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[X86] Freeze vXi8 shl(x,1) -> add(x,x) vector fold (PR50468)

Authored by RKSimon on Aug 24 2021, 8:08 AM.

Description

[X86] Freeze vXi8 shl(x,1) -> add(x,x) vector fold (PR50468)

We don't have any vXi8 shift instructions (other than on XOP which is handled separately), so replace the shl(x,1) -> add(x,x) fold with shl(x,1) -> add(freeze(x),freeze(x)) to avoid the undef issues identified in PR50468.

Split off from D106675 as I'm still looking at whether we can fix the vXi16/i32/i64 issues with the D106679 alternative.

Differential Revision: https://reviews.llvm.org/D108139

Details

Committed
RKSimonAug 24 2021, 8:08 AM
Differential Revision
D108139: [X86] Freeze vXi8 shl(x,1) -> add(x,x) vector fold (PR50468)
Parents
rGa643bd3189ae: [mlir] add permutation utility
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