diff options
Diffstat (limited to 'arch/x86/math-emu/div_Xsig.S')
| -rw-r--r-- | arch/x86/math-emu/div_Xsig.S | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/arch/x86/math-emu/div_Xsig.S b/arch/x86/math-emu/div_Xsig.S new file mode 100644 index 000000000..8c270ab41 --- /dev/null +++ b/arch/x86/math-emu/div_Xsig.S @@ -0,0 +1,367 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + .file "div_Xsig.S" +/*---------------------------------------------------------------------------+ + | div_Xsig.S | + | | + | Division subroutine for 96 bit quantities | + | | + | Copyright (C) 1994,1995 | + | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | + | Australia. E-mail billm@jacobi.maths.monash.edu.au | + | | + | | + +---------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------+ + | Divide the 96 bit quantity pointed to by a, by that pointed to by b, and | + | put the 96 bit result at the location d. | + | | + | The result may not be accurate to 96 bits. It is intended for use where | + | a result better than 64 bits is required. The result should usually be | + | good to at least 94 bits. | + | The returned result is actually divided by one half. This is done to | + | prevent overflow. | + | | + | .aaaaaaaaaaaaaa / .bbbbbbbbbbbbb -> .dddddddddddd | + | | + | void div_Xsig(Xsig *a, Xsig *b, Xsig *dest) | + | | + +---------------------------------------------------------------------------*/ + +#include "exception.h" +#include "fpu_emu.h" + + +#define XsigLL(x) (x) +#define XsigL(x) 4(x) +#define XsigH(x) 8(x) + + +#ifndef NON_REENTRANT_FPU +/* + Local storage on the stack: + Accumulator: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0 + */ +#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_3 -20(%ebp) +#define FPU_result_2 -24(%ebp) +#define FPU_result_1 -28(%ebp) + +#else +.data +/* + Local storage in a static area: + Accumulator: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0 + */ + .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_3: + .long 0 +FPU_result_2: + .long 0 +FPU_result_1: + .long 0 +#endif /* NON_REENTRANT_FPU */ + + +.text +SYM_FUNC_START(div_Xsig) + pushl %ebp + movl %esp,%ebp +#ifndef NON_REENTRANT_FPU + subl $28,%esp +#endif /* NON_REENTRANT_FPU */ + + pushl %esi + pushl %edi + pushl %ebx + + movl PARAM1,%esi /* pointer to num */ + movl PARAM2,%ebx /* pointer to denom */ + +#ifdef PARANOID + testl $0x80000000, XsigH(%ebx) /* Divisor */ + je L_bugged +#endif /* PARANOID */ + + +/*---------------------------------------------------------------------------+ + | Divide: Return arg1/arg2 to 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 | + | | + +---------------------------------------------------------------------------*/ + + /* Save extended dividend in local register */ + + /* Divide by 2 to prevent overflow */ + clc + movl XsigH(%esi),%eax + rcrl %eax + movl %eax,FPU_accum_3 + movl XsigL(%esi),%eax + rcrl %eax + movl %eax,FPU_accum_2 + movl XsigLL(%esi),%eax + rcrl %eax + movl %eax,FPU_accum_1 + movl $0,%eax + rcrl %eax + movl %eax,FPU_accum_0 + + movl FPU_accum_2,%eax /* Get the current num */ + movl FPU_accum_3,%edx + +/*----------------------------------------------------------------------*/ +/* Initialization done. + Do the first 32 bits. */ + + /* We will divide by a number which is too large */ + movl XsigH(%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_3 /* Put the result in the answer */ + + mull XsigH(%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_3,%eax /* Get the result back */ + mull XsigL(%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_3 /* Correct the answer */ + + movl XsigL(%ebx),%eax + movl XsigH(%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 XsigH(%ebx),%edx + jb LDo_2nd_div + ja LPrevent_2nd_overflow + + cmpl XsigL(%ebx),%eax + jb LDo_2nd_div + +LPrevent_2nd_overflow: +/* The numerator is greater or equal, would cause overflow */ + /* prevent overflow */ + subl XsigL(%ebx),%eax + sbbl XsigH(%ebx),%edx + movl %edx,FPU_accum_2 + movl %eax,FPU_accum_1 + + incl FPU_result_3 /* 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_2 /* Put the result in the answer */ + + mull XsigH(%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_2,%eax /* Get the result back */ + mull XsigL(%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 XsigL(%ebx),%eax + movl XsigH(%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_2 /* Correct the answer */ + adcl $0,FPU_result_3 + +#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: + /* We use an approximation for the third 32 bits. + To take account of the 3rd 32 bits of the divisor + (call them del), we subtract del * (a/b) */ + + movl FPU_result_3,%eax /* a/b */ + mull XsigLL(%ebx) /* del */ + + subl %edx,FPU_accum_1 + + /* A borrow indicates that the result is negative */ + jnb LTest_over + + movl XsigH(%ebx),%edx + addl %edx,FPU_accum_1 + + subl $1,FPU_result_2 /* Adjust the answer */ + sbbl $0,FPU_result_3 + + /* The above addition might not have been enough, check again. */ + movl FPU_accum_1,%edx /* get the reduced num */ + cmpl XsigH(%ebx),%edx /* denom */ + jb LDo_3rd_div + + movl XsigH(%ebx),%edx + addl %edx,FPU_accum_1 + + subl $1,FPU_result_2 /* Adjust the answer */ + sbbl $0,FPU_result_3 + jmp LDo_3rd_div + +LTest_over: + movl FPU_accum_1,%edx /* get the reduced num */ + + /* need to check for possible subsequent overflow */ + cmpl XsigH(%ebx),%edx /* denom */ + jb LDo_3rd_div + + /* prevent overflow */ + subl XsigH(%ebx),%edx + movl %edx,FPU_accum_1 + + addl $1,FPU_result_2 /* Reflect the subtraction in the answer */ + adcl $0,FPU_result_3 + +LDo_3rd_div: + movl FPU_accum_0,%eax + movl FPU_accum_1,%edx + divl XsigH(%ebx) + + movl %eax,FPU_result_1 /* Rough estimate of third word */ + + movl PARAM3,%esi /* pointer to answer */ + + movl FPU_result_1,%eax + movl %eax,XsigLL(%esi) + movl FPU_result_2,%eax + movl %eax,XsigL(%esi) + movl FPU_result_3,%eax + movl %eax,XsigH(%esi) + +L_exit: + popl %ebx + popl %edi + popl %esi + + leave + RET + + +#ifdef PARANOID +/* The logic is wrong if we got here */ +L_bugged: + pushl EX_INTERNAL|0x240 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged_1: + pushl EX_INTERNAL|0x241 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged_2: + pushl EX_INTERNAL|0x242 + call EXCEPTION + pop %ebx + jmp L_exit +#endif /* PARANOID */ +SYM_FUNC_END(div_Xsig) |