[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

Hello,

I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang. 

After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed. 

In crt0.S
bl debug_print
ldr pc, =board_init_r

In board_init_r
puts("In board_init_r\n"); // Right at start

void debug_print(void)
{
    // Defined in board file
    puts("Debug print\n");
}

My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.

An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
ldr r3, =board_init_r
add r3, #1
bx r3

No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.

Any pointers?

Thanks & Regards,
Sanchayan Maity.  

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Wolfgang Denk]

Dear Victor Ascroft,

In message <5464DC59.2040707@gmail.com> you wrote:
> 
> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang. 

Saving 1 MB?  So how big is your U-Boot image, then?


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
It is important to note that probably no large operating system using
current design  technology  can  withstand  a  determined  and  well-
coordinated  attack,  and that most such documented penetrations have
been remarkably easy.
- B. Hebbard, "A Penetration Analysis of the Michigan Terminal System",
Operating Systems Review, Vol. 14, No. 1, June 1980, pp. 7-20

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

Hello,

On 11/14/2014 02:23 AM, Wolfgang Denk wrote:
> Dear Victor Ascroft,
> 
> In message <5464DC59.2040707@gmail.com> you wrote:
>>
>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang. 
> 
> Saving 1 MB?  So how big is your U-Boot image, then?

To be exact

For a thumb build:
363288 bytes

For a non thumb build:
482072 bytes

> 
> 
> Best regards,
> 
> Wolfgang Denk
> 

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Wolfgang Denk]

Dear Victor,

In message <54658577.3090807@gmail.com> you wrote:
> 
> >> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang
> . 
> > 
> > Saving 1 MB?  So how big is your U-Boot image, then?
> 
> To be exact
> 
> For a thumb build:
> 363288 bytes
> 
> For a non thumb build:
> 482072 bytes

That saves 118784 bytes or 116 KiB.  This is still a lot, but far from
the dramatic "1 MB" you claimed...

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
The use of COBOL cripples the mind; its teaching  should,  therefore,
be regarded as a criminal offence.
          -- Edsger W. Dijkstra, SIGPLAN Notices, Volume 17, Number 5

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

On 11/14/2014 11:13 AM, Wolfgang Denk wrote:
> Dear Victor,
> 
> In message <54658577.3090807@gmail.com> you wrote:
>>
>>>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang
>> . 
>>>
>>> Saving 1 MB?  So how big is your U-Boot image, then?
>>
>> To be exact
>>
>> For a thumb build:
>> 363288 bytes
>>
>> For a non thumb build:
>> 482072 bytes
> 
> That saves 118784 bytes or 116 KiB.  This is still a lot, but far from
> the dramatic "1 MB" you claimed...

Argh...Sorry my bad. I made a mistake there in interpreting the KB and MB. 


> 
> Best regards,
> 
> Wolfgang Denk
> 

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Simon Glass]

Hi Victor,

On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
> Hello,
>
> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>
> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>
> In crt0.S
> bl debug_print
> ldr pc, =board_init_r
>
> In board_init_r
> puts("In board_init_r\n"); // Right at start
>
> void debug_print(void)
> {
>     // Defined in board file
>     puts("Debug print\n");
> }
>
> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>
> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
> ldr r3, =board_init_r
> add r3, #1
> bx r3
>
> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>
> Any pointers?

I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
for me. The code sequence you refer to came out as below for me.

23e01e10 <clbss_l>:
23e01e10:       e1500001        cmp     r0, r1
23e01e14:       35802000        strcc   r2, [r0]
23e01e18:       32800004        addcc   r0, r0, #4
23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
23e01e24:       fb000deb        blx     23e055da <red_led_on>
23e01e28:       e1a00009        mov     r0, r9
23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
<clbss_l+0x30>
23e01e34:       02073800        .word   0x02073800
23e01e38:       23e41eb0        .word   0x23e41eb0
23e01e3c:       23e77bf0        .word   0x23e77bf0
23e01e40:       23e057a9        .word   0x23e057a9

The 'ldr pc' line is loading from 23e01e40 which does have an odd address.

What toolchain are you using? I tried with gcc 4.8.2 - including
linaro's 2013.10 release.

In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
armv7-a, and this may cause it to generate Thumb code instead of Thumb
2. But you should get errors if that happens.

It's hard to debug with such limited visibility. But if I put a puts()
at the start of board_init_r(), I see it on the serial console.

Regards,
Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Simon,

On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass <sjg@chromium.org>
wrote:
> Hi Victor,
> 
> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
> > Hello,
> >
> > I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
> >
> > After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
> >
> > In crt0.S
> > bl debug_print
> > ldr pc, =board_init_r
> >
> > In board_init_r
> > puts("In board_init_r\n"); // Right at start
> >
> > void debug_print(void)
> > {
> >     // Defined in board file
> >     puts("Debug print\n");
> > }
> >
> > My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
> >
> > An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
> > ldr r3, =board_init_r
> > add r3, #1
> > bx r3
> >
> > No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
> >
> > Any pointers?

Victor,

In addition to Simon's question below on the toolchain, I would like to
know which commit you're trying to build.

> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
> for me. The code sequence you refer to came out as below for me.
> 
> 23e01e10 <clbss_l>:
> 23e01e10:       e1500001        cmp     r0, r1
> 23e01e14:       35802000        strcc   r2, [r0]
> 23e01e18:       32800004        addcc   r0, r0, #4
> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
> 23e01e28:       e1a00009        mov     r0, r9
> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
> <clbss_l+0x30>
> 23e01e34:       02073800        .word   0x02073800
> 23e01e38:       23e41eb0        .word   0x23e41eb0
> 23e01e3c:       23e77bf0        .word   0x23e77bf0
> 23e01e40:       23e057a9        .word   0x23e057a9
> 
> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
> 
> What toolchain are you using? I tried with gcc 4.8.2 - including
> linaro's 2013.10 release.
> 
> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
> armv7-a, and this may cause it to generate Thumb code instead of Thumb
> 2. But you should get errors if that happens.
> 
> It's hard to debug with such limited visibility. But if I put a puts()
> at the start of board_init_r(), I see it on the serial console.

Simon,

I believe you've built crt0.S for ARM, not Thumb.

