[PATCH] D110231: [AMDGPU] Add constrained shift pattern matches.

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D110231#3015225 <https://reviews.llvm.org/D110231#3015225>, @foad wrote:

> Would it be better to do this as some kind of DAGCombine, so that other patterns involving shifts (like for v_lshl_add etc instructions) can take advantage of it too? I wonder how other targets do this. I see X86 has isUnneededShiftMask() which is used in PatFrags for shift instruction selection.

A combine would be painful because then we have to have custom nodes with these semantics. IIRC X86ISelDAGToDAG does the same basic thing


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https://reviews.llvm.org/D110231