Public bug reported:
A "C" source of a Lowpass DSP filter function hangs on CC1 for avr-gcc
4.8x and above but is OK with avr-gcc 4.7x
This code compiled OK with avr-gcc 4.7x on Kubuntu 13.10 but hangs at
CC1 with near 100% CPU usage for any later version of avr-gcc and
Kubuntu. The compilation does complete after a long pause. The code
below demonstrates this problem when compiled to assembler with "avr-gcc
-Wall -S filter.c". The later versions of gcc will compile this code
using "gcc -Wall -S filter.c" without this problem. Kubuntu 14.10, GCC
version 4.9.1 (Ubuntu 4.9.1-16ubuntu6) is OK but the corresponding
version of GCC-AVR for Kubuntu 14.10, gcc-avr 4.8.1+Atmel3.4.4-2 will
hang with near 100% CPU usage, but does eventually complete.
The code below has been part of a commercial production product's
firmware for a number of years and were compiled with gcc-avr on earlier
versions of Kubuntu 13.10.
long Lowpass(long ADC_In)
{
static long long xv[4] = {0,0,0,0};
static long long yv[4] = {0,0,0,0};
// "Mkfilter" Low Pass Filter for the ADC value
// 3rd order IIR Butterworth 0.2Hz corner frequency
// Sample Rate 50Hz
xv[0] = xv[1];
xv[1] = xv[2];
xv[2] = xv[3];
xv[3] = (long long)ADC_In;
yv[0] = yv[1];
yv[1] = yv[2];
yv[2] = yv[3];
yv[3] = (xv[0] + xv[3]) + 3 * (xv[1] + xv[2]);
yv[3] += (( 950976L * yv[0] ) + ( -2900727L * yv[1] )) / 1000000L;
yv[3] += ( 2949736L * yv[2] ) / 1000000L;
// Scale for filter GAIN and resolution of 10bit ADC
ADC_In = (long)(yv[3] >> 18);
return (ADC_In);
}
** Affects: gcc-avr (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1446462
Title:
CC1 hangs on DSP filter function
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