> Regards,
> Simon
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot



Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Simon Glass]

Hi Albert,

On 14 November 2014 08:26, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
> Hello Simon,
>
> On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass <sjg@chromium.org>
> wrote:
>> Hi Victor,
>>
>> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>> > Hello,
>> >
>> > I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>> >
>> > After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>> >
>> > In crt0.S
>> > bl debug_print
>> > ldr pc, =board_init_r
>> >
>> > In board_init_r
>> > puts("In board_init_r\n"); // Right at start
>> >
>> > void debug_print(void)
>> > {
>> >     // Defined in board file
>> >     puts("Debug print\n");
>> > }
>> >
>> > My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>> >
>> > An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>> > ldr r3, =board_init_r
>> > add r3, #1
>> > bx r3
>> >
>> > No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>> >
>> > Any pointers?
>
> Victor,
>
> In addition to Simon's question below on the toolchain, I would like to
> know which commit you're trying to build.
>
>> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
>> for me. The code sequence you refer to came out as below for me.
>>
>> 23e01e10 <clbss_l>:
>> 23e01e10:       e1500001        cmp     r0, r1
>> 23e01e14:       35802000        strcc   r2, [r0]
>> 23e01e18:       32800004        addcc   r0, r0, #4
>> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
>> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
>> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
>> 23e01e28:       e1a00009        mov     r0, r9
>> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
>> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
>> <clbss_l+0x30>
>> 23e01e34:       02073800        .word   0x02073800
>> 23e01e38:       23e41eb0        .word   0x23e41eb0
>> 23e01e3c:       23e77bf0        .word   0x23e77bf0
>> 23e01e40:       23e057a9        .word   0x23e057a9
>>
>> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
>>
>> What toolchain are you using? I tried with gcc 4.8.2 - including
>> linaro's 2013.10 release.
>>
>> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
>> armv7-a, and this may cause it to generate Thumb code instead of Thumb
>> 2. But you should get errors if that happens.
>>
>> It's hard to debug with such limited visibility. But if I put a puts()
>> at the start of board_init_r(), I see it on the serial console.
>
> Simon,
>
> I believe you've built crt0.S for ARM, not Thumb.

Yes, but I suspect that is a function of the build system. I checked
the rest of U-Boot and most of it (including SPL) is Thumb 2. I
suppose we could use Thumb 2 for crt0.S if all the instructions are
supported.

Regards,
Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

On 11/15/2014 07:26 AM, Simon Glass wrote:
> Hi Albert,
> 
> On 14 November 2014 08:26, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>> Hello Simon,
>>
>> On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass <sjg@chromium.org>
>> wrote:
>>> Hi Victor,
>>>
>>> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>>>> Hello,
>>>>
>>>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>>>>
>>>> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>>>>
>>>> In crt0.S
>>>> bl debug_print
>>>> ldr pc, =board_init_r
>>>>
>>>> In board_init_r
>>>> puts("In board_init_r\n"); // Right at start
>>>>
>>>> void debug_print(void)
>>>> {
>>>>     // Defined in board file
>>>>     puts("Debug print\n");
>>>> }
>>>>
>>>> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>>>>
>>>> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>>>> ldr r3, =board_init_r
>>>> add r3, #1
>>>> bx r3
>>>>
>>>> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>>>>
>>>> Any pointers?
>>
>> Victor,
>>
>> In addition to Simon's question below on the toolchain, I would like to
>> know which commit you're trying to build.

I am using u-boot 2014.10, but, I have a modified branch which supports my hardware
and I also have changes for having USB Host and Client support for the Vybrid platform.

The toolchain I am using is gcc-linaro-arm-linux-gnueabihf-2012.09-20120921

http://www.codesourcery.com/public/gnu_toolchain/arm-none-linux-gnueabi/arm-2009q3-67-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

I have downloaded it from the above link.

>>
>>> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
>>> for me. The code sequence you refer to came out as below for me.
>>>
>>> 23e01e10 <clbss_l>:
>>> 23e01e10:       e1500001        cmp     r0, r1
>>> 23e01e14:       35802000        strcc   r2, [r0]
>>> 23e01e18:       32800004        addcc   r0, r0, #4
>>> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
>>> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
>>> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
>>> 23e01e28:       e1a00009        mov     r0, r9
>>> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
>>> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
>>> <clbss_l+0x30>
>>> 23e01e34:       02073800        .word   0x02073800
>>> 23e01e38:       23e41eb0        .word   0x23e41eb0
>>> 23e01e3c:       23e77bf0        .word   0x23e77bf0
>>> 23e01e40:       23e057a9        .word   0x23e057a9
>>>
>>> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
>>>
>>> What toolchain are you using? I tried with gcc 4.8.2 - including
>>> linaro's 2013.10 release.
>>>
>>> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
>>> armv7-a, and this may cause it to generate Thumb code instead of Thumb
>>> 2. But you should get errors if that happens.
>>>
>>> It's hard to debug with such limited visibility. But if I put a puts()
>>> at the start of board_init_r(), I see it on the serial console.
>>
>> Simon,
>>
>> I believe you've built crt0.S for ARM, not Thumb.
> 
> Yes, but I suspect that is a function of the build system. I checked
> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
> suppose we could use Thumb 2 for crt0.S if all the instructions are
> supported.

Yes Simon, you had it for ARM. I also believed it is a function of the
build system. But, does crt0.S have to be in Thumb2? Thumb interop is 
not enough with ARM and Thumb co-existing?
 
Does CONFIG_SYS_THUMB_BUILD require any specific changes to the build
system. I was under the impression, the configuration would take care
of it. I can do any changes are required, but, I have no knowledge of
it. 
> 
> Regards,
> Simon
> 

Regards,
Victor.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

On 11/15/2014 10:56 AM, Victor Ascroft wrote:
> On 11/15/2014 07:26 AM, Simon Glass wrote:
>> Hi Albert,
>>
>> On 14 November 2014 08:26, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>>> Hello Simon,
>>>
>>> On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass <sjg@chromium.org>
>>> wrote:
>>>> Hi Victor,
>>>>
>>>> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>>>>> Hello,
>>>>>
>>>>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>>>>>
>>>>> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>>>>>
>>>>> In crt0.S
>>>>> bl debug_print
>>>>> ldr pc, =board_init_r
>>>>>
>>>>> In board_init_r
>>>>> puts("In board_init_r\n"); // Right at start
>>>>>
>>>>> void debug_print(void)
>>>>> {
>>>>>     // Defined in board file
>>>>>     puts("Debug print\n");
>>>>> }
>>>>>
>>>>> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>>>>>
>>>>> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>>>>> ldr r3, =board_init_r
>>>>> add r3, #1
>>>>> bx r3
>>>>>
>>>>> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>>>>>
>>>>> Any pointers?
>>>
>>> Victor,
>>>
>>> In addition to Simon's question below on the toolchain, I would like to
>>> know which commit you're trying to build.
> 
> I am using u-boot 2014.10, but, I have a modified branch which supports my hardware
> and I also have changes for having USB Host and Client support for the Vybrid platform.
> 
> The toolchain I am using is gcc-linaro-arm-linux-gnueabihf-2012.09-20120921
> 
> http://www.codesourcery.com/public/gnu_toolchain/arm-none-linux-gnueabi/arm-2009q3-67-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

http://launchpad.net/linaro-toolchain-binaries/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-2012.09-20120921_linux.tar.bz2

