Messages in this thread | | | Date | Fri, 1 May 2015 18:46:40 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86: Optimize variable_test_bit() |
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On Fri, May 01, 2015 at 06:33:29PM +0200, Jakub Jelinek wrote: > On Fri, May 01, 2015 at 09:03:32AM -0700, Linus Torvalds wrote: > > > PPS. Jakub, I see gcc5.1 still hasn't got output operands for asm goto; > > > is this something we can get 'fixed' ? > > CCing Richard as author of asm goto and Vlad as register allocator > maintainer. There are a few enhancement requests to support this, like > http://gcc.gnu.org/PR59615 and http://gcc.gnu.org/PR52381 , but indeed the > reason why no outputs are allowed is the register allocation issue. > Don't know if LRA would be better suited to handle that case, but it would > indeed be pretty hard.
So it would b awesome if we could use these freshly modeled flags as output for regular asm stmts; that would obviate much of the asm goto hackery we now do/have and allow gcc to pick the right branch for likely/unlikely.
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