inline assembly code in c++???

avianRR · 2001-07-28T08:55:01

Now that I''ve got all my header files I need to know how to convert some code. This is what I''m useing under windows, I need to convert it to something that can compile under linux... __asm{ // cli pushfd pop eax mov ebx,eax xor eax, 0x00200000 push eax popfd pushfd pop eax // sti cmp eax,ebx jz NO_CPUID mov [CPUID_AVAILABLE] , 0x01 NO_CPUID: } I''ve tryed... asm pushfd asm pop eax asm mov ebx,eax asm xor eax,0x00200000 asm push eax asm popfd asm pushfd asm pop eax asm cmp eax,ebx asm jz NO_CPUID asm mov [CPUID_AVAILABLE], 0x01 asm NO_CPUID: and... asm{ pushfd pop eax mov ebx,eax xor eax,0x00200000 push eax popfd pushfd pop eax cmp eax,ebx jz NO_CPUID mov [CPUID_AVAILABLE], 0x01 NO_CPUID: } I even tryed replacing asm with _asm or __asm and I keep getting parse errors, any help would be appreciated...

Everything Unix Technical

Started by avianRR July 16, 2001 09:10 PM

15 comments, last by avianRR 22 years, 8 months ago

avianRR

100

Author

July 19, 2001 09:53 PM

quote:Original post by Martee
You can''t directly use variables in inline ASM. I think this might do what you''re looking for:

int info = 0;
__asm__(
"mov $0x01,%eax\n\t"
"cpuid\n\t"
:"=a"(info)
);

~~~~~~~~~~
Martee

Tryed that, it generates parse errors (as does any of the input output syntexing stuff) I can''t even get the sample code from linuxassembly.org to compile with out the same errors. However they do also say that the way I have it should work and at least it compiles, but it then just can''t resolve the variables in the linker

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Nurgle

269

July 21, 2001 07:45 AM

main() {    int info = 0;     __asm__ (        "mov $0x01, %%eax        cpuid"        : "=edx" (info)    );     printf("cpuid=%d\n", info);     if (info & 0x00800000) printf("MMX supported\n");    if (info & 0x00200000) printf("SSE supported\n");    if (info & 0x00400000) printf("SSE2 supported\n");     return 1;}

compiles (note the double % on eax in the instructions. that's needed when you have an input/output/modifier).

After careful deliberation, I have come to the conclusion that Nazrix is not cool. I am sorry for any inconvienience my previous mistake may have caused. We now return you to the original programming

Edited by - Godfree^ on July 21, 2001 8:52:43 AM

Edited by - Godfree^ on July 21, 2001 8:54:45 AM

After careful deliberation, I have come to the conclusion that Nazrix is not cool. I am sorry for any inconvienience my previous mistake may have caused. We now return you to the original programming

avianRR

100

Author

July 21, 2001 05:07 PM

Thanks Godfree^, That''s it! MY PROGRAM WORKS!

That''s what I missed. When I went back and looked at linux assembly.org again I realized that I must have missed that part.
Thanks to everyone that helped!

And happy coding...

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avianRR

100

Author

July 21, 2001 05:27 PM

Well, not entirly...
I went back through all the code cleaning up my comments and getting rid of all the commented out test lines of code and found that I still had one section commented out becuase it had anotherer error, the following is copyed from a previous post of mine...

I have to push and pop the eflags register (pushfd, popfd) I can''t however find the equivelant operation under linux and they come up with the warning "no such 386 instruction"

example...
"pushfd\n\t"
produces the error "/tmp/ccjs1zp.s: 305: no such 386 instruction: ''pushfd''"

I''ve searched Sandpile.org and can''t find any info there eather.
thanks,
Rob

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avianRR

100

Author

July 23, 2001 03:35 AM

Well, I found it...
pushfd in msvc is pushf in gas.
I figured it out by looking at the disasembly of my win32 version to get the opcode then looked up the opcode at sandpile.org to get the mnemonic.

Again, thanks for the help everyone.

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Prefect

373

July 24, 2001 12:53 PM

Why don''t you just read out /proc/cpuinfo for CPUID on Linux?

Of course this thread was worth it for the sake of learning ASM, but the /proc/cpuinfo can give you other details (esp. on SMP systems).

cu,
Prefect

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Nurgle

269

July 28, 2001 08:55 AM

Prefect, parsing /proc/cpuinfo can be quite a hefty chunk of code, where cpuid is a lot quicker, and you get a nice value which you can check bits on.

It''s more efficient to use cpuid....

After careful deliberation, I have come to the conclusion that Nazrix is not cool. I am sorry for any inconvienience my previous mistake may have caused. We now return you to the original programming

inline assembly code in c++???

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