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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_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)