[clang-tools-extra] [clang-tidy] Detect std::rot[lr] pattern within modernize.use-std-bit (PR #186324)

[Victor Chernyakin via cfe-commits]

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@@ -141,6 +154,48 @@ void UseStdBitCheck::check(const MatchFinder::MatchResult &Result) {
            << IncludeInserter.createIncludeInsertion(
                   Source.getFileID(MatchedExpr->getBeginLoc()), "<bit>");
     }
+  } else if (const auto *MatchedExpr =
+                 Result.Nodes.getNodeAs<BinaryOperator>("rotate_expr")) {
+    const auto *MatchedVarDecl = Result.Nodes.getNodeAs<VarDecl>("v");
+    const auto ShiftLeftAmount =
+        Result.Nodes.getNodeAs<IntegerLiteral>("shift_left_amount")->getValue();
+    const auto ShiftRightAmount =
+        Result.Nodes.getNodeAs<IntegerLiteral>("shift_right_amount")
+            ->getValue();
+    const uint64_t MatchedVarSize =
+        Context.getTypeSize(MatchedVarDecl->getType());
+
+    // Overflowing shifts
+    if (ShiftLeftAmount.sge(MatchedVarSize))
+      return;
+    if (ShiftRightAmount.sge(MatchedVarSize))
+      return;
+    // Not a rotation.
+    if (MatchedVarSize != (ShiftLeftAmount + ShiftRightAmount))
+      return;
+
+    const bool NeedsIntCast =
+        MatchedExpr->getType() != MatchedVarDecl->getType();
+    const bool IsRotl = ShiftRightAmount.sge(ShiftLeftAmount);
+
+    const StringRef ReplacementFuncName = IsRotl ? "rotl" : "rotr";
+    const uint64_t ReplacementShiftAmount =
+        (IsRotl ? ShiftLeftAmount : ShiftRightAmount).getZExtValue();
+    auto Diag = diag(MatchedExpr->getBeginLoc(), "use 'std::%0' instead")
+                << ReplacementFuncName;
+    if (auto R = MatchedExpr->getSourceRange();
+        !R.getBegin().isMacroID() && !R.getEnd().isMacroID()) {
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localspook wrote:

This could also be written as an early return

https://github.com/llvm/llvm-project/pull/186324