==============================
*  SOURCE
==============================
char a;

char With_switch()
{
	switch(a)
	{
	case '0':
		return 0;
	case '1':
		return 1;
	case 'A':
		return 2;
	case 'B':
		return 3;
	default:
		return 255;
	}
}

char With_if()
{
	     if(a=='0') return 0;
	else if(a=='1')	return 1;
	else if(a=='A')	return 2;
	else if(a=='B')	return 3;
	else return 255;
}



==============================
*  Compiled with -O0
==============================

   8:main.c        **** char With_switch()
   9:main.c        **** {
  66               		.stabn 68,0,9,.LM4-With_switch
  67               	.LM4:
  68               	/* prologue: frame size=4 */
  69 000c CF93      		push r28
  70 000e DF93      		push r29
  71 0010 CDB7      		in r28,__SP_L__
  72 0012 DEB7      		in r29,__SP_H__
  73 0014 2497      		sbiw r28,4
  74 0016 0FB6      		in __tmp_reg__,__SREG__
  75 0018 F894      		cli
  76 001a DEBF      		out __SP_H__,r29
  77 001c 0FBE      		out __SREG__,__tmp_reg__
  78 001e CDBF      		out __SP_L__,r28
  79               	/* prologue end (size=10) */
  10:main.c        **** 	switch(a)
  80               		.stabn 68,0,10,.LM5-With_switch
  81               	.LM5:
  82 0020 8091 0000 		lds r24,a
  83 0024 282F      		mov r18,r24
  84 0026 3327      		clr r19
  85 0028 2B83      		std Y+3,r18
  86 002a 3C83      		std Y+4,r19
  87 002c 8B81      		ldd r24,Y+3
  88 002e 9C81      		ldd r25,Y+4
  89 0030 8133      		cpi r24,49
  90 0032 9105      		cpc r25,__zero_reg__
  91 0034 C9F0      		breq .L8
  92 0036 2B81      		ldd r18,Y+3
  93 0038 3C81      		ldd r19,Y+4
  94 003a 2233      		cpi r18,50
  95 003c 3105      		cpc r19,__zero_reg__
  96 003e 34F4      		brge .L13
  97 0040 8B81      		ldd r24,Y+3
  98 0042 9C81      		ldd r25,Y+4
  99 0044 8033      		cpi r24,48
 100 0046 9105      		cpc r25,__zero_reg__
 101 0048 61F0      		breq .L7
 102 004a 1DC0      		rjmp .L11
 103               	.L13:
 104 004c 2B81      		ldd r18,Y+3
 105 004e 3C81      		ldd r19,Y+4
 106 0050 2134      		cpi r18,65
 107 0052 3105      		cpc r19,__zero_reg__
 108 0054 71F0      		breq .L9
 109 0056 8B81      		ldd r24,Y+3
 110 0058 9C81      		ldd r25,Y+4
 111 005a 8234      		cpi r24,66
 112 005c 9105      		cpc r25,__zero_reg__
 113 005e 71F0      		breq .L10
 114 0060 12C0      		rjmp .L11
 115               	.L7:
  11:main.c        **** 	{
  12:main.c        **** 	case '0':
  13:main.c        **** 		return 0;
 116               		.stabn 68,0,13,.LM6-With_switch
 117               	.LM6:
 118 0062 1982      		std Y+1,__zero_reg__
 119 0064 1A82      		std Y+2,__zero_reg__
 120 0066 13C0      		rjmp .L5
 121               	.L8:
  14:main.c        **** 	case '1':
  15:main.c        **** 		return 1;
 122               		.stabn 68,0,15,.LM7-With_switch
 123               	.LM7:
 124 0068 21E0      		ldi r18,lo8(1)
 125 006a 30E0      		ldi r19,hi8(1)
 126 006c 2983      		std Y+1,r18
 127 006e 3A83      		std Y+2,r19
 128 0070 0EC0      		rjmp .L5
 129               	.L9:
  16:main.c        **** 	case 'A':
  17:main.c        **** 		return 2;
 130               		.stabn 68,0,17,.LM8-With_switch
 131               	.LM8:
 132 0072 82E0      		ldi r24,lo8(2)
 133 0074 90E0      		ldi r25,hi8(2)
 134 0076 8983      		std Y+1,r24
 135 0078 9A83      		std Y+2,r25
 136 007a 09C0      		rjmp .L5
 137               	.L10:
  18:main.c        **** 	case 'B':
  19:main.c        **** 		return 3;
 138               		.stabn 68,0,19,.LM9-With_switch
 139               	.LM9:
 140 007c 23E0      		ldi r18,lo8(3)
 141 007e 30E0      		ldi r19,hi8(3)
 142 0080 2983      		std Y+1,r18
 143 0082 3A83      		std Y+2,r19
 144 0084 04C0      		rjmp .L5
 145               	.L11:
  20:main.c        **** 	default:
  21:main.c        **** 		return 255;
 146               		.stabn 68,0,21,.LM10-With_switch
 147               	.LM10:
 148 0086 8FEF      		ldi r24,lo8(255)
 149 0088 90E0      		ldi r25,hi8(255)
 150 008a 8983      		std Y+1,r24
 151 008c 9A83      		std Y+2,r25
  22:main.c        **** 	}
  23:main.c        **** }
 152               		.stabn 68,0,23,.LM11-With_switch
 153               	.LM11:
 154               	.L5:
 155 008e 8981      		ldd r24,Y+1
 156 0090 9A81      		ldd r25,Y+2
 157               	/* epilogue: frame size=4 */
 158 0092 2496      		adiw r28,4
 159 0094 0FB6      		in __tmp_reg__,__SREG__
 160 0096 F894      		cli
 161 0098 DEBF      		out __SP_H__,r29
 162 009a 0FBE      		out __SREG__,__tmp_reg__
 163 009c CDBF      		out __SP_L__,r28
 164 009e DF91      		pop r29
 165 00a0 CF91      		pop r28
 166 00a2 0895      		ret
 167               	/* epilogue end (size=9) */
 168               	/* function With_switch size 76 (57) */




