[clang] [analyzer] Improve solver (PR #112583)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Balazs Benics (steakhal)

<details>
<summary>Changes</summary>

This PR should be review commit by commit, and ought to be rebase-merged.
See the individual commits for their summary.

Once these two commits are reviewed, I'll force push to this PR the first commit, and open a new PR for the second commit because rebase-merge is not an option for upstream llvm, but I still wanted to let you know the whole picture, and that these two commits are related.

---
Full diff: https://github.com/llvm/llvm-project/pull/112583.diff


3 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp (+20-5) 
- (modified) clang/test/Analysis/infeasible-sink.c (+6-17) 
- (modified) clang/test/Analysis/unary-sym-expr.c (+1-2) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp b/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
index 70d5a609681790..2ee86a90a1f6d2 100644
--- a/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
@@ -1249,6 +1249,8 @@ class SymbolicRangeInferrer
         // calculate the effective range set by intersecting the range set
         // for A - B and the negated range set of B - A.
         getRangeForNegatedSymSym(SSE),
+        // If commutative, we may have constaints for the commuted variant.
+        getRangeCommutativeSymSym(SSE),
         // If Sym is a comparison expression (except <=>),
         // find any other comparisons with the same operands.
         // See function description.
@@ -1485,6 +1487,18 @@ class SymbolicRangeInferrer
         Sym->getType());
   }
 
+  std::optional<RangeSet> getRangeCommutativeSymSym(const SymSymExpr *SSE) {
+    bool IsCommutative = llvm::is_contained({BO_Add, BO_Mul}, SSE->getOpcode());
+    if (!IsCommutative)
+      return std::nullopt;
+
+    SymbolRef Commuted = State->getSymbolManager().getSymSymExpr(
+        SSE->getRHS(), BO_Add, SSE->getLHS(), SSE->getType());
+    if (const RangeSet *Range = getConstraint(State, Commuted))
+      return *Range;
+    return std::nullopt;
+  }
+
   // Returns ranges only for binary comparison operators (except <=>)
   // when left and right operands are symbolic values.
   // Finds any other comparisons with the same operands.
@@ -1939,11 +1953,8 @@ class RangeConstraintManager : public RangedConstraintManager {
   RangeSet::Factory F;
 
   RangeSet getRange(ProgramStateRef State, SymbolRef Sym);
-  RangeSet getRange(ProgramStateRef State, EquivalenceClass Class);
   ProgramStateRef setRange(ProgramStateRef State, SymbolRef Sym,
                            RangeSet Range);
-  ProgramStateRef setRange(ProgramStateRef State, EquivalenceClass Class,
-                           RangeSet Range);
 
   RangeSet getSymLTRange(ProgramStateRef St, SymbolRef Sym,
                          const llvm::APSInt &Int,
@@ -2866,12 +2877,14 @@ ConditionTruthVal RangeConstraintManager::checkNull(ProgramStateRef State,
 
 const llvm::APSInt *RangeConstraintManager::getSymVal(ProgramStateRef St,
                                                       SymbolRef Sym) const {
-  const RangeSet *T = getConstraint(St, Sym);
-  return T ? T->getConcreteValue() : nullptr;
+  auto &MutableSelf = const_cast<RangeConstraintManager &>(*this);
+  return MutableSelf.getRange(St, Sym).getConcreteValue();
 }
 
 const llvm::APSInt *RangeConstraintManager::getSymMinVal(ProgramStateRef St,
                                                          SymbolRef Sym) const {
+  // TODO: Use `getRange()` like in `getSymVal()`, but that would make some
+  // of the reports of `BitwiseShiftChecker` look awkward.
   const RangeSet *T = getConstraint(St, Sym);
   if (!T || T->isEmpty())
     return nullptr;
@@ -2880,6 +2893,8 @@ const llvm::APSInt *RangeConstraintManager::getSymMinVal(ProgramStateRef St,
 
 const llvm::APSInt *RangeConstraintManager::getSymMaxVal(ProgramStateRef St,
                                                          SymbolRef Sym) const {
+  // TODO: Use `getRange()` like in `getSymVal()`, but that would make some
+  // of the reports of `BitwiseShiftChecker` look awkward.
   const RangeSet *T = getConstraint(St, Sym);
   if (!T || T->isEmpty())
     return nullptr;
diff --git a/clang/test/Analysis/infeasible-sink.c b/clang/test/Analysis/infeasible-sink.c
index 9cb66fcac0b6be..d5b4e82268f5b6 100644
--- a/clang/test/Analysis/infeasible-sink.c
+++ b/clang/test/Analysis/infeasible-sink.c
@@ -38,7 +38,7 @@ void test1(int x) {
 }
 
 int a, b, c, d, e;
-void test2() {
+void test2(void) {
 
   if (a == 0)
     return;
@@ -50,28 +50,17 @@ void test2() {
   b = d;
   a -= d;
 
+  clang_analyzer_warnIfReached(); // expected-warning {{REACHABLE}}
+
   if (a != 0)
     return;
 
-  clang_analyzer_warnIfReached(); // expected-warning{{REACHABLE}}
-
-  /* The BASELINE passes these checks ('wrning' is used to avoid lit to match)
-  // The parent state is already infeasible, look at this contradiction:
-  clang_analyzer_eval(b > 0);  // expected-wrning{{FALSE}}
-  clang_analyzer_eval(b <= 0); // expected-wrning{{FALSE}}
-  // Crashes with expensive checks.
-  if (b > 0) {
-    clang_analyzer_warnIfReached(); // no-warning, OK
-    return;
-  }
-  // Should not be reachable.
-  clang_analyzer_warnIfReached(); // expected-wrning{{REACHABLE}}
-  */
+  clang_analyzer_warnIfReached(); // no-warning: Even the parent state is unreachable.
 
   // The parent state is already infeasible, but we realize that only if b is
   // constrained.
-  clang_analyzer_eval(b > 0);  // expected-warning{{UNKNOWN}}
-  clang_analyzer_eval(b <= 0); // expected-warning{{UNKNOWN}}
+  clang_analyzer_eval(b > 0);  // no-warning
+  clang_analyzer_eval(b <= 0); // no-warning
   if (b > 0) {
     clang_analyzer_warnIfReached(); // no-warning
     return;
diff --git a/clang/test/Analysis/unary-sym-expr.c b/clang/test/Analysis/unary-sym-expr.c
index 7c4774f3cca82f..7ce7a3c5c24e35 100644
--- a/clang/test/Analysis/unary-sym-expr.c
+++ b/clang/test/Analysis/unary-sym-expr.c
@@ -33,8 +33,7 @@ void test_svalbuilder_simplification(int x, int y) {
   if (x + y != 3)
     return;
   clang_analyzer_eval(-(x + y) == -3); // expected-warning{{TRUE}}
-  // FIXME Commutativity is not supported yet.
-  clang_analyzer_eval(-(y + x) == -3); // expected-warning{{UNKNOWN}}
+  clang_analyzer_eval(-(y + x) == -3); // expected-warning{{TRUE}}
 }
 
 int test_fp(int flag) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/112583