Impulse Support Forums > Translation error

Impulse Support Forums > Impulse Forums > Impulse C Support Forum

Curreri

Jul 15 2009, 01:16 PM

The block of code below is used to write to an array. There is an Impulse C translation mistake from source code to hardware. Upon inspection of the generated HDL, it is observed that Impulse-C performs an erroneous 5-bit comparison of c2 and c1 (line 4). The 64-bit comparison of 4294967286 > 4294967296 (which evaluates to false) becomes a 5-bit comparison of 22 > 0 (which evaluates to true), allowing the array address to become negative (line 4). In contrast, the simulator executing the source code on the CPU sets the address to zero (line 5).

CODE

1 co_uint64 c2, c1;
2 co_int32 address, array[20], out;
3 c2 = 4294967286; c1 = 4294967296;
4 if (c2 > c1) address = c2 - c1;
5 else address = 0;
6 out = user(address);

The code was executed on the XD1000 platform. Impulse-C version 3.30 and Quartus 8.1 was used.

RalphBodenner

Jul 21 2009, 03:41 PM

Thanks for the report, John. I'll try to reproduce this with the latest compiler release.

Regards,
Ralph

RalphBodenner

Aug 25 2009, 10:30 PM

Hi John,

This bug will be fixed in the upcoming 3.60 release.

Regards,
Ralph

This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.