   25:main.c        **** char With_if()
  26:main.c        **** {
 176               		.stabn 68,0,26,.LM12-With_if
 177               	.LM12:
 178               	/* prologue: frame size=2 */
 179 00a4 CF93      		push r28
 180 00a6 DF93      		push r29
 181 00a8 CDB7      		in r28,__SP_L__
 182 00aa DEB7      		in r29,__SP_H__
 183 00ac 2297      		sbiw r28,2
 184 00ae 0FB6      		in __tmp_reg__,__SREG__
 185 00b0 F894      		cli
 186 00b2 DEBF      		out __SP_H__,r29
 187 00b4 0FBE      		out __SREG__,__tmp_reg__
 188 00b6 CDBF      		out __SP_L__,r28
 189               	/* prologue end (size=10) */
  27:main.c        **** 	     if(a=='0') return 0;
 190               		.stabn 68,0,27,.LM13-With_if
 191               	.LM13:
 192 00b8 8091 0000 		lds r24,a
 193 00bc 8033      		cpi r24,lo8(48)
 194 00be 19F4      		brne .L15
 195 00c0 1982      		std Y+1,__zero_reg__
 196 00c2 1A82      		std Y+2,__zero_reg__
 197 00c4 1FC0      		rjmp .L14
 198               	.L15:
  28:main.c        **** 	else if(a=='1')	return 1;
 199               		.stabn 68,0,28,.LM14-With_if
 200               	.LM14:
 201 00c6 8091 0000 		lds r24,a
 202 00ca 8133      		cpi r24,lo8(49)
 203 00cc 29F4      		brne .L17
 204 00ce 81E0      		ldi r24,lo8(1)
 205 00d0 90E0      		ldi r25,hi8(1)
 206 00d2 8983      		std Y+1,r24
 207 00d4 9A83      		std Y+2,r25
 208 00d6 16C0      		rjmp .L14
 209               	.L17:
  29:main.c        **** 	else if(a=='A')	return 2;
 210               		.stabn 68,0,29,.LM15-With_if
 211               	.LM15:
 212 00d8 8091 0000 		lds r24,a
 213 00dc 8134      		cpi r24,lo8(65)
 214 00de 29F4      		brne .L19
 215 00e0 82E0      		ldi r24,lo8(2)
 216 00e2 90E0      		ldi r25,hi8(2)
 217 00e4 8983      		std Y+1,r24
 218 00e6 9A83      		std Y+2,r25
 219 00e8 0DC0      		rjmp .L14
 220               	.L19:
  30:main.c        **** 	else if(a=='B')	return 3;
 221               		.stabn 68,0,30,.LM16-With_if
 222               	.LM16:
 223 00ea 8091 0000 		lds r24,a
 224 00ee 8234      		cpi r24,lo8(66)
 225 00f0 29F4      		brne .L21
 226 00f2 83E0      		ldi r24,lo8(3)
 227 00f4 90E0      		ldi r25,hi8(3)
 228 00f6 8983      		std Y+1,r24
 229 00f8 9A83      		std Y+2,r25
 230 00fa 04C0      		rjmp .L14
 231               	.L21:
  31:main.c        **** 	else return 255;
 232               		.stabn 68,0,31,.LM17-With_if
 233               	.LM17:
 234 00fc 8FEF      		ldi r24,lo8(255)
 235 00fe 90E0      		ldi r25,hi8(255)
 236 0100 8983      		std Y+1,r24
 237 0102 9A83      		std Y+2,r25
  32:main.c        **** }
 238               		.stabn 68,0,32,.LM18-With_if
 239               	.LM18:
 240               	.L14:
 241 0104 8981      		ldd r24,Y+1
 242 0106 9A81      		ldd r25,Y+2
 243               	/* epilogue: frame size=2 */
 244 0108 2296      		adiw r28,2
 245 010a 0FB6      		in __tmp_reg__,__SREG__
 246 010c F894      		cli
 247 010e DEBF      		out __SP_H__,r29
 248 0110 0FBE      		out __SREG__,__tmp_reg__
 249 0112 CDBF      		out __SP_L__,r28
 250 0114 DF91      		pop r29
 251 0116 CF91      		pop r28
 252 0118 0895      		ret
 253               	/* epilogue end (size=9) */
 254               	/* function With_if size 59 (40) */