Sorry I gave the link for the soft floating one by mistake :(.
> 
> I have downloaded it from the above link.
> 
>>>
>>>> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
>>>> for me. The code sequence you refer to came out as below for me.
>>>>
>>>> 23e01e10 <clbss_l>:
>>>> 23e01e10:       e1500001        cmp     r0, r1
>>>> 23e01e14:       35802000        strcc   r2, [r0]
>>>> 23e01e18:       32800004        addcc   r0, r0, #4
>>>> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
>>>> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
>>>> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
>>>> 23e01e28:       e1a00009        mov     r0, r9
>>>> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
>>>> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
>>>> <clbss_l+0x30>
>>>> 23e01e34:       02073800        .word   0x02073800
>>>> 23e01e38:       23e41eb0        .word   0x23e41eb0
>>>> 23e01e3c:       23e77bf0        .word   0x23e77bf0
>>>> 23e01e40:       23e057a9        .word   0x23e057a9
>>>>
>>>> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
>>>>
>>>> What toolchain are you using? I tried with gcc 4.8.2 - including
>>>> linaro's 2013.10 release.
>>>>
>>>> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
>>>> armv7-a, and this may cause it to generate Thumb code instead of Thumb
>>>> 2. But you should get errors if that happens.
>>>>
>>>> It's hard to debug with such limited visibility. But if I put a puts()
>>>> at the start of board_init_r(), I see it on the serial console.
>>>
>>> Simon,
>>>
>>> I believe you've built crt0.S for ARM, not Thumb.
>>
>> Yes, but I suspect that is a function of the build system. I checked
>> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
>> suppose we could use Thumb 2 for crt0.S if all the instructions are
>> supported.
> 
> Yes Simon, you had it for ARM. I also believed it is a function of the
> build system. But, does crt0.S have to be in Thumb2? Thumb interop is 
> not enough with ARM and Thumb co-existing?
>  
> Does CONFIG_SYS_THUMB_BUILD require any specific changes to the build
> system. I was under the impression, the configuration would take care
> of it. I can do any changes are required, but, I have no knowledge of
> it. 
>>
>> Regards,
>> Simon
>>
> 
> Regards,
> Victor.
> 

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Simon,

On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
wrote:

> > I believe you've built crt0.S for ARM, not Thumb.
> 
> Yes, but I suspect that is a function of the build system. I checked
> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
> suppose we could use Thumb 2 for crt0.S if all the instructions are
> supported.

Ok. Just in case, I'll run a check on whether crt0.S can be assembled
for Thumb and still wrk as expected. :)

Do you have a list of source files which still build for ARM under
CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
consistence, except probably... exception :) entry points -- and even
these should be able to run in full Thumb 2.

> Regards,
> Simon

Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Simon Glass]

Hi Albert,

On 15 November 2014 05:30, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
> Hello Simon,
>
> On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
> wrote:
>
>> > I believe you've built crt0.S for ARM, not Thumb.
>>
>> Yes, but I suspect that is a function of the build system. I checked
>> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
>> suppose we could use Thumb 2 for crt0.S if all the instructions are
>> supported.
>
> Ok. Just in case, I'll run a check on whether crt0.S can be assembled
> for Thumb and still wrk as expected. :)
>
> Do you have a list of source files which still build for ARM under
> CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
> consistence, except probably... exception :) entry points -- and even
> these should be able to run in full Thumb 2.

No I don't have a list, but it might be all assembler files. I don't
see why cro0.S would be special.

Regards,
Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Simon,

On Sat, 15 Nov 2014 15:10:47 -0700, Simon Glass <sjg@chromium.org>
wrote:
> Hi Albert,
> 
> On 15 November 2014 05:30, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
> > Hello Simon,
> >
> > On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
> > wrote:
> >
> >> > I believe you've built crt0.S for ARM, not Thumb.
> >>
> >> Yes, but I suspect that is a function of the build system. I checked
> >> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
> >> suppose we could use Thumb 2 for crt0.S if all the instructions are
> >> supported.
> >
> > Ok. Just in case, I'll run a check on whether crt0.S can be assembled
> > for Thumb and still wrk as expected. :)
> >
> > Do you have a list of source files which still build for ARM under
> > CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
> > consistence, except probably... exception :) entry points -- and even
> > these should be able to run in full Thumb 2.
> 
> No I don't have a list, but it might be all assembler files. I don't
> see why cro0.S would be special.

Ok, so after some research, .S files voluntarily not assembled in Thumb
mode when -mthumb is defined in gcc because of this:

Answer: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27237

(summary: -mthumb for gcc means 'use thumb2', while it means 'use
dumb, 16-bit, thumb1' for GNU as, so this option is voluntarily not
passed on to GNU as. You have to use .thumb in the .S file instead.) 

Second: getting a successful, though quick'n'dirty, build with vectors.S
assembled in Thumb-2 mode needed surprisingly little change in
vectors.S. I tried this with mx53loco, and it only required:

	- adding '.syntax unified';

	- adding a .thumb directive -- *after* the vectors per se, which
	  must still be assembled in ARM mode because current hardware
	  always executes exceptions vectors in ARM mode (1);

	- using '.balign' instead of '.balignl' which causes the
	  assembler to complain that it cannot fit an integer
	  number of '0xdeadbeef' in the filling space;

	- making macro get_bad_stack use lr instead of r13, which
	  Thumb does not allow in 'msr spsr,' instructions;

	- adding '.thumb_func' to all routines so that the linker makes
	  all references to them odd and therefore, cause the CPU to
	  enforce Thumb mode when branching to them.

	(1) although you *could* produce an ARM-based SoC that runs in
	Thumb mode by default. In this case, you'd have to make the
	vectors themselves Thumb too.

Third: getting a successful *run* of the resulting file will require
some work which I'm not going to do without a good incentive :) -- and
so does producing a clean vectors.S, i.e. one which will assemble
correctly for both ARM and Thumb.

> Regards,
> Simon

Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Simon Glass]

Hi Albert,

On 16 November 2014 07:50, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
> Hello Simon,
>
> On Sat, 15 Nov 2014 15:10:47 -0700, Simon Glass <sjg@chromium.org>
> wrote:
>> Hi Albert,
>>
>> On 15 November 2014 05:30, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>> > Hello Simon,
>> >
>> > On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
>> > wrote:
>> >
>> >> > I believe you've built crt0.S for ARM, not Thumb.
>> >>
>> >> Yes, but I suspect that is a function of the build system. I checked
>> >> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
>> >> suppose we could use Thumb 2 for crt0.S if all the instructions are
>> >> supported.
>> >
>> > Ok. Just in case, I'll run a check on whether crt0.S can be assembled
>> > for Thumb and still wrk as expected. :)
>> >
>> > Do you have a list of source files which still build for ARM under
>> > CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
>> > consistence, except probably... exception :) entry points -- and even
>> > these should be able to run in full Thumb 2.
>>
>> No I don't have a list, but it might be all assembler files. I don't
>> see why cro0.S would be special.
>
> Ok, so after some research, .S files voluntarily not assembled in Thumb
> mode when -mthumb is defined in gcc because of this:
>
> Answer: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27237
>
> (summary: -mthumb for gcc means 'use thumb2', while it means 'use
> dumb, 16-bit, thumb1' for GNU as, so this option is voluntarily not
> passed on to GNU as. You have to use .thumb in the .S file instead.)
>
> Second: getting a successful, though quick'n'dirty, build with vectors.S
> assembled in Thumb-2 mode needed surprisingly little change in
> vectors.S. I tried this with mx53loco, and it only required:
>
>         - adding '.syntax unified';
>
>         - adding a .thumb directive -- *after* the vectors per se, which
>           must still be assembled in ARM mode because current hardware
>           always executes exceptions vectors in ARM mode (1);
>
>         - using '.balign' instead of '.balignl' which causes the
>           assembler to complain that it cannot fit an integer
>           number of '0xdeadbeef' in the filling space;
>
>         - making macro get_bad_stack use lr instead of r13, which
>           Thumb does not allow in 'msr spsr,' instructions;
>
>         - adding '.thumb_func' to all routines so that the linker makes
>           all references to them odd and therefore, cause the CPU to
>           enforce Thumb mode when branching to them.
>
>         (1) although you *could* produce an ARM-based SoC that runs in
>         Thumb mode by default. In this case, you'd have to make the
>         vectors themselves Thumb too.
>
> Third: getting a successful *run* of the resulting file will require
> some work which I'm not going to do without a good incentive :) -- and
> so does producing a clean vectors.S, i.e. one which will assemble
> correctly for both ARM and Thumb.

