C++: Remove safeFloor in simple range analysis

Author: paldepind

cpp/ql/lib/semmle/code/cpp/rangeanalysis/SimpleRangeAnalysis.qll

@@ -158,22 +158,6 @@ private class UnsignedBitwiseAndExpr extends BitwiseAndExpr {
   }
 }
 
-/**
- * Gets the floor of `v`, with additional logic to work around issues with
- * large numbers.
- */
-bindingset[v]
-float safeFloor(float v) {
-  // return the floor of v
-  v.abs() < 2.pow(31) and
-  result = v.floor()
-  or
-  // `floor()` doesn't work correctly on large numbers (since it returns an integer),
-  // so fall back to unrounded numbers at this scale.
-  not v.abs() < 2.pow(31) and
-  result = v
-}
-
 /** A `MulExpr` where exactly one operand is constant. */
 private class MulByConstantExpr extends MulExpr {
   float constant;
@@ -1266,7 +1250,7 @@ private float getLowerBoundsImpl(Expr expr) {
       rsExpr = expr and
       left = getFullyConvertedLowerBounds(rsExpr.getLeftOperand()) and
       right = getValue(rsExpr.getRightOperand().getFullyConverted()).toInt() and
-      result = safeFloor(left / 2.pow(right))
+      result = (left / 2.pow(right)).floorFloat()
     )
     // Not explicitly modeled by a SimpleRangeAnalysisExpr
   ) and
@@ -1475,7 +1459,7 @@ private float getUpperBoundsImpl(Expr expr) {
       rsExpr = expr and
       left = getFullyConvertedUpperBounds(rsExpr.getLeftOperand()) and
       right = getValue(rsExpr.getRightOperand().getFullyConverted()).toInt() and
-      result = safeFloor(left / 2.pow(right))
+      result = (left / 2.pow(right)).floorFloat()
     )
     // Not explicitly modeled by a SimpleRangeAnalysisExpr
   ) and

cpp/ql/test/library-tests/rangeanalysis/SimpleRangeAnalysis/lowerBound.expected

@@ -351,7 +351,7 @@
 | test.c:330:14:330:14 | r | -2147483648 |
 | test.c:333:10:333:14 | total | -2147483648 |
 | test.c:341:32:341:34 | odd | 9007199254740991 |
-| test.c:343:10:343:16 | shifted | 4503599627370495.5 |
+| test.c:343:10:343:16 | shifted | 4503599627370495 |
 | test.c:348:7:348:7 | x | -2147483648 |
 | test.c:352:10:352:10 | i | 0 |
 | test.c:353:5:353:5 | i | 0 |

cpp/ql/test/library-tests/rangeanalysis/SimpleRangeAnalysis/upperBound.expected

@@ -351,7 +351,7 @@
 | test.c:330:14:330:14 | r | 2147483647 |
 | test.c:333:10:333:14 | total | 2147483647 |
 | test.c:341:32:341:34 | odd | 9007199254740991 |
-| test.c:343:10:343:16 | shifted | 4503599627370495.5 |
+| test.c:343:10:343:16 | shifted | 4503599627370495 |
 | test.c:348:7:348:7 | x | 2147483647 |
 | test.c:352:10:352:10 | i | 7 |
 | test.c:353:5:353:5 | i | 2 |

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.cpp

@@ -38,8 +38,8 @@ int extreme_values(void)
 	if (x >> 1 >= 0x7FFFFFFFFFFFFFFF) {} // always true [NOT DETECTED]
 	if (x >> 1 >= 0xFFFFFFFFFFFFFFF) {} // always true [NOT DETECTED]
 
-	if (y >> 1 >= 0xFFFFFFFFFFFF) {} // always false [INCORRECT MESSAGE]
-	if (y >> 1 >= 0x800000000000) {} // always false [INCORRECT MESSAGE]
-	if (y >> 1 >= 0x7FFFFFFFFFFF) {} // always true [INCORRECT MESSAGE]
-	if (y >> 1 >= 0xFFFFFFFFFFF) {} // always true [INCORRECT MESSAGE]
+	if (y >> 1 >= 0xFFFFFFFFFFFF) {} // always false
+	if (y >> 1 >= 0x800000000000) {} // always false
+	if (y >> 1 >= 0x7FFFFFFFFFFF) {} // always true
+	if (y >> 1 >= 0xFFFFFFFFFFF) {} // always true
 }

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected

@@ -45,9 +45,9 @@
 | PointlessComparison.c:391:12:391:20 | ... < ... | Comparison is always false because ... * ... >= 6. |
 | PointlessComparison.c:414:7:414:16 | ... == ... | Comparison is always false because ... * ... >= 18446744073709551616. |
 | PointlessComparison.cpp:36:6:36:33 | ... >= ... | Comparison is always false because ... >> ... <= 9223372036854775808. |
-| PointlessComparison.cpp:41:6:41:29 | ... >= ... | Comparison is always false because ... >> ... <= 140737488355327.5. |
-| PointlessComparison.cpp:42:6:42:29 | ... >= ... | Comparison is always false because ... >> ... <= 140737488355327.5. |
-| PointlessComparison.cpp:43:6:43:29 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327.5. |
-| PointlessComparison.cpp:44:6:44:28 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327.5. |
+| PointlessComparison.cpp:41:6:41:29 | ... >= ... | Comparison is always false because ... >> ... <= 140737488355327. |
+| PointlessComparison.cpp:42:6:42:29 | ... >= ... | Comparison is always false because ... >> ... <= 140737488355327. |
+| PointlessComparison.cpp:43:6:43:29 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327. |
+| PointlessComparison.cpp:44:6:44:28 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327. |
 | RegressionTests.cpp:57:7:57:22 | ... <= ... | Comparison is always true because * ... <= 4294967295. |
 | Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |