[CIR] Upstream overflow builtins

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -1628,6 +1628,82 @@ def CIR_CmpOp : CIR_Op<"cmp", [Pure, SameTypeOperands]> {
   let isLLVMLoweringRecursive = true;
 }
 
+//===----------------------------------------------------------------------===//
+// BinOpOverflowOp
+//===----------------------------------------------------------------------===//
+
+def CIR_BinOpOverflowKind : CIR_I32EnumAttr<
+  "BinOpOverflowKind", "checked binary arithmetic operation kind", [
+    I32EnumAttrCase<"Add", 0, "add">,
+    I32EnumAttrCase<"Sub", 1, "sub">,
+    I32EnumAttrCase<"Mul", 2, "mul">
+]>;
+
+def CIR_BinOpOverflowOp : CIR_Op<"binop.overflow", [Pure, SameTypeOperands]> {
+  let summary = "Perform binary integral arithmetic with overflow checking";
+  let description = [{
+    `cir.binop.overflow` performs binary arithmetic operations with overflow
+    checking on integral operands.
+
+    The `kind` argument specifies the kind of arithmetic operation to perform.
+    It can be either `add`, `sub`, or `mul`. The `lhs` and `rhs` arguments
+    specify the input operands of the arithmetic operation. The types of `lhs`
+    and `rhs` must be the same.
+
+    `cir.binop.overflow` produces two SSA values. `result` is the result of the
+    arithmetic operation truncated to its specified type. `overflow` is a
+    boolean value indicating whether overflow happens during the operation.
+
+    The exact semantic of this operation is as follows:
+
+      - `lhs` and `rhs` are promoted to an imaginary integral type that has
+        infinite precision.
+      - The arithmetic operation is performed on the promoted operands.
+      - The infinite-precision result is truncated to the type of `result`. The
+        truncated result is assigned to `result`.
+      - If the truncated result is equal to the un-truncated result, `overflow`
+        is assigned to false. Otherwise, `overflow` is assigned to true.
+  }];
+
+  let arguments = (ins
+    CIR_BinOpOverflowKind:$kind,
+    CIR_IntType:$lhs,
+    CIR_IntType:$rhs
+  );
+
+  let results = (outs CIR_IntType:$result, CIR_BoolType:$overflow);
+
+  let assemblyFormat = [{
+    `(` $kind `,` $lhs `,` $rhs `)` `:` qualified(type($lhs)) `->`
+    `(` qualified(type($result)) `,` qualified(type($overflow)) `)`
+    attr-dict
+  }];
+
+  let builders = [
+    OpBuilder<(ins "cir::IntType":$resultTy,
+                   "cir::BinOpOverflowKind":$kind,
+                   "mlir::Value":$lhs,
+                   "mlir::Value":$rhs), [{
+      auto overflowTy = cir::BoolType::get($_builder.getContext());
+      build($_builder, $_state, resultTy, overflowTy, kind, lhs, rhs);
+    }]>
+  ];
+
+  let extraLLVMLoweringPatternDecl = [{
+    static std::string getLLVMIntrinName(cir::BinOpOverflowKind opKind,
+                                         bool isSigned, unsigned width);
+
+    struct EncompassedTypeInfo {
+      bool sign;
+      unsigned width;
+    };
+
+    static EncompassedTypeInfo computeEncompassedTypeWidth(cir::IntType operandTy,
+                                                           cir::IntType resultTy);
+  }];
+}
+
+
 //===----------------------------------------------------------------------===//
 // BinOp
 //===----------------------------------------------------------------------===//

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

@@ -58,6 +58,45 @@ static RValue emitBuiltinBitOp(CIRGenFunction &cgf, const CallExpr *e,
   return RValue::get(result);
 }
 
