Re: Should ghc -msse imply gcc -msse
Simon Marlow <marlowsd <at> gmail.com>
2013-01-17 20:29:01 GMT
On 17/01/13 20:06, Johan Tibell wrote:
> On Thu, Jan 17, 2013 at 12:01 PM, Johan Tibell <johan.tibell <at> gmail.com> wrote:
>> I forgot I once raised this on the GHC bug tracker:
>> Here's what Simon M had to say back then:
>> "The right thing is to put -msse in the cc-options field of your
>> .cabal file, if that's what you want.
>> I'm distinctly uneasy about having -msse magically pass through to gcc.
>> * There are many flags that we do not pass through to gcc, so having
>> one that we do pass through could be confusing (and lead to lots more
>> requests for more flags to be passed through)
>> * What if there is a variant of -msse that gcc supports but we don't?
>> Wouldn't we have to keep them in sync?
>> I'm going to close this as wontfix, but please feel free to reopen and
> One problem with having the user set cc-options in addition to passing
> -msse to GHC, is that the user might not realize that he/she needs to
> do this. This is bad if you use -fllvm, as your -msse will essentially
> just be ignored as the LLVM primitives we use in the LLVM backend
> (e.g. for popcnt) won't convert to SSE instructions.
> Even worse, LLVM doesn't support a -msse flag, instead you need to use
> -mattr=+sse, so the user needs to be aware of this difference and