>>>>> +u64 __umoddi3(u64 num, u64 den)
>>>>>>> +{
>>>>>>> +       u64 v = 0;
>>>>>>> +
>>>>>>> +       _64bit_divide(num, den, &v);
>>>>>>> +       return v;
>>>>>>> +}
>>>>>>> diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
>>>>>>> deleted file mode 100644
>>>>>>> index 3c70d790d4..0000000000
>>>>>>> --- a/arch/x86/lib/gcc.c
>>>>>>> +++ /dev/null
>>>>>>> @@ -1,29 +0,0 @@
>>>>>>> -/*
>>>>>>> - * This file is part of the coreboot project.
>>>>>>> - *
>>>>>>> - * Copyright (C) 2009 coresystems GmbH
>>>>>>> - *
>>>>>>> - * SPDX-License-Identifier:    GPL-2.0
>>>>>>> - */
>>>>>>> -
>>>>>>> -#ifdef __GNUC__
>>>>>>> -
>>>>>>> -/*
>>>>>>> - * GCC's libgcc handling is quite broken. While the libgcc functions
>>>>>>> - * are always regparm(0) the code that calls them uses whatever the
>>>>>>> - * compiler call specifies. Therefore we need a wrapper around those
>>>>>>> - * functions. See gcc bug PR41055 for more information.
>>>>>>> - */
>>>>>>> -#define WRAP_LIBGCC_CALL(type, name) \
>>>>>>> -       type __normal_##name(type a, type b)
>>>>>>> __attribute__((regparm(0)));
>>>>>>> \
>>>>>>> -       type __wrap_##name(type a, type b); \
>>>>>>> -       type __attribute__((no_instrument_function)) \
>>>>>>> -               __wrap_##name(type a, type b) \
>>>>>>> -                { return __normal_##name(a, b); }
>>>>>>> -
>>>>>>> -WRAP_LIBGCC_CALL(long long, __divdi3)
>>>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
>>>>>>> -WRAP_LIBGCC_CALL(long long, __moddi3)
>>>>>>> -WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
>>>>>>> -
>>>>>>> -#endif
>>>>>>> --
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> I don't see __divdi3 and __moddi3 in the new implementation. Are they
>>>>>> not needed?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Yes, at least I couldn't find any problems compiling U-Boot for x86
>>>>> with
>>>>> this patch.
>>>>>
>>>>> BTW: The code size also did shrink a bit with this patch.
>>>>
>>>>
>>>>
>>>> But this is needed in fact. If you write some codes doing signed
>>>> 64-bit integer division, you will get link errors.
>>>>
>>>>    undefined reference to `__divdi3'
>>>
>>>
>>>
>>> You wrote some additional code to test this, that is currently not
>>> in mainline, right? Writing code with divisions should be done very
>>> carefully from my point of view. And as far as I know, using do_div()
>>> and the functions from lib/div64 is preferred here.
>>>
>>
>> I wrote some codes soemthing like:
>>
>> s64 a, b, c;
>> c = a/b;
>>
>> The compiler will generate codes to call __divdi3. This works before your
>> patch.
>
>
> Yes, I understand this. But right now, we don't have any code
> generating this error. And if this will happen at some time, I would
> prefer to investigate this code sequence introducing this division, to
> use the division functions / macros available in U-Boot (as mentioned
> above) and in the kernel instead.
>
> Here a short explanation, why this new version is preferred to the
> currently available functions pulled from libgcc: We are fixing an
> "ugly" Yocto build problem with this patch, related to 32bit binaries
> with 64bit toolchains (multilib) building by not relying on anything
> from libgcc. Please see this thread for some more details:
>
> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>
> I hope this helps a bit to understand the motivation behind this patch.
>

Thanks for the background. I am not familiar with yocto project, but
is the build broken due to the gcc on the build host does not ship
with multilib?
I am using a 64-bit host with gcc multilib, and there is no such build
error observed.

