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1623 |
jcastillo |
.file "reg_u_div.S"
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/*---------------------------------------------------------------------------+
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| reg_u_div.S |
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| Core division routines |
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| Copyright (C) 1992,1993,1995 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@jacobi.maths.monash.edu.au |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| Kernel for the division routines. |
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| void reg_u_div(FPU_REG *a, FPU_REG *a, |
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| FPU_REG *dest, unsigned int control_word) |
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| Does not compute the destination exponent, but does adjust it. |
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+---------------------------------------------------------------------------*/
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#include "exception.h"
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#include "fpu_emu.h"
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#include "control_w.h"
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/* #define dSIGL(x) (x) */
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/* #define dSIGH(x) 4(x) */
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#ifndef NON_REENTRANT_FPU
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/*
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Local storage on the stack:
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Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
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Overflow flag: ovfl_flag
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*/
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#define FPU_accum_3 -4(%ebp)
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#define FPU_accum_2 -8(%ebp)
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#define FPU_accum_1 -12(%ebp)
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#define FPU_accum_0 -16(%ebp)
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#define FPU_result_1 -20(%ebp)
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#define FPU_result_2 -24(%ebp)
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#define FPU_ovfl_flag -28(%ebp)
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#else
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.data
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/*
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Local storage in a static area:
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Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
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Overflow flag: ovfl_flag
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*/
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.align 2,0
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FPU_accum_3:
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.long 0
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FPU_accum_2:
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.long 0
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FPU_accum_1:
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.long 0
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FPU_accum_0:
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.long 0
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FPU_result_1:
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.long 0
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FPU_result_2:
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.long 0
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FPU_ovfl_flag:
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.byte 0
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#endif NON_REENTRANT_FPU
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.text
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ENTRY(reg_u_div)
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pushl %ebp
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movl %esp,%ebp
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#ifndef NON_REENTRANT_FPU
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subl $28,%esp
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#endif NON_REENTRANT_FPU
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pushl %esi
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pushl %edi
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pushl %ebx
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movl PARAM1,%esi /* pointer to num */
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movl PARAM2,%ebx /* pointer to denom */
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movl PARAM3,%edi /* pointer to answer */
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#ifdef DENORM_OPERAND
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movl EXP(%esi),%eax
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cmpl EXP_UNDER,%eax
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jg xOp1_not_denorm
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call SYMBOL_NAME(denormal_operand)
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orl %eax,%eax
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jnz fpu_Arith_exit
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xOp1_not_denorm:
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movl EXP(%ebx),%eax
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cmpl EXP_UNDER,%eax
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jg xOp2_not_denorm
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call SYMBOL_NAME(denormal_operand)
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orl %eax,%eax
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jnz fpu_Arith_exit
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xOp2_not_denorm:
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#endif DENORM_OPERAND
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ENTRY(divide_kernel)
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#ifdef PARANOID
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/* testl $0x80000000, SIGH(%esi) // Dividend */
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/* je L_bugged */
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testl $0x80000000, SIGH(%ebx) /* Divisor */
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je L_bugged
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#endif PARANOID
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/* Check if the divisor can be treated as having just 32 bits */
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cmpl $0,SIGL(%ebx)
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jnz L_Full_Division /* Can't do a quick divide */
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/* We should be able to zip through the division here */
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movl SIGH(%ebx),%ecx /* The divisor */
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movl SIGH(%esi),%edx /* Dividend */
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movl SIGL(%esi),%eax /* Dividend */
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cmpl %ecx,%edx
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setaeb FPU_ovfl_flag /* Keep a record */
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jb L_no_adjust
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subl %ecx,%edx /* Prevent the overflow */
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L_no_adjust:
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/* Divide the 64 bit number by the 32 bit denominator */
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divl %ecx
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movl %eax,FPU_result_2
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/* Work on the remainder of the first division */
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xorl %eax,%eax
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divl %ecx
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movl %eax,FPU_result_1
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/* Work on the remainder of the 64 bit division */
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xorl %eax,%eax
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divl %ecx
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testb $255,FPU_ovfl_flag /* was the num > denom ? */
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je L_no_overflow
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/* Do the shifting here */
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/* increase the exponent */
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incl EXP(%edi)
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/* shift the mantissa right one bit */
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stc /* To set the ms bit */
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rcrl FPU_result_2
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rcrl FPU_result_1
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rcrl %eax
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L_no_overflow:
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jmp LRound_precision /* Do the rounding as required */
