Displaying 3 results from an estimated 3 matches for "operatiosn".
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2017 May 26
3
Poison/Undef at CodeGen level Was: [poison] is select-of-select to logic+select allowed?
...; like to hear further feedback:
>
> - I think we should not introduce a notion of poison (which I would
> call "delayed UB") at the SelectionDAG/CodeGen level[1]
> - Instructions either produce UB immediately, so while there are
> nsw/nuw flags on SelectionDAG arithmetic operatiosn I think we can
> only assume that they produce a target specific value on overflow, but
> not arbitrary behavior. Instructions that can produce UB should marked
> "hasSideEffect" and code motion around it be limited.
You mean like every integer division? Having arbitrary side...
2017 May 23
6
[poison] is select-of-select to logic+select allowed?
Regarding the patches, there are two concerns AFAICT:
1. It’s a new instruction and as usual when introducing a new instruction it will require work for some time until most optimizations know about it, and to get rid of any potential perf regression. No big deal; we just need to do the work (and we have already done some of it).
2. The patch was written by a student, which may not have time to
2011 Jun 26
2
Why is looping in R inefficient, but in C not?
Hey,
I just read another post about calling R from C. Someone on
stackoverflow (DWin makes me suspect its David W.?) referenced this:
http://www.math.univ-montp2.fr/~pudlo/R_files/call_R.pdf
Which made me think: Why is a loop in R bad, but in C not?
And where exactly does looping cost the most? I wrote a piece of code
for my bachelor's thesis where I loop from 1 to 500, and estimate a