[BUG] Support unqualified btr, bts

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#1

Hi,

I happened to notice that linux.git uses plenty of btr and bts
instructions (not btrl, btrw, btsl, btsw). For examples, see
arch/x86/include/asm/bitops.h. LLVM barfs on these due to ambiguity,
while GNU as is fine with them. Surely, there must be architectures
where the w/l variant is unavailable? LLVM must support those
architectures, no?

Thanks.

#2

Both variants have existed since the Intel 386.

That said, we should probably handle this like GNU as because the
variants behave almost identically. Please file a bug.

-Eli

#3

I don't consider this a bug. Just like certain FP instructions, they
*are* ambigious and there is no reason to depend on magic assembler
choices.

Joerg