Linus Torvalds wrote: >> btrl $1, 0 >> btr $1, 0 >> btsl $1, 0 >> bts $1, 0 > > What the heck is that supposed to show?
I was trying to show a reduced case where gas doesn't complain, but llvm-mc does. Try compiling this with llvm-mc, and you'll get: .text btrl $1, 0 in.s:2:1: error: ambiguous instructions require an explicit suffix (could be 'btrw', 'btrl', or 'btrq') btr $1, 0 ^ btsl $1, 0 in.s:4:1: error: ambiguous instructions require an explicit suffix (could be 'btsw', 'btsl', or 'btsq') bts $1, 0 ^ Obviously, I misunderstood something major and screwed up the commit message. > int main(int argc, char **argv) > { > asm("bt %1,%0":"=m" (**argv): "a" (argc)); > asm("bt %1,%0":"=m" (**argv): "a" ((unsigned long)(argc))); > } Right, so in: int main(int argc, char **argv) { asm("bts %1,%0":"=m" (**argv): "r" (argc)); asm("btsl %1,%0":"=m" (**argv): "r" (argc)); asm("btr %1,%0":"=m" (**argv): "r" ((unsigned long)(argc))); asm("btrq %1,%0":"=m" (**argv): "r" ((unsigned long)(argc))); } bts disambiguates to btsl, and btr disambiguates to btrq, as advertised. Is it dependent on whether I have a 32-bit machine or 64-bit machine, or just on the operand lengths? Either way, this is not a very enlightening example, because clang also compiles this fine, and doesn't complain about any ambiguity. To see the ambiguity I'm talking about, try to compile linux.git with clang; I'll paste one error: arch/x86/include/asm/bitops.h:129:15: error: ambiguous instructions require an explicit suffix (could be 'btrw', 'btrl', or 'btrq') asm volatile("btr %1,%0" : ADDR : "Ir" (nr)); ^ <inline asm>:1:2: note: instantiated into assembly here btr $0,(%rsi) ^ Since nr is an int, and ADDR is *(volatile long *), this should disambiguate to btrl, right? Any clue why clang is complaining? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/