static unsigned char key_pressed;

778:    80 b3           in    r24, 0x10; 16
  if (key_pressed != (PIND & 1)) {
77a:    40 91 6a 00     lds    r20, 0x006A
77e:    80 b3           in    r24, 0x10; 16
780:    24 2f           mov    r18, r20
782:    30 e0           ldi    r19, 0x00; 0
784:    90 e0           ldi    r25, 0x00; 0
786:    81 70           andi    r24, 0x01; 1
788:    90 70           andi    r25, 0x00; 0
78a:    28 17           cp    r18, r24
78c:    39 07           cpc    r19, r25
78e:    59 f0           breq    .+22    ; 0x7a6 <KeyExe+0x2e>

  static unsigned char key_pressed;
  unsigned char s = PIND & 1;
778:    80 b3           in    r24, 0x10; 16
  if (key_pressed != s) {
77a:    90 91 6a 00     lds    r25, 0x006A
77e:    81 70           andi    r24, 0x01; 1
780:    98 17           cp    r25, r24
782:    59 f0           breq    .+22    ; 0x79a <KeyExe+0x22>

58:main.cpp      **** static volatile unsigned char key_pressed;

  62:main.cpp      ****     if(key_pressed != (PINC & 1))
  85                       .loc 1 62 0
  86 0000 9091 0000         lds r25,_ZL11key_pressed
  87 0004 86B1              in r24,0x6
  88 0006 8170              andi r24,lo8(1)
  89 0008 9817              cp r25,r24
  90 000a 01F0              breq .L10
  63:main.cpp      ****         asm volatile ("nop" ::);
  91                       .loc 1 63 0
  92                   /* #APP */
  93                   ;  63 "main.cpp" 1
  94 000c 0000              nop
  95                   ;  0 "" 2
  96                   /* #NOAPP */
  97                   .L10:

avr-gcc  -mmcu=atmega48 -Wall -gdwarf-2  -DF_CPU=4000000UL -Os  -MD -MP -MT ./release/obj/main.o -MF ./release/dep/main.o.d  -ffunction-sections  -fdata-sections -Wa,-ahlmsd=./release/lst/main.lst -c  main.cpp -o release/obj/main.o

$ avr-gcc --version
avr-gcc (GCC) 4.8.2

avr-gcc (WinAVR 20100110) 4.3.3

5cc:    90 91 6b 00     lds    r25, 0x006B
5d0:    80 b3           in    r24, 0x10; 16
5d2:    69 2f           mov    r22, r25
5d4:    70 e0           ldi    r23, 0x00; 0
5d6:    86 95           lsr    r24
5d8:    21 e0           ldi    r18, 0x01; 1
5da:    82 27           eor    r24, r18
5dc:    48 2f           mov    r20, r24
5de:    41 70           andi    r20, 0x01; 1
5e0:    50 e0           ldi    r21, 0x00; 0
5e2:    64 17           cp    r22, r20
5e4:    75 07           cpc    r23, r21
5e6:    49 f0           breq    .+18     ; 0x5fa <KeyExe+0x2e>

avr-gcc (GCC) 4.9.2 20140912 (prerelease)

  if (key_pressed != (!(PIND & 2))) {

avr-gcc -c -mmcu=attiny2313 -I. -gdwarf-2 -DF_CPU=1000000UL -Os -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-adhlns=./../inc/ky.lst -I../inc -std=gnu99 -MMD -MP -MF .dep/ky.o.d ../inc/ky.c -o ../inc/ky.o

static unsigned char key_pressed;