Lazy and Speculative Execution

15 January 2007

Lampson: Lazy and Speculative Execution

Reordering and Conditionals

Lazy

t:=L; !A; !B(t) Þ !A; !B(L) latency only

t:=L; !A; x → !B(t) Þ !A; x → !B(L) less work if ~x

t:=L; !A; x → !B(t) Þ t:=L1; !A; x → !B(L2(t)) more general

Speculative

!A; x → !B(S) Þ t:=S; !A; x → !B(t)

!A; x → !B(S) Þ t:=S1; !A; x → !B(S2(t)) more general

n You bet on the outcome of the conditional

! marks actions that have output/side effects