[PATCH] D59227: [GlobalISel][Utils] Teach getConstantVRegVal how to look through trunc and z|sext

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added a comment.

> Why wouldn't G_CONSTANT be legalized? This doesn't make any sense to me

Because they are just place holder.
When doing selection, only the ones that won't be folded into immediate should be materialized and at this point, we just have to materialize load immediate into valid registers.

The only reason the constant show up as instructions right now is because we wanted to handle machine operand uniformly via vreg. Otherwise, they would just be immediate operands. If you imagine that setting, I guess it is more obvious why we don't legalize them.

Does it make sense?


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  https://reviews.llvm.org/D59227/new/

https://reviews.llvm.org/D59227