https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117974
--- Comment #4 from Vineet Gupta <vineetg at gcc dot gnu.org> --- (In reply to JuzheZhong from comment #2) > We need to split all insns since some of them are not the ultimate RVV > instruction pattern that depend on VL/VTYPE. > And I don't think the vsetvli should be keep close VLE, Because ? > instead, They are > redundant, I think the problem is VSETVLI PASS fail to eliminate them since > look into the RTL IR before VSETVLI PASS: Are you really sure they are redundant ? It seems the unrolled loop iterator is being manipulated via sub and then fed as input to VSETVL, whose output then feeds to next iteration. So there does seem to be data dependency and it might not be redundant after all. > > https://godbolt.org/z/WdrjoYj49 > > (reg:DI 15 a5 [orig:139 _31 ] [139]) > > vsetvli a5,a1,e32,m1,tu,ma > vle32.v v2,0(a0) > sub a1,a1,a5 <-- input to next vsetvl > sh2add a0,a5,a0 > vfmacc.vv v1,v2,v2 > vsetvli a5,a1,e32,m1,tu,ma <-- vsetvl output > beq a1,zero,.L12 > vle32.v v2,0(a0) > sub a1,a1,a5 <-- used here > sh2add a0,a5,a0 ....