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/*---------------------------------------------------------------------------+
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| Divide: Return arg1/arg2 to arg3. |
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| This routine does not use the exponents of arg1 and arg2, but does |
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| adjust the exponent of arg3. |
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| The maximum returned value is (ignoring exponents) |
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| .ffffffff ffffffff |
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| ------------------ = 1.ffffffff fffffffe |
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| .80000000 00000000 |
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| and the minimum is |
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| .80000000 00000000 |
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| ------------------ = .80000000 00000001 (rounded) |
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| .ffffffff ffffffff |
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+---------------------------------------------------------------------------*/
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L_Full_Division:
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/* Save extended dividend in local register */
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movl SIGL(%esi),%eax
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movl %eax,FPU_accum_2
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movl SIGH(%esi),%eax
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movl %eax,FPU_accum_3
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xorl %eax,%eax
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movl %eax,FPU_accum_1 /* zero the extension */
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movl %eax,FPU_accum_0 /* zero the extension */
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movl SIGL(%esi),%eax /* Get the current num */
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movl SIGH(%esi),%edx
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/*----------------------------------------------------------------------*/
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/* Initialization done.
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Do the first 32 bits. */
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movb $0,FPU_ovfl_flag
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cmpl SIGH(%ebx),%edx /* Test for imminent overflow */
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jb LLess_than_1
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ja LGreater_than_1
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cmpl SIGL(%ebx),%eax
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jb LLess_than_1
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LGreater_than_1:
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/* The dividend is greater or equal, would cause overflow */
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setaeb FPU_ovfl_flag /* Keep a record */
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subl SIGL(%ebx),%eax
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sbbl SIGH(%ebx),%edx /* Prevent the overflow */
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movl %eax,FPU_accum_2
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movl %edx,FPU_accum_3
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| 214 |
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LLess_than_1:
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/* At this point, we have a dividend < divisor, with a record of
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adjustment in FPU_ovfl_flag */
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| 218 |
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/* We will divide by a number which is too large */
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| 219 |
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movl SIGH(%ebx),%ecx
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addl $1,%ecx
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jnc LFirst_div_not_1
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| 223 |
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/* here we need to divide by 100000000h,
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| 224 |
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i.e., no division at all.. */
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| 225 |
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mov %edx,%eax
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jmp LFirst_div_done
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| 228 |
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LFirst_div_not_1:
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divl %ecx /* Divide the numerator by the augmented
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denom ms dw */
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| 232 |
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LFirst_div_done:
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| 233 |
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movl %eax,FPU_result_2 /* Put the result in the answer */
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| 235 |
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mull SIGH(%ebx) /* mul by the ms dw of the denom */
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| 236 |
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| 237 |
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subl %eax,FPU_accum_2 /* Subtract from the num local reg */
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| 238 |
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sbbl %edx,FPU_accum_3
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| 239 |
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| 240 |
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movl FPU_result_2,%eax /* Get the result back */
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| 241 |
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mull SIGL(%ebx) /* now mul the ls dw of the denom */
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| 242 |
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| 243 |
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subl %eax,FPU_accum_1 /* Subtract from the num local reg */
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| 244 |
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sbbl %edx,FPU_accum_2
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| 245 |
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sbbl $0,FPU_accum_3
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| 246 |
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je LDo_2nd_32_bits /* Must check for non-zero result here */
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| 247 |
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| 248 |
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#ifdef PARANOID
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| 249 |
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jb L_bugged_1
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| 250 |
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#endif PARANOID
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| 251 |
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| 252 |
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/* need to subtract another once of the denom */
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| 253 |
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incl FPU_result_2 /* Correct the answer */
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| 254 |
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| 255 |
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movl SIGL(%ebx),%eax
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| 256 |
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movl SIGH(%ebx),%edx
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| 257 |
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subl %eax,FPU_accum_1 /* Subtract from the num local reg */
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| 258 |
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sbbl %edx,FPU_accum_2
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| 259 |
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| 260 |
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#ifdef PARANOID
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| 261 |
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sbbl $0,FPU_accum_3
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| 262 |
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jne L_bugged_1 /* Must check for non-zero result here */
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| 263 |
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#endif PARANOID
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| 264 |
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| 265 |
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/*----------------------------------------------------------------------*/
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| 266 |
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/* Half of the main problem is done, there is just a reduced numerator
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| 267 |
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to handle now.