Regards,
Bin
Stefan Roese Nov. 29, 2017, 8:42 a.m. UTC | #8 
Hi Bin,

On 29.11.2017 09:30, Bin Meng wrote:

<snip>

>>> I wrote some codes soemthing like:
>>>
>>> s64 a, b, c;
>>> c = a/b;
>>>
>>> The compiler will generate codes to call __divdi3. This works before your
>>> patch.
>>
>>
>> Yes, I understand this. But right now, we don't have any code
>> generating this error. And if this will happen at some time, I would
>> prefer to investigate this code sequence introducing this division, to
>> use the division functions / macros available in U-Boot (as mentioned
>> above) and in the kernel instead.
>>
>> Here a short explanation, why this new version is preferred to the
>> currently available functions pulled from libgcc: We are fixing an
>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>> with 64bit toolchains (multilib) building by not relying on anything
>> from libgcc. Please see this thread for some more details:
>>
>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>
>> I hope this helps a bit to understand the motivation behind this patch.
>>
> 
> Thanks for the background. I am not familiar with yocto project, but
> is the build broken due to the gcc on the build host does not ship
> with multilib?

Please take a look at the email thread mentioned above for a detailed
explanation. Especially this post should answer your questions:

https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html

> I am using a 64-bit host with gcc multilib, and there is no such build
> error observed.

Right. This issue is only seen on Yocto builds (AFAIK). But again,
I would really like to see U-Boot x86 being self-contained without
any host libgcc dependencies as on other architectures as well.

Thanks,
Stefan
Bin Meng Nov. 29, 2017, 9:23 a.m. UTC | #9 
Hi Stefan,

On Wed, Nov 29, 2017 at 4:42 PM, Stefan Roese <sr@denx.de> wrote:
> Hi Bin,
>
> On 29.11.2017 09:30, Bin Meng wrote:
>
> <snip>
>
>>>> I wrote some codes soemthing like:
>>>>
>>>> s64 a, b, c;
>>>> c = a/b;
>>>>
>>>> The compiler will generate codes to call __divdi3. This works before
>>>> your
>>>> patch.
>>>
>>>
>>>
>>> Yes, I understand this. But right now, we don't have any code
>>> generating this error. And if this will happen at some time, I would
>>> prefer to investigate this code sequence introducing this division, to
>>> use the division functions / macros available in U-Boot (as mentioned
>>> above) and in the kernel instead.
>>>
>>> Here a short explanation, why this new version is preferred to the
>>> currently available functions pulled from libgcc: We are fixing an
>>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>>> with 64bit toolchains (multilib) building by not relying on anything
>>> from libgcc. Please see this thread for some more details:
>>>
>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>>
>>> I hope this helps a bit to understand the motivation behind this patch.
>>>
>>
>> Thanks for the background. I am not familiar with yocto project, but
>> is the build broken due to the gcc on the build host does not ship
>> with multilib?
>
>
> Please take a look at the email thread mentioned above for a detailed
> explanation. Especially this post should answer your questions:
>
> https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html

Now I see. Thank you.

>
>> I am using a 64-bit host with gcc multilib, and there is no such build
>> error observed.
>
>
> Right. This issue is only seen on Yocto builds (AFAIK). But again,
> I would really like to see U-Boot x86 being self-contained without
> any host libgcc dependencies as on other architectures as well.

So to completely resolve such issue to make U-Boot self-contained, we
should remove the reference to the host libgcc.a in
arch/x86/lib/Makefile, and use CONFIG_USE_PRIVATE_GCC to include the
build for div64.o. Thoughts?

