The Unallocated Memory Hint instruction should execute as a NOP, but the CPU generates an UNDEF exception when bits [15:12] of the instruction encoding are not 0x0F.
In practice, this issue is not expected to be significant because such instruction encodings are not to be generated by the compiler, nor used in handcrafted programs.
The work-arounds consist of modifying the instruction encoding so bits [15:12] = 0x0F or make the exception handler emulate the expected behavior of the instruction (i.e., NOP) before returning to normal program execution.
| Impact: | Minor. Work-arounds are used by compilers and handcrafted programs. |
Work-around: | Modify the hint instruction encoding so bits [15:12] = 0x0F or make the exception handler emulate the expected behavior of the instruction (i.e., NOP) before returning to normal program execution. |
Configurations Affected: | Systems that use one or both ARM processors. |
| Device Revision(s) Affected: | All, no plan to fix. Refer to (Xilinx Answer 47916) Zynq-7000 SoC Silicon Revision Differences Answer Record. |
Modify the hint instruction encoding so bits [15:12] = 0x0F or make the exception handler emulate the expected behavior of the instruction (i.e., NOP) before returning to normal program execution.
| AR# 47558 | |
|---|---|
| Date | 06/13/2018 |
| Status | Active |
| Type | Design Advisory |
| Devices | |