[clang] 1474244 - Reland "[analyzer] Canonicalize SymIntExpr so the RHS is positive when possible"
Balazs Benics via cfe-commits
cfe-commits at lists.llvm.org
Thu May 12 06:40:29 PDT 2022
Author: Tomasz Kamiński
Date: 2022-05-12T15:40:11+02:00
New Revision: 14742443a25826547e480189657b16c7a11664e7
URL: https://github.com/llvm/llvm-project/commit/14742443a25826547e480189657b16c7a11664e7
DIFF: https://github.com/llvm/llvm-project/commit/14742443a25826547e480189657b16c7a11664e7.diff
LOG: Reland "[analyzer] Canonicalize SymIntExpr so the RHS is positive when possible"
This PR changes the `SymIntExpr` so the expression that uses a
negative value as `RHS`, for example: `x +/- (-N)`, is modeled as
`x -/+ N` instead.
This avoids producing a very large `RHS` when the symbol is cased to
an unsigned number, and as consequence makes the value more robust in
presence of casts.
Note that this change is not applied if `N` is the lowest negative
value for which negation would not be representable.
Reviewed By: steakhal
Patch By: tomasz-kaminski-sonarsource!
Differential Revision: https://reviews.llvm.org/D124658
Added:
clang/test/Analysis/additive-op-on-sym-int-expr.c
Modified:
clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
clang/test/Analysis/expr-inspection.c
Removed:
################################################################################
diff --git a/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp b/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
index 65c2564637c18..03a751845fe1e 100644
--- a/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -104,6 +104,23 @@ SVal SimpleSValBuilder::evalComplement(NonLoc X) {
}
}
+// Checks if the negation the value and flipping sign preserve
+// the semantics on the operation in the resultType
+static bool isNegationValuePreserving(const llvm::APSInt &Value,
+ APSIntType ResultType) {
+ const unsigned ValueBits = Value.getSignificantBits();
+ if (ValueBits == ResultType.getBitWidth()) {
+ // The value is the lowest negative value that is representable
+ // in signed integer with bitWith of result type. The
+ // negation is representable if resultType is unsigned.
+ return ResultType.isUnsigned();
+ }
+
+ // If resultType bitWith is higher that number of bits required
+ // to represent RHS, the sign flip produce same value.
+ return ValueBits < ResultType.getBitWidth();
+}
+
//===----------------------------------------------------------------------===//
// Transfer function for binary operators.
//===----------------------------------------------------------------------===//
@@ -197,6 +214,17 @@ SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
}
+ } else if (BinaryOperator::isAdditiveOp(op) && RHS.isNegative()) {
+ // Change a+(-N) into a-N, and a-(-N) into a+N
+ // Adjust addition/subtraction of negative value, to
+ // subtraction/addition of the negated value.
+ APSIntType resultIntTy = BasicVals.getAPSIntType(resultTy);
+ if (isNegationValuePreserving(RHS, resultIntTy)) {
+ ConvertedRHS = &BasicVals.getValue(-resultIntTy.convert(RHS));
+ op = (op == BO_Add) ? BO_Sub : BO_Add;
+ } else {
+ ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
+ }
} else
ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
@@ -636,16 +664,26 @@ SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
const llvm::APSInt &second = IntType.convert(*RHSValue);
+ // If the op and lop agrees, then we just need to
+ // sum the constants. Otherwise, we change to operation
+ // type if substraction would produce negative value
+ // (and cause overflow for unsigned integers),
+ // as consequence x+1U-10 produces x-9U, instead
+ // of x+4294967287U, that would be produced without this
+ // additional check.
const llvm::APSInt *newRHS;
- if (lop == op)
+ if (lop == op) {
newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
- else
+ } else if (first >= second) {
newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
+ op = lop;
+ } else {
+ newRHS = BasicVals.evalAPSInt(BO_Sub, second, first);
+ }
assert(newRHS && "Invalid operation despite common type!");
rhs = nonloc::ConcreteInt(*newRHS);
lhs = nonloc::SymbolVal(symIntExpr->getLHS());
- op = lop;
continue;
}
}
diff --git a/clang/test/Analysis/additive-op-on-sym-int-expr.c b/clang/test/Analysis/additive-op-on-sym-int-expr.c
new file mode 100644
index 0000000000000..bd951c4443a1b
--- /dev/null
+++ b/clang/test/Analysis/additive-op-on-sym-int-expr.c
@@ -0,0 +1,169 @@
+// RUN: %clang_analyze_cc1 -triple=x86_64-unknown-linux-gnu -analyzer-checker=core,apiModeling,debug.ExprInspection -analyzer-config eagerly-assume=false -verify %s
+
+void clang_analyzer_dump(int);
+void clang_analyzer_dumpL(long);
+void clang_analyzer_warnIfReached();
+
+void testInspect(int x) {
+ if ((x < 10) || (x > 100)) {
+ return;
+ }
+ // x: [10, 100]
+
+ int i = x + 1;
+ long l = i - 10U;
+ clang_analyzer_dump(i); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) + 1 }}
+ clang_analyzer_dumpL(l); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) - 9U }} instead of + 4294967287U
+ clang_analyzer_dumpL(l + 0L); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) - 9 }} instead of + 4294967287
+
+ if ((l - 1000) > 0) {
+ clang_analyzer_warnIfReached(); // no-warning
+ }
+ if (l > 1000) {
+ clang_analyzer_warnIfReached(); // no-warning
+ }
+ if (l > 1000L) {
+ clang_analyzer_warnIfReached(); // no-warning
+ }
+ if ((l + 0L) > 1000) {
+ clang_analyzer_warnIfReached(); // no-warning
+ }
+
+ i = x - 1;
+ l = i + 10U;
+ clang_analyzer_dumpL(l); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) + 9U }} instead of - 4294967287U
+
+ i = x + (-1);
+ l = i - 10U;
+ clang_analyzer_dumpL(l); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) - 11U }} instead of + 4294967285U
