[Bug target/71053] [6/7 Regression] Volatile read optimized into endless loop

[Bug target/71053] [6/7 Regression] Volatile read optimized into endless loop

[bseifert at gmx dot at]

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71053

Berni <bseifert at gmx dot at> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bseifert at gmx dot at

--- Comment #3 from Berni <bseifert at gmx dot at> ---
I also reproduced the bug after building the avr gcc 6.1.0 tool chain.

if you wait for the ADC to complete a measurement, you use the following code:

while (ADCSRA & _BV(ADSC));

which looks like the following after the post processor:

while ((*(volatile uint8_t *)(0x7A)) & (1 << (6)));

which looks fine, but it compiles to:

    3c38:       80 91 7a 00     lds     r24, 0x007A
    3c3c:       80 74           andi    r24, 0x40       ; 64
    3c3e:       81 11           cpse    r24, r1
    3c40:       fe cf           rjmp    .-4             ; 0x3c3e <main+0x12>

this is an endless loop. It does not respect the volatile keyword.
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Date: Thu, 12 May 2016 09:51:00 -0000
From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
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To: RaghuShankar <mcsraghu@gmail.com>, gcc-bugs@gcc.gnu.org
Subject: Re: GCC 6.1.0 ARM cross compiling xgcc error not producing output file from .S files
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Hi,

On 12/05/16 10:46, RaghuShankar wrote:
> Hi,
>
> I am trying to cross compile the latest gcc 6.1.0 to arm architecture.
>
> At the end of libgcc compilation i am getting the error
> *"root/embeddedlinux/gcc/armcrosstool/arm-linux-gnueabi/bin/ar:
> _thumb1_case_sqi.o: No such file or directory"*
>
> *But when i cross checked libgcc compilation it has compiled the
> "_thumb1_case_sqi.dep" file and tried to create .o file but it is not? Hence
> the error.*
>
> /root/embeddedlinux/gcc/gcc-6.1.0/build/./gcc/xgcc
> -B/root/embeddedlinux/gcc/gcc-6.1.0/build/./gcc/
> -B/root/embeddedlinux/gcc/armcrosstool/arm-linux-gnueabi/bin/
> -B/root/embeddedlinux/gcc/armcrosstool/arm-linux-gnueabi/lib/ -isystem
> /root/embeddedlinux/gcc/armcrosstool/arm-linux-gnueabi/include -isystem
> /root/embeddedlinux/gcc/armcrosstool/arm-linux-gnueabi/sys-include    -g -O2
> -O2  -g -O2 -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE  -W -Wall -Wno-narrowing
> -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes
> -Wold-style-definition  -isystem ./include   -fPIC -fno-inline -g
> -DIN_LIBGCC2 -fbuilding-libgcc -fno-stack-protector -Dinhibit_libc  -fPIC
> -fno-inline   -DUSE_EMUTLS -o _thumb1_case_sqi.o -MT _thumb1_case_sqi.o -MD
> -MP -MF _thumb1_case_sqi.dep -DL_thumb1_case_sqi -xassembler-with-cpp -c
> ../../../libgcc/config/arm/lib1funcs.S -include _thumb1_case_sqi.vis
>
> For further error information please check the attached error file.
> gcc-6.txt <http://gcc.1065356.n5.nabble.com/file/n1262876/gcc-6.txt>
>
> If any body having solution please let us know.

This list is for the automatic emails generated by the GCC bug tracker.
It's unlikely that people will find your post.

Try gcc-help@gcc.gnu.org.

If you think you have found a bug in GCC please report it according to the
instructions at https://gcc.gnu.org/bugs/

Cheers,
Kyrill

> Thanking you
>
>
>
>
>
>
> --
> View this message in context: http://gcc.1065356.n5.nabble.com/GCC-6-1-0-ARM-cross-compiling-xgcc-error-not-producing-output-file-from-S-files-tp1262876.html
> Sent from the gcc - bugs mailing list archive at Nabble.com.
>