--- /dev/null
+ .file "reg_u_div.S"
+/*---------------------------------------------------------------------------+
+ | reg_u_div.S |
+ | |
+ | Divide one FPU_REG by another and put the result in a destination FPU_REG.|
+ | |
+ | Copyright (C) 1992,1993,1995,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | Call from C as: |
+ | int FPU_u_div(FPU_REG *a, FPU_REG *b, FPU_REG *dest, |
+ | unsigned int control_word, char *sign) |
+ | |
+ | Does not compute the destination exponent, but does adjust it. |
+ | |
+ | Return value is the tag of the answer, or-ed with FPU_Exception if |
+ | one was raised, or -1 on internal error. |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "fpu_emu.h"
+#include "control_w.h"
+
+
+/* #define dSIGL(x) (x) */
+/* #define dSIGH(x) 4(x) */
+
+
+#ifndef NON_REENTRANT_FPU
+/*
+ Local storage on the stack:
+ Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
+ Overflow flag: ovfl_flag
+ */
+#define FPU_accum_3 -4(%ebp)
+#define FPU_accum_2 -8(%ebp)
+#define FPU_accum_1 -12(%ebp)
+#define FPU_accum_0 -16(%ebp)
+#define FPU_result_1 -20(%ebp)
+#define FPU_result_2 -24(%ebp)
+#define FPU_ovfl_flag -28(%ebp)
+
+#else
+.data
+/*
+ Local storage in a static area:
+ Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
+ Overflow flag: ovfl_flag
+ */
+ .align 4,0
+FPU_accum_3:
+ .long 0
+FPU_accum_2:
+ .long 0
+FPU_accum_1:
+ .long 0
+FPU_accum_0:
+ .long 0
+FPU_result_1:
+ .long 0
+FPU_result_2:
+ .long 0
+FPU_ovfl_flag:
+ .byte 0
+#endif /* NON_REENTRANT_FPU */
+
+#define REGA PARAM1
+#define REGB PARAM2
+#define DEST PARAM3
+
+.text
+ENTRY(FPU_u_div)
+ pushl %ebp
+ movl %esp,%ebp
+#ifndef NON_REENTRANT_FPU
+ subl $28,%esp
+#endif /* NON_REENTRANT_FPU */
+
+ pushl %esi
+ pushl %edi
+ pushl %ebx
+
+ movl REGA,%esi
+ movl REGB,%ebx
+ movl DEST,%edi
+
+ movswl EXP(%esi),%edx
+ movswl EXP(%ebx),%eax
+ subl %eax,%edx
+ addl EXP_BIAS,%edx
+
+ /* A denormal and a large number can cause an exponent underflow */
+ cmpl EXP_WAY_UNDER,%edx
+ jg xExp_not_underflow
+
+ /* Set to a really low value allow correct handling */
+ movl EXP_WAY_UNDER,%edx
+
+xExp_not_underflow:
+
+ movw %dx,EXP(%edi)
+
+#ifdef PARANOID
+/* testl $0x80000000, SIGH(%esi) // Dividend */
+/* je L_bugged */
+ testl $0x80000000, SIGH(%ebx) /* Divisor */
+ je L_bugged
+#endif /* PARANOID */
+
+/* Check if the divisor can be treated as having just 32 bits */
+ cmpl $0,SIGL(%ebx)
+ jnz L_Full_Division /* Can't do a quick divide */
+
+/* We should be able to zip through the division here */
+ movl SIGH(%ebx),%ecx /* The divisor */
+ movl SIGH(%esi),%edx /* Dividend */
+ movl SIGL(%esi),%eax /* Dividend */
+
+ cmpl %ecx,%edx
+ setaeb FPU_ovfl_flag /* Keep a record */
+ jb L_no_adjust
+
+ subl %ecx,%edx /* Prevent the overflow */
+
+L_no_adjust:
+ /* Divide the 64 bit number by the 32 bit denominator */
+ divl %ecx
+ movl %eax,FPU_result_2
+
+ /* Work on the remainder of the first division */
+ xorl %eax,%eax
+ divl %ecx
+ movl %eax,FPU_result_1
+
+ /* Work on the remainder of the 64 bit division */
+ xorl %eax,%eax
+ divl %ecx
+
+ testb $255,FPU_ovfl_flag /* was the num > denom ? */
+ je L_no_overflow
+
+ /* Do the shifting here */
+ /* increase the exponent */
+ incw EXP(%edi)
+
+ /* shift the mantissa right one bit */
+ stc /* To set the ms bit */
+ rcrl FPU_result_2
+ rcrl FPU_result_1
+ rcrl %eax
+
+L_no_overflow:
+ jmp LRound_precision /* Do the rounding as required */
+
+
+/*---------------------------------------------------------------------------+
+ | Divide: Return arg1/arg2 to arg3. |
+ | |
+ | This routine does not use the exponents of arg1 and arg2, but does |
+ | adjust the exponent of arg3. |
+ | |
+ | The maximum returned value is (ignoring exponents) |
+ | .ffffffff ffffffff |
+ | ------------------ = 1.ffffffff fffffffe |
+ | .80000000 00000000 |
+ | and the minimum is |
+ | .80000000 00000000 |
+ | ------------------ = .80000000 00000001 (rounded) |
+ | .ffffffff ffffffff |
+ | |
+ +---------------------------------------------------------------------------*/
+
+
+L_Full_Division:
+ /* Save extended dividend in local register */
+ movl SIGL(%esi),%eax
+ movl %eax,FPU_accum_2
+ movl SIGH(%esi),%eax
+ movl %eax,FPU_accum_3
+ xorl %eax,%eax
+ movl %eax,FPU_accum_1 /* zero the extension */
+ movl %eax,FPU_accum_0 /* zero the extension */
+
+ movl SIGL(%esi),%eax /* Get the current num */
+ movl SIGH(%esi),%edx
+
+/*----------------------------------------------------------------------*/
+/* Initialization done.
