https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98178
--- Comment #3 from Segher Boessenkool ---
Yup, this is true in general, we almost never say why we don't combine so
far. Patches welcome! (Make sure you use TDF_DETAILS for such prints).
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98178
--- Comment #2 from Uroš Bizjak ---
On a related note, the combine splitter is a very mysterious beast, and does
not easily tell, why the particular combination is rejected. Without any debug
in debug logs it is very frustrating to figure out the
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98178
--- Comment #1 from Uroš Bizjak ---
The attached patch with the following testcase:
--cut here--
int test (int a, int b)
{
return a << (b & 31);
}
--cut here--
fails to generate a single shift insn, because it does not trigger the call to
comb
