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Re: [PATCH] Fix PR middle-end/17793

On Tue, 19 Oct 04 18:56:11 EDT, (Richard Kenner) wrote:

>     Hmm?  It makes no sense to have a NOP_EXPR inside a VIEW_CONVERT_EXPR.
>     A NOP_EXPR is an rvalue conversion; a VIEW_CONVERT_EXPR is an lvalue
>     conversion, which cannot be applied to the rvalue produced by a
>     NOP_EXPR.
> Sure it can.  In normal usage, all of the conversions return values.
> VIEW_CONVERT_EXPR can be used as part of an LHS, while NOP_EXPR can't,
> but that's a minor distinction and that usage is sort of dubious anyway.

Minor?  It seems pretty central to me.  VIEW_CONVERT_EXPR operates on the
reference, NOP_EXPR on the value.

>     This seems like a front end bug; the NOP_EXPR should be
>     stripped when the VIEW_CONVERT_EXPR is added.
> I don't think that's necessarily correct: I can easily see cases where
> you'd want both.  For example, you have an 8-bit integer and NOP_EXPR
> that converts it into 32-bit integer, then a VIEW_CONVERT_EXPR that
> converts it into an array of four 8-bit integers.

Hmm, OK.  I would expect gimplification of that example to create a
temporary for the NOP_EXPR.


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