(* Author: Tobias Nipkow *)
theory AbsInt0_const
imports AbsInt0
begin
subsection "Constant Propagation"
datatype cval = Const val | Any
fun rep_cval where
"rep_cval (Const n) = {n}" |
"rep_cval (Any) = UNIV"
fun plus_cval where
"plus_cval (Const m) (Const n) = Const(m+n)" |
"plus_cval _ _ = Any"
instantiation cval :: SL_top
begin
fun le_cval where
"_ \<sqsubseteq> Any = True" |
"Const n \<sqsubseteq> Const m = (n=m)" |
"Any \<sqsubseteq> Const _ = False"
fun join_cval where
"Const m \<squnion> Const n = (if n=m then Const m else Any)" |
"_ \<squnion> _ = Any"
definition "Top = Any"
instance
proof
case goal1 thus ?case by (cases x) simp_all
next
case goal2 thus ?case by(cases z, cases y, cases x, simp_all)
next
case goal3 thus ?case by(cases x, cases y, simp_all)
next
case goal4 thus ?case by(cases y, cases x, simp_all)
next
case goal5 thus ?case by(cases z, cases y, cases x, simp_all)
next
case goal6 thus ?case by(simp add: Top_cval_def)
qed
end
interpretation Rep rep_cval
proof
case goal1 thus ?case
by(cases a, cases b, simp, simp, cases b, simp, simp)
qed
interpretation Val_abs rep_cval Const plus_cval
proof
case goal1 show ?case by simp
next
case goal2 thus ?case
by(cases a1, cases a2, simp, simp, cases a2, simp, simp)
qed
interpretation Abs_Int rep_cval Const plus_cval
defines AI_const is AI
and aval'_const is aval'
..
text{* Straight line code: *}
definition "test1_const =
''y'' ::= N 7;
''z'' ::= Plus (V ''y'') (N 2);
''y'' ::= Plus (V ''x'') (N 0)"
value [code] "list (AI_const test1_const Top)"
text{* Conditional: *}
definition "test2_const =
IF Less (N 41) (V ''x'') THEN ''x'' ::= N 5 ELSE ''x'' ::= N 5"
value "list (AI_const test2_const Top)"
text{* Conditional, test is ignored: *}
definition "test3_const =
''x'' ::= N 42;
IF Less (N 41) (V ''x'') THEN ''x'' ::= N 5 ELSE ''x'' ::= N 6"
value "list (AI_const test3_const Top)"
text{* While: *}
definition "test4_const =
''x'' ::= N 0; WHILE B True DO ''x'' ::= N 0"
value [code] "list (AI_const test4_const Top)"
text{* While, test is ignored: *}
definition "test5_const =
''x'' ::= N 0; WHILE Less (V ''x'') (N 1) DO ''x'' ::= N 1"
value [code] "list (AI_const test5_const Top)"
text{* Iteration is needed: *}
definition "test6_const =
''x'' ::= N 0; ''y'' ::= N 0; ''z'' ::= N 2;
WHILE Less (V ''x'') (N 1) DO (''x'' ::= V ''y''; ''y'' ::= V ''z'')"
value [code] "list (AI_const test6_const Top)"
text{* More iteration would be needed: *}
definition "test7_const =
''x'' ::= N 0; ''y'' ::= N 0; ''z'' ::= N 0; ''u'' ::= N 3;
WHILE B True DO (''x'' ::= V ''y''; ''y'' ::= V ''z''; ''z'' ::= V ''u'')"
value [code] "list (AI_const test7_const Top)"
end