[llvm] r191393 - Teach DAGCombiner how to canonicalize dags according to the rule

[Andrea_DiBiagio at sn.scee.net]

> From: Rafael Espíndola <rafael.espindola at gmail.com>
> 
> This causes llc to crash on
> 
> -----------------------------
> define void @g(i32 %a) {
>   %b = lshr i32 %a, 2
>   %c = zext i32 %b to i64
>   %d = add i64 %c, 1
>   %e = shl i64 %c, 2
>   tail call void @f(i64 %e)
>   ret void
> }
> 
> declare void @f(i64)
> -----------------------------
> 
> which is pr17380.
> 
> Could you please take a look?

Sure, I'll have a look.
I am going to revert the change.

Andrea Di Biagio

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