==============================
*  Compiled with -O3
==============================

    8:main.c        **** char With_switch()
   9:main.c        **** {
  65               		.stabn 68,0,9,.LM4-With_switch
  66               	.LM4:
  67               	/* prologue: frame size=0 */
  68               	/* prologue end (size=0) */
  10:main.c        **** 	switch(a)
  69               		.stabn 68,0,10,.LM5-With_switch
  70               	.LM5:
  71 000a 8091 0000 		lds r24,a
  72 000e 9927      		clr r25
  73 0010 8133      		cpi r24,49
  74 0012 9105      		cpc r25,__zero_reg__
  75 0014 B9F0      		breq .L8
  76 0016 8233      		cpi r24,50
  77 0018 9105      		cpc r25,__zero_reg__
  78 001a 44F4      		brge .L13
  79 001c C097      		sbiw r24,48
  80 001e 19F0      		breq .L7
  81               	.L11:
  11:main.c        **** 	{
  12:main.c        **** 	case '0':
  13:main.c        **** 		return 0;
  14:main.c        **** 	case '1':
  15:main.c        **** 		return 1;
  16:main.c        **** 	case 'A':
  17:main.c        **** 		return 2;
  18:main.c        **** 	case 'B':
  19:main.c        **** 		return 3;
  20:main.c        **** 	default:
  21:main.c        **** 		return 255;
  82               		.stabn 68,0,21,.LM6-With_switch
  83               	.LM6:
  84 0020 8FEF      		ldi r24,lo8(255)
  85 0022 90E0      		ldi r25,hi8(255)
  22:main.c        **** 	}
  23:main.c        **** }
  86               		.stabn 68,0,23,.LM7-With_switch
  87               	.LM7:
  88 0024 0895      		ret
  89               	.L7:
  90               		.stabn 68,0,13,.LM8-With_switch
  91               	.LM8:
  92 0026 80E0      		ldi r24,lo8(0)
  93 0028 90E0      		ldi r25,hi8(0)
  94               		.stabn 68,0,23,.LM9-With_switch
  95               	.LM9:
  96 002a 0895      		ret
  97               	.L13:
  98 002c 8134      		cpi r24,65
  99 002e 9105      		cpc r25,__zero_reg__
 100 0030 31F0      		breq .L9
 101 0032 8234      		cpi r24,66
 102 0034 9105      		cpc r25,__zero_reg__
 103 0036 A1F7      		brne .L11
 104               		.stabn 68,0,19,.LM10-With_switch
 105               	.LM10:
 106 0038 83E0      		ldi r24,lo8(3)
 107 003a 90E0      		ldi r25,hi8(3)
 108               		.stabn 68,0,23,.LM11-With_switch
 109               	.LM11:
 110 003c 0895      		ret
 111               	.L9:
 112               		.stabn 68,0,17,.LM12-With_switch
 113               	.LM12:
 114 003e 82E0      		ldi r24,lo8(2)
 115 0040 90E0      		ldi r25,hi8(2)
 116               		.stabn 68,0,23,.LM13-With_switch
 117               	.LM13:
