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armcc problem?
Ric Peregrino
over 12 years ago
Note: This was originally posted on 20th April 2009 at
http://forums.arm.com
Hello,
We're using armcc here version:
ARM/Thumb C/C++ Compiler, RVCT3.1 [Build 739]
And it seems to have an issue. Here's some simple c-code:
main () {
volatile unsigned int tmp32;
printf ("GPIO: 1_reset: before\n");
// touch tb_gpio
*(unsigned int *)(0x50000004) = 0x12345678;
tmp32 = *((volatile unsigned int *)(0x50000004));
printf ("GPIO: tmp32 = 0x%0x\n", tmp32);
printf ("GPIO: tmp32 = 0x%0x\n", tmp32);
if (tmp32 != 0x12345678) printf("FAIL: 1st tb_gpio WRV failed!\n");
Here's the resulting output:
# GPIO: 1_reset: before
# GPIO: tmp32 = 0x12345678
# GPIO: tmp32 = 0x0
# FAIL: 1st tb_gpio WRV failed!
Why is the 2nd printf of tmp32 different? Here's the disassembled code, and it seems that the first printf is printing not tmp32 which is in r4, but the literal that was written, which is in r6:
0x00040082: 4e2b +N LDR r6,[pc,#172] ; [0x40130] = 0x12345678
0x00040084: f04f45a0 O..E MOV r5,#0x50000000
0x00040088: 606e n` STR r6,[r5,#4]
0x0004008a: 686c lh LDR r4,[r5,#4]
0x0004008c: 4631 1F MOV r1,r6
0x0004008e: a029 ). ADR r0,{pc}+0xa6 ; 0x40134
0x00040090: f000fcf6 .... BL __0printf ; 0x40a80
0x00040094: 4621 !F MOV r1,r4
0x00040096: a027 '. ADR r0,{pc}+0x9e ; 0x40134
0x00040098: f000fcf2 .... BL __0printf ; 0x40a80
This make sense? Is this an armcc bug? If so, what next?
Cheers,
Ric Peregrino
Dust Networks
Ric Peregrino
over 12 years ago
Note: This was originally posted on 22nd April 2009 at
http://forums.arm.com
Downloaded and tried again with:
[rperegrino@hdev02 1_reset]$ armcc --vsn
ARM/Thumb C/C++ Compiler, RVCT3.1 [Build 794]
For support see [url="
http://www.arm.com/support/
"]
http://www.arm.com/support/[/url]
Software supplied by: ARM Limited
and got same result. Here's the invocation of the compiler and linker:
armcc -g -DVLOGTIME -DTIME -O3 -Otime --no_inline --cpu Cortex-M3 -c 1_reset.c -
o 1_reset.o
armcc -g -DVLOGTIME -DTIME -O3 -Otime --no_inline --cpu Cortex-M3 -c clib.c -o c
lib.o
"clib.c", line 66: Warning: #167-D: argument of type "unsigned char *" is incom
patible with parameter of type "char *"
sendchar(&tempch);
^
clib.c: 1 warning, 0 errors
armcc -g -DVLOGTIME -DTIME -O3 -Otime --no_inline --cpu Cortex-M3 -c exceptions.
c -o exceptions.o
armlink --info totals --symbols --inline \
--scatter cm3_code_on_codebus.scat \
--entry=__main --map \
--keep=exceptions.o\(exceptions_area\) \
1_reset.o clib.o exceptions.o\
--callgraph --elf -o 1_reset.elf > link.txt
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Samar Samar
over 12 years ago
Note: This was originally posted on 24th April 2009 at
http://forums.arm.com
Can you try to make tmp32 global and check the assembly? Also please make sure you can actually write and read back from 0x50000004 location.
The move from r6 to r1 may be because it does not think tmp32 to be volatile. In fact it did not even assign a memory location to tmp32.
Move from r4 to r1 looks correct to me but i am surprised to see 0 in the second line of output. That makes me think that the location 0x50000004 wasnt written to properly or is not read properly.
Another thing you can try is:
volatile unsigned int *loc = (volatile unsigned int *)0x50000004;
main () {
unsigned int tmp32;
printf ("GPIO: 1_reset: before\n");
// touch tb_gpio
*loc = 0x12345678;
tmp32 = *loc;
printf ("GPIO: tmp32 = 0x%0x\n", tmp32);
*loc = 0x87654321;
tmp32 = *loc;
printf ("GPIO: tmp32 = 0x%0x\n", tmp32);
if (tmp32 != 0x12345678) printf("FAIL: 1st tb_gpio WRV failed!\n");
Please share the findings.
Samar
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Peter Harris
over 12 years ago
Note: This was originally posted on 21st April 2009 at
http://forums.arm.com
That looks like a compiler bug to me - although I'm not a C spec expert...
Can you try patching RVCT to the latest patch level (3.1 Build 794) and see if the issue still occurs? There were some known issues with volatiles in builds at high optimization levels which have since been fixed.
The patch download can be found here: [url="
http://www.arm.com/support/downloads/RVDS_31.html
"]
http://www.arm.com/support/downloads/RVDS_31.html[/url]
If you still have a problem can you also post the compiler and linker command lines you used?
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Peter Harris
over 12 years ago
Note: This was originally posted on 22nd April 2009 at
http://forums.arm.com
Hi Ric,
My usual fixes for compiler bugs when no patch is available it to try a lower optimization level for the file in which the bug occurs, or try restructuring the code to see if it "goes away".
Splitting the known buggy function out into a separate file can reduce the impact of the lower optimization level, because the other code can still be compiled at -O3.
Raising the issue formally with ARM support (email
support@arm.com
) may be able to provide more information.
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