r225244 - Sema: analyze I,J,K,M,N,O constraints

Joerg Sonnenberger joerg at britannica.bec.de
Wed Jan 14 12:47:38 PST 2015

On Sun, Jan 11, 2015 at 02:21:53PM +0100, Joerg Sonnenberger wrote:
> > Fortunately, pixman is the only example of code I have seen that was
> > regressed by this, and the code in pixman I think can even fail with GCC
> > under the right circumstances, so I don't see this as a problem.
> Not true, variants like the attached code have been in use for a while.
> In fact, my clang 3.5.0 build does the correct thing here where ToT now
> complains.

I am still waiting for an actual test case where ToT or 3.5 didn't
already bail out. So far this is strictly a regression. Code that
compiled before failed and as the given example, some code no longer can
be expressed optimally. It has been discussed on IRC that the x86
backend is somewhat weak with regards to range checks of immediates, but
that is a problem with or without inline asm constrraints. In summary:
I'd like to see this reverted for ToT and 3.6.


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