[9] RFR (M): 8011858: Use Compile::live_nodes() instead of Compile::unique() in appropriate places

Vlad Ureche vlad.ureche at gmail.com
Fri Jul 17 22:47:15 UTC 2015


Please review the following patch for JDK-8011858. Big thanks to Vladimir
Kozlov for his patient guidance while working on this!

*Bug:* https://bugs.openjdk.java.net/browse/JDK-8011858

*Problem:* Throughout C2, local stacks are used to prevent recursive calls
from blowing up the system stack. These are sized based on the total number
of nodes in the compilation run (e.g. C->unique()). Instead, they should be
sized based on the live node count (C->live_nodes()).

Now, with the increased difference between live_nodes (limited at
LiveNodeCountInliningCutoff, set to 40K) and unique nodes (which can go up
to 240K), it is important to not over-estimate the size of stacks.

*Solution:* This patch mirrors a patch written by Vladimir Kozlov for
JDK8u. It replaces the initial sizes from C->unique() to C->live_nodes(),
preserving any shifts (divisions) and offsets. For example, in the compile.cpp

-  Node_Stack nstack(unique() >> 1);
+  Node_Stack nstack(live_nodes() >> 1);

There is an issue described at
https://bugs.openjdk.java.net/browse/JDK-8131702 where I took the
workaround from Vladimir’s patch.

*Webrev:* http://cr.openjdk.java.net/~kvn/8011858/webrev/ or
(updated, includes a link to bug 8121702)

*Tests:* Running jtreg with the compiler, runtime and gc tests on the dev
<http://hg.openjdk.java.net/jdk9/dev> branch shows the same status before
and after the patch: 808 tests passed, 16 failed and 6 errors
<http://vladureche.ro/webrev/8011858/JTreport/html/index.html>. What would
be a stable point where all tests are expected to pass, so I can test the
patch there? Maybe jdk9 <http://hg.openjdk.java.net/jdk9/jdk9>?

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