RFR: 8279225: C1 longs comparison operation destroys argument registers

[Sergey Nazarkin]

Several regression tests are failed on arm32 CPU if tiered compilation is enabled.

The list includes
java/math/BigDecimal/DivideMcTests
java/util/Arrays/Sorting.java
java/util/Arrays/SortingNearlySortedPrimitive.java
java/util/concurrent/tck/JSR166TestCase
java/util/stream/SliceOpTest.java
etc

It appears C1 comp_op for long operands destroys arguments registers:
void LIR_Assembler::comp_op(LIR_Condition condition, LIR_Opr opr1, LIR_Opr opr2, LIR_Op2* op) {
....
      Register ylo = opr2->as_register_lo();
      Register yhi = opr2->as_register_hi();
      if (condition == lir_cond_equal || condition == lir_cond_notEqual) {
        __ teq(xhi, yhi);
        __ teq(xlo, ylo, eq);
      } else {
        __ subs(xlo, xlo, ylo); // <<< incorrect
        __ sbcs(xhi, xhi, yhi); // <<< incorrect
      }
...
} 

Tested with hotspot_tier2, jdk_tier3 on linux_arm

-------------

Commit messages:
 - 8279225: C1 longs comparison operation destroys argument registers

Changes: https://git.openjdk.java.net/jdk/pull/6934/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6934&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279225
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6934.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6934/head:pull/6934

PR: https://git.openjdk.java.net/jdk/pull/6934