topic Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I in Intel® Integrated Performance Primitives

ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

andybc — Mon, 19 Dec 2005 19:30:17 GMT

hello there.

im just a newbie with these cool libraries. im just wondering what could be possibly wrong when i encounter the above illegal instruction. im using the trial version of ipp v.5 and trying to run the application in pentium3 under wince .net 4.2.

any comments will be appreciated.

cheers!

andy

Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

abuatnext04 — Tue, 20 Dec 2005 16:11:53 GMT

have you use an aligned memory buffer to push your dct data into the ipp function ...

try to use aligned memory on 16-byte boundary with all optimized function ipp or other mmx/sse/sse2 optimized function,

it could be solve your issue

Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

Vladimir_Dudnik — Wed, 21 Dec 2005 00:57:51 GMT

Could you please provide simple test case to demostrate this wrong behaviour?

Regards,
Vladimir

Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

andybc — Wed, 21 Dec 2005 16:53:33 GMT

thanks for the comments. but the 16-bit allignment did not solve the problem. originally the code is bit alligned as it runs with other platforms. the same source code runs perfectly with a pentium 3 stepping 8 (can anybody tell me what is meant by this stepping nomenclature. :smileyhappy:) but with a pentium 3 stepping 3, it does not. both have the same os. wince .net 4.2.

the following is the dissassembly code in which the illegal instruction occurs. it stops at pshufw instruction. hope this helps to furtherly analyze the problem.

_a6_dct_8x8_inv_16s:
1E03C920 mov ecx,dword ptr [esp+4]
1E03C924 mov edx,dword ptr [esp+8]
1E03C928 movq mm0,mmword ptr [ecx]
1E03C92B movq mm1,mmword ptr [ecx+8]
1E03C92F movq mm2,mm0
1E03C932 movq mm3,mmword ptr ds:[67CE0h]
1E03C939 pshufw mm0,mm0,88h

thanks in advance.

Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

andybc — Thu, 22 Dec 2005 14:03:11 GMT

please accept my apologies.sorry for taking your time for this thread. i've just discovered that the cpu is a via!!!#$#%&!

i've trusted eMbedded C++ tool which says that the CPU is a PIII, but when i used cpuid, it revealed that it was not. :smileymad:

fortunately, this via cpu supports mmx and hopefully i can use a "mmx-only" ipp library for my dct calls.

does v5.0 supports mmx-only? if yes, which specific library should be used? if not, which version does?

thanks again.

Re: ILLEGAL INSTRUCTION : ippiDCT8x8Inv_16s_C1I

Vladimir_Dudnik — Fri, 23 Dec 2005 01:53:30 GMT

Hi,

You need to use PX libraries, if your cpu is not 100% Intel compatible. Note, IPP dispatcher chooses PX libraries automatically in such cases, but seems you linked directly with A6 code, which is Pentium III specific.

Regards,
Vladimir