linux / linux / kernel / git / torvalds / linux / a21b0696261c2865d329afa4156ce15fcdf5e772 / . / arch / powerpc / boot / div64.S

/* | |

* Divide a 64-bit unsigned number by a 32-bit unsigned number. | |

* This routine assumes that the top 32 bits of the dividend are | |

* non-zero to start with. | |

* On entry, r3 points to the dividend, which get overwritten with | |

* the 64-bit quotient, and r4 contains the divisor. | |

* On exit, r3 contains the remainder. | |

* | |

* Copyright (C) 2002 Paul Mackerras, IBM Corp. | |

* | |

* This program is free software; you can redistribute it and/or | |

* modify it under the terms of the GNU General Public License | |

* as published by the Free Software Foundation; either version | |

* 2 of the License, or (at your option) any later version. | |

*/ | |

#include "ppc_asm.h" | |

.globl __div64_32 | |

__div64_32: | |

lwz r5,0(r3) # get the dividend into r5/r6 | |

lwz r6,4(r3) | |

cmplw r5,r4 | |

li r7,0 | |

li r8,0 | |

blt 1f | |

divwu r7,r5,r4 # if dividend.hi >= divisor, | |

mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor | |

subf. r5,r0,r5 # dividend.hi %= divisor | |

beq 3f | |

1: mr r11,r5 # here dividend.hi != 0 | |

andis. r0,r5,0xc000 | |

bne 2f | |

cntlzw r0,r5 # we are shifting the dividend right | |

li r10,-1 # to make it < 2^32, and shifting | |

srw r10,r10,r0 # the divisor right the same amount, | |

add r9,r4,r10 # rounding up (so the estimate cannot | |

andc r11,r6,r10 # ever be too large, only too small) | |

andc r9,r9,r10 | |

or r11,r5,r11 | |

rotlw r9,r9,r0 | |

rotlw r11,r11,r0 | |

divwu r11,r11,r9 # then we divide the shifted quantities | |

2: mullw r10,r11,r4 # to get an estimate of the quotient, | |

mulhwu r9,r11,r4 # multiply the estimate by the divisor, | |

subfc r6,r10,r6 # take the product from the divisor, | |

add r8,r8,r11 # and add the estimate to the accumulated | |

subfe. r5,r9,r5 # quotient | |

bne 1b | |

3: cmplw r6,r4 | |

blt 4f | |

divwu r0,r6,r4 # perform the remaining 32-bit division | |

mullw r10,r0,r4 # and get the remainder | |

add r8,r8,r0 | |

subf r6,r10,r6 | |

4: stw r7,0(r3) # return the quotient in *r3 | |

stw r8,4(r3) | |

mr r3,r6 # return the remainder in r3 | |

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