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// picoChip ASM file

//

//   Support for 16-bit unsigned division/modulus.

//

//   Copyright (C) 2003, 2004, 2005, 2008, 2009  Free Software Foundation, Inc.

//   Contributed by Picochip Ltd.

//   Maintained by Daniel Towner (daniel.towner@picochip.com)

//

//   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.

//

//   This file 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

//   .

.section .text

.global __divmod15

__divmod15:

_picoMark_FUNCTION_BEGIN=

// picoChip Function Prologue : &__divmod15 = 0 bytes

        // The picoChip instruction set has a divstep instruction which

        // is used to perform one iteration of a binary division algorithm.

        // The instruction allows 16-bit signed division to be implemented.

        // It does not directly allow 16-bit unsigned division to be

        // implemented. Thus, this function pulls out the common division

        // iteration for 15-bits unsigned, and then special wrappers

        // provide the logic to change this into a 16-bit signed or

        // unsigned division, as appropriate. This allows the two

        // versions of division to share a common implementation, reducing

        // code size when the two are used together. It also reduces

        // the maintenance overhead.

        // Input:

        //      r0 - dividend

        //      r1 - divisor

        // Output:

        //      r0 - quotient

        //      r1 - remainder

        // R5 is unused

        // Check for special cases. The emphasis is on detecting these as

        // quickly as possible, so that the main division can be started. If

        // the user requests division by one, division by self, and so on

        // then they will just have to accept that this won't be particularly

        // quick (relatively), whereas a real division (e.g., dividing a

        // large value by a small value) will run as fast as possible

        // (i.e., special case detection should not slow down the common case)

        //

        // Special cases to consider:

        //

        //      Division by zero.

        //      Division of zero.

        //      Inputs are equal

        //      Divisor is bigger than dividend

        //      Division by power of two (can be shifted instead).

        //      Division by 1 (special case of power of two division)

        //

        // Division/modulus by zero is undefined (ISO C:6.5.5), so

        // don't bother handling this special case.

        //

        // The special cases of division by a power of 2 are ignored, since

        // they cause the general case to slow down. Omitting these

        // special cases also reduces code size considerably.

        // Handle divisor >= dividend separately. Note that this also handles

        // the case where the dividend is zero. Note that the flags must be

        // preserved, since they are also used at the branch destination.

        sub.0 r1,r0,r15

        sbc r0,r2 \ bge divisorGeDividend

=->     sbc r1,r4

        // Compute the shift count. The amount by which the divisor

        // must be shifted left to be aligned with the dividend.

        sub.0 r4,r2,r3

        // Align the divisor to the dividend. Execute a divstep (since at

        // least one will always be executed). Skip the remaining loop

        // if the shift count is zero.

        lsl.0 r1,r3,r1 \ beq skipLoop

=->     divstep r0,r1 \ add.1 r3,1,r2

        // Execute the divstep loop until temp is 0. This assumes that the

        // loop count is at least one.

        sub.0 r3,1,r4

divLoop:

        divstep r0,r1 \ bne divLoop

=->     sub.0 r4,1,r4

skipLoop:

        // The top bits of the result are the remainder. The bottom

        // bits are the quotient.

        lsr.0 r0,r2,r1 \ sub.1 16,r2,r4

        jr (lr ) \ lsl.0 r0,r4,r0

=->     lsr.0 r0,r4,r0

// Special case.

divisorGeDividend:

        // The divisor is greater than or equal to the dividend. The flags

        // indicate which of these alternatives it is. The COPYNE can be used

        // to set the result appropriately, without introducing any more

        // branches.

        copy.0 r0,r1 \ copy.1 0,r0

        jr (lr) \ copyeq r0,r1

=->     copyeq 1,r0

_picoMark_FUNCTION_END=

// picoChip Function Epilogue : __divmod15

//============================================================================

// All DWARF information between this marker, and the END OF DWARF

// marker should be included in the source file. Search for

// FUNCTION_STACK_SIZE_GOES_HERE and FUNCTION NAME GOES HERE, and

// provide the relevent information. Add markers called

// _picoMark_FUNCTION_BEGIN and _picoMark_FUNCTION_END around the

// function in question.

//============================================================================

//============================================================================

// Frame information.

//============================================================================

.section .debug_frame

_picoMark_DebugFrame=

// Common CIE header.

