99 lines
3.2 KiB
ArmAsm
Executable File
99 lines
3.2 KiB
ArmAsm
Executable File
;; 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)
|