That doesn't sound too trciky, but I agree it's not a huge deal. I
suppose the main benefit is consistency, since the code size
improvement would be small.

Regards,
Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Victor Ascroft]

On Monday 17 November 2014 11:58 AM, Simon Glass wrote:
> Hi Albert,
>
> On 16 November 2014 07:50, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>> Hello Simon,
>>
>> On Sat, 15 Nov 2014 15:10:47 -0700, Simon Glass <sjg@chromium.org>
>> wrote:
>>> Hi Albert,
>>>
>>> On 15 November 2014 05:30, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>>>> Hello Simon,
>>>>
>>>> On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
>>>> wrote:
>>>>
>>>>>> I believe you've built crt0.S for ARM, not Thumb.
>>>>> Yes, but I suspect that is a function of the build system. I checked
>>>>> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
>>>>> suppose we could use Thumb 2 for crt0.S if all the instructions are
>>>>> supported.
>>>> Ok. Just in case, I'll run a check on whether crt0.S can be assembled
>>>> for Thumb and still wrk as expected. :)
>>>>
>>>> Do you have a list of source files which still build for ARM under
>>>> CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
>>>> consistence, except probably... exception :) entry points -- and even
>>>> these should be able to run in full Thumb 2.
>>> No I don't have a list, but it might be all assembler files. I don't
>>> see why cro0.S would be special.
>> Ok, so after some research, .S files voluntarily not assembled in Thumb
>> mode when -mthumb is defined in gcc because of this:
>>
>> Answer: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27237
>>
>> (summary: -mthumb for gcc means 'use thumb2', while it means 'use
>> dumb, 16-bit, thumb1' for GNU as, so this option is voluntarily not
>> passed on to GNU as. You have to use .thumb in the .S file instead.)
>>
>> Second: getting a successful, though quick'n'dirty, build with vectors.S
>> assembled in Thumb-2 mode needed surprisingly little change in
>> vectors.S. I tried this with mx53loco, and it only required:
>>
>>         - adding '.syntax unified';
>>
>>         - adding a .thumb directive -- *after* the vectors per se, which
>>           must still be assembled in ARM mode because current hardware
>>           always executes exceptions vectors in ARM mode (1);
>>
>>         - using '.balign' instead of '.balignl' which causes the
>>           assembler to complain that it cannot fit an integer
>>           number of '0xdeadbeef' in the filling space;
>>
>>         - making macro get_bad_stack use lr instead of r13, which
>>           Thumb does not allow in 'msr spsr,' instructions;
>>
>>         - adding '.thumb_func' to all routines so that the linker makes
>>           all references to them odd and therefore, cause the CPU to
>>           enforce Thumb mode when branching to them.
>>
>>         (1) although you *could* produce an ARM-based SoC that runs in
>>         Thumb mode by default. In this case, you'd have to make the
>>         vectors themselves Thumb too.
>>
>> Third: getting a successful *run* of the resulting file will require
>> some work which I'm not going to do without a good incentive :) -- and
>> so does producing a clean vectors.S, i.e. one which will assemble
>> correctly for both ARM and Thumb.
So to use the thumb build correctly, all the .S files have to be changed to use
thumb instructions, by specifying the .thumb option?

-Regards,
Victor.

> That doesn't sound too trciky, but I agree it's not a huge deal. I
> suppose the main benefit is consistency, since the code size
> improvement would be small.
>
> Regards,
> Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Simon Glass]

Hi Victor,

On 18 November 2014 03:32, Victor Ascroft <victorascroft@gmail.com> wrote:
>
> On Monday 17 November 2014 11:58 AM, Simon Glass wrote:
>> Hi Albert,
>>
>> On 16 November 2014 07:50, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>>> Hello Simon,
>>>
>>> On Sat, 15 Nov 2014 15:10:47 -0700, Simon Glass <sjg@chromium.org>
>>> wrote:
>>>> Hi Albert,
>>>>
>>>> On 15 November 2014 05:30, Albert ARIBAUD <albert.u.boot@aribaud.net> wrote:
>>>>> Hello Simon,
>>>>>
>>>>> On Fri, 14 Nov 2014 18:56:07 -0700, Simon Glass <sjg@chromium.org>
>>>>> wrote:
>>>>>
>>>>>>> I believe you've built crt0.S for ARM, not Thumb.
>>>>>> Yes, but I suspect that is a function of the build system. I checked
>>>>>> the rest of U-Boot and most of it (including SPL) is Thumb 2. I
>>>>>> suppose we could use Thumb 2 for crt0.S if all the instructions are
>>>>>> supported.
>>>>> Ok. Just in case, I'll run a check on whether crt0.S can be assembled
>>>>> for Thumb and still wrk as expected. :)
>>>>>
>>>>> Do you have a list of source files which still build for ARM under
>>>>> CONFIG_SYS_THUMB_BUILD? I' would prefer all of the code to be thumb for
>>>>> consistence, except probably... exception :) entry points -- and even
>>>>> these should be able to run in full Thumb 2.
>>>> No I don't have a list, but it might be all assembler files. I don't
>>>> see why cro0.S would be special.
>>> Ok, so after some research, .S files voluntarily not assembled in Thumb
>>> mode when -mthumb is defined in gcc because of this:
>>>
>>> Answer: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27237
>>>
>>> (summary: -mthumb for gcc means 'use thumb2', while it means 'use
>>> dumb, 16-bit, thumb1' for GNU as, so this option is voluntarily not
>>> passed on to GNU as. You have to use .thumb in the .S file instead.)
>>>
>>> Second: getting a successful, though quick'n'dirty, build with vectors.S
>>> assembled in Thumb-2 mode needed surprisingly little change in
>>> vectors.S. I tried this with mx53loco, and it only required:
>>>
>>>         - adding '.syntax unified';
>>>
>>>         - adding a .thumb directive -- *after* the vectors per se, which
>>>           must still be assembled in ARM mode because current hardware
>>>           always executes exceptions vectors in ARM mode (1);
>>>
>>>         - using '.balign' instead of '.balignl' which causes the
>>>           assembler to complain that it cannot fit an integer
>>>           number of '0xdeadbeef' in the filling space;
>>>
>>>         - making macro get_bad_stack use lr instead of r13, which
>>>           Thumb does not allow in 'msr spsr,' instructions;
>>>
>>>         - adding '.thumb_func' to all routines so that the linker makes
>>>           all references to them odd and therefore, cause the CPU to
>>>           enforce Thumb mode when branching to them.
>>>
>>>         (1) although you *could* produce an ARM-based SoC that runs in
>>>         Thumb mode by default. In this case, you'd have to make the
>>>         vectors themselves Thumb too.
>>>
>>> Third: getting a successful *run* of the resulting file will require
>>> some work which I'm not going to do without a good incentive :) -- and
>>> so does producing a clean vectors.S, i.e. one which will assemble
>>> correctly for both ARM and Thumb.
> So to use the thumb build correctly, all the .S files have to be changed to use
> thumb instructions, by specifying the .thumb option?

