CSG: Analysis within a Basic Block
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•
A variable is
live
if it is used later in the block
live
next use
Example:
…
No occurrence
of
variable “
a
”
Question:
How to detect live variables effectively?
Answer:
Apply
backward
finding
¾
that is, read
the instructions from the block end towards its begin
…
(i)
a
:= b + c
(j) d :=
a
+ b