 118 0042 0895      		ret
 119               	.L8:
 120               		.stabn 68,0,15,.LM14-With_switch
 121               	.LM14:
 122 0044 81E0      		ldi r24,lo8(1)
 123 0046 90E0      		ldi r25,hi8(1)
 124               		.stabn 68,0,23,.LM15-With_switch
 125               	.LM15:
 126 0048 0895      		ret
 127               	/* epilogue: frame size=0 */
 128 004a 0895      		ret
 129               	/* epilogue end (size=1) */
 130               	/* function With_switch size 34 (33) */





  25:main.c        **** char With_if()
  26:main.c        **** {
 138               		.stabn 68,0,26,.LM16-With_if
 139               	.LM16:
 140               	/* prologue: frame size=0 */
 141               	/* prologue end (size=0) */
  27:main.c        **** 	     if(a=='0') return 0;
 142               		.stabn 68,0,27,.LM17-With_if
 143               	.LM17:
 144 004c 8091 0000 		lds r24,a
 145 0050 8033      		cpi r24,lo8(48)
 146 0052 91F0      		breq .L23
  28:main.c        **** 	else if(a=='1')	return 1;
 147               		.stabn 68,0,28,.LM18-With_if
 148               	.LM18:
 149 0054 8133      		cpi r24,lo8(49)
 150 0056 69F0      		breq .L24
  29:main.c        **** 	else if(a=='A')	return 2;
 151               		.stabn 68,0,29,.LM19-With_if
 152               	.LM19:
 153 0058 8134      		cpi r24,lo8(65)
 154 005a 41F0      		breq .L25
  30:main.c        **** 	else if(a=='B')	return 3;
 155               		.stabn 68,0,30,.LM20-With_if
 156               	.LM20:
 157 005c 8234      		cpi r24,lo8(66)
 158 005e 19F0      		breq .L26
  31:main.c        **** 	else return 255;
 159               		.stabn 68,0,31,.LM21-With_if
 160               	.LM21:
 161 0060 8FEF      		ldi r24,lo8(255)
 162 0062 90E0      		ldi r25,hi8(255)
  32:main.c        **** }
 163               		.stabn 68,0,32,.LM22-With_if
 164               	.LM22:
 165 0064 0895      		ret
 166               	.L26:
 167 0066 83E0      		ldi r24,lo8(3)
 168 0068 90E0      		ldi r25,hi8(3)
 169 006a 0895      		ret
 170               	.L25:
 171 006c 82E0      		ldi r24,lo8(2)
 172 006e 90E0      		ldi r25,hi8(2)
 173 0070 0895      		ret
 174               	.L24:
 175 0072 81E0      		ldi r24,lo8(1)
 176 0074 90E0      		ldi r25,hi8(1)
 177 0076 0895      		ret
 178               	.L23:
 179 0078 80E0      		ldi r24,lo8(0)
 180 007a 90E0      		ldi r25,hi8(0)
 181 007c 0895      		ret
 182               	/* epilogue: frame size=0 */
 183 007e 0895      		ret
 184               	/* epilogue end (size=1) */
 185               	/* function With_if size 26 (25) */



