Continual reading from the PowerPc time base register is not stable

[Segher Boessenkool]

> Yes indeed.  Could you post the relevant piece if disassembly from
> your original binary (the one that has the problem)?  Or send me the
> binary (not to the mailing list), I'll do it then.

Ah scratch that.  I compiled your original code (after fixing the
compile errors -- there is no such type as "bool" in C).

The problem is that  (upper << 32) | lower  thing.  "upper" is a 32-bit
type, so shifting it by 32 or more bits is undefined.  GCC compiles this
to (shortened):

0: mftbu 9 ; mftbl 11 ; mftbu 0 ; cmpw 0,9 ; bne 0b  # so far so good
   slwi 0,0,0 ; or 4,0,11 ; li 3,0 ; blr

so it shifts by 0, i.e. it does  upper | lower .

Case closed, no hardware problem :-)


Segher