[cost] Add tests for ZERO_EXECUTION_COST

Summary: We had no tests that resulted in `ZERO_EXECUTION_COST`. Let's fix that.

Reviewed By: skcho

Differential Revision: D20097504

fbshipit-source-id: 56c23fea0

infer/tests/codetoanalyze/c/performance/exit.c

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+void exit_unreachable_zero() {
+  exit(0); // modeled as unreachable
+}
+
+// constraint solver resolves all nodes to 0 cost
+void compute_exit_unreachable_zero() {
+  int k = 0;
+  exit(0);
+}
+
+void linear(int p) {
+  for (int i = 0; i < p; i++) {
+  }
+}
+
+void call_exit_unreachable_zero(int p) {
+  linear(p);
+  exit(0);
+}
+
+// constraint solver doesn't behave consistently and gets confused
+// when resolving constraints and gets linear cost
+void inline_exit_unreachable_FP(int p) {
+  for (int i = 0; i < p; i++) {
+  }
+  exit(0);
+}
+
+void call_unreachable_constant() { exit_unreachable_zero(); }

infer/tests/codetoanalyze/c/performance/issues.exp

@@ -48,6 +48,11 @@ codetoanalyze/c/performance/cost_test_deps.c, simulated_while, 10, INTEGER_OVERF
 codetoanalyze/c/performance/cost_test_deps.c, simulated_while, 12, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 215, O(1), degree = 0]
 codetoanalyze/c/performance/cost_test_deps.c, two_loops, 5, INTEGER_OVERFLOW_L5, no_bucket, ERROR, [<LHS trace>,Assignment,Binary operation: ([3, +oo] + 1):signed32]
 codetoanalyze/c/performance/cost_test_deps.c, two_loops, 7, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 546, O(1), degree = 0]
+codetoanalyze/c/performance/exit.c, call_exit_unreachable_zero, 0, ZERO_EXECUTION_TIME, no_bucket, ERROR, []
+codetoanalyze/c/performance/exit.c, compute_exit_unreachable_zero, 0, ZERO_EXECUTION_TIME, no_bucket, ERROR, []
+codetoanalyze/c/performance/exit.c, exit_unreachable_zero, 0, ZERO_EXECUTION_TIME, no_bucket, ERROR, []
+codetoanalyze/c/performance/exit.c, inline_exit_unreachable_FP, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 3 ⋅ p + 2 ⋅ (1+max(0, p)), O(p), degree = 1,{1+max(0, p)},Loop at line 30, column 3,{p},Loop at line 30, column 3]
+codetoanalyze/c/performance/exit.c, linear, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 2 + 3 ⋅ p + 2 ⋅ (1+max(0, p)), O(p), degree = 1,{1+max(0, p)},Loop at line 18, column 3,{p},Loop at line 18, column 3]
 codetoanalyze/c/performance/instantiate.c, do_2K_times_Bad, 0, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 14006, O(1), degree = 0]
 codetoanalyze/c/performance/instantiate.c, do_half_m2_times, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 2 + 5 ⋅ (m - 1) × m + 7 ⋅ m + 2 ⋅ m × (max(1, m)) + 2 ⋅ (1+max(0, m)), O(m × m), degree = 2,{1+max(0, m)},Loop at line 31, column 3,{max(1, m)},call to do_n_times,Loop at line 12, column 3,{m},Loop at line 31, column 3,{m},Loop at line 31, column 3,{m - 1},call to do_n_times,Loop at line 12, column 3]
 codetoanalyze/c/performance/instantiate.c, do_m2_times, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 2 + 7 ⋅ m + 5 ⋅ m × m + 2 ⋅ m × (1+max(0, m)) + 2 ⋅ (1+max(0, m)), O(m × m), degree = 2,{1+max(0, m)},Loop at line 24, column 3,{1+max(0, m)},call to do_n_times,Loop at line 12, column 3,{m},call to do_n_times,Loop at line 12, column 3,{m},Loop at line 24, column 3]