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###################################-

#

#  Copyright 2009, 2010, 2011 Free Software Foundation, Inc.

#

#  Contributed by Michael Eager .

#

#  This file 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 3, or (at your option) any

#  later version.

#

#  GCC 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.

#

#  Under Section 7 of GPL version 3, you are granted additional

#  permissions described in the GCC Runtime Library Exception, version

#  3.1, as published by the Free Software Foundation.

#

#  You should have received a copy of the GNU General Public License and

#  a copy of the GCC Runtime Library Exception along with this program;

#  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

#  .

#

#  muldi3_hard.S

#

#  Multiply operation for 64 bit integers, for devices with hard multiply

#       Input : Operand1[H] in Reg r5

#               Operand1[L] in Reg r6

#               Operand2[H] in Reg r7

#               Operand2[L] in Reg r8

#       Output: Result[H] in Reg r3

#               Result[L] in Reg r4

#

#  Explaination:

#

#       Both the input numbers are divided into 16 bit number as follows

#               op1 = A B C D

#               op2 = E F G H

#       result =    D * H

#                + (C * H + D * G) << 16

#                + (B * H + C * G + D * F) << 32

#                + (A * H + B * G + C * F + D * E) << 48

#

#       Only 64 bits of the output are considered

#

#######################################

        .globl  muldi3_hardproc

        .ent    muldi3_hardproc

muldi3_hardproc:

        addi    r1,r1,-40

#  Save the input operands on the caller's stack

        swi     r5,r1,44

        swi     r6,r1,48

        swi     r7,r1,52

        swi     r8,r1,56

# Store all the callee saved registers

        sw      r20,r1,r0

        swi     r21,r1,4

        swi     r22,r1,8

        swi     r23,r1,12

        swi     r24,r1,16

        swi     r25,r1,20

        swi     r26,r1,24

        swi     r27,r1,28

# Load all the 16 bit values for A thru H

        lhui    r20,r1,44   # A

        lhui    r21,r1,46   # B

        lhui    r22,r1,48   # C

        lhui    r23,r1,50   # D

        lhui    r24,r1,52   # E

        lhui    r25,r1,54   # F

        lhui    r26,r1,56   # G

        lhui    r27,r1,58   # H

# D * H ==> LSB of the result on stack ==> Store1

        mul     r9,r23,r27

        swi     r9,r1,36    # Pos2 and Pos3

# Hi (Store1) + C * H + D * G ==> Store2 ==> Pos1 and Pos2

# Store the carry generated in position 2 for Pos 3

        lhui    r11,r1,36   # Pos2

        mul     r9,r22,r27   # C * H

        mul     r10,r23,r26  # D * G

        add     r9,r9,r10

        addc    r12,r0,r0

        add     r9,r9,r11

        addc    r12,r12,r0    # Store the Carry

        shi     r9,r1,36    # Store Pos2

        swi     r9,r1,32

        lhui    r11,r1,32

        shi     r11,r1,34   # Store Pos1

# Hi (Store2) + B * H + C * G + D * F ==> Store3 ==> Pos0 and Pos1

        mul     r9,r21,r27  # B * H

        mul     r10,r22,r26 # C * G

        mul     r7,r23,r25 # D * F

        add     r9,r9,r11

        add     r9,r9,r10

        add     r9,r9,r7

        swi     r9,r1,32   # Pos0 and Pos1

# Hi (Store3) + A * H + B * G + C * F + D * E ==> Store3 ==> Pos0

        lhui    r11,r1,32  # Pos0

        mul     r9,r20,r27  # A * H

        mul     r10,r21,r26 # B * G

        mul     r7,r22,r25 # C * F

        mul     r8,r23,r24 # D * E

        add     r9,r9,r11

        add     r9,r9,r10

        add     r9,r9,r7

        add     r9,r9,r8

        sext16  r9,r9       # Sign extend the MSB

        shi     r9,r1,32

# Move results to r3 and r4

        lhui    r3,r1,32

        add     r3,r3,r12

        shi     r3,r1,32

        lwi     r3,r1,32  # Hi Part

        lwi     r4,r1,36  # Lo Part

# Restore Callee saved registers

        lw      r20,r1,r0

        lwi     r21,r1,4

        lwi     r22,r1,8

        lwi     r23,r1,12

        lwi     r24,r1,16

        lwi     r25,r1,20

        lwi     r26,r1,24

        lwi     r27,r1,28

# Restore Frame and return

        rtsd    r15,8

        addi    r1,r1,40

.end muldi3_hardproc