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

[Balazs Benics via cfe-commits]

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

>From dfb86a3ddad88a9a97fff054af1bf86d746ee49d Mon Sep 17 00:00:00 2001
From: Balazs Benics <benicsbalazs at gmail.com>
Date: Wed, 16 Oct 2024 15:52:31 +0200
Subject: [PATCH] [analyzer][Solver] Improve getSymVal and friends (1/2)

Instead of just doing a lookup in the existing constraints,
let's use `getRange()` for dissambling SymSymExprs and inferring from
the constraint system what end range set we can simplify.

This means that `getSymVal` gets more expensive while getting smarter.
I don't expect it to be an issue as this API is only rarely used, and
`getRange` is used a lot more often - yet without any observable hit on
performance.

This patch also removes dead declarations of EQClass overloads.
---
 .../Checkers/BitwiseShiftChecker.cpp          |  3 +-
 .../Core/RangeConstraintManager.cpp           | 21 +++++---------
 clang/test/Analysis/infeasible-sink.c         | 29 +++----------------
 3 files changed, 14 insertions(+), 39 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/BitwiseShiftChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/BitwiseShiftChecker.cpp
index 339927c165fe00..17f1214195b3ee 100644
--- a/clang/lib/StaticAnalyzer/Checkers/BitwiseShiftChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/BitwiseShiftChecker.cpp
@@ -177,7 +177,8 @@ BugReportPtr BitwiseShiftValidator::checkOvershift() {
     RightOpStr = formatv(" '{0}'", ConcreteRight->getValue());
   else {
     SValBuilder &SVB = Ctx.getSValBuilder();
-    if (const llvm::APSInt *MinRight = SVB.getMinValue(FoldedState, Right)) {
+    if (const llvm::APSInt *MinRight = SVB.getMinValue(FoldedState, Right);
+        MinRight && *MinRight >= LHSBitWidth) {
       LowerBoundStr = formatv(" >= {0},", MinRight->getExtValue());
     }
   }
diff --git a/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp b/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
index 70d5a609681790..ecf7974c838650 100644
--- a/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
@@ -1939,11 +1939,8 @@ 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,
@@ -2866,24 +2863,22 @@ 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 {
-  const RangeSet *T = getConstraint(St, Sym);
-  if (!T || T->isEmpty())
-    return nullptr;
-  return &T->getMinValue();
+  auto &MutableSelf = const_cast<RangeConstraintManager &>(*this);
+  RangeSet Range = MutableSelf.getRange(St, Sym);
+  return Range.isEmpty() ? nullptr : &Range.getMinValue();
 }
 
 const llvm::APSInt *RangeConstraintManager::getSymMaxVal(ProgramStateRef St,
                                                          SymbolRef Sym) const {
-  const RangeSet *T = getConstraint(St, Sym);
-  if (!T || T->isEmpty())
-    return nullptr;
-  return &T->getMaxValue();
+  auto &MutableSelf = const_cast<RangeConstraintManager &>(*this);
+  RangeSet Range = MutableSelf.getRange(St, Sym);
+  return Range.isEmpty() ? nullptr : &Range.getMaxValue();
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/test/Analysis/infeasible-sink.c b/clang/test/Analysis/infeasible-sink.c
index 9cb66fcac0b6be..a88ca42f27e441 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;
@@ -50,31 +50,10 @@ void test2() {
   b = d;
   a -= d;
 
-  if (a != 0)
-    return;
-
-  clang_analyzer_warnIfReached(); // expected-warning{{REACHABLE}}
+  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
+  if (a != 0)
     return;
-  }
-  // Should not be reachable.
-  clang_analyzer_warnIfReached(); // expected-wrning{{REACHABLE}}
-  */
 
-  // 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}}
-  if (b > 0) {
-    clang_analyzer_warnIfReached(); // no-warning
-    return;
-  }
-  clang_analyzer_warnIfReached(); // no-warning
+  clang_analyzer_warnIfReached(); // no-warning: Unreachable due to contradiction.
 }