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| 268 |
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Work with the second 32 bits, FPU_accum_0 not used from now on */
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| 269 |
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LDo_2nd_32_bits:
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| 270 |
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movl FPU_accum_2,%edx /* get the reduced num */
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| 271 |
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movl FPU_accum_1,%eax
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| 272 |
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| 273 |
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/* need to check for possible subsequent overflow */
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| 274 |
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cmpl SIGH(%ebx),%edx
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| 275 |
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jb LDo_2nd_div
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| 276 |
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ja LPrevent_2nd_overflow
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| 277 |
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| 278 |
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cmpl SIGL(%ebx),%eax
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| 279 |
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jb LDo_2nd_div
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| 280 |
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| 281 |
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LPrevent_2nd_overflow:
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| 282 |
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/* The numerator is greater or equal, would cause overflow */
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| 283 |
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/* prevent overflow */
|
| 284 |
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subl SIGL(%ebx),%eax
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| 285 |
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sbbl SIGH(%ebx),%edx
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| 286 |
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movl %edx,FPU_accum_2
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| 287 |
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movl %eax,FPU_accum_1
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| 288 |
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|
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| 289 |
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incl FPU_result_2 /* Reflect the subtraction in the answer */
|
| 290 |
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| 291 |
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#ifdef PARANOID
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| 292 |
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je L_bugged_2 /* Can't bump the result to 1.0 */
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| 293 |
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#endif PARANOID
|
| 294 |
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|
| 295 |
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LDo_2nd_div:
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| 296 |
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cmpl $0,%ecx /* augmented denom msw */
|
| 297 |
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jnz LSecond_div_not_1
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| 298 |
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|
| 299 |
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/* %ecx == 0, we are dividing by 1.0 */
|
| 300 |
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mov %edx,%eax
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| 301 |
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jmp LSecond_div_done
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| 302 |
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| 303 |
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LSecond_div_not_1:
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| 304 |
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divl %ecx /* Divide the numerator by the denom ms dw */
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| 305 |
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| 306 |
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LSecond_div_done:
|
| 307 |
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movl %eax,FPU_result_1 /* Put the result in the answer */
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| 308 |
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|
| 309 |
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mull SIGH(%ebx) /* mul by the ms dw of the denom */
|
| 310 |
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|
| 311 |
