Message-ID:	<3246D282.27AE@megabaud.fi>
Date:	Mon, 23 Sep 1996 21:10:10 +0300
From:	Antti Sinkman <sinkman AT megabaud DOT fi>
Reply-To:	sinkman AT megabaud DOT fi
MIME-Version:	1.0
To:	djgpp AT delorie DOT com
Subject:	Possible bug in gcc

Hi, everybody!

I was coding my gouraud-filler, when I got an strange error-message from

GCC. It was like this:



gpoly.c: In function 'FillGPoly3':

gpoly.c:144: fixed or forbidden register was spilled.

This may be due to a compiler bug or to impossible asm 

statements or clauses.



I looked through my source, but I didn't find any bugs in it. I don't

include any files I was told to include in DJGPPFAQ.TXT, because I think

those (autoexec, config, etc.) don't matter here. Of course I'm using

DJGPP v2.



Here's the source:



#include <go32.h>

#include <dos.h>



typedef unsigned char byte;

typedef struct

{

    unsigned short x, y;

    byte color;

} gpoint2d;



void FillGPoly3( gpoint2d *A, gpoint2d *B, gpoint2d *C );

void PrepPal( void );

void SetMode( byte mode );

void getch( void );



void main( void )

{

    short i;

    gpoint2d A, B, C;

    A.x = 0; A.y = 0; A.color = 0;

    B.x = 319; B.y = 0; B.color = 255;

    C.x = 0; C.y = 199; C.color = 90;

    SetMode( 0x13 );

    PrepPal();

    FillGPoly3( &A, &B, &C );

    getch();

    SetMode( 0x03 );

}



void FillGPoly3( gpoint2d *A, gpoint2d *B, gpoint2d *C )

{

    gpoint2d *top, *bottom, *middle;

    int x, xinc; 

    int color, cinc;

    unsigned short *LeftEdge, *RightEdge,

                   LeftEdgeArray[200], RightEdgeArray[200],

                   i, j; 

    byte *LeftColor, *RightColor,

         LeftColorArray[200], RightColorArray[200];



    LeftEdge = LeftEdgeArray;

    RightEdge = RightEdgeArray;

    LeftColor = LeftColorArray;

    RightColor = RightColorArray;



    top = A;

    if( B->y < top->y ) top = B;

    if( C->y < top->y ) top = C;

    bottom = A;

    if( B->y > bottom->y ) bottom = B;

    if( C->y > bottom->y ) bottom = C;



    if( ((top == A) && (bottom == B)) || ((top == B) && (bottom == A)) )

        middle = C;



    if( ((top == B) && (bottom == C)) || ((top == C) && (bottom == B)) )

        middle = A;



    if( ((top == A) && (bottom == C)) || ((top == C) && (bottom == A)) )

        middle = B;

    

    if( (bottom->y - top->y) > 0 )

    {

        xinc = (int) ((bottom->x - top->x) << 8) / (bottom->y - top->y);

        x = (int) top->x << 8;

        cinc = (int) ((bottom->color - top->color) << 8) / (bottom->y -

top->y);

        color = (int) top->color << 8;

        for( i = top->y; i <= bottom->y; i++ )

        {

            LeftEdge[i] = (unsigned short) (x >> 8);

            LeftColor[i] = color >> 8;

            x += xinc;

            color += cinc;

        }

    }

    if( (middle->y - top->y) > 0 )

    {

        xinc = (int) ((middle->x - top->x) << 8) / (middle->y - top->y);

        x = (int) top->x << 8;

        cinc = (int) ((middle->color - (int)top->color) << 8) /

(middle->y - top->y);

        color = (int) top->color << 8;

        for( i = top->y; i <= middle->y; i++ )

        {

            RightEdge[i] = (unsigned short) (x >> 8);

            RightColor[i] = color >> 8;

            x += xinc;

            color += cinc;

        }

    }

    if( (bottom->y - middle->y) > 0 )

    {

        xinc = (int) ((bottom->x - middle->x) << 8) / (bottom->y -

middle->y);

        x = (int) middle->x << 8;

        cinc = (int) ((bottom->color - (int)middle->color)<< 8)/

(bottom->y - middle->y);

        color = (int) middle->color << 8;

        for( i = middle->y; i <= bottom->y; i++ )

        {

            RightEdge[i] = (unsigned short) (x >> 8);

            RightColor[i] = color >> 8;

            x += xinc;

            color += cinc;

        }

    }



    if( RightEdge[middle->y] < LeftEdge[middle->y] )

    {

        RightEdge = LeftEdgeArray;

        LeftEdge = RightEdgeArray;

        RightColor = LeftColorArray;

        LeftColor = RightColorArray;

    }



    for( i = top->y; i <= bottom->y; i++ )

        asm (

        "

                movw    %%ax,%%fs

                movl    $0xA0000,%%edi

                movw    %2,%%di

                movw    %%di,%%ax

                shlw    $8,%%di

                shlw    $6,%%ax

                addw    %%ax,%%di

                addw    %0,%%di         # edi = display memory start

                movzwl  %1,%%ecx

                subw    %0,%%cx         # cx = x2 - x1

                movw    %4,%%ah

                subw    %3,%%ah

                xorb    %%al,%%al

                xorw    %%dx,%dx

                idivw   %%cx

                movw    %%ax,%%dx       # dx = fixed point colorinc

            ghloop:

                movb    %%ah,%%fs:(%%edi)

                addw    %%dx,%%ax

                incl    %%edi

                decl    %%ecx

                jnz     ghloop

        "

        :

        : "g" (LeftEdge[i]), "g" (RightEdge[i]), "g" (i),

          "g" (LeftColor[i]), "g" (RightColor[i]), "a" (_dos_ds)

        : "ax", "cx", "dx", "di"

        );

}



void PrepPal( void )

{

    short i;

    for( i = 0; i <= 255; i++ )

    {

        outportb( 0x3c8, (byte) i );

        outportb( 0x3c9, 0 );

        outportb( 0x3c9, 0 );

        outportb( 0x3c9, i / 4 );

    }

}



void SetMode( byte mode )

{

    asm ( "int  $0x10" : : "a" (mode) );

}



void getch( void )

{

    asm (

    "   mov     $1,%ah

        int     $0x21

    ");

}





Antti Sinkman,

sinkman AT walrus DOT megabaud DOT fi

- Raw text -