+namespace {
+struct WidthAndSignedness {
+  unsigned width;
+  bool isSigned;
+};
+} // namespace
+
+static WidthAndSignedness
+getIntegerWidthAndSignedness(const clang::ASTContext &astContext,
+                             const clang::QualType type) {
+  assert(type->isIntegerType() && "Given type is not an integer.");
+  unsigned width = type->isBooleanType()  ? 1
+                   : type->isBitIntType() ? astContext.getIntWidth(type)
+                                          : astContext.getTypeInfo(type).Width;
+  bool isSigned = type->isSignedIntegerType();
+  return {width, isSigned};
+}
+
+// Given one or more integer types, this function produces an integer type that
+// encompasses them: any value in one of the given types could be expressed in
+// the encompassing type.
+static struct WidthAndSignedness
+EncompassingIntegerType(ArrayRef<struct WidthAndSignedness> types) {
+  assert(types.size() > 0 && "Empty list of types.");
+
+  // If any of the given types is signed, we must return a signed type.
+  bool isSigned = llvm::any_of(types, [](const auto &t) { return t.isSigned; });
+
+  // The encompassing type must have a width greater than or equal to the width
+  // of the specified types.  Additionally, if the encompassing type is signed,
+  // its width must be strictly greater than the width of any unsigned types
+  // given.
+  unsigned width = 0;
+  for (const auto &type : types)
+    width = std::max(width, type.width + (isSigned && !type.isSigned));
+
+  return {width, isSigned};
+}
+
 RValue CIRGenFunction::emitRotate(const CallExpr *e, bool isRotateLeft) {
   mlir::Value input = emitScalarExpr(e->getArg(0));
   mlir::Value amount = emitScalarExpr(e->getArg(1));
@@ -491,6 +530,154 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
     cir::PrefetchOp::create(builder, loc, address, locality, isWrite);
     return RValue::get(nullptr);
   }
+  case Builtin::BI__builtin_add_overflow:
+  case Builtin::BI__builtin_sub_overflow:
+  case Builtin::BI__builtin_mul_overflow: {
+    const clang::Expr *LeftArg = e->getArg(0);
+    const clang::Expr *RightArg = e->getArg(1);
+    const clang::Expr *ResultArg = e->getArg(2);
+
+    clang::QualType ResultQTy =
+        ResultArg->getType()->castAs<clang::PointerType>()->getPointeeType();
+
+    WidthAndSignedness LeftInfo =
+        getIntegerWidthAndSignedness(cgm.getASTContext(), LeftArg->getType());
+    WidthAndSignedness RightInfo =
+        getIntegerWidthAndSignedness(cgm.getASTContext(), RightArg->getType());
+    WidthAndSignedness ResultInfo =
+        getIntegerWidthAndSignedness(cgm.getASTContext(), ResultQTy);
+
+    // Note we compute the encompassing type with the consideration to the
+    // result type, so later in LLVM lowering we don't get redundant integral
+    // extension casts.
+    WidthAndSignedness EncompassingInfo =
+        EncompassingIntegerType({LeftInfo, RightInfo, ResultInfo});
+
+    auto EncompassingCIRTy = cir::IntType::get(
+        &getMLIRContext(), EncompassingInfo.width, EncompassingInfo.isSigned);
+    auto ResultCIRTy = mlir::cast<cir::IntType>(cgm.convertType(ResultQTy));
+
+    mlir::Value Left = emitScalarExpr(LeftArg);
+    mlir::Value Right = emitScalarExpr(RightArg);
+    Address ResultPtr = emitPointerWithAlignment(ResultArg);
+
+    // Extend each operand to the encompassing type, if necessary.
+    if (Left.getType() != EncompassingCIRTy)
+      Left =
+          builder.createCast(cir::CastKind::integral, Left, EncompassingCIRTy);
+    if (Right.getType() != EncompassingCIRTy)
+      Right =
+          builder.createCast(cir::CastKind::integral, Right, EncompassingCIRTy);
+
+    // Perform the operation on the extended values.
+    cir::BinOpOverflowKind OpKind;
+    switch (builtinID) {
+    default:
+      llvm_unreachable("Unknown overflow builtin id.");
+    case Builtin::BI__builtin_add_overflow:
+      OpKind = cir::BinOpOverflowKind::Add;
+      break;
+    case Builtin::BI__builtin_sub_overflow:
+      OpKind = cir::BinOpOverflowKind::Sub;
+      break;
+    case Builtin::BI__builtin_mul_overflow:
