C++: Undo the hack.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll

@@ -432,23 +432,7 @@ private class DirectUseImpl extends UseImpl, TDirectUseImpl {
   override string toString() { result = "Use of " + this.getSourceVariable() }
 
   final override predicate hasIndexInBlock(IRBlock block, int index) {
-    // See the comment in `ssa0`'s `OperandBasedUse` for an explanation of this
-    // predicate's implementation.
-    if this.getBase().getAst() = any(Cpp::PostfixCrementOperation c).getOperand()
-    then
-      exists(Operand op, int indirection, Instruction base |
-        indirection = this.getIndirection() and
-        base = this.getBase() and
-        op =
-          min(Operand cand, int i |
-            isUse(_, cand, base, indirection, indirectionIndex) and
-            block.getInstruction(i) = cand.getUse()
-          |
-            cand order by i
-          ) and
-        block.getInstruction(index) = op.getUse()
-      )
-    else operand.getUse() = block.getInstruction(index)
+    operand.getUse() = block.getInstruction(index)
   }
 
   private BaseSourceVariableInstruction getBase() { isUse(_, operand, result, _, indirectionIndex) }

cpp/ql/test/library-tests/dataflow/dataflow-tests/test-source-sink.expected

@@ -378,8 +378,11 @@ irFlow
 | test.cpp:1195:10:1195:24 | *call to indirect_source | test.cpp:1224:19:1224:37 | ** ... |
 | test.cpp:1195:10:1195:24 | *call to indirect_source | test.cpp:1227:10:1227:29 | * ... |
 | test.cpp:1258:11:1258:16 | call to source | test.cpp:1259:8:1259:10 | ... ++ |
+| test.cpp:1258:11:1258:16 | call to source | test.cpp:1260:8:1260:8 | x |
 | test.cpp:1262:7:1262:12 | call to source | test.cpp:1263:8:1263:10 | ... -- |
+| test.cpp:1262:7:1262:12 | call to source | test.cpp:1264:8:1264:8 | x |
 | test.cpp:1284:11:1284:16 | call to source | test.cpp:1285:8:1285:20 | ... ? ... : ... |
+| test.cpp:1284:11:1284:16 | call to source | test.cpp:1286:8:1286:8 | x |
 | test.cpp:1288:7:1288:12 | call to source | test.cpp:1290:8:1290:8 | x |
 | test.cpp:1292:7:1292:12 | call to source | test.cpp:1294:8:1294:8 | x |
 | test.cpp:1296:7:1296:12 | call to source | test.cpp:1297:8:1297:18 | ... ? ... : ... |
@@ -388,6 +391,7 @@ irFlow
 | test.cpp:1300:7:1300:12 | call to source | test.cpp:1302:8:1302:8 | x |
 | test.cpp:1304:7:1304:12 | call to source | test.cpp:1306:8:1306:8 | x |
 | test.cpp:1308:7:1308:12 | call to source | test.cpp:1309:8:1309:16 | ... ++ |
+| test.cpp:1308:7:1308:12 | call to source | test.cpp:1310:8:1310:8 | x |
 | test.cpp:1312:7:1312:12 | call to source | test.cpp:1313:8:1313:24 | ... ? ... : ... |
 | test.cpp:1312:7:1312:12 | call to source | test.cpp:1314:8:1314:8 | x |
 | true_upon_entry.cpp:9:11:9:16 | call to source | true_upon_entry.cpp:13:8:13:8 | x |

cpp/ql/test/library-tests/dataflow/dataflow-tests/test.cpp

@@ -1257,11 +1257,11 @@ namespace globals_without_explicit_def {
 void crement_test1() {
   int x = source();
   sink(x++); // $ ir ast
-  sink(x);
+  sink(x); // $ SPURIOUS: ir
 
   x = source();
   sink(x--); // $ ir ast
-  sink(x);
+  sink(x); // $ SPURIOUS: ir
 
   x = source();
   sink(++x); // $ SPURIOUS: ast
@@ -1283,7 +1283,7 @@ void crement_test1() {
 void crement_test2(bool b, int y) {
   int x = source();
   sink(b ? x++ : x--); // $ ir ast
-  sink(x);
+  sink(x); // $ SPURIOUS: ir
 
   x = source();
   sink((b ? x : y)++); // $ ast MISSING: ir
@@ -1307,7 +1307,7 @@ void crement_test2(bool b, int y) {
 
   x = source();
   sink((long)x++); // $ ir ast
-  sink(x);
+  sink(x); // $ SPURIOUS: ir
 
   x = source();
   sink(b ? (long)x++ : 0); // $ ir ast