RFR: 8288022: c2: Transform (CastLL (AddL into (AddL (CastLL when possible [v2]

[Roland Westrelin]

> This implements a transformation that already exists for CastII and
> ConvI2L and helps code generation. The tricky part is that:
> 
> (CastII (AddI into (AddI (CastII
> 
> is performed by first computing the bounds of the type of the AddI. To
> protect against overflow, jlong variables are used. With CastLL/AddL
> nodes there's no larger integer type to promote the bounds to. As a
> consequence the logic in the patch explicitly tests for overflow. That
> logic is shared by the int and long cases. The previous logic for the
> int cases that promotes values to long is used as verification.
> 
> This patch also widens the type of CastLL nodes after loop opts the
> way it's done for CastII/ConvI2L to allow commoning of nodes.
> 
> This was observed to help with Memory Segment micro benchmarks.

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

  Update test/hotspot/jtreg/compiler/c2/irTests/TestPushAddThruCast.java
  
  Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9139/files
  - new: https://git.openjdk.org/jdk/pull/9139/files/5579e664..80577689

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9139&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9139&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9139.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9139/head:pull/9139

PR: https://git.openjdk.org/jdk/pull/9139