[Bug target/71921] [15/16 Regression] missed vectorization optimization

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71921

--- Comment #21 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Trying 22 -> 27:
   22: r118:V4SF=r113:V4SF<const_vector
      REG_EQUAL r113:V4SF<const_vector
   27: r121:V4SF=~r118:V4SF&r113:V4SF
      REG_DEAD r118:V4SF
      REG_DEAD r113:V4SF
Failed to match this instruction:
(set (reg:V4SF 121)
    (and:V4SF (not:V4SF (lt:V4SF (reg:V4SF 113 [ MEM <const vector(4) float>
[(const float *)input_12(D) + ivtmp.21_83 * 1] ])
                (const_vector:V4SF [
                        (const_double:SF 0.0 [0x0.0p+0]) repeated x4
                    ])))
        (reg:V4SF 113 [ MEM <const vector(4) float> [(const float *)input_12(D)
+ ivtmp.21_83 * 1] ])))


Since we know the vector is 0, this should be changed to:
(if_then_else (lt r113 0) 0 r113)

Which then can be recongized ...