------- Comment #2 from ubizjak at gmail dot com 2010-04-12 17:11 ------- configure should detect if assembler supports sahf mnemonic.
In your build directory, check gcc/config.log for: configure:23019: checking assembler for sahf mnemonic configure:23028: /usr/local/x86_64-unknown-linux-gnu/bin/as -o conftest.o conftest.s >&5 configure:23031: $? = 0 configure:23042: result: yes Based on this result, gcc outputs: (define_insn "x86_sahf_1" [(set (reg:CC FLAGS_REG) (unspec:CC [(match_operand:HI 0 "register_operand" "a")] UNSPEC_SAHF))] "TARGET_SAHF" { #ifdef HAVE_AS_IX86_SAHF return "sahf"; #else return ASM_BYTE "0x9e"; #endif } -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43733