[PATCH] GVN: merge overflow intrinsics with non-overflow instructions.

[Erik Verbruggen]

1 week ping!

Added Owen Anderson as advised by someone on irc...

-- Erik.

On 28 Feb 2014, at 11:07, Erik Verbruggen <erik.verbruggen at me.com> wrote:

> When an overflow intrinsic is followed by a non-overflow instruction,
> replace the latter with an extract. For example:
> 
>  %sadd = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
>  %sadd3 = add i32 %a, %b
> 
> Here the add statement will be replaced by an extract.
> 
> When an overflow intrinsic follows a non-overflow instruction, a clone
> of the intrinsic is inserted before the normal instruction, which makes
> it the same as the previous case. Subsequent runs of GVN can then clean
> up the duplicate instructions and insert the extract.
> 
> This fixes PR8817.

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