I tried to compile gsl-1.5 with the actual snapshot of gcc40 and got an ICE when I use -ffast-math.
Michael Cieslinski gcc40 -ffast-math -c infnan.i -o infnan.o -pipe -v Reading specs from /usr/local/gcc40f/lib/gcc/powerpc-unknown-linux- gnu/4.0.0/specs Configured with: ../gcc40/configure --prefix=/usr/local/gcc40f --program- suffix=40f --with-cpu=G5 --enable-altivec --enable-languages=c,c++ --enable- checking Thread model: posix gcc version 4.0.0 20041114 (experimental) /usr/local/gcc40f/libexec/gcc/powerpc-unknown-linux-gnu/4.0.0/cc1 - fpreprocessed infnan.i -quiet -dumpbase infnan.i -mcpu=G5 -auxbase-strip infnan.o -version -ffast-math -fPIC -o - | as -mpower4 -maltivec -many -V -Qy -K PIC -o infnan.o - GNU C version 4.0.0 20041114 (experimental) (powerpc-unknown-linux-gnu) compiled by GNU C version 4.0.0 20041114 (experimental). GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 GNU assembler version 2.15.90 (ppc-redhat-linux) using BFD version 2.15.90 20040225 infnan.c: In function "gsl_isnan": infnan.c:109: internal compiler error: in emit_store_flag, at expmed.c:5081 Please submit a full bug report, with preprocessed source if appropriate. -- Summary: ICE in emit_store_flag, at expmed.c:5081 Product: gcc Version: 4.0.0 Status: UNCONFIRMED Severity: normal Priority: P2 Component: middle-end AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: micis at gmx dot de CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: powerpc-unknown-linux-gnu GCC host triplet: powerpc-unknown-linux-gnu GCC target triplet: powerpc-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18520