[Bug target/86771] [9 Regression] gfortran.dg/actual_array_constructor_1.f90 fails on arm after combine 2 insns to 2 insns patch
segher at gcc dot gnu.org
Mon Aug 20 20:58:00 GMT 2018
--- Comment #16 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Wilco from comment #14)
> Note there is also an issue with costs, if the cost is zero then it seems to
> behave like infinite cost.
0 means unknown cost. Any known cost is treated as at least as good as
> It would be better to properly cost an
> instruction sequence given there is a new interface for this now.
> If the
> cost is still zero, it could get the default cost rather than being treated
> like infinite cost, resulting in non-optimal replacements.
Treating unknown cost as minimal cost is still non-optimal. It might work
better for your case of course. But it means for example that combine will
modify parallels less often.
More information about the Gcc-bugs