1// picoChip ASM file
2//
3//   Support for 16-bit unsigned division/modulus.
4//
5//   Copyright (C) 2003, 2004, 2005, 2008, 2009  Free Software Foundation, Inc.
6//   Contributed by picoChip Designs Ltd.
7//   Maintained by Daniel Towner (daniel.towner@picochip.com)
8//
9//   This file is free software; you can redistribute it and/or modify it
10//   under the terms of the GNU General Public License as published by the
11//   Free Software Foundation; either version 3, or (at your option) any
12//   later version.
13//
14//   This file is distributed in the hope that it will be useful, but
15//   WITHOUT ANY WARRANTY; without even the implied warranty of
16//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17//   General Public License for more details.
18//
19//   Under Section 7 of GPL version 3, you are granted additional
20//   permissions described in the GCC Runtime Library Exception, version
21//   3.1, as published by the Free Software Foundation.
22//
23//   You should have received a copy of the GNU General Public License and
24//   a copy of the GCC Runtime Library Exception along with this program;
25//   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
26//   <http://www.gnu.org/licenses/>.
27	
28.section .text
29
30.global __udivmodhi4
31__udivmodhi4:
32_picoMark_FUNCTION_BEGIN=
33	
34// picoChip Function Prologue : &__udivmodhi4 = 6 bytes
35
36	// 16-bit unsigned division. The divstep function is only capable of
37	// handling 15-bit division (plus a sign to give 16-bits). It is not 
38	// capable of handling unsigned division directly. Instead, take 
39	// advantage of the special property that 
40	// ((divisor / 2) / dividend) * 2 will be almost good enough. The 
41	// error in the result is only 0 or 1, and this can be easily
42	// tested and corrected. A full description of the algorithm can
43	// be found in `Hacker's Delight', by Henry Warren, page 146.
44
45	// Input:
46	//	r0 - dividend
47	//	r1 - divisor
48	// Output:
49	//	r0 - quotient
50	//	r1 - remainder
51	
52	// Note that the lr, and original inputs are speculatively saved. They
53	// will only be restored if the 15-bit division function is called.
54	
55	sub.0 r1,0,r15 \ stl r[0:1],(fp)-1
56	bge divisorIs15bit
57=->	sub.0 r0,r1,r2 \ stw lr,(fp)-3
58	
59	// The divisor is >= 2^15.
60	bhs quotientIs1
61
62	// The dividend < divisor. The quotient is thus 0, and the
63	// remainder is the dividend.
64	copy.0 r0,r1 \ jr (lr)
65=->	copy.0 0,r0
66	
67quotientIs1:	
68	// The dividend >= divisor. The quotient is thus 1, and the
69	// remainder can be computed directly by subtraction (i.e., the
70	// result of the comparison already performed to branch here).
71	jr (lr) \ copy.0 r2,r1
72=->	copy.0 1,r0
73	
74divisorIs15bit:
75	// The divisor is < 2^15.
76
77	// Divide the original dividend by 2, and call the 15-bit division.
78	// Note that the original dividend is stored in r5, which is
79	// known to be unused by the called function, so that
80	// a memory stall isn't introduced immediately after the
81	// function returns, to reload this value from memory.
82	
83	jl (&__divmod15) \ copy.0 r0,r5  // fn_call &__divmod15
84=->     lsr.0 r0,1,r0
85	
86	// Compute the new quotient and remainder by multiplying them by 2.
87	// The remainder will be 1 out, if the original dividend was odd.
88	and.0 r5,1,r5 \ ldl (fp)-1,r[2:3]
89	add.0 [lsl r1,1],r5,r1 \ lsl.1 r0,1,r0
90	
91	// The error in the quotient is 0 or 1. The error can be determined
92	// by comparing the remainder to the original divisor. If the 
93	// remainder is bigger, then an error of 1 has been introduced.
94	sub.0 r1,r3,r15 \ ldw (fp)-3,lr
95	blo noCompensation
96=->	nop	
97	add.0 r0,1,r0 \ sub.1 r1,r3,r1
98noCompensation:
99	jr (lr)
100
101_picoMark_FUNCTION_END=
102// picoChip Function Epilogue : udivmodhi4
103
104	
105//============================================================================
106// All DWARF information between this marker, and the END OF DWARF
107// marker should be included in the source file. Search for
108// FUNCTION_STACK_SIZE_GOES_HERE and FUNCTION NAME GOES HERE, and
109// provide the relevent information. Add markers called
110// _picoMark_FUNCTION_BEGIN and _picoMark_FUNCTION_END around the
111// function in question.
112//============================================================================
113
114//============================================================================
115// Frame information. 
116//============================================================================
117
118.section .debug_frame
119_picoMark_DebugFrame=
120
121// Common CIE header.
