RFR: 8372634: C2: Materialize type information from instanceof checks

[Vladimir Ivanov]

Even though `instanceof` check (and reflective `Class.isInstance` call) narrows operand's type, sharpened type information is not explicitly materialized in the IR.

There's a `SubTypeCheck` node present, but it is not a substitute for a `CheckCastPP` node with a proper type.

The difference can be illustrated with the following simple cases:

   class A { void m() {} }
   class B extends A { void m() {} }

    void testInstanceOf(A obj) {
        if (obj instanceof B) {
            obj.m();
        }
    }

InstanceOf::testInstanceOf (12 bytes)
  @ 8 InstanceOf$A::m (0 bytes) failed to inline: virtual call

vs

    void testInstanceOfCast(A obj) {
        if (obj instanceof B) {
            B b = (B)obj;
            b.m();
        }
    }

InstanceOf::testInstanceOfCast (17 bytes)
  @ 13 InstanceOf$B::m (1 bytes) inline (hot)


Proposed fix annotates operands of subtype checks with proper type information which reflects the effects of subtype check. Not-yet-canonicalized IR shape poses some challenges, but I decided to match it early so information is available right away, rather than waiting for IGVN pass and delay inlining to post-parse phase.

FTR it is not a complete fix. It works for trivial cases, but for more complex conditions the IR shape becomes too complex during parsing (as illustrated by some test cases). I experimented with annotating subtype checks after initial parsing pass is over, but the crucial simplification step happens as part of split-if transformation which happens when no more inlining is possible. So, the only possible benefit (without forcing split-if optimization earlier) is virtual-to-direct call strength reduction. I plan to explore it separately.

Testing: hs-tier1 - hs-tier5

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

Commit messages:
 - bugid
 - C2: Materialize type information from instanceof checks

Changes: https://git.openjdk.org/jdk/pull/28517/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28517&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372634
  Stats: 558 lines in 10 files changed: 524 ins; 0 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/28517.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28517/head:pull/28517

PR: https://git.openjdk.org/jdk/pull/28517