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subl %eax,FPU_accum_1 /* Subtract from the num local reg */
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| 312 |
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sbbl %edx,FPU_accum_2
|
| 313 |
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|
|
| 314 |
|
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#ifdef PARANOID
|
| 315 |
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jc L_bugged_2
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| 316 |
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#endif PARANOID
|
| 317 |
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|
| 318 |
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movl FPU_result_1,%eax /* Get the result back */
|
| 319 |
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mull SIGL(%ebx) /* now mul the ls dw of the denom */
|
| 320 |
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|
| 321 |
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subl %eax,FPU_accum_0 /* Subtract from the num local reg */
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| 322 |
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sbbl %edx,FPU_accum_1 /* Subtract from the num local reg */
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| 323 |
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sbbl $0,FPU_accum_2
|
| 324 |
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|
| 325 |
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#ifdef PARANOID
|
| 326 |
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jc L_bugged_2
|
| 327 |
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#endif PARANOID
|
| 328 |
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|
|
| 329 |
|
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jz LDo_3rd_32_bits
|
| 330 |
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|
|
| 331 |
|
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#ifdef PARANOID
|
| 332 |
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cmpl $1,FPU_accum_2
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| 333 |
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jne L_bugged_2
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| 334 |
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#endif PARANOID
|
| 335 |
|
|
|
| 336 |
|
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/* need to subtract another once of the denom */
|
| 337 |
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movl SIGL(%ebx),%eax
|
| 338 |
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movl SIGH(%ebx),%edx
|
| 339 |
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subl %eax,FPU_accum_0 /* Subtract from the num local reg */
|
| 340 |
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sbbl %edx,FPU_accum_1
|
| 341 |
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sbbl $0,FPU_accum_2
|
| 342 |
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|
| 343 |
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#ifdef PARANOID
|
| 344 |
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jc L_bugged_2
|
| 345 |
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jne L_bugged_2
|
| 346 |
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#endif PARANOID
|
| 347 |
|
|
|
| 348 |
|
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addl $1,FPU_result_1 /* Correct the answer */
|
| 349 |
|
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adcl $0,FPU_result_2
|
| 350 |
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|
|
| 351 |
|
|
#ifdef PARANOID
|
| 352 |
|
|
jc L_bugged_2 /* Must check for non-zero result here */
|
| 353 |
|
|
#endif PARANOID
|
| 354 |
|
|
|
| 355 |
|
|
/*----------------------------------------------------------------------*/
|
| 356 |
|
|
/* The division is essentially finished here, we just need to perform
|
| 357 |
|
|
tidying operations.
|
| 358 |
|
|
Deal with the 3rd 32 bits */
|
| 359 |
|
|
LDo_3rd_32_bits:
|
| 360 |
|
|
movl FPU_accum_1,%edx /* get the reduced num */
|
| 361 |
|
|
movl FPU_accum_0,%eax
|
| 362 |
|
|
|
| 363 |
|
|
/* need to check for possible subsequent overflow */
|
| 364 |
|
|
cmpl SIGH(%ebx),%edx /* denom */
|
| 365 |
|
|
jb LRound_prep
|
| 366 |
|
|
ja LPrevent_3rd_overflow
|
| 367 |
|
|
|
| 368 |
|
|
cmpl SIGL(%ebx),%eax /* denom */
|
| 369 |
|
|
jb LRound_prep
|
| 370 |
|
|
|
| 371 |
|
|
LPrevent_3rd_overflow:
|
| 372 |
|
|
/* prevent overflow */
|
| 373 |
|
|
subl SIGL(%ebx),%eax
|
| 374 |
|
|
sbbl SIGH(%ebx),%edx
|
| 375 |
|
|
movl %edx,FPU_accum_1
|
| 376 |
|
|
movl %eax,FPU_accum_0
|
| 377 |
|
|
|
| 378 |
|
|
addl $1,FPU_result_1 /* Reflect the subtraction in the answer */
|
| 379 |
|
|
adcl $0,FPU_result_2
|
| 380 |
|
|
jne LRound_prep
|
| 381 |
|
|
jnc LRound_prep
|
| 382 |
|
|
|
| 383 |
|
|
/* This is a tricky spot, there is an overflow of the answer */
|
| 384 |
|
|
movb $255,FPU_ovfl_flag /* Overflow -> 1.000 */
|
| 385 |
|
|
|
| 386 |
|
|
LRound_prep:
|
| 387 |
|
|
/*
|
| 388 |
|
|
* Prepare for rounding.
|
| 389 |
|
|
* To test for rounding, we just need to compare 2*accum with the
|
| 390 |
|
|
* denom.
