search for: phinodefoldingthreshold

Displaying 3 results from an estimated 3 matches for "phinodefoldingthreshold".

2014 May 28
2
[LLVMdev] Why does Select have a higher speculation cost than other instructions?
...is is? I would like SimplifyCFG to be able to speculatively execute Select instructions. Which of these solutions makes the most sense: 1. Change speculation cost of Select from 2 to 1. 2. Add a TargetTransformInfo callback for Select speculation cost. 3. Add a TargetTransformInfo callback for PhiNodeFoldingThreshold to enable speculation of more expensive instructions. 4. Something else. Thanks, Tom
2017 Jul 05
3
Dataflow analysis regression in 3.7
Hi all, I just found an optimization regression regarding simple dataflow/constprop analysis: https://godbolt.org/g/Uz8P7t This code ``` int dataflow(int b) { int a; if (b==4) a = 3*b; // fully optimized when changed to a = 3; else a = 5; if (a == 4) return 0; else return 1; } ``` is no longer optimized to just a "return 1". The regression happened in LLVM
2017 Jul 06
2
Dataflow analysis regression in 3.7
...t > don't > > really know which keywords to look for...) > > > > Kind regards, > > Johan > > > > This regressed when SimplifyCFG changed the threshold for PHI nodes > folding from 1 to 2. > > (see lib/Transforms/Utils/SimplifyCFG.cpp) > > +PHINodeFoldingThreshold("phi-node-folding-threshold", cl::Hidden, > cl::init(2), > + cl::desc("Control the amount of phi node folding to perform > (default = 2)")); > > This could be re-evaluated, maybe, or some other transformation could > catch this case. > I'm sure that a...