RFR: 8207345: AArch64: Trampoline generation code reads from uninitialized memory

[Andrew Haley]

At present, the AArch64 back end does this when generating trampolines:

  if (far_branches() && !Compile::current()->in_scratch_emit_size()) {
    address stub = emit_trampoline_stub(start_offset, entry.target());

This is only correct for C2 compilation. The class Compile is, despite
its name, only present in C2, so we must check that we are
C2-compiling before calling it.

http://cr.openjdk.java.net/~aph/8207345/

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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