Regards,
Bin
Stefan Roese Nov. 29, 2017, 10:01 a.m. UTC | #10 
Hi Bin,

On 29.11.2017 10:23, Bin Meng wrote:
> On Wed, Nov 29, 2017 at 4:42 PM, Stefan Roese <sr@denx.de> wrote:
>> Hi Bin,
>>
>> On 29.11.2017 09:30, Bin Meng wrote:
>>
>> <snip>
>>
>>>>> I wrote some codes soemthing like:
>>>>>
>>>>> s64 a, b, c;
>>>>> c = a/b;
>>>>>
>>>>> The compiler will generate codes to call __divdi3. This works before
>>>>> your
>>>>> patch.
>>>>
>>>>
>>>>
>>>> Yes, I understand this. But right now, we don't have any code
>>>> generating this error. And if this will happen at some time, I would
>>>> prefer to investigate this code sequence introducing this division, to
>>>> use the division functions / macros available in U-Boot (as mentioned
>>>> above) and in the kernel instead.
>>>>
>>>> Here a short explanation, why this new version is preferred to the
>>>> currently available functions pulled from libgcc: We are fixing an
>>>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>>>> with 64bit toolchains (multilib) building by not relying on anything
>>>> from libgcc. Please see this thread for some more details:
>>>>
>>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>>>
>>>> I hope this helps a bit to understand the motivation behind this patch.
>>>>
>>>
>>> Thanks for the background. I am not familiar with yocto project, but
>>> is the build broken due to the gcc on the build host does not ship
>>> with multilib?
>>
>>
>> Please take a look at the email thread mentioned above for a detailed
>> explanation. Especially this post should answer your questions:
>>
>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html
> 
> Now I see. Thank you.
> 
>>
>>> I am using a 64-bit host with gcc multilib, and there is no such build
>>> error observed.
>>
>>
>> Right. This issue is only seen on Yocto builds (AFAIK). But again,
>> I would really like to see U-Boot x86 being self-contained without
>> any host libgcc dependencies as on other architectures as well.
> 
> So to completely resolve such issue to make U-Boot self-contained, we
> should remove the reference to the host libgcc.a in
> arch/x86/lib/Makefile, and use CONFIG_USE_PRIVATE_GCC to include the
> build for div64.o. Thoughts?

I was under the impression, that I already removed the host libgcc
reference completely for x86 with my patch. But you are correct - there
still is a reference in this Makefile which is used by the standalone
code, AFAICT.

Any quick idea on how to rid of this one as well?

Thanks,
Stefan
Bin Meng Nov. 29, 2017, 12:31 p.m. UTC | #11 
Hi Stefan,

On Wed, Nov 29, 2017 at 6:01 PM, Stefan Roese <sr@denx.de> wrote:
> Hi Bin,
>
>
> On 29.11.2017 10:23, Bin Meng wrote:
>>
>> On Wed, Nov 29, 2017 at 4:42 PM, Stefan Roese <sr@denx.de> wrote:
>>>
>>> Hi Bin,
>>>
>>> On 29.11.2017 09:30, Bin Meng wrote:
>>>
>>> <snip>
>>>
>>>>>> I wrote some codes soemthing like:
>>>>>>
>>>>>> s64 a, b, c;
>>>>>> c = a/b;
>>>>>>
>>>>>> The compiler will generate codes to call __divdi3. This works before
>>>>>> your
>>>>>> patch.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Yes, I understand this. But right now, we don't have any code
>>>>> generating this error. And if this will happen at some time, I would
>>>>> prefer to investigate this code sequence introducing this division, to
>>>>> use the division functions / macros available in U-Boot (as mentioned
>>>>> above) and in the kernel instead.
>>>>>
>>>>> Here a short explanation, why this new version is preferred to the
>>>>> currently available functions pulled from libgcc: We are fixing an
>>>>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>>>>> with 64bit toolchains (multilib) building by not relying on anything
>>>>> from libgcc. Please see this thread for some more details:
>>>>>
>>>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>>>>
>>>>> I hope this helps a bit to understand the motivation behind this patch.
>>>>>
>>>>
>>>> Thanks for the background. I am not familiar with yocto project, but
>>>> is the build broken due to the gcc on the build host does not ship
>>>> with multilib?
>>>
>>>
>>>
>>> Please take a look at the email thread mentioned above for a detailed
>>> explanation. Especially this post should answer your questions:
>>>
>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html
>>
>>
>> Now I see. Thank you.
>>
>>>
>>>> I am using a 64-bit host with gcc multilib, and there is no such build
>>>> error observed.
>>>
>>>
>>>
>>> Right. This issue is only seen on Yocto builds (AFAIK). But again,
>>> I would really like to see U-Boot x86 being self-contained without
>>> any host libgcc dependencies as on other architectures as well.
>>
>>
>> So to completely resolve such issue to make U-Boot self-contained, we
>> should remove the reference to the host libgcc.a in
>> arch/x86/lib/Makefile, and use CONFIG_USE_PRIVATE_GCC to include the
>> build for div64.o. Thoughts?
>
>
> I was under the impression, that I already removed the host libgcc
> reference completely for x86 with my patch. But you are correct - there
> still is a reference in this Makefile which is used by the standalone
> code, AFAICT.
>
> Any quick idea on how to rid of this one as well?
>

I believe we need change

obj-y  += div64.o

to

lib-$(CONFIG_USE_PRIVATE_LIBGCC) += div64.o

To remove the libgcc dependency completely.

