глюк в AVRStudio

решил протестировать AVRStudio 4.19

набираю код
long tz=7;
void ssb(long t){
tz=t+sizeof(long);
}
int main()
{
ssb(6);
ssb(7);
ssb(6);
return 0;
}
смотрю листинг на ассемблере
5: void ssb(long t){
+00000026: 93DF PUSH R29 Push register on stack
+00000027: 93CF PUSH R28 Push register on stack
+00000028: D000 RCALL PC+0x0001 Relative call subroutine
+00000029: D000 RCALL PC+0x0001 Relative call subroutine
+0000002A: B7CD IN R28,0x3D In from I/O location
+0000002B: B7DE IN R29,0x3E In from I/O location
+0000002C: 8369 STD Y+1,R22 Store indirect with displacement
+0000002D: 837A STD Y+2,R23 Store indirect with displacement
+0000002E: 838B STD Y+3,R24 Store indirect with displacement
+0000002F: 839C STD Y+4,R25 Store indirect with displacement
7: tz=t+sizeof(long);
+00000030: 8189 LDD R24,Y+1 Load indirect with displacement
+00000031: 819A LDD R25,Y+2 Load indirect with displacement
+00000032: 81AB LDD R26,Y+3 Load indirect with displacement
+00000033: 81BC LDD R27,Y+4 Load indirect with displacement
+00000034: 9604 ADIW R24,0x04 Add immediate to word
+00000035: 1DA1 ADC R26,R1 Add with carry
+00000036: 1DB1 ADC R27,R1 Add with carry
+00000037: 93800060 STS 0x0060,R24 Store direct to data space
+00000039: 93900061 STS 0x0061,R25 Store direct to data space
+0000003B: 93A00062 STS 0x0062,R26 Store direct to data space
+0000003D: 93B00063 STS 0x0063,R27 Store direct to data space
8: }
+0000003F: 900F POP R0 Pop register from stack
+00000040: 900F POP R0 Pop register from stack
+00000041: 900F POP R0 Pop register from stack
+00000042: 900F POP R0 Pop register from stack
+00000043: 91CF POP R28 Pop register from stack
+00000044: 91DF POP R29 Pop register from stack
+00000045: 9508 RET Subroutine return
@00000046: main
12: {
+00000046: 93DF PUSH R29 Push register on stack
+00000047: 93CF PUSH R28 Push register on stack
+00000048: B7CD IN R28,0x3D In from I/O location
+00000049: B7DE IN R29,0x3E In from I/O location
13: ssb(6);
+0000004A: E066 LDI R22,0x06 Load immediate
+0000004B: E070 LDI R23,0x00 Load immediate
+0000004C: E080 LDI R24,0x00 Load immediate
+0000004D: E090 LDI R25,0x00 Load immediate
+0000004E: DFD7 RCALL PC-0x0028 Relative call subroutine
14: ssb(7);
+0000004F: E067 LDI R22,0x07 Load immediate
+00000050: E070 LDI R23,0x00 Load immediate
+00000051: E080 LDI R24,0x00 Load immediate
+00000052: E090 LDI R25,0x00 Load immediate
+00000053: DFD2 RCALL PC-0x002D Relative call subroutine
15: ssb(6);
+00000054: E066 LDI R22,0x06 Load immediate
+00000055: E070 LDI R23,0x00 Load immediate
+00000056: E080 LDI R24,0x00 Load immediate
+00000057: E090 LDI R25,0x00 Load immediate
+00000058: DFCD RCALL PC-0x0032 Relative call subroutine
16: return 0;
+00000059: E080 LDI R24,0x00 Load immediate
+0000005A: E090 LDI R25,0x00 Load immediate
17: }

Откуда взялось :
+0000002A: B7CD IN R28,0x3D In from I/O location
+0000002B: B7DE IN R29,0x3E In from I/O location
Это что глюк?

 

Это загрузка указателя стека в регистр Y.

 

а причём тут порты?

 

Потому что c регистром SP (как и вообще любым регистром кроме r0-r31)работают через in/out инструкции. Можно использовать и прямое чтение из SRAM, но это менее эффективно.