247 lines
8.4 KiB
ArmAsm
247 lines
8.4 KiB
ArmAsm
// picoChip ASM file
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//
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// Support for 16-bit signed division/modulus.
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//
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// Copyright (C) 2003-2013 Free Software Foundation, Inc.
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// Contributed by Picochip Ltd.
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// Maintained by Daniel Towner (daniel.towner@picochip.com)
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//
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// This file is free software; you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option) any
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// later version.
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//
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// This file is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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//
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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.section .text
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.align 8
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.global __divmodhi4
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__divmodhi4:
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_picoMark_FUNCTION_BEGIN=
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// picoChip Function Prologue : &__divmodhi4 = 4 bytes
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// 16-bit signed division. Most of the special cases are dealt
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// with by the 15-bit signed division library (e.g., division by
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// zero, division by 1, and so on). This wrapper simply inverts
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// any negative inputs, calls the 15-bit library, and flips any
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// results as necessary. The
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// only special cases to be handled here are where either the
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// divisor or the dividend are the maximum negative values.
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// Encode r5 with a bit pattern which indicates whether the
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// outputs of the division must be negated. The MSB will be set
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// to the sign of the dividend (which controls the remainder's
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// sign), while the LSB will store the XOR of the two signs,
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// which indicates the quotient's sign. R5 is not modified by the
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// 15-bit divmod routine.
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sub.0 r1,16#8000#,r15 \ asr.1 r0,15,r4
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beq divisorIsLargestNegative \ lsr.0 r1,15,r3
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=-> sub.0 r0,16#8000#,r15 \ xor.1 r3,r4,r5
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// Handle least negative dividend with a special case. Note that the
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// absolute value of the divisor is also computed here.
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add.0 [asr r1,15],r1,r3 \ beq dividendIsLargestNegative
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=-> xor.0 [asr r1,15],r3,r1 \ stw lr,(fp)-1
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// Compute the absolute value of the dividend, and call the main
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// divide routine.
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add.0 r4,r0,r2 \ jl (&__divmod15) // fn_call &__divmod15
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=-> xor.0 r4,r2,r0
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handleNegatedResults:
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// Speculatively store the negation of the results.
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sub.0 0,r0,r2 \ sub.1 0,r1,r3
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// Does the quotient need negating? The LSB indicates this.
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and.0 r5,1,r15 \ ldw (fp)-1,lr
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copyne r2,r0
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asr.0 r5,15,r15 \ jr (lr)
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=-> copyne r3,r1
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dividendIsLargestNegative:
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// Divide the constant -32768. Use the Hacker's Delight
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// algorithm (i.e., ((dividend / 2) / divisor) * 2) gives
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// approximate answer). This code is a special case, so no
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// great effort is made to make it fast, only to make it
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// small.
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lsr.0 r0,1,r0 \ jl (&__divmod15) // fn_call &__divmod15
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=-> stw r1,(fp)-2
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// Load the original divisor, and compute the new quotient and
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// remainder.
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lsl.0 r0,1,r0 \ ldw (fp)-2,r3
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lsl.0 r1,1,r1 // Fill stall slot
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// The error in the quotient is 0 or 1. The error can be determined
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// by comparing the remainder to the original divisor. If the
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// remainder is bigger, then an error of 1 has been introduced,
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// which must be fixed.
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sub.0 r1,r3,r15
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blo noCompensationForError
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=-> nop
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add.0 r0,1,r0 \ sub.1 r1,r3,r1
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noCompensationForError:
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bra handleNegatedResults
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=-> nop
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divisorIsLargestNegative:
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// The flags indicate whether the dividend is also the maximum negative
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copy.0 r0,r1 \ copy.1 0,r0
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copyeq r0,r1 \ jr (lr)
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=-> copyeq 1,r0
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_picoMark_FUNCTION_END=
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// picoChip Function Epilogue : __divmodhi4
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//============================================================================
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// All DWARF information between this marker, and the END OF DWARF
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// marker should be included in the source file. Search for
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// FUNCTION_STACK_SIZE_GOES_HERE and FUNCTION NAME GOES HERE, and
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// provide the relevant information. Add markers called
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// _picoMark_FUNCTION_BEGIN and _picoMark_FUNCTION_END around the
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// function in question.
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//============================================================================
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//============================================================================
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// Frame information.
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//============================================================================
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.section .debug_frame
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_picoMark_DebugFrame=
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// Common CIE header.
