the predicate registers. Even though the ITLB and DTLB interrupts
happen often enough, this bug didn't do much harm. The reason
is that the interrupt handlers only modify p1 and since this is
a preserved (callee-saved) register it is hardly used in code
generated by the compiler. Compilers use scratch registers by
default. Changing the interrupt handlers to use p6 (ie a scratch
register) proved that the bug was in fact fatal.
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