The problem was that synchronous Maglev OSR potentially caused
code deoptimization during compilation dependency finalization; this
led to a lazy deopt when returning from the call to
Runtime_CompileOptimizedOSRFromMaglev. However, a lazy deopt is
disallowed at this point, since a) Maglev doesn't support marking an opcode as both lazy- and eager deopt, and b) the JumpLoop opcode
is already marked as eager deopt since that's how OSR is implemented
under the hood. See also the comment in runtime-compiler.cc.
We fix this by changing synchronous Maglev-to-Turbofan OSR
behavior s.t. actual OSR compilation is triggered from Ignition
(and not from Maglev). In other words, when synchronous OSR is
requested:
1. trigger an eager deopt from Maglev to Ignition by returning a
non-null code object from Runtime_CompileOptimizedOSRFromMaglev.
2. Ignition handles the pending OSR compile request (through
osr_urgency).
This CL also reverts previous partial fixes:
This reverts commit 21969e8e24.
This reverts commit 6bcbcfed5c.
Bug: chromium:1394279,v8:13585,v8:7700
Change-Id: I3d64aa39575ad806ba2623102092176ca160ef0b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4110740
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84922}
5d95bd39ca