| ??? 05/03/08 14:54 Read: times |
#154344 - *(buffer+8+index)? Responding to: ???'s previous message |
That's not what I would call high-level; it's rather abusing the pointer arithmetics of C (which in itself is not a HLL idea either).
I don't have Keil's at hand here. Can you please try to compile the following snippet (this is sdcc so please modify whatever needed for Keil's), and present the resulting asm here, so that we can chew more at it? JW
typedef unsigned char uint8_t;
uint8_t buffer[10];
uint8_t xdata xbuffer[300];
uint8_t code cbuffer[10] = {'A','B','C','D','E','F','G','H','I','J'};
uint8_t index;
void main(void) {
for (index = 250; index < 255; index++) {
if (*(buffer+8+index) == 0x47) break;
if (buffer[index + 8] == 0x47) break;
if (*(xbuffer+8+index) == 0x47) break;
if (xbuffer[index + 8] == 0x47) break;
if (*(cbuffer+8+index) == 0x47) break;
if (cbuffer[index + 8] == 0x47) break;
}
}
SDCC v2.7.4: 141 ; p1.c:8: for (index = 250; index < 255; index++) {
0000 75*0A FA 142 mov _index,#0xFA
0003 143 00113$:
0003 74 01 144 mov a,#0x100 - 0xFF
0005 25*0A 145 add a,_index
0007 50 01 146 jnc 00127$
0009 22 147 ret
000A 148 00127$:
149 ; p1.c:9: if (*(buffer+8+index) == 0x47) break;
000A E5*0A 150 mov a,_index
000C 24r08 151 add a,#(_buffer + 0x0008)
000E F8 152 mov r0,a
000F 86 02 153 mov ar2,@r0
0011 BA 47 01 154 cjne r2,#0x47,00128$
0014 22 155 ret
0015 156 00128$:
157 ; p1.c:10: if (buffer[index + 8] == 0x47) break;
0015 74 08 158 mov a,#0x08
0017 25*0A 159 add a,_index
0019 24r00 160 add a,#_buffer
001B F8 161 mov r0,a
001C 86 02 162 mov ar2,@r0
001E BA 47 01 163 cjne r2,#0x47,00129$
0021 22 164 ret
0022 165 00129$:
166 ; p1.c:11: if (*(xbuffer+8+index) == 0x47) break;
0022 E5*0A 167 mov a,_index
0024 24r08 168 add a,#(_xbuffer + 0x0008)
0026 F5 82 169 mov dpl,a
0028 E4 170 clr a
0029 34s00 171 addc a,#((_xbuffer + 0x0008) >> 8)
002B F5 83 172 mov dph,a
002D E0 173 movx a,@dptr
002E FA 174 mov r2,a
002F BA 47 01 175 cjne r2,#0x47,00130$
0032 22 176 ret
0033 177 00130$:
178 ; p1.c:12: if (xbuffer[index + 8] == 0x47) break;
0033 AA*0A 179 mov r2,_index
0035 7B 00 180 mov r3,#0x00
0037 74 08 181 mov a,#0x08
0039 2A 182 add a,r2
003A FA 183 mov r2,a
003B E4 184 clr a
003C 3B 185 addc a,r3
003D FB 186 mov r3,a
003E EA 187 mov a,r2
003F 24r00 188 add a,#_xbuffer
0041 F5 82 189 mov dpl,a
0043 EB 190 mov a,r3
0044 34s00 191 addc a,#(_xbuffer >> 8)
0046 F5 83 192 mov dph,a
0048 E0 193 movx a,@dptr
0049 FA 194 mov r2,a
004A BA 47 01 195 cjne r2,#0x47,00131$
004D 22 196 ret
004E 197 00131$:
198 ; p1.c:13: if (*(cbuffer+8+index) == 0x47) break;
004E E5*0A 199 mov a,_index
0050 90s00r08 200 mov dptr,#(_cbuffer + 0x0008)
0053 93 201 movc a,@a+dptr
0054 FA 202 mov r2,a
0055 BA 47 01 203 cjne r2,#0x47,00132$
0058 22 204 ret
0059 205 00132$:
206 ; p1.c:14: if (cbuffer[index + 8] == 0x47) break;
0059 74 08 207 mov a,#0x08
005B 25*0A 208 add a,_index
005D 90s00r00 209 mov dptr,#_cbuffer
0060 93 210 movc a,@a+dptr
0061 FA 211 mov r2,a
0062 BA 47 01 212 cjne r2,#0x47,00133$
0065 22 213 ret
0066 214 00133$:
215 ; p1.c:8: for (index = 250; index < 255; index++) {
0066 05*0A 216 inc _index
0068 02s00r03 217 ljmp 00113$
|
| Topic | Author | Date |
| "Real C" vs '51 C | 01/01/70 00:00 | |
| there is nothing wrong except... | 01/01/70 00:00 | |
| if you are not , why are you even here | 01/01/70 00:00 | |
| *(buffer+8+index)? | 01/01/70 00:00 | |
| none of the above | 01/01/70 00:00 | |
| OK then how? | 01/01/70 00:00 | |
| like this | 01/01/70 00:00 | |
| but it's basically the same... | 01/01/70 00:00 | |
| YCMV | 01/01/70 00:00 | |
| No | 01/01/70 00:00 | |
| assumptions | 01/01/70 00:00 | |
| Re: assumptions | 01/01/70 00:00 | |
| I took a \'known\' example | 01/01/70 00:00 | |
| Compiler-independent efficient C | 01/01/70 00:00 | |
| a clarification and an example | 01/01/70 00:00 | |
| Two kinds of "efficiency" | 01/01/70 00:00 | |
| Compiler smarter than coder | 01/01/70 00:00 | |
| Getting the least out of your compiler | 01/01/70 00:00 | |
| Real C is inherently reentrant | 01/01/70 00:00 | |
which, even when possible, often is ill advised | 01/01/70 00:00 |