ppc_fsubs.s

powerpc 405 优化过的硬浮点库

/* fpopt/ppc_fsubs.S, pl_FPE_common, pl_linux 11/24/03 16:17:38                                                                  */
/*----------------------------------------------------------------------------- */
/*  Copyright (c) 2003, IBM Corporation                                         */
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/*                                                                              */
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/*                                                                              */
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/*                                                                              */
/*----------------------------------------------------------------------------- */
/*                                                                              */
/* Function: subtract two single floating point numbers. frt = fpa - fpb        */
/* Input:    r3(fpa), r4(fpb)                                                   */
/* Output:   r3(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>
#include "fpeLib.inc"

function_prolog(__subsf3)  

.extern     _ppc_fadds_common

/* save cr in r0                                                                */
     mfcr    r0
     
/* load fpa into r8,r9.  load fpb into  r12                        */
     xoris   r4,r4,0x8000         /* flip sign bit of fpb */
     mr      r9,r3                  /* load fpa.S, fpa.exp, fpa.hi */
     mr      r12,r4                 /* load fpb.S, fpb.exp, fpb.hi */
     rlwinm  r8,r9,9,0xff           /* isolate exponent of fpa */
     b       _ppc_fadds_common    /* go to common routine */
 
function_epilog(__subsf3)