Crash - Launch a new game - ZDoom for Linux

[Blzut3]

Is there a particular way you want me to do this? I can probably disassemble r_main.

[Blzut3]

Here's the output from the disassembler for a version which works (MAKECONSTDivScale(32)) and the broken function. The line numbers may be a little off due to my modifications but you can find DivScale32() in there.

[Guest]

Hi !

Years later, I have the same problem (divide by 0) and I don't understand the fix in "r_main.cpp" or in "gccinlines.h"
Could you give me more precisions ?

Thanx

[randi]

What happens if you change it to this?

Code: Select all

static inline SDWORD DivScale32 (SDWORD a, SDWORD b)
{
   SDWORD result, dummy;

   asm volatile
      ("idivl %3"
      :"=&a,a" (result),
       "=d,d" (dummy)
      : "a,a" (0),
        "d,d" (a),
        "r,m" (b)
      : "%cc");
   return result;
} 

[Blzut3]

Code: Select all

/home/blzut3/Code/ZDoom/src/gccinlines.h: In member function ‘virtual void AActor::Tick()’:
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: can't find a register in class ‘AREG’ while reloading ‘asm’
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: can't find a register in class ‘AREG’ while reloading ‘asm’
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: can't find a register in class ‘AREG’ while reloading ‘asm’
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: ‘asm’ operand has impossible constraints
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: ‘asm’ operand has impossible constraints
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: ‘asm’ operand has impossible constraints
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: ‘asm’ operand has impossible constraints
/home/blzut3/Code/ZDoom/src/gccinlines.h:292:15: error: ‘asm’ operand has impossible constraints

[randi]

Okay, what about this?

Code: Select all

static inline SDWORD DivScale32 (SDWORD a, SDWORD b)
{
   SDWORD result, dummy;
   int zero = 0;

   asm volatile
      ("idivl %3"
      :"=&a,a" (result),
       "=d,d" (dummy)
      : "a,a" (zero),
        "d,d" (a),
        "r,m" (b)
      : "%cc");
   return result;
}  

[Blzut3]

Same, only a line lower.

Edit: changing it to "idivl %4" and dropping the ampersand on the result line works (latter fixes the errors, former to avoid a different division by zero error). You can even use (0) per the first attempt as well this way. I, of course, have no idea what I'm doing, but that's what works.

[Blzut3]

Randy, do you want me to go ahead and commit what I have working or do you intend to find a better solution?

[randi]

Sorry, I forgot about this.

How does this fare:

Code: Select all

static inline SDWORD DivScale32 (SDWORD a, SDWORD b)
{
    SDWORD result, dummy;

    asm volatile
        ("xor %%eax,%%eax\n\t"
         "idivl %3"
        :"=&a,&a" (result),
         "=d,d" (dummy)
        : "d,d" (a),
          "r,m" (b)
        : "%cc");
    return result;
} 

Actually, I think I like this version better:

Code: Select all

    int result = 0, dummy;

    asm volatile
        ("idivl %3"
        :"+a,a" (result),
         "=d,d" (dummy)
        : "d,d" (a),
          "r,m" (b)
        : "%cc");
    return result;

[Blzut3]

Seems to work.

Edit: Still need to check the 2nd version. It will take awhile though since my 32-bit laptop isn't very fast.

Edit 2: Second version works as well.

[randi]

Alright. Sounds good.

[nerotriple6]

Cool, thanks a lot!

Sorry but I just found this thread, relocated. Anywhoo, does it work to compile it normally now or is there some hocus pocus to be done?

[Edward-san]

You should update the svn revision and recompile. This is all

[nerotriple6]

Wicked. Thanks for fixing guys!