On Sunday 23 October 2011, 19:33:55, Daniel Díaz Casanueva wrote:
Hi, cafe!
I wrote a program and had the following message while compiling (with -O2):
SpecConstr Function `addOc{v s6RL} [lid]' has four call patterns, but the limit is 3 Use -fspec-constr-count=n to set the bound Use -dppr-debug to see specialisations
What it means? Is it bad? It only happens when compiling with -O2.
It's nothing serious. It's just a message (that accidentally was output by default in the 7.0.* series) that the spec-constr pass could have done more specialising, but the limit forbade it. More specialising on constructors means - certainly bigger code - potentially faster code but it could also become slower (most likely because of worse cache locality). It's not even a warning, just a notification.
addOc is a local function (defined in a where clause). If it helps, here is the definition:
addOc x [] = [(x,1)] addOc x ((y,n):ys) = if x == y then (y,n+1) : ys else (y,n) : addOc x ys
I want to know if there is something wrong or a I don't need to take care about this.
You need not take care of it, but you can try out and pass -fspec-constr-count=N on the command line (here, N = 4 is a good start) to see if the generated code is faster.
Thanks in advance, Daniel Díaz.