ppc_fsub.s

powerpc 405 优化过的硬浮点库

/* fpopt/ppc_fsub.S, pl_FPE_common, pl_linux 11/24/03 16:17:37                                                                  */
/*----------------------------------------------------------------------------- */
/*  Copyright (c) 2003, IBM Corporation                                         */
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/*                                                                              */
/*----------------------------------------------------------------------------- */
/*                                                                              */
/* Function: subtract two double floating point numbers. frt = fpa - fpb        */
/* Input:    r3,r4(fpa)                                                         */
/*           r5,r6(fpb)                                                         */
/* Output:   r3,r4(frt)                                                         */
/* Notes:   1. No stack frame is created for this function, so the following    */
/*             registers must be preserved, as required by ABI specification:   */
/*               LR, CR0, R1, R2, R13-R31                                       */
/*          2. operation performed according to IEEE754-1985 standard with      */
/*             rounding mode = nearest even.                                    */
/*                                                                              */
/*----------------------------------------------------------------------------- */
  
#include <ppc4xx.inc>

.extern   _ppc_fadd_common
     
function_prolog(__subdf3)

     mr        r7, r5                   /* load B(high) */
     xoris     r7, r7,     0x8000       /* flip sign of B */
     b         _ppc_fadd_common         /* now pretend this is add */

function_epilog(__subdf3)