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armcc problem?
Offline
Ric Peregrino
over 7 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
Parents
Offline
Peter Harris
over 7 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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Peter Harris
over 7 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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