https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112447
--- Comment #11 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
As a hack I commented out set_delete() to see what the extraneous vsetvli
would have been.
```
.L36:
# bb 3: start of outer loop: off 0
vsetvli zero,zero,e8,mf2,ta,ma # insn 2915
vse8.v v1,0(t3) # insn 2874, bb 3
vse8.v v1,0(t6)
vse8.v v1,0(s0)
...
# bb 181
addi a4,a4,1
li a7,15
bne a4,a7,.L36 # insn 1082
# bb 182: start of outer loop: off 1
vsetvli zero,zero,e32,mf2,ta,ma # insn 2919
vmv.x.s a3,v1 # insn 1858
vsetvli zero,zero,e16,mf2,ta,ma
sw a3,8(sp)
vmv.x.s a3,v1
```
Essentially phase 2 is fusing vsetvl info for insn 2874 and insn 1858
But the fused info doesn't seem right.
vsetvli zero,zero,e32,m2,ta,ma
j .L36
Manually modifying it to orig value fixes the test.
vsetvli zero,zero,e8,mf2,ta,ma
j .L36
Phase 2 logs
```
Try lift up 1.
earliest:
Edge(bb 0 -> bb 2): n_bits = 13, set = {0 }
Edge(bb 62 -> bb 63): n_bits = 13, set = {4 }
Edge(bb 180 -> bb 181): n_bits = 13, set = {8 }
Edge(bb 181 -> bb 3): n_bits = 13, set = {2 }
Fuse curr info since prev info compatible with it:
prev_info: VALID (insn 1858, bb 181) <-- due to Edge(bb 181 -> bb
3)
Demand fields: demand_sew_only
SEW=32, VLMUL=mf2, RATIO=64, MAX_SEW=64
TAIL_POLICY=agnostic, MASK_POLICY=agnostic
AVL=(nil)
VL=(nil)
curr_info: VALID (insn 2874, bb 3)
Demand fields: demand_ratio_only demand_avl
SEW=8, VLMUL=mf2, RATIO=16, MAX_SEW=64
TAIL_POLICY=agnostic, MASK_POLICY=agnostic
AVL=(const_int 8 [0x8])
VL=(nil)
prev_info after fused: VALID (insn 1858, bb 181)
Demand fields: demand_sew_lmul demand_avl
SEW=32, VLMUL=m2, RATIO=16, MAX_SEW=64
TAIL_POLICY=agnostic, MASK_POLICY=agnostic
AVL=(const_int 8 [0x8])
VL=(nil)
```
This fuse in turn is happening from
DEF_SEW_LMUL_RULE (sew_only, ratio_only, sew_lmul,
next_ratio_valid_for_prev_sew_p, always_false,
modify_lmul_with_next_ratio)
I'm not really sure if the merge callback here is correct.
