RFR: 8171537: aarch64: compiler/c1/Test6849574.java generates guarantee failure in C1

[Edward Nevill]

Hi,

Please review the following webrev

http://cr.openjdk.java.net/~enevill/8171537/webrev

JIRA Issue: https://bugs.openjdk.java.net/browse/JDK-8171537

This fixes an issue where the JTreg hotspot test compiler/c1/Test6849574.java fails with a guarantee failure when run with -XX:TieredStopAtLevel=1 to force use of C1.

# A fatal error has been detected by the Java Runtime Environment: 
# 
# Internal Error (assembler_aarch64.hpp:232), pid=8576, tid=8601 
# guarantee(val < (1U << nbits)) failed: Field too big for insn 

The problem is the following call in LIR_Assembler::atomic_op in src/cpu/aarch64/vm/c1_LIRAssembler_aarch64.cpp

  Address addr = as_Address(src->as_address_ptr(), noreg);

(noreg has the value -1)

as_Address looks like

Address LIR_Assembler::as_Address(LIR_Address* addr, Register tmp) {
....
    intptr_t addr_offset = intptr_t(addr->disp());
    if (Address::offset_ok_for_immed(addr_offset, addr->scale()))
      return Address(base, addr_offset, Address::lsl(addr->scale()));
    else {
      __ mov(tmp, addr_offset);  <<<<< tmp is used here, but has value -1
      return Address(base, tmp, Address::lsl(addr->scale()));
    }
}

The proposed solution is to change the call to

  Address addr = as_Address(src->as_address_ptr());

which calls the two argument form with rscratch1 as the tmp register instead of -1.

All the best,
Ed.