+ Do the first 32 bits. */
+
+ movb $0,FPU_ovfl_flag
+ cmpl SIGH(%ebx),%edx /* Test for imminent overflow */
+ jb LLess_than_1
+ ja LGreater_than_1
+
+ cmpl SIGL(%ebx),%eax
+ jb LLess_than_1
+
+LGreater_than_1:
+/* The dividend is greater or equal, would cause overflow */
+ setaeb FPU_ovfl_flag /* Keep a record */
+
+ subl SIGL(%ebx),%eax
+ sbbl SIGH(%ebx),%edx /* Prevent the overflow */
+ movl %eax,FPU_accum_2
+ movl %edx,FPU_accum_3
+
+LLess_than_1:
+/* At this point, we have a dividend < divisor, with a record of
+ adjustment in FPU_ovfl_flag */
+
+ /* We will divide by a number which is too large */
+ movl SIGH(%ebx),%ecx
+ addl $1,%ecx
+ jnc LFirst_div_not_1
+
+ /* here we need to divide by 100000000h,
+ i.e., no division at all.. */
+ mov %edx,%eax
+ jmp LFirst_div_done
+
+LFirst_div_not_1:
+ divl %ecx /* Divide the numerator by the augmented
+ denom ms dw */
+
+LFirst_div_done:
+ movl %eax,FPU_result_2 /* Put the result in the answer */
+
+ mull SIGH(%ebx) /* mul by the ms dw of the denom */
+
+ subl %eax,FPU_accum_2 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_3
+
+ movl FPU_result_2,%eax /* Get the result back */
+ mull SIGL(%ebx) /* now mul the ls dw of the denom */
+
+ subl %eax,FPU_accum_1 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_2
+ sbbl $0,FPU_accum_3
+ je LDo_2nd_32_bits /* Must check for non-zero result here */
+
+#ifdef PARANOID
+ jb L_bugged_1
+#endif /* PARANOID */
+
+ /* need to subtract another once of the denom */
+ incl FPU_result_2 /* Correct the answer */
+
+ movl SIGL(%ebx),%eax
+ movl SIGH(%ebx),%edx
+ subl %eax,FPU_accum_1 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_2
+
+#ifdef PARANOID
+ sbbl $0,FPU_accum_3
+ jne L_bugged_1 /* Must check for non-zero result here */
+#endif /* PARANOID */
+
+/*----------------------------------------------------------------------*/
+/* Half of the main problem is done, there is just a reduced numerator
+ to handle now.
+ Work with the second 32 bits, FPU_accum_0 not used from now on */
+LDo_2nd_32_bits:
+ movl FPU_accum_2,%edx /* get the reduced num */
+ movl FPU_accum_1,%eax
+
+ /* need to check for possible subsequent overflow */
+ cmpl SIGH(%ebx),%edx
+ jb LDo_2nd_div
+ ja LPrevent_2nd_overflow
+
+ cmpl SIGL(%ebx),%eax
+ jb LDo_2nd_div
+
+LPrevent_2nd_overflow:
+/* The numerator is greater or equal, would cause overflow */
+ /* prevent overflow */
+ subl SIGL(%ebx),%eax
+ sbbl SIGH(%ebx),%edx
+ movl %edx,FPU_accum_2
+ movl %eax,FPU_accum_1
+
+ incl FPU_result_2 /* Reflect the subtraction in the answer */
+
+#ifdef PARANOID
+ je L_bugged_2 /* Can't bump the result to 1.0 */
+#endif /* PARANOID */
+
+LDo_2nd_div:
+ cmpl $0,%ecx /* augmented denom msw */
+ jnz LSecond_div_not_1
+
+ /* %ecx == 0, we are dividing by 1.0 */
+ mov %edx,%eax
+ jmp LSecond_div_done
+
+LSecond_div_not_1:
+ divl %ecx /* Divide the numerator by the denom ms dw */
+
+LSecond_div_done:
+ movl %eax,FPU_result_1 /* Put the result in the answer */
+
+ mull SIGH(%ebx) /* mul by the ms dw of the denom */
+
+ subl %eax,FPU_accum_1 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_2
+
+#ifdef PARANOID
+ jc L_bugged_2
+#endif /* PARANOID */
+
+ movl FPU_result_1,%eax /* Get the result back */
+ mull SIGL(%ebx) /* now mul the ls dw of the denom */
+
+ subl %eax,FPU_accum_0 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_1 /* Subtract from the num local reg */
+ sbbl $0,FPU_accum_2
+
+#ifdef PARANOID
+ jc L_bugged_2
+#endif /* PARANOID */
+
+ jz LDo_3rd_32_bits
+
+#ifdef PARANOID
+ cmpl $1,FPU_accum_2
+ jne L_bugged_2
+#endif /* PARANOID */
+
+ /* need to subtract another once of the denom */
+ movl SIGL(%ebx),%eax
+ movl SIGH(%ebx),%edx
+ subl %eax,FPU_accum_0 /* Subtract from the num local reg */
+ sbbl %edx,FPU_accum_1
+ sbbl $0,FPU_accum_2
+
+#ifdef PARANOID
+ jc L_bugged_2
+ jne L_bugged_2
+#endif /* PARANOID */
+
+ addl $1,FPU_result_1 /* Correct the answer */
+ adcl $0,FPU_result_2
+
+#ifdef PARANOID
+ jc L_bugged_2 /* Must check for non-zero result here */
+#endif /* PARANOID */
+
+/*----------------------------------------------------------------------*/
+/* The division is essentially finished here, we just need to perform
+ tidying operations.