No this is purely an optional idea. For me, the current Thumb support
works fine on Exynos 54xx (which is Cortex A7/A15). The issue you are
seeing may be specific to the A5 CPU, or your platform/toolchain. You
could perhaps try a newer toolchain (e.g. linaro). crt0.S does not
need to be in Thumb code. You could also check that -mthumb-interwork
is defined correctly. You can use 'make V=1 ...' to see full verbose
output. You could also disassemble the code sequence as I did to check
it.

I am assuming you have changed nothing else between building with Thumb and ARM.

Regards,
Simon

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Stefan Agner]

On 2014-11-14 15:01, Simon Glass wrote:
> Hi Victor,
> 
> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>> Hello,
>>
>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>>
>> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>>
>> In crt0.S
>> bl debug_print
>> ldr pc, =board_init_r
>>
>> In board_init_r
>> puts("In board_init_r\n"); // Right at start
>>
>> void debug_print(void)
>> {
>>     // Defined in board file
>>     puts("Debug print\n");
>> }
>>
>> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>>
>> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>> ldr r3, =board_init_r
>> add r3, #1
>> bx r3
>>
>> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>>
>> Any pointers?
> 
> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
> for me. The code sequence you refer to came out as below for me.
> 
> 23e01e10 <clbss_l>:
> 23e01e10:       e1500001        cmp     r0, r1
> 23e01e14:       35802000        strcc   r2, [r0]
> 23e01e18:       32800004        addcc   r0, r0, #4
> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
> 23e01e28:       e1a00009        mov     r0, r9
> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
> <clbss_l+0x30>
> 23e01e34:       02073800        .word   0x02073800
> 23e01e38:       23e41eb0        .word   0x23e41eb0
> 23e01e3c:       23e77bf0        .word   0x23e77bf0
> 23e01e40:       23e057a9        .word   0x23e057a9
> 
> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
> 
> What toolchain are you using? I tried with gcc 4.8.2 - including
> linaro's 2013.10 release.
> 
> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
> armv7-a, and this may cause it to generate Thumb code instead of Thumb
> 2. But you should get errors if that happens.
> 
> It's hard to debug with such limited visibility. But if I put a puts()
> at the start of board_init_r(), I see it on the serial console.
> 

Just checked that on Vybrid, it actually looks good too:

3f408f58 <clbss_l>:
3f408f58:	e1500001 	cmp	r0, r1
3f408f5c:	35802000 	strcc	r2, [r0]
3f408f60:	32800004 	addcc	r0, r0, #4
3f408f64:	3afffffb 	bcc	3f408f58 <clbss_l>
3f408f68:	fb000da8 	blx	3f40c612 <coloured_LED_init>
3f408f6c:	fa000da8 	blx	3f40c614 <red_led_on>
3f408f70:	e1a00009 	mov	r0, r9
3f408f74:	e599102c 	ldr	r1, [r9, #44]	; 0x2c
3f408f78:	e59ff008 	ldr	pc, [pc, #8]	; 3f408f88 <clbss_l+0x30>
3f408f7c:	3f07ff50 	.word	0x3f07ff50
3f408f80:	3f44c9d0 	.word	0x3f44c9d0
3f408f84:	3f482fc0 	.word	0x3f482fc0
3f408f88:	3f40c7c5 	.word	0x3f40c7c5

According to the map, this is the address of board_init_r
 .text.board_init_r                                                     
        
                0x000000003f40c7c4       0x10 common/built-in.o         
                                
                0x000000003f40c7c4                board_init_r

Currently I use GCC from a old Yocto/Angstrom build linger around. It's
a Linaro 2013.09 GCC 4.7.4.

I will have a look into it what exactly happens here.

--
Stefan


> Regards,
> Simon
> _______________________________________________
> U-Boot mailing list
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[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Stefan Agner]

On 2014-11-14 15:01, Simon Glass wrote:
> Hi Victor,
> 
> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>> Hello,
>>
>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>>
>> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>>
>> In crt0.S
>> bl debug_print
>> ldr pc, =board_init_r
>>
>> In board_init_r
>> puts("In board_init_r\n"); // Right at start
>>
>> void debug_print(void)
>> {
>>     // Defined in board file
>>     puts("Debug print\n");
>> }
>>
>> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>>
>> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>> ldr r3, =board_init_r
>> add r3, #1
>> bx r3
>>
>> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>>
>> Any pointers?
> 
> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
> for me. The code sequence you refer to came out as below for me.
> 
> 23e01e10 <clbss_l>:
> 23e01e10:       e1500001        cmp     r0, r1
> 23e01e14:       35802000        strcc   r2, [r0]
> 23e01e18:       32800004        addcc   r0, r0, #4
> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
> 23e01e28:       e1a00009        mov     r0, r9
> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
> <clbss_l+0x30>
> 23e01e34:       02073800        .word   0x02073800
> 23e01e38:       23e41eb0        .word   0x23e41eb0
> 23e01e3c:       23e77bf0        .word   0x23e77bf0
> 23e01e40:       23e057a9        .word   0x23e057a9
> 
> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
> 
> What toolchain are you using? I tried with gcc 4.8.2 - including
> linaro's 2013.10 release.
> 
> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
> armv7-a, and this may cause it to generate Thumb code instead of Thumb
> 2. But you should get errors if that happens.
> 
> It's hard to debug with such limited visibility. But if I put a puts()
> at the start of board_init_r(), I see it on the serial console.

Ok, turns out the problem with Thumb2 only appear when using
CONFIG_USE_ARCH_MEMCPY (hence added Matthias to CC). Does peach_pi still
works with that config enabled? On the Vybrid board we use that to speed
up NAND access, with the current NAND driver, data get copied by the
CPU.

In setup_reloc, common/board_f.c, probably the first use of memcpy,
things started to get weird. The code after memcpy doesn't get executed,
I think something with the stack goes wrong, but not really sure what
happens.

