[LLVMdev] [PATCH] x86: disambiguate unqualified btr, bts

Joerg Sonnenberger joerg at britannica.bec.de
Thu Jul 11 05:00:13 PDT 2013

On Thu, Jul 11, 2013 at 10:59:32AM +0530, Ramkumar Ramachandra wrote:
> For the record, I don't think matching linux.git/gas is a problem:
> they're very authoritative pieces of software that have been around
> for a _really_ long time.

That's a very, very weak argument. There are a lot of things Clang
rejects as errors by default that has been used in old code bases,
because GCC accepted it.

> Eli Friedman wrote:
> > The reason it's the right thing to do is that the mem/imm forms of
> > btsw and btsl have exactly the same semantics.
> Not sure I understand this.

There is no way to tell from the arguments whether bts should be btsw or
btsl. That's the ambiguity it is complaining about. Fixing it is
trivial. There are other cases with similar issues in the 8087 syntax
with size of the floating point operand.


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