https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121076
--- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Trying 6 -> 7:
6: {r117:HI=bswap(r122:DI#6);clobber scratch;}
REG_DEAD r122:DI
7: r121:DI=zero_extend(r117:HI)
REG_DEAD r117:HI
Failed to match this instruction:
(set (reg:DI 121 [ _2+-6 ])
(zero_extend:DI (bswap:HI (subreg/s/v:HI (reg:DI 122 [ in+-6 ]) 6))))
We could do a splitter for this easily.
I don't know why "bswaphi2_reg" splits to three insns -- we can always do it
with only two, pretty trivially. Perhaps in the past this was automatically
optimised to something better, but in that case we have regressed :-(
So this needs fixing as well.
