[9] RFR(S) 8065618: C2 RA incorrectly removes kill projections

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/8065618/webrev/
https://bugs.openjdk.java.net/browse/JDK-8065618

Some nodes have SCMemProj projection node to keep them alive even when 
their result is not used because they have memory side effects.
For example, EncodeISOArrayNode and loadstore nodes like 
CompareAndSwapPNode. Generated code for such nodes may kill some 
registers and flags during execution. Killed registers are declared in 
'effect' list in mach nodes definitions in .ad files. For each killed 
register MachProj node is created without use:

  112    encode_iso_array        ===  103  125  113  114  108  119  120 
  121  122  [[ 116  117  118  123  124  127  131  134  102  156 ]] 
!jvms: ISO_8859_1$Encoder::encode @ bci:32 Test6896617::test @ bci:26
  116    MachProj        ===  112  [[]] #1
  117    MachProj        ===  112  [[]] #2
  118    MachProj        ===  112  [[]] #3
  127    SCMemProj       ===  112  [[ 126  136  138  139  140  150  160 
]]   Memory: @BotPTR *+bot, idx=Bot; !jvms: ISO_8859_1$Encoder::encode @ 
bci:32 Test6896617::test @ bci:26
  123    MachProj        ===  112  [[]] #4
  124    MachProj        ===  112  [[]] #5

Register Allocator in PhaseChaitin::build_ifg_physical() removes nodes 
which are not used (dead). Nodes with

To keep such nodes alive when their result is not used there method 
PhaseChaitin::add_input_to_liveout() puts node's LiveRange on liveout 
list when the node has SCMemProj projection.

Unfortunately SCMemProj node could be placed in a block in such order 
that kill MachProj nodes are processed first (as in example above). When 
those MachProj are processed the def node looks like dead and these 
nodes are removed from graph. As result killed register is not marked as 
killed anymore and it could be used after code which kills/modifies it.

I was not able to write test with existing VM code. encodeISOArray() 
method can't be called directly - it is part of 
sun.nio.cs.ISO_8859_1$Encoder::encode() which calls it in a loop. There 
is enough code after encodeISOArray() call in encode() method which 
prevents using the same register after encode(). I have experimental 
project with intrinsics which hits this problem and I verified the fix 
with it.

Thanks,
Vladimir