RFR: 8314580: PhaseIdealLoop::transform_long_range_checks fails with assert "was tested before"

[Roland Westrelin]

For long counted loops, `PhaseIdealLoop::create_loop_nest()` first
goes over the loop body to collect range checks, then transforms the
long counted loop into a loop nest and then goes over the list of
range checks it collected to transfrom them. For that last step,
`PhaseIdealLoop::transform_long_range_checks()` needs to extract the
parameters of the range check from the range check expression. It
should still recognize the range check expression even though the loop
was transformed in the meantime. That's what fails here. The reason is
that the range check expression uses the long loop increment as input
which, in the creation of the loop nest, is transformed to `outer
phi + inner incr`. That breaks pattern matching of the range check
expression. I propose removing the transformation:


incr=>(outer_phi+inner_incr)


entireley. After looking at this code again, I don't think it's
needed. The transformation:


phi=>(outer_phi+inner_phi)


should be all that's needed to correctly transform the loop.

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

Commit messages:
 - fix & test

Changes: https://git.openjdk.org/jdk/pull/15411/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15411&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314580
  Stats: 52 lines in 2 files changed: 46 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15411.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15411/head:pull/15411

PR: https://git.openjdk.org/jdk/pull/15411