[lworld] RFR: 8361465: [lworld] testlibrary_tests/ir_framework/tests/TestPhaseIRMatching.java fails

[Marc Chevalier]

The constraint `failOn = IRNode.STORE` on `NoCompilationOutput.badPhase2` in `test/hotspot/jtreg/testlibrary_tests/ir_framework/tests/TestPhaseIRMatching.java` does not fail for the phase `ITER_GVN_AFTER_ELIMINATION`:

AFTER: ITER_GVN_AFTER_ELIMINATION
  0  Root  === 0 21  [[ 0 1 3 ]]
  3  Start  === 3 0  [[ 3 5 6 7 8 9 ]]  #{0:control, 1:abIO, 2:memory, 3:rawptr:BotPTR, 4:return_address, 5:ir_framework/tests/NoCompilationOutput:NotNull *}
  5  Parm  === 3  [[ 21 ]] Control !jvms: NoCompilationOutput::badPhase2 @ bci:-1 (line 353)
  6  Parm  === 3  [[ 21 ]] I_O !jvms: NoCompilationOutput::badPhase2 @ bci:-1 (line 353)
  7  Parm  === 3  [[ 21 ]] Memory  Memory: @BotPTR *+bot, idx=Bot; !jvms: NoCompilationOutput::badPhase2 @ bci:-1 (line 353)
  8  Parm  === 3  [[ 21 ]] FramePtr !jvms: NoCompilationOutput::badPhase2 @ bci:-1 (line 353)
  9  Parm  === 3  [[ 21 ]] ReturnAdr !jvms: NoCompilationOutput::badPhase2 @ bci:-1 (line 353)
 21  Return  === 5 6 7 8 9  [[ 0 ]]

which is not surprising given this method has an empty body.

What is surprising is that `ITER_GVN_AFTER_ELIMINATION` gives some output, which is what the test is about (cf. `@ExpectedFailure(ruleId = 1, hasCompilation = false,`).

So, if we just remove this phase in the test, we are good... as long as it's legitimate to do so. And I think it is: #1447 added some macro expansions (including an IGVN round with phase `PHASE_ITER_GVN_AFTER_ELIMINATION`) to `Compile::Optimize` just before the escape analysis, one of those being unconditional:
https://github.com/openjdk/valhalla/blob/7e4c1bc1753bcd9655214eca32c391d28af43267/src/hotspot/share/opto/compile.cpp#L2858-L2867
And this code being Valhalla-specific, that explains why our test is failing only on Valhalla.

So the fix is just as simple as not trying to find a failure for this phase.

I think it's very fine because this test is more about testing IR framework features than making sure this particular phase is missing on this method.

Thanks,
Marc

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

Commit messages:
 - Don't expect ITER_GVN_AFTER_ELIMINATION from NoCompilationOutput.badPhase2

Changes: https://git.openjdk.org/valhalla/pull/1508/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1508&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361465
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1508.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1508/head:pull/1508

PR: https://git.openjdk.org/valhalla/pull/1508