C6X: library code

Original port to early 2.6 kernel using TI COFF toolchain.
Brought up to date by Mark Salter <msalter@redhat.com>

Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 98 insertions, 0 deletions

diff --git a/arch/c6x/lib/divu.S b/arch/c6x/lib/divu.S
new file mode 100644
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+++ b/arch/c6x/lib/divu.S
@@ -0,0 +1,98 @@
+;;  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)