https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106415
Kewen Lin <linkw at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |linkw at gcc dot gnu.org
--- Comment #5 from Kewen Lin <linkw at gcc dot gnu.org> ---
At the top of tree-ssa-loop-ivopts.cc file, there are some useful comments
describing the costs for iv candidate itself and group, it may help.
<Candidate Costs>:
cand cost
0 5
1 5
2 5
3 4
4 5
5 5
6 5
7 5
8 5
This part is for "variable costs".
<Group-candidate Costs>:
Group 0:
cand cost compl. inv.expr. inv.vars
0 400 0 NIL; NIL;
7 0 0 NIL; NIL;
8 400 0 NIL; NIL;
This part is for "group/use costs".
There would be no dumping for a candidate when it has infinite cost for the
group, so the above means only candidate 0, 7 and 8 are valid to be used for
group 0.
Final cost looks like:
cost: 7 (complexity 0)
reg_cost: 2
cand_cost: 5
cand_group_cost: 0 (complexity 0)
candidates: 7
group:0 --> iv_cand:7, cost=(0,0)
group:1 --> iv_cand:7, cost=(0,0)
invariant variables:
invariant expressions:
----
By quick checking, it looks the inf cost for the pair (cand 3, group 0) is due
to:
/* Check if we have enough precision to express the values of use. */
if (TYPE_PRECISION (utype) > TYPE_PRECISION (ctype))
return infinite_cost;
