| // picoChip ASM file |
| // |
| // Support for 16-bit unsigned division/modulus. |
| // |
| // Copyright (C) 2003-2014 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 |
| |
| .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 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 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 |