==============================
*  Compiled with -Os
==============================



   8:main.c        **** char With_switch()
   9:main.c        **** {
  65               		.stabn 68,0,9,.LM4-With_switch
  66               	.LM4:
  67               	/* prologue: frame size=0 */
  68               	/* prologue end (size=0) */
  10:main.c        **** 	switch(a)
  69               		.stabn 68,0,10,.LM5-With_switch
  70               	.LM5:
  71 000a 8091 0000 		lds r24,a
  72 000e 9927      		clr r25
  73 0010 8133      		cpi r24,49
  74 0012 9105      		cpc r25,__zero_reg__
  75 0014 81F0      		breq .L8
  76 0016 8233      		cpi r24,50
  77 0018 9105      		cpc r25,__zero_reg__
  78 001a 1CF4      		brge .L13
  79 001c C097      		sbiw r24,48
  80 001e 41F0      		breq .L7
  81 0020 13C0      		rjmp .L11
  82               	.L13:
  83 0022 8134      		cpi r24,65
  84 0024 9105      		cpc r25,__zero_reg__
  85 0026 51F0      		breq .L9
  86 0028 8234      		cpi r24,66
  87 002a 9105      		cpc r25,__zero_reg__
  88 002c 51F0      		breq .L10
  89 002e 0CC0      		rjmp .L11
  90               	.L7:
  11:main.c        **** 	{
  12:main.c        **** 	case '0':
  13:main.c        **** 		return 0;
  91               		.stabn 68,0,13,.LM6-With_switch
  92               	.LM6:
  93 0030 80E0      		ldi r24,lo8(0)
  94 0032 90E0      		ldi r25,hi8(0)
  14:main.c        **** 	case '1':
  15:main.c        **** 		return 1;
  16:main.c        **** 	case 'A':
  17:main.c        **** 		return 2;
  18:main.c        **** 	case 'B':
  19:main.c        **** 		return 3;
  20:main.c        **** 	default:
  21:main.c        **** 		return 255;
  22:main.c        **** 	}
  23:main.c        **** }
  95               		.stabn 68,0,23,.LM7-With_switch
  96               	.LM7:
  97 0034 0895      		ret
  98               	.L8:
  99               		.stabn 68,0,15,.LM8-With_switch
 100               	.LM8:
 101 0036 81E0      		ldi r24,lo8(1)
 102 0038 90E0      		ldi r25,hi8(1)
 103               		.stabn 68,0,23,.LM9-With_switch
 104               	.LM9:
 105 003a 0895      		ret
 106               	.L9:
 107               		.stabn 68,0,17,.LM10-With_switch
 108               	.LM10:
 109 003c 82E0      		ldi r24,lo8(2)
 110 003e 90E0      		ldi r25,hi8(2)
 111               		.stabn 68,0,23,.LM11-With_switch
 112               	.LM11:
 113 0040 0895      		ret
 114               	.L10:
 115               		.stabn 68,0,19,.LM12-With_switch
 116               	.LM12:
 117 0042 83E0      		ldi r24,lo8(3)
 118 0044 90E0      		ldi r25,hi8(3)
 119               		.stabn 68,0,23,.LM13-With_switch
 120               	.LM13:
 121 0046 0895      		ret
 122               	.L11:
 123               		.stabn 68,0,21,.LM14-With_switch
 124               	.LM14:
 125 0048 8FEF      		ldi r24,lo8(255)
 126 004a 90E0      		ldi r25,hi8(255)
 127               		.stabn 68,0,23,.LM15-With_switch
 128               	.LM15:
 129 004c 0895      		ret
 130               	/* epilogue: frame size=0 */
 131 004e 0895      		ret
 132               	/* epilogue end (size=1) */
 133               	/* function With_switch size 36 (35) */