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.unalignedInitLong _picoMark_CieEnd-_picoMark_CieBegin
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_picoMark_CieBegin=
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.unalignedInitLong 0xffffffff
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.initByte 0x1 // CIE Version
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.ascii 16#0# // CIE Augmentation
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.uleb128 0x1 // CIE Code Alignment Factor
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.sleb128 2 // CIE Data Alignment Factor
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.initByte 0xc // CIE RA Column
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.initByte 0xc // DW_CFA_def_cfa
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.uleb128 0xd
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.uleb128 0x0
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.align 2
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_picoMark_CieEnd=
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// FDE
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_picoMark_LSFDE0I900821033007563=
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.unalignedInitLong _picoMark_FdeEnd-_picoMark_FdeBegin
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_picoMark_FdeBegin=
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.unalignedInitLong _picoMark_DebugFrame // FDE CIE offset
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.unalignedInitWord _picoMark_FUNCTION_BEGIN // FDE initial location
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.unalignedInitWord _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
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.initByte 0xe // DW_CFA_def_cfa_offset
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.uleb128 0x4 // <-- FUNCTION_STACK_SIZE_GOES_HERE
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.initByte 0x4 // DW_CFA_advance_loc4
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.unalignedInitLong _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
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.initByte 0xe // DW_CFA_def_cfa_offset
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.uleb128 0x0
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.align 2
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_picoMark_FdeEnd=
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//============================================================================
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// Abbrevation information.
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//============================================================================
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.section .debug_abbrev
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_picoMark_ABBREVIATIONS=
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.section .debug_abbrev
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.uleb128 0x1 // (abbrev code)
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.uleb128 0x11 // (TAG: DW_TAG_compile_unit)
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.initByte 0x1 // DW_children_yes
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.uleb128 0x10 // (DW_AT_stmt_list)
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.uleb128 0x6 // (DW_FORM_data4)
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.uleb128 0x12 // (DW_AT_high_pc)
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.uleb128 0x1 // (DW_FORM_addr)
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.uleb128 0x11 // (DW_AT_low_pc)
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.uleb128 0x1 // (DW_FORM_addr)
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.uleb128 0x25 // (DW_AT_producer)
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.uleb128 0x8 // (DW_FORM_string)
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.uleb128 0x13 // (DW_AT_language)
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.uleb128 0x5 // (DW_FORM_data2)
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.uleb128 0x3 // (DW_AT_name)
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.uleb128 0x8 // (DW_FORM_string)
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.initByte 0x0
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.initByte 0x0
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.uleb128 0x2 ;# (abbrev code)
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.uleb128 0x2e ;# (TAG: DW_TAG_subprogram)
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.initByte 0x0 ;# DW_children_no
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.uleb128 0x3 ;# (DW_AT_name)
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.uleb128 0x8 ;# (DW_FORM_string)
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.uleb128 0x11 ;# (DW_AT_low_pc)
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.uleb128 0x1 ;# (DW_FORM_addr)
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.uleb128 0x12 ;# (DW_AT_high_pc)
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.uleb128 0x1 ;# (DW_FORM_addr)
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.initByte 0x0
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.initByte 0x0
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.initByte 0x0
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//============================================================================
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// Line information. DwarfLib requires this to be present, but it can
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// be empty.
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//============================================================================
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.section .debug_line
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_picoMark_LINES=
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//============================================================================
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// Debug Information
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//============================================================================
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.section .debug_info
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//Fixed header.
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.unalignedInitLong _picoMark_DEBUG_INFO_END-_picoMark_DEBUG_INFO_BEGIN
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_picoMark_DEBUG_INFO_BEGIN=
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.unalignedInitWord 0x2
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.unalignedInitLong _picoMark_ABBREVIATIONS
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.initByte 0x2
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// Compile unit information.
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.uleb128 0x1 // (DIE 0xb) DW_TAG_compile_unit)
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.unalignedInitLong _picoMark_LINES
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.unalignedInitWord _picoMark_FUNCTION_END
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.unalignedInitWord _picoMark_FUNCTION_BEGIN
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// Producer is `picoChip'
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.ascii 16#70# 16#69# 16#63# 16#6f# 16#43# 16#68# 16#69# 16#70# 16#00#
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.unalignedInitWord 0xcafe // ASM language
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.ascii 16#0# // Name. DwarfLib expects this to be present.
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.uleb128 0x2 ;# (DIE DW_TAG_subprogram)
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// FUNCTION NAME GOES HERE. Use `echo name | od -t x1' to get the hex. Each hex
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// digit is specified using the format 16#XX#
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.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'
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.unalignedInitWord _picoMark_FUNCTION_BEGIN // DW_AT_low_pc
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.unalignedInitWord _picoMark_FUNCTION_END // DW_AT_high_pc
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.initByte 0x0 // end of compile unit children.
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_picoMark_DEBUG_INFO_END=
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//============================================================================
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// END OF DWARF
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//============================================================================
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.section .endFile
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