.unalignedInitLong _picoMark_CieEnd-_picoMark_CieBegin

_picoMark_CieBegin=

.unalignedInitLong 0xffffffff

.initByte 0x1   // CIE Version

.ascii 16#0#    // CIE Augmentation

.uleb128 0x1    // CIE Code Alignment Factor

.sleb128 2      // CIE Data Alignment Factor

.initByte 0xc   // CIE RA Column

.initByte 0xc   // DW_CFA_def_cfa

.uleb128 0xd

.uleb128 0x0

.align 2

_picoMark_CieEnd=

// FDE

_picoMark_LSFDE0I900821033007563=

.unalignedInitLong _picoMark_FdeEnd-_picoMark_FdeBegin

_picoMark_FdeBegin=

.unalignedInitLong _picoMark_DebugFrame // FDE CIE offset

.unalignedInitWord _picoMark_FUNCTION_BEGIN     // FDE initial location

.unalignedInitWord _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN

.initByte 0xe   // DW_CFA_def_cfa_offset

.uleb128 0x0    // <-- FUNCTION_STACK_SIZE_GOES_HERE

.initByte 0x4   // DW_CFA_advance_loc4

.unalignedInitLong _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN

.initByte 0xe   // DW_CFA_def_cfa_offset

.uleb128 0x0

.align 2

_picoMark_FdeEnd=

//============================================================================

// Abbrevation information.

//============================================================================

.section .debug_abbrev

_picoMark_ABBREVIATIONS=

.section .debug_abbrev

        .uleb128 0x1    // (abbrev code)

        .uleb128 0x11   // (TAG: DW_TAG_compile_unit)

        .initByte 0x1   // DW_children_yes

        .uleb128 0x10   // (DW_AT_stmt_list)

        .uleb128 0x6    // (DW_FORM_data4)

        .uleb128 0x12   // (DW_AT_high_pc)

        .uleb128 0x1    // (DW_FORM_addr)

        .uleb128 0x11   // (DW_AT_low_pc)

        .uleb128 0x1    // (DW_FORM_addr)

        .uleb128 0x25   // (DW_AT_producer)

        .uleb128 0x8    // (DW_FORM_string)

        .uleb128 0x13   // (DW_AT_language)

        .uleb128 0x5    // (DW_FORM_data2)

        .uleb128 0x3    // (DW_AT_name)

        .uleb128 0x8    // (DW_FORM_string)

.initByte 0x0

.initByte 0x0

        .uleb128 0x2    ;# (abbrev code)

        .uleb128 0x2e   ;# (TAG: DW_TAG_subprogram)

.initByte 0x0   ;# DW_children_no

        .uleb128 0x3    ;# (DW_AT_name)

        .uleb128 0x8    ;# (DW_FORM_string)

        .uleb128 0x11   ;# (DW_AT_low_pc)

        .uleb128 0x1    ;# (DW_FORM_addr)

        .uleb128 0x12   ;# (DW_AT_high_pc)

        .uleb128 0x1    ;# (DW_FORM_addr)

.initByte 0x0

.initByte 0x0

.initByte 0x0

//============================================================================

// Line information. DwarfLib requires this to be present, but it can

// be empty.

//============================================================================

.section .debug_line

_picoMark_LINES=

//============================================================================

// Debug Information

//============================================================================

.section .debug_info

//Fixed header.

.unalignedInitLong _picoMark_DEBUG_INFO_END-_picoMark_DEBUG_INFO_BEGIN

_picoMark_DEBUG_INFO_BEGIN=

.unalignedInitWord 0x2

.unalignedInitLong _picoMark_ABBREVIATIONS

.initByte 0x2

// Compile unit information.

.uleb128 0x1    // (DIE 0xb) DW_TAG_compile_unit)

.unalignedInitLong _picoMark_LINES

.unalignedInitWord _picoMark_FUNCTION_END

.unalignedInitWord _picoMark_FUNCTION_BEGIN

// Producer is `picoChip'

.ascii 16#70# 16#69# 16#63# 16#6f# 16#43# 16#68# 16#69# 16#70# 16#00#

.unalignedInitWord 0xcafe // ASM language

.ascii 16#0# // Name. DwarfLib expects this to be present.

.uleb128 0x2    ;# (DIE DW_TAG_subprogram)

// FUNCTION NAME GOES HERE. Use `echo name | od -t x1' to get the hex. Each hex

// digit is specified using the format 16#XX#

.ascii 16#5f# 16#64# 16#69# 16#76# 16#6d# 16#6f# 16#64# 16#31# 16#35# 16#0# // Function name `_divmod15'

.unalignedInitWord _picoMark_FUNCTION_BEGIN     // DW_AT_low_pc

.unalignedInitWord _picoMark_FUNCTION_END       // DW_AT_high_pc

.initByte 0x0   // end of compile unit children.

_picoMark_DEBUG_INFO_END=

//============================================================================

// END OF DWARF

//============================================================================

.section .endFile

// End of picoChip ASM file