+      OpKind = cir::BinOpOverflowKind::Mul;
+      break;
+    }
+
+    auto Loc = getLoc(e->getSourceRange());
+    auto arithOp =
+        cir::BinOpOverflowOp::create(builder, Loc, ResultCIRTy, OpKind, Left, Right);
+
+    // Here is a slight difference from the original clang CodeGen:
+    //   - In the original clang CodeGen, the checked arithmetic result is
+    //     first computed as a value of the encompassing type, and then it is
+    //     truncated to the actual result type with a second overflow checking.
+    //   - In CIRGen, the checked arithmetic operation directly produce the
+    //     checked arithmetic result in its expected type.
+    //
+    // So we don't need a truncation and a second overflow checking here.
+
+    // Finally, store the result using the pointer.
+    bool isVolatile =
+        ResultArg->getType()->getPointeeType().isVolatileQualified();
+    builder.createStore(Loc, emitToMemory(ArithOp.getResult(), ResultQTy),
+                        ResultPtr, isVolatile);
+
+    return RValue::get(ArithOp.getOverflow());
+  }
+
+  case Builtin::BI__builtin_uadd_overflow:
+  case Builtin::BI__builtin_uaddl_overflow:
+  case Builtin::BI__builtin_uaddll_overflow:
+  case Builtin::BI__builtin_usub_overflow:
+  case Builtin::BI__builtin_usubl_overflow:
+  case Builtin::BI__builtin_usubll_overflow:
+  case Builtin::BI__builtin_umul_overflow:
+  case Builtin::BI__builtin_umull_overflow:
+  case Builtin::BI__builtin_umulll_overflow:
+  case Builtin::BI__builtin_sadd_overflow:
+  case Builtin::BI__builtin_saddl_overflow:
+  case Builtin::BI__builtin_saddll_overflow:
+  case Builtin::BI__builtin_ssub_overflow:
+  case Builtin::BI__builtin_ssubl_overflow:
+  case Builtin::BI__builtin_ssubll_overflow:
+  case Builtin::BI__builtin_smul_overflow:
+  case Builtin::BI__builtin_smull_overflow:
+  case Builtin::BI__builtin_smulll_overflow: {
+    // Scalarize our inputs.
+    mlir::Value X = emitScalarExpr(e->getArg(0));
+    mlir::Value Y = emitScalarExpr(e->getArg(1));
+
+    const clang::Expr *ResultArg = e->getArg(2);
+    Address ResultPtr = emitPointerWithAlignment(ResultArg);
+
+    // Decide which of the arithmetic operation we are lowering to:
+    cir::BinOpOverflowKind ArithKind;
+    switch (builtinID) {
+    default:
+      llvm_unreachable("Unknown overflow builtin id.");
+    case Builtin::BI__builtin_uadd_overflow:
+    case Builtin::BI__builtin_uaddl_overflow:
+    case Builtin::BI__builtin_uaddll_overflow:
+    case Builtin::BI__builtin_sadd_overflow:
+    case Builtin::BI__builtin_saddl_overflow:
+    case Builtin::BI__builtin_saddll_overflow:
+      ArithKind = cir::BinOpOverflowKind::Add;
+      break;
+    case Builtin::BI__builtin_usub_overflow:
+    case Builtin::BI__builtin_usubl_overflow:
+    case Builtin::BI__builtin_usubll_overflow:
+    case Builtin::BI__builtin_ssub_overflow:
+    case Builtin::BI__builtin_ssubl_overflow:
+    case Builtin::BI__builtin_ssubll_overflow:
+      ArithKind = cir::BinOpOverflowKind::Sub;
+      break;
+    case Builtin::BI__builtin_umul_overflow:
+    case Builtin::BI__builtin_umull_overflow:
+    case Builtin::BI__builtin_umulll_overflow:
+    case Builtin::BI__builtin_smul_overflow:
+    case Builtin::BI__builtin_smull_overflow:
+    case Builtin::BI__builtin_smulll_overflow:
+      ArithKind = cir::BinOpOverflowKind::Mul;
+      break;
+    }
+
+    clang::QualType ResultQTy =
+        ResultArg->getType()->castAs<clang::PointerType>()->getPointeeType();
+    auto ResultCIRTy = mlir::cast<cir::IntType>(cgm.convertType(ResultQTy));
+
+    auto Loc = getLoc(e->getSourceRange());
+    cir::BinOpOverflowOp ArithOp =
+        cir::BinOpOverflowOp::create(builder, Loc, ResultCIRTy, ArithKind, X, Y);
+
+    bool isVolatile =
+        ResultArg->getType()->getPointeeType().isVolatileQualified();
+    builder.createStore(Loc, emitToMemory(ArithOp.getResult(), ResultQTy),
+                        ResultPtr, isVolatile);
+
+    return RValue::get(ArithOp.getOverflow());
+  }
   }
 
   // If this is an alias for a lib function (e.g. __builtin_sin), emit