RFR: 8253756: C2 CompilerThread0 crash in Node::add_req(Node*) [v2]

[Roland Westrelin]

> The outer strip mined loop is initially created as a skeleton and then
> expanded once loop opts are over. As long as it is a skeleton, the
> OuterStripMinedLoopEndNode cannot be constant folded because its input
> is a place holder. So OuterStripMinedLoopEndNode::Value() blocks
> constant folding. This bug triggers because the
> OuterStripMinedLoopEndNode input after expansion is a constant but the
> OuterStripMinedLoopEndNode is not constant folded (i.e. it's a dead
> loop but it stays in the graph). The fix I propose is to change the
> behavior OuterStripMinedLoopEndNode::Value() so it blocks constant
> folding only until expansion but not after.

Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:

  remove debugging code

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/537/files
  - new: https://git.openjdk.java.net/jdk/pull/537/files/f511b8f9..407a2fda

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=537&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=537&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/537.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/537/head:pull/537

PR: https://git.openjdk.java.net/jdk/pull/537