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Commit 874a8004 authored by QingShan Zhang's avatar QingShan Zhang
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[PowerPC] Exploit the rlwinm instructions for "and" with constant

For now, PowerPC will using several instructions to get the constant and "and" it with the following case:

define i32 @test1(i32 %a) {
  %and = and i32 %a, -2
  ret i32 %and
}

However, we could exploit it with the rotate mask instructions.
               MB  ME
+----------------------+
|xxxxxxxxxxx00011111000|
+----------------------+
 0         32         64
Notice that, we can only do it if the MB is larger than 32 and MB <= ME as
RLWINM will replace the content of [0 - 32) with [32 - 64) even we didn't rotate it.

Differential Revision: https://reviews.llvm.org/D71829
parent 266cd771
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