https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69734
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> --- A simpler testcase: [hjl@gnu-6 interrupt-2]$ cat k.c void __attribute__((interrupt)) fn (void *frame) { asm ("#" : : : "k1"); } [hjl@gnu-6 interrupt-2]$ make k.o /export/build/gnu/gcc-5/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc-5/build-x86_64-linux/gcc/ -c -O2 -march=knl k.c /tmp/cceKHse9.s: Assembler messages: /tmp/cceKHse9.s:13: Error: register save offset not a multiple of 8 Makefile:29: recipe for target 'k.o' failed make: *** [k.o] Error 1 [hjl@gnu-6 interrupt-2]$