  25:main.c        **** char With_if()
  26:main.c        **** {
 141               		.stabn 68,0,26,.LM16-With_if
 142               	.LM16:
 143               	/* prologue: frame size=0 */
 144               	/* prologue end (size=0) */
  27:main.c        **** 	     if(a=='0') return 0;
 145               		.stabn 68,0,27,.LM17-With_if
 146               	.LM17:
 147 0050 8091 0000 		lds r24,a
 148 0054 8033      		cpi r24,lo8(48)
 149 0056 19F4      		brne .L15
 150 0058 80E0      		ldi r24,lo8(0)
 151 005a 90E0      		ldi r25,hi8(0)
  28:main.c        **** 	else if(a=='1')	return 1;
  29:main.c        **** 	else if(a=='A')	return 2;
  30:main.c        **** 	else if(a=='B')	return 3;
  31:main.c        **** 	else return 255;
  32:main.c        **** }
 152               		.stabn 68,0,32,.LM18-With_if
 153               	.LM18:
 154 005c 0895      		ret
 155               	.L15:
 156               		.stabn 68,0,28,.LM19-With_if
 157               	.LM19:
 158 005e 8133      		cpi r24,lo8(49)
 159 0060 19F4      		brne .L17
 160 0062 81E0      		ldi r24,lo8(1)
 161 0064 90E0      		ldi r25,hi8(1)
 162               		.stabn 68,0,32,.LM20-With_if
 163               	.LM20:
 164 0066 0895      		ret
 165               	.L17:
 166               		.stabn 68,0,29,.LM21-With_if
 167               	.LM21:
 168 0068 8134      		cpi r24,lo8(65)
 169 006a 19F4      		brne .L19
 170 006c 82E0      		ldi r24,lo8(2)
 171 006e 90E0      		ldi r25,hi8(2)
 172               		.stabn 68,0,32,.LM22-With_if
 173               	.LM22:
 174 0070 0895      		ret
 175               	.L19:
 176               		.stabn 68,0,30,.LM23-With_if
 177               	.LM23:
 178 0072 8234      		cpi r24,lo8(66)
 179 0074 19F4      		brne .L21
 180 0076 83E0      		ldi r24,lo8(3)
 181 0078 90E0      		ldi r25,hi8(3)
 182               		.stabn 68,0,32,.LM24-With_if
 183               	.LM24:
 184 007a 0895      		ret
 185               	.L21:
 186               		.stabn 68,0,31,.LM25-With_if
 187               	.LM25:
 188 007c 8FEF      		ldi r24,lo8(255)
 189 007e 90E0      		ldi r25,hi8(255)
 190               		.stabn 68,0,32,.LM26-With_if
 191               	.LM26:
 192 0080 0895      		ret
 193               	/* epilogue: frame size=0 */
 194 0082 0895      		ret
 195               	/* epilogue end (size=1) */
 196               	/* function With_if size 26 (25) */