[14] RFR(S): 8228888: C2 compilation fails with assert "m has strange control"

Tobias Hartmann tobias.hartmann at oracle.com
Wed Aug 7 14:13:44 UTC 2019


please review the following patch:

I found this while trying to write a regression test for another bug. The assert triggers when OSR
compiling an infinite loop with two back branches (see StrangeControl.jasm):

PhaseIdealLoop::has_local_phi_input() tries to determine if all inputs of n (118 Phi) are block
local phis. When looking at input m (108 StoreI), the assert fires because m is not a Phi and
control of m (102 IfFalse) does not dominate control of n (83 Region).

I think the assert which was added by [1] is too strong. If n is a Phi itself, control of all its
inputs does not need to dominate its own control.


[1] https://bugs.openjdk.java.net/browse/JDK-8187822

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