SSA: Make phiWithoutTwoPriorRefs consistency check more informative

Author: hvitved

rust/ql/test/query-tests/security/CWE-089/CONSISTENCY/SsaConsistency.expected

@@ -1,4 +1,4 @@
 uselessPhiNode
-| sqlx.rs:155:5:157:5 | phi | 1 |
+| sqlx.rs:155:5:157:5 | SSA phi(arg0) | 1 |
 phiWithoutTwoPriorRefs
-| sqlx.rs:155:5:157:5 | phi | 1 |
+| sqlx.rs:155:5:157:5 | SSA phi(arg0) | sqlx.rs:155:5:157:5 | if enable_remote {...} | sqlx.rs:156:17:156:86 | arg0 | 1 |

shared/ssa/codeql/ssa/Ssa.qll

@@ -1412,13 +1412,12 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     }
 
     /** Holds if `phi` has less than 2 immediately prior references. */
-    query predicate phiWithoutTwoPriorRefs(PhiNode phi, int inputRefs) {
-      exists(BasicBlock bbPhi, SourceVariable v |
-        phi.definesAt(v, bbPhi, _) and
-        inputRefs =
-          count(BasicBlock bb, int i | AdjacentSsaRefs::adjacentRefPhi(bb, i, _, bbPhi, v)) and
-        inputRefs < 2
-      )
+    query predicate phiWithoutTwoPriorRefs(
+      PhiNode phi, BasicBlock bbPhi, SourceVariable v, int inputRefs
+    ) {
+      phi.definesAt(v, bbPhi, _) and
+      inputRefs = count(BasicBlock bb, int i | AdjacentSsaRefs::adjacentRefPhi(bb, i, _, bbPhi, v)) and
+      inputRefs < 2
     }
 
     /**