possible constant synthesis bug about souper HOT 3 CLOSED

$ souper-check $SOUPER_SOLVER -infer-rhs -souper-infer-iN syn-bug.opt 
; RHS inferred successfully
result 0:i32

$ llvm-as syn-bug.ll -o - | souper $SOUPER_SOLVER -souper-infer-iN
; Listing valid replacements.
; Using solver: Z3 + internal cache

; Static profile 1
; Function: vnum_test10
%0:i32 = var
%1:i32 = var
%2:i1 = eq %0, %1
pc %2 1:i1
%3:i32 = addnsw 1:i32, %0
%4:i32 = addnsw 1:i32, %1
%5:i32 = subnsw %3, %4
cand %5 0:i32

; Static profile 1
; Function: vnum_test10
%0:i32 = var
%1:i32 = var
%2:i1 = eq %0, %1
pc %2 1:i1
%3:i32 = addnsw 1:i32, %0
%4:i32 = addnsw 1:i32, %1
%5:i32 = subnsw %3, %4
%6:i32 = mulnsw 21:i32, %5
cand %6 0:i32