122.unalignedInitLong _picoMark_CieEnd-_picoMark_CieBegin
123_picoMark_CieBegin=
124.unalignedInitLong 0xffffffff
125.initByte 0x1	// CIE Version
126.ascii 16#0#	// CIE Augmentation
127.uleb128 0x1	// CIE Code Alignment Factor
128.sleb128 2	// CIE Data Alignment Factor
129.initByte 0xc	// CIE RA Column
130.initByte 0xc	// DW_CFA_def_cfa
131.uleb128 0xd
132.uleb128 0x0
133.align 2
134_picoMark_CieEnd=
135
136// FDE 
137_picoMark_LSFDE0I900821033007563=
138.unalignedInitLong _picoMark_FdeEnd-_picoMark_FdeBegin
139_picoMark_FdeBegin=
140.unalignedInitLong _picoMark_DebugFrame	// FDE CIE offset
141.unalignedInitWord _picoMark_FUNCTION_BEGIN	// FDE initial location
142.unalignedInitWord _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
143.initByte 0xe	// DW_CFA_def_cfa_offset
144.uleb128 0x6	// <-- FUNCTION_STACK_SIZE_GOES_HERE
145.initByte 0x4	// DW_CFA_advance_loc4
146.unalignedInitLong _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
147.initByte 0xe	// DW_CFA_def_cfa_offset
148.uleb128 0x0
149.align 2
150_picoMark_FdeEnd=
151
152//============================================================================
153// Abbrevation information.
154//============================================================================
155
156.section .debug_abbrev
157_picoMark_ABBREVIATIONS=
158
159.section .debug_abbrev
160	.uleb128 0x1	// (abbrev code)
161	.uleb128 0x11	// (TAG: DW_TAG_compile_unit)
162	.initByte 0x1	// DW_children_yes
163	.uleb128 0x10	// (DW_AT_stmt_list)
164	.uleb128 0x6	// (DW_FORM_data4)
165	.uleb128 0x12	// (DW_AT_high_pc)
166	.uleb128 0x1	// (DW_FORM_addr)
167	.uleb128 0x11	// (DW_AT_low_pc)
168	.uleb128 0x1	// (DW_FORM_addr)
169	.uleb128 0x25	// (DW_AT_producer)
170	.uleb128 0x8	// (DW_FORM_string)
171	.uleb128 0x13	// (DW_AT_language)
172	.uleb128 0x5	// (DW_FORM_data2)
173	.uleb128 0x3	// (DW_AT_name)
174	.uleb128 0x8	// (DW_FORM_string)
175.initByte 0x0
176.initByte 0x0
177
178	.uleb128 0x2	;# (abbrev code)
179	.uleb128 0x2e	;# (TAG: DW_TAG_subprogram)
180.initByte 0x0	;# DW_children_no
181	.uleb128 0x3	;# (DW_AT_name)
182	.uleb128 0x8	;# (DW_FORM_string)
183	.uleb128 0x11	;# (DW_AT_low_pc)
184	.uleb128 0x1	;# (DW_FORM_addr)
185	.uleb128 0x12	;# (DW_AT_high_pc)
186	.uleb128 0x1	;# (DW_FORM_addr)
187.initByte 0x0
188.initByte 0x0
189
190.initByte 0x0
191
192//============================================================================
193// Line information. DwarfLib requires this to be present, but it can
194// be empty.
195//============================================================================
196
197.section .debug_line
198_picoMark_LINES=
199
200//============================================================================
201// Debug Information
202//============================================================================
203.section .debug_info
204
205//Fixed header.
206.unalignedInitLong _picoMark_DEBUG_INFO_END-_picoMark_DEBUG_INFO_BEGIN
207_picoMark_DEBUG_INFO_BEGIN=
208.unalignedInitWord 0x2
209.unalignedInitLong _picoMark_ABBREVIATIONS
210.initByte 0x2
211
212// Compile unit information.
213.uleb128 0x1	// (DIE 0xb) DW_TAG_compile_unit)
214.unalignedInitLong _picoMark_LINES
215.unalignedInitWord _picoMark_FUNCTION_END
216.unalignedInitWord _picoMark_FUNCTION_BEGIN
217// Producer is `picoChip'
218.ascii 16#70# 16#69# 16#63# 16#6f# 16#43# 16#68# 16#69# 16#70# 16#00#
219.unalignedInitWord 0xcafe // ASM language
220.ascii 16#0# // Name. DwarfLib expects this to be present.
221
222.uleb128 0x2	;# (DIE DW_TAG_subprogram)
223
224// FUNCTION NAME GOES HERE. Use `echo name | od -t x1' to get the hex. Each hex
225// digit is specified using the format 16#XX#
226.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'
227.unalignedInitWord _picoMark_FUNCTION_BEGIN	// DW_AT_low_pc
228.unalignedInitWord _picoMark_FUNCTION_END	// DW_AT_high_pc
229
230.initByte 0x0	// end of compile unit children.
231
232_picoMark_DEBUG_INFO_END=
233
234//============================================================================
235// END OF DWARF
236//============================================================================
237.section .endFile
238// End of picoChip ASM file
239