|
| 391 |
|
|
*/
|
| 392 |
|
|
movl FPU_accum_0,%ecx
|
| 393 |
|
|
movl FPU_accum_1,%edx
|
| 394 |
|
|
movl %ecx,%eax
|
| 395 |
|
|
orl %edx,%eax
|
| 396 |
|
|
jz LRound_ovfl /* The accumulator contains zero. */
|
| 397 |
|
|
|
| 398 |
|
|
/* Multiply by 2 */
|
| 399 |
|
|
clc
|
| 400 |
|
|
rcll $1,%ecx
|
| 401 |
|
|
rcll $1,%edx
|
| 402 |
|
|
jc LRound_large /* No need to compare, denom smaller */
|
| 403 |
|
|
|
| 404 |
|
|
subl SIGL(%ebx),%ecx
|
| 405 |
|
|
sbbl SIGH(%ebx),%edx
|
| 406 |
|
|
jnc LRound_not_small
|
| 407 |
|
|
|
| 408 |
|
|
movl $0x70000000,%eax /* Denom was larger */
|
| 409 |
|
|
jmp LRound_ovfl
|
| 410 |
|
|
|
| 411 |
|
|
LRound_not_small:
|
| 412 |
|
|
jnz LRound_large
|
| 413 |
|
|
|
| 414 |
|
|
movl $0x80000000,%eax /* Remainder was exactly 1/2 denom */
|
| 415 |
|
|
jmp LRound_ovfl
|
| 416 |
|
|
|
| 417 |
|
|
LRound_large:
|
| 418 |
|
|
movl $0xff000000,%eax /* Denom was smaller */
|
| 419 |
|
|
|
| 420 |
|
|
LRound_ovfl:
|
| 421 |
|
|
/* We are now ready to deal with rounding, but first we must get
|
| 422 |
|
|
the bits properly aligned */
|
| 423 |
|
|
testb $255,FPU_ovfl_flag /* was the num > denom ? */
|
| 424 |
|
|
je LRound_precision
|
| 425 |
|
|
|
| 426 |
|
|
incl EXP(%edi)
|
| 427 |
|
|
|
| 428 |
|
|
/* shift the mantissa right one bit */
|
| 429 |
|
|
stc /* Will set the ms bit */
|
| 430 |
|
|
rcrl FPU_result_2
|
| 431 |
|
|
rcrl FPU_result_1
|
| 432 |
|
|
rcrl %eax
|
| 433 |
|
|
|
| 434 |
|
|
/* Round the result as required */
|
| 435 |
|
|
LRound_precision:
|
| 436 |
|
|
decl EXP(%edi) /* binary point between 1st & 2nd bits */
|
| 437 |
|
|
|
| 438 |
|
|
movl %eax,%edx
|
| 439 |
|
|
movl FPU_result_1,%ebx
|
| 440 |
|
|
movl FPU_result_2,%eax
|
| 441 |
|
|
jmp fpu_reg_round
|
| 442 |
|
|
|
| 443 |
|
|
|
| 444 |
|
|
#ifdef PARANOID
|
| 445 |
|
|
/* The logic is wrong if we got here */
|
| 446 |
|
|
L_bugged:
|
| 447 |
|
|
pushl EX_INTERNAL|0x202
|
| 448 |
|
|
call EXCEPTION
|
| 449 |
|
|
pop %ebx
|
| 450 |
|
|
jmp L_exit
|
| 451 |
|
|
|
| 452 |
|
|
L_bugged_1:
|
| 453 |
|
|
pushl EX_INTERNAL|0x203
|
| 454 |
|
|
call EXCEPTION
|
| 455 |
|
|
pop %ebx
|
| 456 |
|
|
jmp L_exit
|
| 457 |
|
|
|
| 458 |
|
|
L_bugged_2:
|
| 459 |
|
|
pushl EX_INTERNAL|0x204
|
| 460 |
|
|
call EXCEPTION
|
| 461 |
|
|
pop %ebx
|
| 462 |
|
|
jmp L_exit
|
| 463 |
|
|
|
| 464 |
|
|
L_exit:
|
| 465 |
|
|
popl %ebx
|
| 466 |
|
|
popl %edi
|
| 467 |
|
|
popl %esi
|
| 468 |
|
|
|
| 469 |
|
|
leave
|
| 470 |
|
|
ret
|
| 471 |
|
|
#endif PARANOID
|