--
Stefan

> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Stefan Agner]

On 2014-11-18 17:07, Stefan Agner wrote:
> On 2014-11-14 15:01, Simon Glass wrote:
>> Hi Victor,
>>
>> On 13 November 2014 09:29, Victor Ascroft <victorascroft@gmail.com> wrote:
>>> Hello,
>>>
>>> I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
>>>
>>> After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
>>>
>>> In crt0.S
>>> bl debug_print
>>> ldr pc, =board_init_r
>>>
>>> In board_init_r
>>> puts("In board_init_r\n"); // Right at start
>>>
>>> void debug_print(void)
>>> {
>>>     // Defined in board file
>>>     puts("Debug print\n");
>>> }
>>>
>>> My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
>>>
>>> An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below
>>> ldr r3, =board_init_r
>>> add r3, #1
>>> bx r3
>>>
>>> No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
>>>
>>> Any pointers?
>>
>> I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK
>> for me. The code sequence you refer to came out as below for me.
>>
>> 23e01e10 <clbss_l>:
>> 23e01e10:       e1500001        cmp     r0, r1
>> 23e01e14:       35802000        strcc   r2, [r0]
>> 23e01e18:       32800004        addcc   r0, r0, #4
>> 23e01e1c:       3afffffb        bcc     23e01e10 <clbss_l>
>> 23e01e20:       fa000dec        blx     23e055d8 <coloured_LED_init>
>> 23e01e24:       fb000deb        blx     23e055da <red_led_on>
>> 23e01e28:       e1a00009        mov     r0, r9
>> 23e01e2c:       e5991030        ldr     r1, [r9, #48]   ; 0x30
>> 23e01e30:       e59ff008        ldr     pc, [pc, #8]    ; 23e01e40
>> <clbss_l+0x30>
>> 23e01e34:       02073800        .word   0x02073800
>> 23e01e38:       23e41eb0        .word   0x23e41eb0
>> 23e01e3c:       23e77bf0        .word   0x23e77bf0
>> 23e01e40:       23e057a9        .word   0x23e057a9
>>
>> The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
>>
>> What toolchain are you using? I tried with gcc 4.8.2 - including
>> linaro's 2013.10 release.
>>
>> In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from
>> armv7-a, and this may cause it to generate Thumb code instead of Thumb
>> 2. But you should get errors if that happens.
>>
>> It's hard to debug with such limited visibility. But if I put a puts()
>> at the start of board_init_r(), I see it on the serial console.
> 
> Ok, turns out the problem with Thumb2 only appear when using
> CONFIG_USE_ARCH_MEMCPY (hence added Matthias to CC). Does peach_pi still
> works with that config enabled? On the Vybrid board we use that to speed
> up NAND access, with the current NAND driver, data get copied by the
> CPU.
> 
> In setup_reloc, common/board_f.c, probably the first use of memcpy,
> things started to get weird. The code after memcpy doesn't get executed,
> I think something with the stack goes wrong, but not really sure what
> happens.

It seems that this memcpy implementation is not able to be run in ARM
mode when called from Thumb2 code. Checked the Linux kernel, since
that's where that file comes from, they compile a Thumb2 version of that
file when compiling the kernel in Thumb2 mode.  With some changes I also
managed to compile that file in Thumb2 in U-Boot:

diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index f0eafd6..ddbc8dc 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -30,6 +30,8 @@ PF_CPPFLAGS_ARM := $(call cc-option, -mthumb
-mthumb-interwork,\
 			$(call cc-option,-marm,)\
 			$(call cc-option,-mno-thumb-interwork,)\
 		)
+AFLAGS_AUTOIT	:=$(call
as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it)
+PF_CPPFLAGS_ARM += $(AFLAGS_AUTOIT)
 else
 PF_CPPFLAGS_ARM := $(call cc-option,-marm,) \
 		$(call cc-option,-mno-thumb-interwork,)
diff --git a/arch/arm/lib/memcpy.S b/arch/arm/lib/memcpy.S
index f655256..fcf028c 100644
--- a/arch/arm/lib/memcpy.S
+++ b/arch/arm/lib/memcpy.S
@@ -12,11 +12,14 @@
 
 #include <asm/assembler.h>
 
-#define W(instr)	instr
+#define W(instr)	instr.w
 
 #define LDR1W_SHIFT	0
 #define STR1W_SHIFT	0
 
+#define CALGN(code...)
+
+
 	.macro ldr1w ptr reg abort
 	W(ldr) \reg, [\ptr], #4
 	.endm
@@ -57,12 +60,15 @@
 
 /* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
 
+	.syntax unified
+	.thumb
+	.thumb_func
 .globl memcpy
 memcpy:
-
+/*
 		cmp	r0, r1
 		moveq	pc, lr
-
+*/
 		enter	r4, lr
 
 		subs	r2, r2, #4
diff --git a/include/configs/colibri_vf.h b/include/configs/colibri_vf.h
index 76564ac..41a0dac 100644
--- a/include/configs/colibri_vf.h
+++ b/include/configs/colibri_vf.h
@@ -53,7 +53,10 @@
 #define CONFIG_CMD_NAND
 #define CONFIG_NAND_VF610_NFC
 #define CONFIG_SYS_NAND_SELF_INIT
+
+#define CONFIG_SYS_THUMB_BUILD
 #define CONFIG_USE_ARCH_MEMCPY
+
 #define CONFIG_SYS_MAX_NAND_DEVICE	1
 #define CONFIG_SYS_NAND_BASE		NFC_BASE_ADDR
 

The main change here is the implicit-it/auto-it functionality. For me it
works when enabling that globally. Is it harmful to enable that
globally? The other changes need a proper ifdef, but should be ok I
guess.

--
Stefan

> 
> --
> Stefan
> 
>> _______________________________________________
>> U-Boot mailing list
>> U-Boot at lists.denx.de
>> http://lists.denx.de/mailman/listinfo/u-boot
> 
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Stefan,

On Tue, 18 Nov 2014 19:37:18 +0100, Stefan Agner <stefan@agner.ch>
wrote:

> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> index f0eafd6..ddbc8dc 100644
> --- a/arch/arm/config.mk
> +++ b/arch/arm/config.mk
> @@ -30,6 +30,8 @@ PF_CPPFLAGS_ARM := $(call cc-option, -mthumb
> -mthumb-interwork,\
>  			$(call cc-option,-marm,)\
>  			$(call cc-option,-mno-thumb-interwork,)\
>  		)
> +AFLAGS_AUTOIT	:=$(call
> as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it)
> +PF_CPPFLAGS_ARM += $(AFLAGS_AUTOIT)
>  else
>  PF_CPPFLAGS_ARM := $(call cc-option,-marm,) \
>  		$(call cc-option,-mno-thumb-interwork,)

> The main change here is the implicit-it/auto-it functionality. For me it
> works when enabling that globally. Is it harmful to enable that
> globally? The other changes need a proper ifdef, but should be ok I
> guess.

-mimplicit-it=always will have no effect on ARM builds as it defaults
to 'arm', meaning that IT instructions are already optional in ARM
mode, and switching to 'always' changes the behavior only for Thumb
mode.

For -mauto-it, it is not documented in the gas documentation online or
in my current as' --target-help. I'll dig this deeper today, but barring
any scream from me, the change above is fine globally in U-Boot.

> --
> Stefan

Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Wolfgang Denk]

Dear Albert,

In message <20141119074214.3d414ce6@lilith> you wrote:
> 
> For -mauto-it, it is not documented in the gas documentation online or
> in my current as' --target-help. I'll dig this deeper today, but barring
> any scream from me, the change above is fine globally in U-Boot.

Apparently this [1] is where it is coming from; no further
documentation there, though.

[1] https://sourceware.org/ml/binutils/2009-05/msg00132.html

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"If people are good only because they fear punishment, and  hope  for
reward, then we are a sorry lot indeed."            - Albert Einstein

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Bill Pringlemeir]

On 19 Nov 2014, wd at denx.de wrote:

> Dear Albert,
>
> In message <20141119074214.3d414ce6@lilith> you wrote:
>>
>> For -mauto-it, it is not documented in the gas documentation online
>> or in my current as' --target-help. I'll dig this deeper today, but
>> barring any scream from me, the change above is fine globally in
>> U-Boot.

