| .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 |
| ENTRY(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 */ |