Regards,
Bin
Stefan Roese Nov. 29, 2017, 3:54 p.m. UTC | #12 
Hi Bin,

On 29.11.2017 13:31, Bin Meng wrote:
> Hi Stefan,
> 
> On Wed, Nov 29, 2017 at 6:01 PM, Stefan Roese <sr@denx.de> wrote:
>> Hi Bin,
>>
>>
>> On 29.11.2017 10:23, Bin Meng wrote:
>>>
>>> On Wed, Nov 29, 2017 at 4:42 PM, Stefan Roese <sr@denx.de> wrote:
>>>>
>>>> Hi Bin,
>>>>
>>>> On 29.11.2017 09:30, Bin Meng wrote:
>>>>
>>>> <snip>
>>>>
>>>>>>> I wrote some codes soemthing like:
>>>>>>>
>>>>>>> s64 a, b, c;
>>>>>>> c = a/b;
>>>>>>>
>>>>>>> The compiler will generate codes to call __divdi3. This works before
>>>>>>> your
>>>>>>> patch.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Yes, I understand this. But right now, we don't have any code
>>>>>> generating this error. And if this will happen at some time, I would
>>>>>> prefer to investigate this code sequence introducing this division, to
>>>>>> use the division functions / macros available in U-Boot (as mentioned
>>>>>> above) and in the kernel instead.
>>>>>>
>>>>>> Here a short explanation, why this new version is preferred to the
>>>>>> currently available functions pulled from libgcc: We are fixing an
>>>>>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>>>>>> with 64bit toolchains (multilib) building by not relying on anything
>>>>>> from libgcc. Please see this thread for some more details:
>>>>>>
>>>>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>>>>>
>>>>>> I hope this helps a bit to understand the motivation behind this patch.
>>>>>>
>>>>>
>>>>> Thanks for the background. I am not familiar with yocto project, but
>>>>> is the build broken due to the gcc on the build host does not ship
>>>>> with multilib?
>>>>
>>>>
>>>>
>>>> Please take a look at the email thread mentioned above for a detailed
>>>> explanation. Especially this post should answer your questions:
>>>>
>>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html
>>>
>>>
>>> Now I see. Thank you.
>>>
>>>>
>>>>> I am using a 64-bit host with gcc multilib, and there is no such build
>>>>> error observed.
>>>>
>>>>
>>>>
>>>> Right. This issue is only seen on Yocto builds (AFAIK). But again,
>>>> I would really like to see U-Boot x86 being self-contained without
>>>> any host libgcc dependencies as on other architectures as well.
>>>
>>>
>>> So to completely resolve such issue to make U-Boot self-contained, we
>>> should remove the reference to the host libgcc.a in
>>> arch/x86/lib/Makefile, and use CONFIG_USE_PRIVATE_GCC to include the
>>> build for div64.o. Thoughts?
>>
>>
>> I was under the impression, that I already removed the host libgcc
>> reference completely for x86 with my patch. But you are correct - there
>> still is a reference in this Makefile which is used by the standalone
>> code, AFAICT.
>>
>> Any quick idea on how to rid of this one as well?
>>
> 
> I believe we need change
> 
> obj-y  += div64.o
> 
> to
> 
> lib-$(CONFIG_USE_PRIVATE_LIBGCC) += div64.o
> 
> To remove the libgcc dependency completely.

Yep. Thanks.

I've posted v3 with this additional removal.

Thanks,
Stefan
diff mbox series

Patch

diff --git a/arch/x86/config.mk b/arch/x86/config.mk
index 8835dcf36f..472ada5490 100644
--- a/arch/x86/config.mk
+++ b/arch/x86/config.mk
@@ -34,9 +34,6 @@  PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden
 PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
 PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
 
-LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
-LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
-
 # This is used in the top-level Makefile which does not include
 # PLATFORM_LDFLAGS
 LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared --no-undefined
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index fe00d7573f..d9b23f5cc4 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -18,7 +18,7 @@  obj-$(CONFIG_SEABIOS) += coreboot_table.o
 obj-y	+= early_cmos.o
 obj-$(CONFIG_EFI) += efi/
 obj-y	+= e820.o
-obj-y	+= gcc.o
+obj-y	+= div64.o
 obj-y	+= init_helpers.o
 obj-y	+= interrupts.o
 obj-y	+= lpc-uclass.o
diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
new file mode 100644
index 0000000000..4efed74037
--- /dev/null
+++ b/arch/x86/lib/div64.c
@@ -0,0 +1,113 @@ 
+/*
+ * This file is copied from the coreboot repository as part of
+ * the libpayload project:
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * SPDX-License-Identifier:     BSD-3-Clause
+ */
+
+#include <common.h>
+
+union overlay64 {
+	u64 longw;
+	struct {
+		u32 lower;
+		u32 higher;
+	} words;
+};
+
+u64 __ashldi3(u64 num, unsigned int shift)
+{
+	union overlay64 output;
+
+	output.longw = num;
+	if (shift >= 32) {
+		output.words.higher = output.words.lower << (shift - 32);
+		output.words.lower = 0;
+	} else {
+		if (!shift)
+			return num;
+		output.words.higher = (output.words.higher << shift) |
+			(output.words.lower >> (32 - shift));
+		output.words.lower = output.words.lower << shift;
+	}
+	return output.longw;
+}
+
+u64 __lshrdi3(u64 num, unsigned int shift)
+{
+	union overlay64 output;
+
+	output.longw = num;
+	if (shift >= 32) {
+		output.words.lower = output.words.higher >> (shift - 32);
+		output.words.higher = 0;
+	} else {
+		if (!shift)
+			return num;
+		output.words.lower = output.words.lower >> shift |
+			(output.words.higher << (32 - shift));
+		output.words.higher = output.words.higher >> shift;
+	}
+	return output.longw;
+}
+
+#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
+
+static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
+{
+	u64 result = 0;
+
+	/*
+	 * If divider is zero - let the rest of the system care about the
+	 * exception.
+	 */
+	if (!divider)
+		return 1 / (u32)divider;
+
+	/* As an optimization, let's not use 64 bit division unless we must. */
+	if (dividend <= MAX_32BIT_UINT) {
+		if (divider > MAX_32BIT_UINT) {
+			result = 0;
+			if (rem_p)
+				*rem_p = divider;
+		} else {
+			result = (u32)dividend / (u32)divider;
+			if (rem_p)
+				*rem_p = (u32)dividend % (u32)divider;
+		}
+		return result;
+	}
+
+	while (divider <= dividend) {
+		u64 locald = divider;
+		u64 limit = __lshrdi3(dividend, 1);
+		int shifts = 0;
+
+		while (locald <= limit) {
+			shifts++;
+			locald = locald + locald;
+		}
+		result |= __ashldi3(1, shifts);
+		dividend -= locald;
+	}
+
+	if (rem_p)
+		*rem_p = dividend;
+
+	return result;
+}
+
+u64 __udivdi3(u64 num, u64 den)
+{
+	return _64bit_divide(num, den, NULL);
+}
+
+u64 __umoddi3(u64 num, u64 den)
+{
+	u64 v = 0;
+
+	_64bit_divide(num, den, &v);
+	return v;
+}
diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
deleted file mode 100644
index 3c70d790d4..0000000000
--- a/arch/x86/lib/gcc.c
+++ /dev/null
@@ -1,29 +0,0 @@ 
-/*
- * This file is part of the coreboot project.
- *
- * Copyright (C) 2009 coresystems GmbH
- *
- * SPDX-License-Identifier:	GPL-2.0
- */
-
-#ifdef __GNUC__
-
-/*
- * GCC's libgcc handling is quite broken. While the libgcc functions
- * are always regparm(0) the code that calls them uses whatever the
- * compiler call specifies. Therefore we need a wrapper around those
- * functions. See gcc bug PR41055 for more information.
- */
-#define WRAP_LIBGCC_CALL(type, name) \
-	type __normal_##name(type a, type b) __attribute__((regparm(0))); \
-	type __wrap_##name(type a, type b); \
-	type __attribute__((no_instrument_function)) \
-		__wrap_##name(type a, type b) \
-		 { return __normal_##name(a, b); }
-
-WRAP_LIBGCC_CALL(long long, __divdi3)
-WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
-WRAP_LIBGCC_CALL(long long, __moddi3)
-WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
-
-#endif