> Apparently this [1] is where it is coming from; no further
> documentation there, though.

> [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html

I would think that if this worked they would make it automatic and not
an option.  Probably this is only in certain binutils/as.

With 4.6.3 and 4.9.1 I do not have this option,

[foo.S]
.syntax unified
.thumb
foo:
   cmp r0, #5
   movne r1,#6
   moveq r1,#2
   bx lr
bar:
   cmp r0, #10
   movhi r1,#3
   movls r1,#7
   moveq r1,#11
   bx lr

$ arm-none-linux-gnueabi.gcc4.6.3/bin/arm-none-linux-gnueabi-as
-mcpu=cortex-a5 -mimplicit-it=always foo.S -o foo.o
$ arm-none-linux-gnueabi-vybrid-4.9.1/bin/arm-none-linux-gnueabi-as
-mcpu=cortex-a5 -mimplicit-it=always foo.S -o foo.o

Both give 'objdump -S foo.o',
foo.o:     file format elf32-littlearm

Disassembly of section .text:

00000000 <foo>:
   0:   2805            cmp     r0, #5
   2:   bf14            ite     ne
   4:   2106            movne   r1, #6
   6:   2102            moveq   r1, #2
   8:   4770            bx      lr

0000000a <bar>:
   a:   280a            cmp     r0, #10
   c:   bf8c            ite     hi
   e:   2103            movhi   r1, #3
  10:   2107            movls   r1, #7
  12:   bf08            it      eq
  14:   210b            moveq   r1, #11
  16:   4770            bx      lr

I think before the patch there would be 'it' values before each and
every condition.  In fact, if you change 'bar' to,

bar:
   cmp r0, #10
   movhi r1,#3
   movlo r1,#7
   moveq r1,#11
   bx lr

You get three 'IT' conditions as 'HI' and 'LO' are not opposite.  The
patch seem to detect things that are the exact opposite.  The 'bar'
above ends up with '11' in r1 if the value is zero, but it temporarily
'7'.  The 2nd bar will only place 11 in r1.

Fwiw,
Bill Pringlemeir.

Ref: https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Conditional_Execution

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Bill,

On Wed, 19 Nov 2014 11:31:05 -0500, Bill Pringlemeir
<bpringlemeir@nbsps.com> wrote:
> On 19 Nov 2014, wd at denx.de wrote:
> 
> > Dear Albert,
> >
> > In message <20141119074214.3d414ce6@lilith> you wrote:
> >>
> >> For -mauto-it, it is not documented in the gas documentation online
> >> or in my current as' --target-help. I'll dig this deeper today, but
> >> barring any scream from me, the change above is fine globally in
> >> U-Boot.
> 
> > Apparently this [1] is where it is coming from; no further
> > documentation there, though.
> 
> > [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html
> 
> I would think that if this worked they would make it automatic and not
> an option.  Probably this is only in certain binutils/as.
> 
> With 4.6.3 and 4.9.1 I do not have this option,

Which option do you mean? -mimplicit-it or -mauto-it?

> [foo.S]
> .syntax unified
> .thumb
> foo:
>    cmp r0, #5
>    movne r1,#6
>    moveq r1,#2
>    bx lr
> bar:
>    cmp r0, #10
>    movhi r1,#3
>    movls r1,#7
>    moveq r1,#11
>    bx lr
> 
> $ arm-none-linux-gnueabi.gcc4.6.3/bin/arm-none-linux-gnueabi-as
> -mcpu=cortex-a5 -mimplicit-it=always foo.S -o foo.o
> $ arm-none-linux-gnueabi-vybrid-4.9.1/bin/arm-none-linux-gnueabi-as
> -mcpu=cortex-a5 -mimplicit-it=always foo.S -o foo.o
> 
> Both give 'objdump -S foo.o',
> foo.o:     file format elf32-littlearm
> 
> Disassembly of section .text:
> 
> 00000000 <foo>:
>    0:   2805            cmp     r0, #5
>    2:   bf14            ite     ne
>    4:   2106            movne   r1, #6
>    6:   2102            moveq   r1, #2
>    8:   4770            bx      lr
> 
> 0000000a <bar>:
>    a:   280a            cmp     r0, #10
>    c:   bf8c            ite     hi
>    e:   2103            movhi   r1, #3
>   10:   2107            movls   r1, #7
>   12:   bf08            it      eq
>   14:   210b            moveq   r1, #11
>   16:   4770            bx      lr
> 
> I think before the patch there would be 'it' values before each and
> every condition.  In fact, if you change 'bar' to,
> 
> bar:
>    cmp r0, #10
>    movhi r1,#3
>    movlo r1,#7
>    moveq r1,#11
>    bx lr
> 
> You get three 'IT' conditions as 'HI' and 'LO' are not opposite.  The
> patch seem to detect things that are the exact opposite.  The 'bar'
> above ends up with '11' in r1 if the value is zero, but it temporarily
> '7'.  The 2nd bar will only place 11 in r1.
> 
> Fwiw,
> Bill Pringlemeir.
> 
> Ref: https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Conditional_Execution

All this is about -mimplicit-it, which *is* documented, *is*
consistently present in common toolchains AFAICT and is and (as)
logcical (as it can be when dealing with backward compatibility of
command lines etc).

However, my problem is not with -mimplicit-it; it is with -mauto-it.

My gut feeling is that -mauto-it is a predecessor of -mimplicit-it.

Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Bill Pringlemeir]

>>> In message <20141119074214.3d414ce6@lilith> you^H^H^H Stefan wrote:

>>>> For -mauto-it, it is not documented in the gas documentation online
>>>> or in my current as' --target-help. I'll dig this deeper today, but
>>>> barring any scream from me, the change above is fine globally in
>>>> U-Boot.

>> On 19 Nov 2014, wd at denx.de wrote:

>>> Apparently this [1] is where it is coming from; no further
>>> documentation there, though.
>>
>>> [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html

> On Wed, 19 Nov 2014 11:31:05 -0500, Bill Pringlemeir

>> I would think that if this worked they would make it automatic and
>> not an option.  Probably this is only in certain binutils/as.
>>
>> With 4.6.3 and 4.9.1 I do not have this option,


On 19 Nov 2014, albert.u.boot at aribaud.net wrote:

> Which option do you mean? -mimplicit-it or -mauto-it?

'-mauto-it' , which I think if it is working correctly would be rolled
into '-mimplicit-it' as it generates better code (for an assembler :).
I followed the thread above and the patch originator says he needs to
fix section issues and the 'command line options' and he would follow up
the proposed patch.

I guess at some version each and every '<inst>xx' was converted to 'it
xx\n<inst>' where <inst> is some conditional instruction.  For the patch
above, '-mauto-it' teaches the assembler to glob them together into
'itet...'  type conditions.  The Thumb2 supports up to four conditions
(and negated condition) instructions.

