manas updated this revision to Diff 483135.
manas added a comment.
Rebase
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D140086/new/
https://reviews.llvm.org/D140086
Files:
clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
clang/test/Analysis/constant-folding.c
Index: clang/test/Analysis/constant-folding.c
===================================================================
--- clang/test/Analysis/constant-folding.c
+++ clang/test/Analysis/constant-folding.c
@@ -303,7 +303,8 @@
if (s1 < 0 && s1 > -4 && u1 > UINT_MAX - 4 && u1 < UINT_MAX - 1) {
// s1: [-3, -1], u1: [UINT_MAX - 3, UINT_MAX - 2]
- clang_analyzer_eval(u1 != s1); // expected-warning{{UNKNOWN}}
+ clang_analyzer_eval(u1 != s1); // expected-warning{{TRUE}}
+ clang_analyzer_eval(s1 != u1); // expected-warning{{TRUE}}
}
if (s1 < 1 && s1 > -6 && s1 != -4 && s1 != -3 &&
@@ -400,12 +401,10 @@
clang_analyzer_eval(uch != sch); // expected-warning{{UNKNOWN}}
}
- // FIXME: Casting smaller signed types to unsigned one may leave us with
- // overlapping values, falsely indicating UNKNOWN, where it is possible to
- // assert TRUE.
if (uch > 1 && sch < 1) {
// uch: [2, UCHAR_MAX], sch: [SCHAR_MIN, 0]
- clang_analyzer_eval(uch != sch); // expected-warning{{UNKNOWN}}
+ clang_analyzer_eval(uch != sch); // expected-warning{{TRUE}}
+ clang_analyzer_eval(sch != uch); // expected-warning{{TRUE}}
}
if (uch <= 1 && uch >= 1 && sch <= 1 && sch >= 1) {
@@ -419,10 +418,9 @@
clang_analyzer_eval(ush != ssh); // expected-warning{{UNKNOWN}}
}
- // FIXME: Casting leave us with overlapping values. Should be TRUE.
if (ush > 1 && ssh < 1) {
// ush: [2, USHRT_MAX], ssh: [SHRT_MIN, 0]
- clang_analyzer_eval(ush != ssh); // expected-warning{{UNKNOWN}}
+ clang_analyzer_eval(ush != ssh); // expected-warning{{TRUE}}
}
if (ush <= 1 && ush >= 1 && ssh <= 1 && ssh >= 1) {
Index: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
+++ clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
@@ -1624,7 +1624,52 @@
if (LHS.getAPSIntType() == RHS.getAPSIntType()) {
if (intersect(RangeFactory, LHS, RHS).isEmpty())
return getTrueRange(T);
+
} else {
+ // We can only lose information if we are casting smaller signed type to
+ // bigger unsigned type. For e.g.,
+ // LHS (unsigned short): [2, USHRT_MAX]
+ // RHS (signed short): [SHRT_MIN, 0]
+ //
+ // Casting RHS to LHS type will leave us with overlapping values
+ // CastedRHS : [0, 0] U [SHRT_MAX + 1, USHRT_MAX]
+ //
+ // We can avoid this by checking if signed type's maximum value is lesser
+ // than unsigned type's minimum value.
+
+ // If both have different signs then only we can get more information.
+ if (LHS.isUnsigned() ^ RHS.isUnsigned()) {
+ if (LHS.isUnsigned() && (LHS.getBitWidth() >= RHS.getBitWidth())) {
+
+ // If signed range is <Zero, then we can simply infer that expression
+ // will return true.
+ llvm::APSInt Zero = RHS.getAPSIntType().getZeroValue();
+ bool IsRHSNegative = RHS.getMaxValue() < Zero;
+ if (IsRHSNegative)
+ return getTrueRange(T);
+
+ // If signed range may have APSInt >=Zero, then maximum value of signed
+ // type should be lesser than minimum value of unsigned type.
+ const llvm::APSInt CastedRHSMax =
+ LHS.getAPSIntType().convert(RHS.getMaxValue());
+
+ if (CastedRHSMax < LHS.getMinValue())
+ return getTrueRange(T);
+
+ } else if (RHS.isUnsigned() && (LHS.getBitWidth() <= RHS.getBitWidth())) {
+
+ llvm::APSInt Zero = LHS.getAPSIntType().getZeroValue();
+ bool IsLHSNegative = LHS.getMaxValue() < Zero;
+ if (IsLHSNegative)
+ return getTrueRange(T);
+
+ const llvm::APSInt CastedLHSMax =
+ RHS.getAPSIntType().convert(LHS.getMaxValue());
+ if (CastedLHSMax < RHS.getMinValue())
+ return getTrueRange(T);
+ }
+ }
+
// Both RangeSets should be casted to bigger unsigned type.
APSIntType CastingType(std::max(LHS.getBitWidth(), RHS.getBitWidth()),
LHS.isUnsigned() || RHS.isUnsigned());
@@ -2147,7 +2192,6 @@
RangeSet::Factory &RangeFactory;
};
-
bool ConstraintAssignor::assignSymExprToConst(const SymExpr *Sym,
const llvm::APSInt &Constraint) {
llvm::SmallSet<EquivalenceClass, 4> SimplifiedClasses;
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