diff options
Diffstat (limited to 'Source/VCExpr/VCExprAST.ssc')
| -rw-r--r-- | Source/VCExpr/VCExprAST.ssc | 36 |
1 files changed, 35 insertions, 1 deletions
diff --git a/Source/VCExpr/VCExprAST.ssc b/Source/VCExpr/VCExprAST.ssc index 4d9d4c20..5a9063cc 100644 --- a/Source/VCExpr/VCExprAST.ssc +++ b/Source/VCExpr/VCExprAST.ssc @@ -137,7 +137,7 @@ namespace Microsoft.Boogie ///////////////////////////////////////////////////////////////////////////
// Versions of the propositional operators that automatically simplify in
- // certain cases (if one of the operators is True or False)
+ // certain cases (for example, if one of the operators is True or False)
public VCExpr! NotSimp(VCExpr! e0) {
if (e0.Equals(True))
@@ -171,8 +171,39 @@ namespace Microsoft.Boogie return NotSimp(e0);
if (e0.Equals(False) || e1.Equals(True))
return True;
+ // attempt to save on the depth of expressions (to reduce chances of stack overflows)
+ while (e1 is VCExprBinary) {
+ VCExprBinary n = (VCExprBinary)e1;
+ if (n.Op == ImpliesOp) {
+ if (AndSize(n[0]) <= AndSize(e0)) {
+ // combine the antecedents
+ e0 = And(e0, n[0]);
+ e1 = n[1];
+ continue;
+ }
+ }
+ break;
+ }
return Implies(e0, e1);
}
+
+ ///<summary>
+ /// Returns some measure of the number of conjuncts in e. This could be the total number of conjuncts in all
+ /// top-most layers of the expression, or it can simply be the length of the left-prong of this and-tree. The
+ /// important thing is that: AndSize(e0) >= AndSize(31) ==> AndSize(And(e0,e1)) > AndSize(e0).
+ ///</summary>
+ int AndSize(VCExpr! e) {
+ int n = 1;
+ while (true) {
+ VCExprNAry nary = e as VCExprNAry;
+ if (nary != null && nary.Op == AndOp && 2 <= nary.Arity) {
+ e = nary[0];
+ n++;
+ } else {
+ return n;
+ }
+ }
+ }
////////////////////////////////////////////////////////////////////////////////
// Further operators
@@ -363,6 +394,9 @@ namespace Microsoft.Boogie }
public VCExpr! LabelNeg(string! label, VCExpr! e) {
+ if (e.Equals(True)) {
+ return e; // don't bother putting negative labels around True (which will expose the True to further peephole optimizations)
+ }
return Function(LabelOp(false, label), e);
}
public VCExpr! LabelPos(string! label, VCExpr! e) {
|