On my version of the tools (I think it is gcc; but maybe binutils), if I
use '-mauto-it' it gives an unknown option error.  I think that Linux
does a probe of this feature and passes it (-mauto-it) if the assembler
accepts it.  So, if we add to u-boot we should probably take care that
the ARM 'as' can take the option.  I also see posts on the web of people
complaining of this option in other code bases.

Fwiw,
Bill.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Bill,

On Wed, 19 Nov 2014 13:34:34 -0500, Bill Pringlemeir
<bpringlemeir@nbsps.com> wrote:
> 
> 
> >>> In message <20141119074214.3d414ce6@lilith> you^H^H^H Stefan wrote:
> 
> >>>> For -mauto-it, it is not documented in the gas documentation online
> >>>> or in my current as' --target-help. I'll dig this deeper today, but
> >>>> barring any scream from me, the change above is fine globally in
> >>>> U-Boot.
> 
> >> On 19 Nov 2014, wd at denx.de wrote:
> 
> >>> Apparently this [1] is where it is coming from; no further
> >>> documentation there, though.
> >>
> >>> [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html
> 
> > On Wed, 19 Nov 2014 11:31:05 -0500, Bill Pringlemeir
> 
> >> I would think that if this worked they would make it automatic and
> >> not an option.  Probably this is only in certain binutils/as.
> >>
> >> With 4.6.3 and 4.9.1 I do not have this option,
> 
> 
> On 19 Nov 2014, albert.u.boot at aribaud.net wrote:
> 
> > Which option do you mean? -mimplicit-it or -mauto-it?
> 
> '-mauto-it' , which I think if it is working correctly would be rolled
> into '-mimplicit-it' as it generates better code (for an assembler :).
> I followed the thread above and the patch originator says he needs to
> fix section issues and the 'command line options' and he would follow up
> the proposed patch.

I am getting lost, even when reading (quickly, I admit) the patch that
adds it; I don't see what -mauto-it does exactly. Can you summarize
and clarify the effects of -mimplicit-it (I guess I know this one but
it's never a bad thing to get a second opinion), -mauto-it and their
interaction?

> I guess at some version each and every '<inst>xx' was converted to 'it
> xx\n<inst>' where <inst> is some conditional instruction.  For the patch
> above, '-mauto-it' teaches the assembler to glob them together into
> 'itet...'  type conditions.  The Thumb2 supports up to four conditions
> (and negated condition) instructions.
> 
> On my version of the tools (I think it is gcc; but maybe binutils), if I
> use '-mauto-it' it gives an unknown option error.  I think that Linux
> does a probe of this feature and passes it (-mauto-it) if the assembler
> accepts it.  So, if we add to u-boot we should probably take care that
> the ARM 'as' can take the option.  I also see posts on the web of people
> complaining of this option in other code bases.

Are they complaining that the option is passed on to an as which does
not know it, or that the option is known but does something wrong?

(I'm still having a hard time understanding whether -mauto-it is an
accepted new feature that is slow to get integrated or the remnant of
an old proposal which did not make it.)

> Fwiw,
> Bill.

Amicalement,
-- 
Albert.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Bill Pringlemeir]

> On Wed, 19 Nov 2014 13:34:34 -0500, Bill Pringlemeir
> <bpringlemeir@nbsps.com> wrote:

>>>>> In message <20141119074214.3d414ce6@lilith> Albert wrote:

>>>>>> For -mauto-it, it is not documented in the gas documentation
>>>>>> online or in my current as' --target-help. I'll dig this deeper
>>>>>> today, but barring any scream from me, the change above is fine
>>>>>> globally in U-Boot.

>>>> On 19 Nov 2014, wd at denx.de wrote:
>>
>>>>> Apparently this [1] is where it is coming from; no further
>>>>> documentation there, though.
>>>>
>>>>> [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html
>>
>>> On Wed, 19 Nov 2014 11:31:05 -0500, Bill Pringlemeir
>>
>>>> I would think that if this worked they would make it automatic and
>>>> not an option.  Probably this is only in certain binutils/as.

>>>> With 4.6.3 and 4.9.1 I do not have this option,

>> On 19 Nov 2014, albert.u.boot at aribaud.net wrote:

>>> Which option do you mean? -mimplicit-it or -mauto-it?

>> '-mauto-it' , which I think if it is working correctly would be
>> rolled into '-mimplicit-it' as it generates better code (for an
>> assembler :).  I followed the thread above and the patch originator
>> says he needs to fix section issues and the 'command line options'
>> and he would follow up the proposed patch.

On 20 Nov 2014, albert.u.boot at aribaud.net wrote:

> I am getting lost, even when reading (quickly, I admit) the patch that
> adds it; I don't see what -mauto-it does exactly. Can you summarize
> and clarify the effects of -mimplicit-it (I guess I know this one but
> it's never a bad thing to get a second opinion), -mauto-it and their
> interaction?

I guess you know how the 'IT' works.  The Ubuntu/Debian people give a
good explanation in a few paragraphs,

 https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Conditional_Execution

My trying to explain this may have confused thing...

Here is Wolfgang's reference,

 https://sourceware.org/ml/binutils/2009-05/msg00132.html

Here is a 2nd reference,

 https://sourceware.org/ml/binutils/2009-06/msg00162.html

Originally Daniel Gutson used '-mauto-it' and then it was converted to
'-mimplicit-it'.

I am not sure if '-mauto-it' exists in the wild.  I have never heard of
that option before seeing this email thread. Also my assembler says,

   Assembler messages:
   Error: unrecognized option -mauto-it

I have built with the most recent binutils, gcc4.9.1 using crosstool-ng.
Maybe only some non-mainline tools picked up this '-mauto-it' patch.  I
don't think it hurts to support '-mauto-it', but an assembler test
should be done to see if it accepts the option.

hth,
Bill Pringlemeir.

[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Bill,

On Thu, 20 Nov 2014 11:34:45 -0500, Bill Pringlemeir
<bpringlemeir@nbsps.com> wrote:

> Originally Daniel Gutson used '-mauto-it' and then it was converted to
> '-mimplicit-it'.

Ok, so I was right in my gut(son)[1] feeling that -mauto-it was a
predecessor of -mimplicit-it -- and actually only in the first
iteration(s) of the patch that would have introduced it.

> I am not sure if '-mauto-it' exists in the wild.  I have never heard of
> that option before seeing this email thread. Also my assembler says,
> 
>    Assembler messages:
>    Error: unrecognized option -mauto-it
> 
> I have built with the most recent binutils, gcc4.9.1 using crosstool-ng.
> Maybe only some non-mainline tools picked up this '-mauto-it' patch.  I
> don't think it hurts to support '-mauto-it', but an assembler test
> should be done to see if it accepts the option.

I've gone through the binutils git tree, and -mauto-it is mentioned
only in a patch that fixes the gas /docs/ which erroneously mentioned
-mauto-it where it should have mentioned -mimplicit-it.

Hence, I think we should not test for -mauto-it at all, and not
mention it even.

Stefan, can you resubmit without the -mauto-it part, and renaming
AFLAGS_AUTOIT into AFLAGS_IMPLICIT_IT?

> hth,
> Bill Pringlemeir.

Amicalement,
-- 
Albert.
[1] I am never ashamed of doing lame puns.