linux-mm / kernel / git / torvalds / linux / 9931faca02c604c22335f5a935a501bb2ace6e20 / . / arch / c6x / lib / divu.S

;; Copyright 2010 Free Software Foundation, Inc. | |

;; Contributed by Bernd Schmidt <bernds@codesourcery.com>. | |

;; | |

;; 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. | |

;; | |

;; This program is distributed in the hope that it will be useful, | |

;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |

;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |

;; GNU General Public License for more details. | |

;; | |

;; You should have received a copy of the GNU General Public License | |

;; along with this program; if not, write to the Free Software | |

;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |

#include <linux/linkage.h> | |

;; ABI considerations for the divide functions | |

;; The following registers are call-used: | |

;; __c6xabi_divi A0,A1,A2,A4,A6,B0,B1,B2,B4,B5 | |

;; __c6xabi_divu A0,A1,A2,A4,A6,B0,B1,B2,B4 | |

;; __c6xabi_remi A1,A2,A4,A5,A6,B0,B1,B2,B4 | |

;; __c6xabi_remu A1,A4,A5,A7,B0,B1,B2,B4 | |

;; | |

;; In our implementation, divu and remu are leaf functions, | |

;; while both divi and remi call into divu. | |

;; A0 is not clobbered by any of the functions. | |

;; divu does not clobber B2 either, which is taken advantage of | |

;; in remi. | |

;; divi uses B5 to hold the original return address during | |

;; the call to divu. | |

;; remi uses B2 and A5 to hold the input values during the | |

;; call to divu. It stores B3 in on the stack. | |

.text | |

ENTRY(__c6xabi_divu) | |

;; We use a series of up to 31 subc instructions. First, we find | |

;; out how many leading zero bits there are in the divisor. This | |

;; gives us both a shift count for aligning (shifting) the divisor | |

;; to the, and the number of times we have to execute subc. | |

;; At the end, we have both the remainder and most of the quotient | |

;; in A4. The top bit of the quotient is computed first and is | |

;; placed in A2. | |

;; Return immediately if the dividend is zero. | |

mv .s2x A4, B1 | |

[B1] lmbd .l2 1, B4, B1 | |

|| [!B1] b .s2 B3 ; RETURN A | |

|| [!B1] mvk .d2 1, B4 | |

mv .l1x B1, A6 | |

|| shl .s2 B4, B1, B4 | |

;; The loop performs a maximum of 28 steps, so we do the | |

;; first 3 here. | |

cmpltu .l1x A4, B4, A2 | |

[!A2] sub .l1x A4, B4, A4 | |

|| shru .s2 B4, 1, B4 | |

|| xor .s1 1, A2, A2 | |

shl .s1 A2, 31, A2 | |

|| [B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

;; RETURN A may happen here (note: must happen before the next branch) | |

_divu_loop: | |

cmpgt .l2 B1, 7, B0 | |

|| [B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

|| [B0] b .s1 _divu_loop | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

[B1] subc .l1x A4,B4,A4 | |

|| [B1] add .s2 -1, B1, B1 | |

;; loop backwards branch happens here | |

ret .s2 B3 | |

|| mvk .s1 32, A1 | |

sub .l1 A1, A6, A6 | |

shl .s1 A4, A6, A4 | |

shru .s1 A4, 1, A4 | |

|| sub .l1 A6, 1, A6 | |

or .l1 A2, A4, A4 | |

shru .s1 A4, A6, A4 | |

nop | |

ENDPROC(__c6xabi_divu) |