RFR: 8221653 [lworld] Calling convention - C1 to Interpreter

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8221653
http://cr.openjdk.java.net/~iklam/valhalla/8221653-c1-calls-interp.v01/

This is the first step of making C1/C2 work together. Since C1 doesn't 
scalarize outgoing parameters, I changed the method dispatch code to 
detect when a call is made by C1 code, and jump to 
Method::_from_compiled_value_entry (in contrast, C2 would jump to 
Method::_from_compiled_entry or Method::_from_compiled_value_ro_entry).

I am not particularly proud of sprinkling caller_is_c1 all over the 
code. Does anyone have a better suggestion?

For testing, I added TestCallingConventionC1.java. I also improved the 
@Test annotation in 
jtreg/compiler/valhalla/valuetypes/ValueTypeTest.java to specify whether 
C1 or C2 should be used.

In addition, I changed the order of how the VM arguments are put 
together in ValueTypeTest::execute_vm(). This allows the individual 
tests to override arguments specified by ValueTypeTest.java.

With this changeset, to test C1-only, the command-line has changed to

         cd test/hotspot/jtreg/compiler/valhalla/valuetypes
         jtreg -Dtest.c1=true \
             -vmoptions:-XX:+EnableValhallaC1 \
             -vmoptions:-XX:TieredStopAtLevel=1 \
             -vmoptions:-XX:-ValueTypePassFieldsAsArgs \
             -vmoptions:-XX:-ValueTypeReturnedAsFields \
             .

Testing:

+ All */valhalla/* tests passed with default configuration (C2 only)
+ All jtreg/compiler/valhalla/* tests passed in C1-only mode

Thanks
- Ioi