RFR(S): 8193927: Optimize scanning code for oops.

[Aleksey Shipilev]

On 12/21/2017 09:30 AM, Lindenmaier, Goetz wrote:
> Add flag ImmediateOopsEmitted to each platform specifying the behavior. 
> Only search code for immediate oops if this flag is set. Make sure no 
> oops are emitted to code if the flag is not set.

From the description, it seems to be equivalent to ScavengeRootsInCode=0?

  diagnostic(intx, ScavengeRootsInCode, 2,                                  \
          "0: do not allow scavengable oops in the code cache; "            \
          "1: allow scavenging from the code cache; "                       \
          "2: emit as many constants as the compiler can see")              \
          range(0, 2)                                                       \

If so, don't we want to reuse that? In fact, IIRC code cache scanning code would even skip
registering nmethods for scan in ScavengeRootsInCode=0.

Thanks,
-Aleksey

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