On Nov 25, 2013, at 10:25 PM, Jan-Benedict Glaw <jbg...@lug-owl.de> wrote:
> Hi! > > Build log at > http://toolchain.lug-owl.de/buildbot/show_build_details.php?id=40865 > > g++ -c -g -O2 -DIN_GCC -DCROSS_DIRECTORY_STRUCTURE -fno-exceptions > -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing > -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -pedantic > -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror > -fno-common -DHAVE_CONFIG_H -I. -I. -I../../../gcc/gcc -I../../../gcc/gcc/. > -I../../../gcc/gcc/../include -I../../../gcc/gcc/../libcpp/include > -I/opt/cfarm/mpc/include -I../../../gcc/gcc/../libdecnumber > -I../../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber > -I../../../gcc/gcc/../libbacktrace -o cfgexpand.o -MT cfgexpand.o -MMD -MP > -MF ./.deps/cfgexpand.TPo ../../../gcc/gcc/cfgexpand.c > ../../../gcc/gcc/cfgexpand.c: In function ‘basic_block_def* > expand_gimple_cond(basic_block, gimple)’: > ../../../gcc/gcc/cfgexpand.c:2027:65: error: comparison is always true due to > limited range of data type [-Werror=type-limits] > else if (BRANCH_COST (optimize_insn_for_speed_p (), false) < 4) > ^ > cc1plus: all warnings being treated as errors > make[2]: *** [cfgexpand.o] Error 1 Interesting. In the pdp11 target, BRANCH_COST is either 0 or 1. So yes, that comparison is always true. Is there a requirement that all targets must have branch cost that it, at least some of the time, 4 or greater? If so, why? If not, then I suppose cfgexpand.c could be changed to defeat this message, but how, or why? In general, it seems perfectly reasonable to have code guarded by conditions that may be always true, or always false. That's what we have optimizers for. Defeating such optimizations by calling them an error seems like a bad idea. paul
