Java Reference
In-Depth Information
x = 3
x = 3
x = 5
= x
= x
= x
Figure 14.69: Constant propagation example.
59. The SSA form discussion in Section 14.7 is limited to programs whose
references to names are explicit. If a programming language includes
pointers, then the names possibly a
ected by a given pointer indirection
are not explicitly stated in the program.
Develop an approach for translating programs with pointers into SSA
form. Distinguish between pointer references as follows:
ff
•
Some pointer references
may alias
a given set of names. Stores or
loads through such pointer references may, or may not, a
ff
ect those
names.
•
Some pointer references
must alias
a given set of names. Stores or
loads through such pointer references are guaranteed to a
ff
ect those
names.
60. Compute SSA form for the program shown in Figure 14.60.
61. The data flow framework for constantpropagationcan be applied to pro-
grams in SSA formby applying the
meet
operator at
φ
-functions [WZ91].
Compare the e
ciency and results of evaluating constant propagation
on Figure 14.60 in its original form and in its SSA form.
