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[PowerPC] Custom lower rotl v1i128 to vector_shuffle.

Authored by Esme on Jun 17 2020, 6:32 PM.

Description

[PowerPC] Custom lower rotl v1i128 to vector_shuffle.

Summary: A bug is reported in bugzilla-45628, where the swap_with_shift case can’t be matched to a single HW instruction xxswapd as expected.
In fact the case matches the idiom of rotate. We have MatchRotate to handle an ‘or’ of two operands and generate a rot[lr] if the case matches the idiom of rotate. While PPC doesn’t support ROTL v1i128. We can custom lower ROTL v1i128 to the vector_shuffle. The vector_shuffle will be matched to a single HW instruction during the phase of instruction selection.

Reviewed By: steven.zhang

Differential Revision: https://reviews.llvm.org/D81076