 |
gen(S) = gen(S1)
kill(S) = kill(S1)
out(S) = out(S1)
in(S1) = in(S) S gen(S1) |
Assumptions : All paths in the flow graph are possible
Suppose E is true and it never goes to S2
gen(S) = gen(S1)
kill(S) = kill(S1)
out(S) = out(S1)
Therefore
true gen(S) ⊂ gen(S)
true kill(S) ⊃ kill(S) |
True is what is computed during execution therefore, this is safe estimate
- Prevents optimization
- No wrong optimization
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