[Cost] Avoid Top to Top performance variations

Reviewed By: ezgicicek

Differential Revision: D14342025

fbshipit-source-id: 55836b60e

infer/src/bufferoverrun/polynomials.ml

@@ -504,7 +504,8 @@ module NonNegativePolynomial = struct
 
 
   let compare_by_degree =
-    AbstractDomain.StackedUtils.compare ~cmp_above:TopTraces.compare ~cmp_below:(fun p1 p2 ->
+    let cmp_above _ _ = 0 (* All Top should be considered equal *) in
+    AbstractDomain.StackedUtils.compare ~cmp_above ~cmp_below:(fun p1 p2 ->
         Degree.compare
           (NonNegativeNonTopPolynomial.degree p1)
           (NonNegativeNonTopPolynomial.degree p2) )

infer/tests/build_systems/differential_of_costs_report/costs_summary.json.exp

@@ -1 +1 @@
-{"top":{"current":1,"previous":0},"zero":{"current":0,"previous":0},"degrees":[{"degree":0,"current":3,"previous":2},{"degree":100,"current":1,"previous":2},{"degree":101,"current":2,"previous":0},{"degree":200,"current":0,"previous":2}]}
+{"top":{"current":2,"previous":1},"zero":{"current":0,"previous":0},"degrees":[{"degree":0,"current":3,"previous":2},{"degree":100,"current":1,"previous":2},{"degree":101,"current":2,"previous":0},{"degree":200,"current":0,"previous":2}]}

infer/tests/build_systems/differential_of_costs_report/introduced.exp

@@ -1,3 +1,3 @@
-INFINITE_EXECUTION_TIME_CALL, no_bucket, src/DiffExample.java, DiffExample.f1(int):void, 0, [Loop at line 25]
+INFINITE_EXECUTION_TIME_CALL, no_bucket, src/DiffExample.java, DiffExample.f1(int):void, 0, [Loop at line 26]
-PERFORMANCE_VARIATION, no_bucket, src/DiffExample.java, DiffExample.f4(int):int, 0, [Updated Cost is 6 + 5 ⋅ k (degree is 1),{k},Loop at line 44]
+PERFORMANCE_VARIATION, no_bucket, src/DiffExample.java, DiffExample.f4(int):int, 0, [Updated Cost is 6 + 5 ⋅ k (degree is 1),{k},Loop at line 45]
 PERFORMANCE_VARIATION, no_bucket, src/DiffExample.java, DiffExample.f5(java.util.ArrayList):void, 0, [Updated Cost is 2 + list.length × log(list.length) (degree is 1 + 1⋅log),{list.length},Modeled call to List.length,{list.length},Modeled call to List.length]

infer/tests/build_systems/differential_of_costs_report/preexisting.exp

@@ -0,0 +1 @@
+INFINITE_EXECUTION_TIME_CALL, no_bucket, src/DiffExample.java, DiffExample.f7(int):void, 0, [call to void DiffExample.f1(int),Loop at line 26]

infer/tests/build_systems/differential_of_costs_report/src/DiffExample.java.current

@@ -16,6 +16,7 @@ import java.util.ArrayList;
 // f4: linear
 // f5: n log n
 // f6: n log n
+// f7: top by call to f1
 
 public class DiffExample {
 
@@ -55,4 +56,9 @@ public class DiffExample {
     private void f6(ArrayList<Integer> list) {
       f5(list);
     }
+
+    // cost: top by call to f1
+    private static void f7(int k) {
+        f1(k);
+    }
 }

infer/tests/build_systems/differential_of_costs_report/src/DiffExample.java.previous

@@ -13,6 +13,7 @@
 // f4: constant
 // f5: linear
 // f6: quadratic
+// f7: top
 
 public class DiffExample {
     // cost: linear
@@ -44,4 +45,12 @@ public class DiffExample {
     private static void f6(int n) {
         f2(n);
     }
+
+    // cost: top
+    private static void f7(int k) {
+        int i = 0;
+        while (i >=0) {
+            i++;
+        }
+    }
 }