// picoChip ASM file // // Support for 16-bit unsigned division/modulus. // // Copyright (C) 2003-2013 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 __udivmodhi4 __udivmodhi4: _picoMark_FUNCTION_BEGIN= // picoChip Function Prologue : &__udivmodhi4 = 6 bytes // 16-bit unsigned division. The divstep function is only capable of // handling 15-bit division (plus a sign to give 16-bits). It is not // capable of handling unsigned division directly. Instead, take // advantage of the special property that // ((divisor / 2) / dividend) * 2 will be almost good enough. The // error in the result is only 0 or 1, and this can be easily // tested and corrected. A full description of the algorithm can // be found in `Hacker's Delight', by Henry Warren, page 146. // Input: // r0 - dividend // r1 - divisor // Output: // r0 - quotient // r1 - remainder // Note that the lr, and original inputs are speculatively saved. They // will only be restored if the 15-bit division function is called. sub.0 r1,0,r15 \ stl r[0:1],(fp)-1 bge divisorIs15bit =-> sub.0 r0,r1,r2 \ stw lr,(fp)-3 // The divisor is >= 2^15. bhs quotientIs1 // The dividend < divisor. The quotient is thus 0, and the // remainder is the dividend. copy.0 r0,r1 \ jr (lr) =-> copy.0 0,r0 quotientIs1: // The dividend >= divisor. The quotient is thus 1, and the // remainder can be computed directly by subtraction (i.e., the // result of the comparison already performed to branch here). jr (lr) \ copy.0 r2,r1 =-> copy.0 1,r0 divisorIs15bit: // The divisor is < 2^15. // Divide the original dividend by 2, and call the 15-bit division. // Note that the original dividend is stored in r5, which is // known to be unused by the called function, so that // a memory stall isn't introduced immediately after the // function returns, to reload this value from memory. jl (&__divmod15) \ copy.0 r0,r5 // fn_call &__divmod15 =-> lsr.0 r0,1,r0 // Compute the new quotient and remainder by multiplying them by 2. // The remainder will be 1 out, if the original dividend was odd. and.0 r5,1,r5 \ ldl (fp)-1,r[2:3] add.0 [lsl r1,1],r5,r1 \ lsl.1 r0,1,r0 // 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. sub.0 r1,r3,r15 \ ldw (fp)-3,lr blo noCompensation =-> nop add.0 r0,1,r0 \ sub.1 r1,r3,r1 noCompensation: jr (lr) _picoMark_FUNCTION_END= // picoChip Function Epilogue : udivmodhi4 //============================================================================ // 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 relevant 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 0x6 // <-- 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#75# 16#64# 16#69# 16#76# 16#6d# 16#6f# 16#64# 16#68# 16#69# 16#34# 16#0# // Function name `_udivmodhi4' .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