If Mask and Amt are not constants and binop1 and binop2 are
the same we can transform to:
(binop (lshift (binop X, Y), Amt), Mask)
If binop is add, lshift must be shl.
If Mask and Amt are constants C and C1 respectively.
We can transform to:
(lshift1 (binop1 (binop2 X, (inv_lshift1 C, C1), Y)), C1)
Saving an instruction IFF:
lshift1 is same opcode as lshift2
Either bitwise1 and/or bitwise2 is and.
Proofs(1/2): https://alive2.llvm.org/ce/z/BjN-m_
Proofs(2/2): https://alive2.llvm.org/ce/z/bZn5QB
This is to help fix the regression caused in D151807