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[RISCV] Optimize bitwise and with constant for the Zbs extension

Authored by benshi001 on Jun 7 2021, 4:26 PM.

Description

[RISCV] Optimize bitwise and with constant for the Zbs extension

This patch optimizes (and r i) to
(BCLRI (BCLRI r, i0), i1) in which i = ~((1<<i0) | (1<<i1)).
or
(BCLRI (ANDI r, i0), i1) in which i = i0 & ~(1<<i1).

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D103743