[PATCH] Long NOP padding

[David Sehr]

The current X86 NOP padding uses one long NOP followed by the remainder in
one-byte NOPs.  If the processor actually executes those NOPs, as it
sometimes does with aligned bundling, this can have a performance impact.
 From my micro-benchmarks run on my one machine, a 15-byte NOP followed by
twelve one-byte NOPs is about 20% worse than a 15 followed by a 12.  This
patch changes NOP emission to emit as many 15-byte (the maximum) as
possible followed by at most one shorter NOP.

David
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