Mindaugasu
Member level 3
Re: Transfer table addres to function using inline ASM?-solv
Ok I have concrete question to those who knows AVR-GCC.
My data is in flash memory:
I have a function which outputs data from this lookup table to PORTD.
I looked in compiled listing and I have noticed that pointer address is given to r24 and r25 registers.
And then within function signalOUT r24 and r25 are passed to r31 and r30 by command movw r30,r24.
Is there any way to show a compiler to pass pointer address directly to r30 and r31 (Z) that I could work with inline asm function:
because according to avrlibc ) directive "e" (signal) in inline asm assigns a Z pointer to value. Is there some kin of a bug or I am missing something.
Thank you
Added after 5 hours 29 minutes:
Added after 2 minutes:
Just in case someone is interested...
Using static inline function makes compiler optimize code this way, that when calling function table pointer is directly passed to r30:r31 register pair.
---------------------------------------------------
http://www.scienceprog.com
Ok I have concrete question to those who knows AVR-GCC.
My data is in flash memory:
Code:
const uint8_t sinewave[] PROGMEM= //256 values
{
0x80,0x83,0x86,0x89,0x8c,0x8f,.....
Code:
void signalOUT1(const uint8_t *signal)
{
uint8_t i=0;
do{
PORTD=pgm_read_byte(&signal[i++]);
}while(1);
}I looked in compiled listing and I have noticed that pointer address is given to r24 and r25 registers.
Code:
2738 05b6 80E0 ldi r24,lo8(sinewave)
2739 05b8 90E0 ldi r25,hi8(sinewave)
2740 .L150:
2741 05ba 99DD rcall signalOUTAnd then within function signalOUT r24 and r25 are passed to r31 and r30 by command movw r30,r24.
Is there any way to show a compiler to pass pointer address directly to r30 and r31 (Z) that I could work with inline asm function:
Code:
void signalOUT(const uint8_t *signal, uint8_t ad2, uint8_t ad1, uint8_t ad0)
{
asm volatile("eor r28, r28 ;r28<-0" "\n\t"
"eor r29, r29 ;r29<-0" "\n\t"
"1:" "\n\t"
"add r28, %0 ;1 cycle" "\n\t"
"adc r29, %1 ;1 cycle" "\n\t"
"adc %A3, %2 ;1 cycle" "\n\t"
"lpm __tmp_reg__, %a3+ ;3 cycles" "\n\t"
"out %4, __tmp_reg__ ;1 cycle" "\n\t"
"rjmp 1b ;2 cycles. Total 9 cycles" "\n\t"
:
:"r" (ad0),"r" (ad1),"r" (ad2),"e" (signal),"I" (_SFR_IO_ADDR(PORTD))
:"r28", "r29"
);
}because according to avrlibc ) directive "e" (signal) in inline asm assigns a Z pointer to value. Is there some kin of a bug or I am missing something.
Thank you
Added after 5 hours 29 minutes:
Added after 2 minutes:
Just in case someone is interested...
Using static inline function makes compiler optimize code this way, that when calling function table pointer is directly passed to r30:r31 register pair.
---------------------------------------------------
http://www.scienceprog.com