[11] RFR(XS): 8202179: Compilation fails with assert(n->is_expensive()) failed: expensive nodes with non-null control here only

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8202179
http://cr.openjdk.java.net/~thartmann/8202179/webrev.00/

Expensive nodes have control inputs to prevent GVN from commoning them which may cause more frequent
execution (see comment of PhaseIdealLoop::process_expensive_nodes()).
Compile::cleanup_expensive_nodes() assumes no expensive nodes are added after parsing and removes
the control input if there's only a single copy of a node. ConvD2FNode::Ideal() then creates a new
SqrtFNode with the control of the input SqrtDNode (which is NULL).

We should only treat the SqrtFNode as expensive if the control input is not NULL.

I was only able to reproduce this with replay compilation and a customer application.

All tests pass.

Thanks,
Tobias