[9] RFR: 8044538: assert(which != imm_operand) failed: instruction is not a movq reg, imm64

[Tobias Hartmann]

Hi,

please review the following patch for bug 8044538.

*Problem*
Executing a debug build of HotSpot with the flags -XX:+PrintRelocations 
-Xcomp hits a ShouldNotReachHere() or an assert in 
Assembler::locate_operand(..) stating that the instruction for which we 
try to find the operand is not valid.

The problem occurs while printing the relocation entries for a C2 
compiled function. The C2 compiler adds internal_word_type relocations 
for the jump table entries in the constant section of a method (see 
Compile::ConstantTable::fill_jump_table(...)). These relocations are 
processed by RelocIterator::print_current(...) and 
internal_word_Relocation::target(). 
Relocation::pd_get_address_from_code() then tries to retrieve the 
address from an instruction but fails because the relocation points into 
the constant section only containing the target address.

Bug: https://bugs.openjdk.java.net/browse/JDK-8044538

*Solution*
The implementation of internal_word_Relocation::target() is changed to 
check if the relocation points into the constant section and if so 
directly returns the target address instead of trying to retrieve it 
from an instruction. The same is already done in 
internal_word_Relocation::fix_relocation_after_move(..).

Webrev: http://cr.openjdk.java.net/~thartmann/8044538/webrev.00/

*Tests*
Failing configuration, JPRT

Apparently this did not show up for any of our tests. Do we need an 
additional test for this?
Since it already fails for JDK 7 and 8. Should we backport the patch?

Thanks,
Tobias


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