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Re: RFC: missed loop optimizations from loop induction variable copies


Hi,

<snip>

> IVOpts cannot identify start_26, start_4 and ivtmp_32_7 to be copies.
> The root cause is that expression 'i + start' is identified as a common
> expression between the test in the header and the index operation in the
> latch. This is unified by copy propagation or FRE prior to loop
> optimizations
> and creates a new induction variable.
> 
> 
> Does this imply we try and not copy propagate or FRE potential induction
> variables? Or is this simply a missed case in IVOpts?

IIRC, at some point maybe year or two ago Sebastian worked on enhancing
scev to analyze such induction variables (thus enabling IVopts to handle them).
But it seems the code did not make it to mainline,

Zdenek


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