RFR: 8257630: ReplacedNodes doesn't handle non-CFG multi nodes

[Tobias Hartmann]

On Wed, 2 Dec 2020 21:21:19 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> When looking up an immediate CFG node, ReplacedNodes assumes that control input is always a CFG node. 
> It's not always the case: for example, a projection on a non-CFG multi node (`SCMemProj` and `LoadStore` respectively).
> 
> Proposed fix is to skip projection nodes first before checking for CFG.
> 
> Testing:
> - [x] hs-tier1-6 w/ -XX:+AlwaysIncrementalInlining

Looks good.

src/hotspot/share/opto/replacednodes.cpp line 157:

> 155:           if (n->is_Proj()) {
> 156:             n = n->in(0);
> 157:           }

I would suggest to merge this with the if below and adjust the comment to something like:
`// Skip non-CFG nodes. Also skip projections, since some of the multi nodes aren't CFG (e.g., LoadStore and SCMemProj).`

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1580