+
+ i = x + 1U;
+ l = i - 10U;
+ clang_analyzer_dumpL(l); // expected-warning-re {{(reg_${{[0-9]+}}<int x>) - 9U }} instead of + 4294967287U
+}
+
+const int intMin = 1 << (sizeof(int) * 8 - 1); // INT_MIN, negation value is not representable
+const long longMin = 1L << (sizeof(long) * 8 - 1); // LONG_MIN, negation value is not representable
+
+void testMin(int i, long l) {
+ clang_analyzer_dump(i + (-1)); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) - 1 }} instead of + -1
+ clang_analyzer_dump(i - (-1)); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + 1 }} instead of - -1
+ clang_analyzer_dumpL(l + (-1)); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) - 1 }} instead of + -1
+ clang_analyzer_dumpL(l - (-1)); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) + 1 }} instead of - -1
+
+ // Do not normalize representation if negation would not be representable
+ clang_analyzer_dump(i + intMin); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + -2147483648 }} no change
+ clang_analyzer_dump(i - intMin); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) - -2147483648 }} no change
+ // Produced value has higher bit with (long) so negation if representable
+ clang_analyzer_dumpL(l + intMin); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) - 2147483648 }} instead of + -2147483648
+ clang_analyzer_dumpL(l - intMin); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) + 2147483648 }} instead of - -2147483648
+}
+
+void changingToUnsinged(unsigned u, int i) {
+ unsigned c = u + (unsigned)i;
+ unsigned d = u - (unsigned)i;
+ if (i == -1) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) - 1U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) + 1U }}
+ return;
+ }
+ if (i == intMin) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) - 2147483648U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) + 2147483648U }}
+ return;
+ }
+}
+
+void extendingToSigned(long l, int i) {
+ long c = l + (long)i;
+ long d = l - (long)i;
+ if (i == -1) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) - 1 }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) + 1 }}
+ return;
+ }
+ if (i == intMin) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) - 2147483648 }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<long l>) + 2147483648 }}
+ return;
+ }
+}
+
+void extendingToUnigned(unsigned long ul, int i) {
+ unsigned long c = ul + (unsigned long)i;
+ unsigned long d = ul - (unsigned long)i;
+ if (i == -1) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned long ul>) - 1U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned long ul>) + 1U }}
+ return;
+ }
+ if (i == intMin) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned long ul>) - 2147483648U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned long ul>) + 2147483648U }}
+ return;
+ }
+}
+
+void truncatingToSigned(int i, long l) {
+ int c = i + (int)l;
+ int d = i - (int)l;
+ if (l == -1L) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) - 1 }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + 1 }}
+ return;
+ }
+ if (l == (long)intMin) { // negation outside of range, no-changes
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + -2147483648 }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + -2147483648 }}
+ return;
+ }
+ if (l == ((long)intMin - 1L)) { // outside or range, no changes
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) + 2147483647 }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<int i>) - 2147483647 }}
+ return;
+ }
+ if (l == longMin) { // outside of range, no changes
+ clang_analyzer_dump(c + 0); // expected-warning-re {{reg_${{[0-9]+}}<int i> }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{reg_${{[0-9]+}}<int i> }}
+ return;
+ }
+}
+
+void truncatingToUnsigned(unsigned u, long l) {
+ unsigned c = u + (unsigned)l;
+ unsigned d = u - (unsigned)l;
+ if (l == -1L) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) - 1U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) + 1U }}
+ return;
+ }
+ if (l == (long)intMin) {
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) - 2147483648U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) + 2147483648U }}
+ return;
+ }
+ if (l == ((long)intMin - 1L)) { // outside or range, no changes
+ clang_analyzer_dump(c + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) + 2147483647U }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{(reg_${{[0-9]+}}<unsigned int u>) - 2147483647U }}
+ return;
+ }
+ if (l == longMin) { // outside of range, no changes
+ clang_analyzer_dump(c + 0); // expected-warning-re {{reg_${{[0-9]+}}<unsigned int u> }}
+ clang_analyzer_dump(d + 0); // expected-warning-re {{reg_${{[0-9]+}}<unsigned int u> }}
+ return;
+ }
+}
+
+// Test for crashes
+typedef long ssize_t;
+ssize_t write(int, const void *, unsigned long);
+
+int crashTest(int x, int fd) {
+ unsigned wres = write(fd, "a", 1);
+ if (wres) {
+ }
+ int t1 = x - wres;
+ if (wres < 0) {
+ }
+ return x + t1; // no crash
+}
diff --git a/clang/test/Analysis/expr-inspection.c b/clang/test/Analysis/expr-inspection.c
index bd05b2b3c3251..33c90f95bc782 100644
--- a/clang/test/Analysis/expr-inspection.c
+++ b/clang/test/Analysis/expr-inspection.c
@@ -11,7 +11,7 @@ void clang_analyzer_numTimesReached(void);
void foo(int x) {
clang_analyzer_dump(x); // expected-warning{{reg_$0<int x>}}
- clang_analyzer_dump(x + (-1)); // expected-warning{{(reg_$0<int x>) + -1}}
+ clang_analyzer_dump(x + (-1)); // expected-warning{{(reg_$0<int x>) - 1}}
int y = 1;
for (; y < 3; ++y) {
clang_analyzer_numTimesReached(); // expected-warning{{2}}
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