RFR(XXS): C1 compilation fails with -XX:+PrintIRDuringConstruction -XX:+Verbose

[Liu Xin]

Hi, Reviewers,

Could you review this very simple bugfix for C1?
JBS: https://bugs.openjdk.java.net/browse/JDK-8235383
Webrev: https://cr.openjdk.java.net/~xliu/8235383/webrev/

The root cause is some instructions are going to be eliminated, so they are
not assigned to any valid bci.
In present of  -XX:+PrintIRDuringConstruction -XX:+Verbose,  C1 will print
them out and then hit the assert.

Yes, I can twiddle graph_builder to assign right BCIs to them,  but I would
like to have a more robust InstructionPrinter::print_line. the CR will
leave blanks in the position of bci.
Eliminated store for object 0:
.      0    a67    a58._24 := a54 (L) next
Eliminated load:
.      0    i35    a11._24 (I) position

thanks,
--lx