> -----Original Message----- > From: avr-gcc-list-bounces+eric.weddington=atmel....@nongnu.org > [mailto:avr-gcc-list-bounces+eric.weddington=atmel....@nongnu.org] On > Behalf Of Georg-Johann Lay > Sent: Sunday, October 07, 2012 2:26 AM > To: avr-gcc-list@nongnu.org > Subject: [avr-gcc-list] May avr-libc use functions from libgcc? > > Is is legitimate that assembler functions in avr-libc call functions > implemented in libgcc directly? > > This would make some assumptions, e.g. on naming conventions. > > Calling directly can lead so smaller and faster code because some > functions in libgcc implement a special ABI. > > For example __udivmodqi4 (unsigned 8-bit quotient and remainder) does > not clobber X or Z so that the caller can hold values in these registers > across the call which reduces register pressure in the caller. > > Are such calls "allowed" in avr-libc provided > > - The special interface is documented in libgcc sources and mentions > that avr-libc makes use of the special interface > > - The functions with their special interface are documented, e.g. in > the GCC wiki > > The question is for code that is not yet part of avr-libc, namely the > upcoming fixed-point support; it's not about optimizing code that's > already there. > > Sean said that CORDIC shows bad rounding for asin, for example. > > I played around with a home-brew asin approach that has no rounding > issues. The performance of the implementation can be improved if > knowledge of libgcc is used.
I'm ok with this using knowledge of libgcc in avr-libc, if the benefits are faster, and especially smaller, code. I'd like to hear from other project members... Eric _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org https://lists.nongnu.org/mailman/listinfo/avr-gcc-list