+ Deal with the 3rd 32 bits */
+LDo_3rd_32_bits:
+ movl FPU_accum_1,%edx /* get the reduced num */
+ movl FPU_accum_0,%eax
+
+ /* need to check for possible subsequent overflow */
+ cmpl SIGH(%ebx),%edx /* denom */
+ jb LRound_prep
+ ja LPrevent_3rd_overflow
+
+ cmpl SIGL(%ebx),%eax /* denom */
+ jb LRound_prep
+
+LPrevent_3rd_overflow:
+ /* prevent overflow */
+ subl SIGL(%ebx),%eax
+ sbbl SIGH(%ebx),%edx
+ movl %edx,FPU_accum_1
+ movl %eax,FPU_accum_0
+
+ addl $1,FPU_result_1 /* Reflect the subtraction in the answer */
+ adcl $0,FPU_result_2
+ jne LRound_prep
+ jnc LRound_prep
+
+ /* This is a tricky spot, there is an overflow of the answer */
+ movb $255,FPU_ovfl_flag /* Overflow -> 1.000 */
+
+LRound_prep:
+/*
+ * Prepare for rounding.
+ * To test for rounding, we just need to compare 2*accum with the
+ * denom.
+ */
+ movl FPU_accum_0,%ecx
+ movl FPU_accum_1,%edx
+ movl %ecx,%eax
+ orl %edx,%eax
+ jz LRound_ovfl /* The accumulator contains zero. */
+
+ /* Multiply by 2 */
+ clc
+ rcll $1,%ecx
+ rcll $1,%edx
+ jc LRound_large /* No need to compare, denom smaller */
+
+ subl SIGL(%ebx),%ecx
+ sbbl SIGH(%ebx),%edx
+ jnc LRound_not_small
+
+ movl $0x70000000,%eax /* Denom was larger */
+ jmp LRound_ovfl
+
+LRound_not_small:
+ jnz LRound_large
+
+ movl $0x80000000,%eax /* Remainder was exactly 1/2 denom */
+ jmp LRound_ovfl
+
+LRound_large:
+ movl $0xff000000,%eax /* Denom was smaller */
+
+LRound_ovfl:
+/* We are now ready to deal with rounding, but first we must get
+ the bits properly aligned */
+ testb $255,FPU_ovfl_flag /* was the num > denom ? */
+ je LRound_precision
+
+ incw EXP(%edi)
+
+ /* shift the mantissa right one bit */
+ stc /* Will set the ms bit */
+ rcrl FPU_result_2
+ rcrl FPU_result_1
+ rcrl %eax
+
+/* Round the result as required */
+LRound_precision:
+ decw EXP(%edi) /* binary point between 1st & 2nd bits */
+
+ movl %eax,%edx
+ movl FPU_result_1,%ebx
+ movl FPU_result_2,%eax
+ jmp fpu_reg_round
+
+
+#ifdef PARANOID
+/* The logic is wrong if we got here */
+L_bugged:
+ pushl EX_INTERNAL|0x202
+ call EXCEPTION
+ pop %ebx
+ jmp L_exit
+
+L_bugged_1:
+ pushl EX_INTERNAL|0x203
+ call EXCEPTION
+ pop %ebx
+ jmp L_exit
+
+L_bugged_2:
+ pushl EX_INTERNAL|0x204
+ call EXCEPTION
+ pop %ebx
+ jmp L_exit
+
+L_exit:
+ movl $-1,%eax
+ popl %ebx
+ popl %edi
+ popl %esi
+
+ leave
+ ret
+#endif /* PARANOID */
Code Review / kvmfornfv.git / blobdiff