http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54461
Bug #: 54461 Summary: [avr] add configure option for better AVR-Libc integration Classification: Unclassified Product: gcc Version: 4.7.1 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: target AssignedTo: g...@gcc.gnu.org ReportedBy: g...@gcc.gnu.org Target: avr For historical reasons, AVR-Libc implements functions that GCC expects to live in libgcc, namely float functions like __fixsfsi. Currently, avr-gcc is not configurable to accommodate that situation which leads to performance loss if the float support functions from libgcc are used. This happens at least in the following situations: * The user does not specify -lm. -lm should only be needed if function from math.h are used, not for language core features like int i = (int) float. * The application is LTO compiled, i.e. linked with -flto. The plugin machinery passes lgcc -lc lgcc through to the linker by means of -plugin-opt=-pass-through=-lgcc etc. so that -lgcc is linked prior to -lm. * The user uses fixed <-> float conversion routines from libgcc. These routines refer float functions, and the linker resolves these function in libgcc if they are there. * avr-g++ is used as linker driver. See also PR28718 and http://lists.gnu.org/archive/html/avr-gcc-list/2012-08/msg00070.html