diff options
Diffstat (limited to 'arch/x86/math-emu/reg_u_mul.S')
| -rw-r--r-- | arch/x86/math-emu/reg_u_mul.S | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/arch/x86/math-emu/reg_u_mul.S b/arch/x86/math-emu/reg_u_mul.S new file mode 100644 index 000000000..21cde47fb --- /dev/null +++ b/arch/x86/math-emu/reg_u_mul.S @@ -0,0 +1,150 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + .file "reg_u_mul.S" +/*---------------------------------------------------------------------------+ + | reg_u_mul.S | + | | + | Core multiplication routine | + | | + | Copyright (C) 1992,1993,1995,1997 | + | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | + | E-mail billm@suburbia.net | + | | + | | + +---------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------+ + | Basic multiplication routine. | + | Does not check the resulting exponent for overflow/underflow | + | | + | FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw); | + | | + | Internal working is at approx 128 bits. | + | Result is rounded to nearest 53 or 64 bits, using "nearest or even". | + +---------------------------------------------------------------------------*/ + +#include "exception.h" +#include "fpu_emu.h" +#include "control_w.h" + + + +#ifndef NON_REENTRANT_FPU +/* Local storage on the stack: */ +#define FPU_accum_0 -4(%ebp) /* ms word */ +#define FPU_accum_1 -8(%ebp) + +#else +/* Local storage in a static area: */ +.data + .align 4,0 +FPU_accum_0: + .long 0 +FPU_accum_1: + .long 0 +#endif /* NON_REENTRANT_FPU */ + + +.text +ENTRY(FPU_u_mul) + pushl %ebp + movl %esp,%ebp +#ifndef NON_REENTRANT_FPU + subl $8,%esp +#endif /* NON_REENTRANT_FPU */ + + pushl %esi + pushl %edi + pushl %ebx + + movl PARAM1,%esi + movl PARAM2,%edi + +#ifdef PARANOID + testl $0x80000000,SIGH(%esi) + jz L_bugged + testl $0x80000000,SIGH(%edi) + jz L_bugged +#endif /* PARANOID */ + + xorl %ecx,%ecx + xorl %ebx,%ebx + + movl SIGL(%esi),%eax + mull SIGL(%edi) + movl %eax,FPU_accum_0 + movl %edx,FPU_accum_1 + + movl SIGL(%esi),%eax + mull SIGH(%edi) + addl %eax,FPU_accum_1 + adcl %edx,%ebx +/* adcl $0,%ecx // overflow here is not possible */ + + movl SIGH(%esi),%eax + mull SIGL(%edi) + addl %eax,FPU_accum_1 + adcl %edx,%ebx + adcl $0,%ecx + + movl SIGH(%esi),%eax + mull SIGH(%edi) + addl %eax,%ebx + adcl %edx,%ecx + + /* Get the sum of the exponents. */ + movl PARAM6,%eax + subl EXP_BIAS-1,%eax + + /* Two denormals can cause an exponent underflow */ + cmpl EXP_WAY_UNDER,%eax + jg Exp_not_underflow + + /* Set to a really low value allow correct handling */ + movl EXP_WAY_UNDER,%eax + +Exp_not_underflow: + +/* Have now finished with the sources */ + movl PARAM3,%edi /* Point to the destination */ + movw %ax,EXP(%edi) + +/* Now make sure that the result is normalized */ + testl $0x80000000,%ecx + jnz LResult_Normalised + + /* Normalize by shifting left one bit */ + shll $1,FPU_accum_0 + rcll $1,FPU_accum_1 + rcll $1,%ebx + rcll $1,%ecx + decw EXP(%edi) + +LResult_Normalised: + movl FPU_accum_0,%eax + movl FPU_accum_1,%edx + orl %eax,%eax + jz L_extent_zero + + orl $1,%edx + +L_extent_zero: + movl %ecx,%eax + jmp fpu_reg_round + + +#ifdef PARANOID +L_bugged: + pushl EX_INTERNAL|0x205 + call EXCEPTION + pop %ebx + jmp L_exit + +L_exit: + popl %ebx + popl %edi + popl %esi + leave + ret +#endif /* PARANOID */ + +ENDPROC(FPU_u_mul) |