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205c0e2c78
This implements the behaviour of the 'wait 0' instruction of pausing execution of instructions until an exception arises. The exceptions that terminate a wait are a pending trace exception, external interrupt request, PMU interrupt request, or decrementer negative exception. These exception conditions terminate a wait even if not enabled to generate an interrupt (e.g. if MSR[EE] is zero). This is implemented by having execute1 assert its busy_out signal while the wait state exists. The wait state is set by the completion of the wait instruction and cleared by a pending exception. If the WC operand of the wait instruction is non-zero, indicating wait for reservation loss or wait for a short period, then the wait instruction does not wait, but just acts as a no-op. In order to make space in the insn_type_t type without going over 64 elements, this combines OP_DCBT and OP_ICBT into a single OP_XCBT, since they were both no-ops (except for their influence on how SRR1 is set on a trace interrupt, where they were identical). Signed-off-by: Paul Mackerras <paulus@ozlabs.org>