1 files changed, 70 insertions, 0 deletions
diff --git a/arch/c6x/lib/remu.S b/arch/c6x/lib/remu.S
new file mode 100644
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+++ b/arch/c6x/lib/remu.S
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+;; SPDX-License-Identifier: GPL-2.0-or-later
+;;  Copyright 2010  Free Software Foundation, Inc.
+;;  Contributed by Bernd Schmidt <bernds@codesourcery.com>.
+;;
+
+#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_remu)
+	;; The ABI seems designed to prevent these functions calling each other,
+	;; so we duplicate most of the divsi3 code here.
+	 mv	.s2x	A4, B1
+	 lmbd	.l2	1, B4, B1
+|| [!B1] b	.s2	B3	; RETURN A
+|| [!B1] mvk	.d2	1, B4
+
+	 mv	.l1x	B1, A7
+||	 shl	.s2	B4, B1, B4
+
+	 cmpltu	.l1x	A4, B4, A1
+   [!A1] sub	.l1x	A4, B4, A4
+	 shru	.s2	B4, 1, B4
+
+_remu_loop:
+	 cmpgt	.l2	B1, 7, B0
+|| [B1]	 subc	.l1x	A4,B4,A4
+|| [B1]	 add	.s2	-1, B1, B1
+	;; RETURN A may happen here (note: must happen before the next branch)
+   [B1]	 subc	.l1x	A4,B4,A4
+|| [B1]	 add	.s2	-1, B1, B1
+|| [B0]	 b	.s1	_remu_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
+   [B1]	 subc	.l1x	A4,B4,A4
+|| [B1]	 add	.s2	-1, B1, B1
+   [B1]	 subc	.l1x	A4,B4,A4
+
+	 extu	.s1	A4, A7, A4
+	 nop	2
+ENDPROC(__c6xabi_remu)