[clang] [analyzer] Simplify SVal for simple NonLoc->Loc casts (PR #66463)

[Ding Fei via cfe-commits]

https://github.com/danix800 updated https://github.com/llvm/llvm-project/pull/66463

>From d48b57387e3dc1c2f3fdeae00fe1596b3466638d Mon Sep 17 00:00:00 2001
From: dingfei <fding at feysh.com>
Date: Fri, 15 Sep 2023 14:01:26 +0800
Subject: [PATCH] [analyzer] Simplify SVal for simple NonLoc->Loc casts

NonLoc symbolic SVal to Loc casts are not supported except for
nonloc::ConcreteInt.

This change simplifies the source SVals so that the more casts can
go through nonloc::ConcreteInt->loc::ConcreteInt path. For example:

  void test_simplified_before_cast_add(long long t1) {
    long long t2 = t1 + 3;
    if (!t2) {
      int *p = (int *) t2;
      clang_analyzer_eval(p == 0); // expected-warning{{TRUE}}
    }
  }

If simplified, 't2' is 0, resulting 'p' is nullptr, otherwise 'p'
is unknown.

Fixes #62232
---
 clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp |  3 ++-
 .../symbol-simplification-nonloc-loc.cpp      | 26 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
index 2a47116db55a1ad..7e431f7e598c4cb 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
@@ -264,7 +264,8 @@ ProgramStateRef ExprEngine::handleLValueBitCast(
   }
   // Delegate to SValBuilder to process.
   SVal OrigV = state->getSVal(Ex, LCtx);
-  SVal V = svalBuilder.evalCast(OrigV, T, ExTy);
+  SVal SimplifiedOrigV = svalBuilder.simplifySVal(state, OrigV);
+  SVal V = svalBuilder.evalCast(SimplifiedOrigV, T, ExTy);
   // Negate the result if we're treating the boolean as a signed i1
   if (CastE->getCastKind() == CK_BooleanToSignedIntegral && V.isValid())
     V = svalBuilder.evalMinus(V.castAs<NonLoc>());
diff --git a/clang/test/Analysis/symbol-simplification-nonloc-loc.cpp b/clang/test/Analysis/symbol-simplification-nonloc-loc.cpp
index 485f68d9a5acfba..619fda824cb70b5 100644
--- a/clang/test/Analysis/symbol-simplification-nonloc-loc.cpp
+++ b/clang/test/Analysis/symbol-simplification-nonloc-loc.cpp
@@ -1,6 +1,8 @@
 // RUN: %clang_analyze_cc1 -analyzer-checker=core %s \
 // RUN:    -triple x86_64-pc-linux-gnu -verify
 
+void clang_analyzer_eval(int);
+
 #define BINOP(OP) [](auto x, auto y) { return x OP y; }
 
 template <typename BinOp>
@@ -73,3 +75,27 @@ void zoo1backwards() {
   *(0 + p) = nullptr;  // warn
   **(0 + p) = 'a';     // no-warning: this should be unreachable
 }
+
+void test_simplified_before_cast_add(long t1) {
+  long long t2 = t1 + 3;
+  if (!t2) {
+    int *p = (int *) t2;
+    clang_analyzer_eval(p == 0); // expected-warning{{TRUE}}
+  }
+}
+
+void test_simplified_before_cast_sub(long t1) {
+  long long t2 = t1 - 3;
+  if (!t2) {
+    int *p = (int *) t2;
+    clang_analyzer_eval(p == 0); // expected-warning{{TRUE}}
+  }
+}
+
+void test_simplified_before_cast_mul(long t1) {
+  long long t2 = t1 * 3;
+  if (!t2) {
+    int *p = (int *) t2;
+    clang_analyzer_eval(p == 0); // expected-warning{{TRUE}}
+  }
+}