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// picoChip ASM file
//
// Support for 16-bit signed 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
// <http://www.gnu.org/licenses/>.
.section .text
.align 8
.global __divmodhi4
__divmodhi4:
_picoMark_FUNCTION_BEGIN=
// picoChip Function Prologue : &__divmodhi4 = 4 bytes
// 16-bit signed division. Most of the special cases are dealt
// with by the 15-bit signed division library (e.g., division by
// zero, division by 1, and so on). This wrapper simply inverts
// any negative inputs, calls the 15-bit library, and flips any
// results as necessary. The
// only special cases to be handled here are where either the
// divisor or the dividend are the maximum negative values.
// Encode r5 with a bit pattern which indicates whether the
// outputs of the division must be negated. The MSB will be set
// to the sign of the dividend (which controls the remainder's
// sign), while the LSB will store the XOR of the two signs,
// which indicates the quotient's sign. R5 is not modified by the
// 15-bit divmod routine.
sub.0 r1,16#8000#,r15 \ asr.1 r0,15,r4
beq divisorIsLargestNegative \ lsr.0 r1,15,r3
=-> sub.0 r0,16#8000#,r15 \ xor.1 r3,r4,r5
// Handle least negative dividend with a special case. Note that the
// absolute value of the divisor is also computed here.
add.0 [asr r1,15],r1,r3 \ beq dividendIsLargestNegative
=-> xor.0 [asr r1,15],r3,r1 \ stw lr,(fp)-1
// Compute the absolute value of the dividend, and call the main
// divide routine.
add.0 r4,r0,r2 \ jl (&__divmod15) // fn_call &__divmod15
=-> xor.0 r4,r2,r0
handleNegatedResults:
// Speculatively store the negation of the results.
sub.0 0,r0,r2 \ sub.1 0,r1,r3
// Does the quotient need negating? The LSB indicates this.
and.0 r5,1,r15 \ ldw (fp)-1,lr
copyne r2,r0
asr.0 r5,15,r15 \ jr (lr)
=-> copyne r3,r1
dividendIsLargestNegative:
// Divide the constant -32768. Use the Hacker's Delight
// algorithm (i.e., ((dividend / 2) / divisor) * 2) gives
// approximate answer). This code is a special case, so no
// great effort is made to make it fast, only to make it
// small.
lsr.0 r0,1,r0 \ jl (&__divmod15) // fn_call &__divmod15
=-> stw r1,(fp)-2
// Load the original divisor, and compute the new quotient and
// remainder.
lsl.0 r0,1,r0 \ ldw (fp)-2,r3
lsl.0 r1,1,r1 // Fill stall slot
// The error in the quotient is 0 or 1. The error can be determined
// by comparing the remainder to the original divisor. If the
// remainder is bigger, then an error of 1 has been introduced,
// which must be fixed.
sub.0 r1,r3,r15
blo noCompensationForError
=-> nop
add.0 r0,1,r0 \ sub.1 r1,r3,r1
noCompensationForError:
bra handleNegatedResults
=-> nop
divisorIsLargestNegative:
// The flags indicate whether the dividend is also the maximum negative
copy.0 r0,r1 \ copy.1 0,r0
copyeq r0,r1 \ jr (lr)
=-> copyeq 1,r0
_picoMark_FUNCTION_END=
// picoChip Function Epilogue : __divmodhi4
//============================================================================
// 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 0x4 // <-- 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#68# 16#69# 16#34# 16#0# // Function name `_divmodhi4'
.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
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