Fix #9549 FP knownConditionTrueFalse (bitshift) (#3616)

lib/valueflow.cpp

@@ -371,9 +371,15 @@ static const Token *getCastTypeStartToken(const Token *parent)
     return nullptr;
 }
 
+// does the operation cause a loss of information?
+static bool isNonInvertibleOperation(const Token* tok)
+{
+    return tok->isComparisonOp() || Token::Match(tok, "%|/|&|%or%|<<|>>");
+}
+
 static bool isComputableValue(const Token* parent, const ValueFlow::Value& value)
 {
-    const bool noninvertible = parent->isComparisonOp() || Token::Match(parent, "%|/|&|%or%");
+    const bool noninvertible = isNonInvertibleOperation(parent);
     if (noninvertible && value.isImpossible())
         return false;
     if (!value.isIntValue() && !value.isFloatValue() && !value.isTokValue() && !value.isIteratorValue())
@@ -669,7 +675,7 @@ static void setTokenValue(Token* tok, ValueFlow::Value value, const Settings* se
              parent->astOperand1() &&
              parent->astOperand2()) {
 
-        const bool noninvertible = parent->isComparisonOp() || Token::Match(parent, "%|/|&|%or%");
+        const bool noninvertible = isNonInvertibleOperation(parent);
 
         // Skip operators with impossible values that are not invertible
         if (noninvertible && value.isImpossible())

test/testcondition.cpp

@@ -3927,6 +3927,16 @@ private:
               "  if (pD) {}\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        // #9549
+        check("void f(const uint32_t v) {\n"
+              "    const uint32_t v16 = v >> 16;\n"
+              "    if (v16) {\n"
+              "        const uint32_t v8 = v16 >> 8;\n"
+              "        if (v8) {}\n"
+              "    }\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void alwaysTrueInfer() {