With the entry "(-mtune=xscale) Target Optimizations" for arm926ej-s The package configuration ignores "Target Optimizations" settings CFLAGS="-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 " CXXFLAGS="-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 "
An option like -mtune should *not* be passed in "Target optimization". The march, mcpu and mtune options are all defined automatically depending on the value you specify in the "Target options" menu, where you select the architecture and architecture variant. Select xscale there and you're all set. Also, the reason why you don't see -mcpu, -mtune and so on is because they are automatically passed by our toolchain wrapper, so they are hidden. Or if you are using an internal toolchain, then the toolchain is configured to build binaries for the specified target, so there is no need to pass mcpu/mtune/march when invoking the compiler.
Apparently no "Target Optimizations" are applied to the CFLAGS and CXXFLAGS, but "Target Linker Options" are applied to LDFLAGS. ? Is this a white flag to red flags? "-mtune=xscale" was an example, my documentation states armv5te compatible with xscale core, and I follow that advice. But that fact is irrelevant in this bug-report. Other uses could be "-flto -fgraphite-identity". These flags are apparently not applied to CFLAGS or the compilation. None are.
In 2015.11-rcX, you no longer see the "Target Optimizations" in the TARGET_CFLAGS because they are handled by the toolchain wrapper. To see exactly which options are passed to gcc, set BR2_DEBUG_WRAPPER=1 in the environment. If you still believe this is not working, please provide: - the buildroot version you are using; - a small defconfig that exposes the problem; - some proof that the flags really are not passed to gcc.