[CIR] Add support for indirect calls (#139748)

This PR adds support for indirect calls to the `cir.call` operation.

Author: Lancern

clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h

@@ -225,6 +225,14 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
                         callee.getFunctionType().getReturnType(), operands);
   }
 
+  cir::CallOp createIndirectCallOp(mlir::Location loc,
+                                   mlir::Value indirectTarget,
+                                   cir::FuncType funcType,
+                                   mlir::ValueRange operands) {
+    return create<cir::CallOp>(loc, indirectTarget, funcType.getReturnType(),
+                               operands);
+  }
+
   //===--------------------------------------------------------------------===//
   // Cast/Conversion Operators
   //===--------------------------------------------------------------------===//

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

@@ -1843,13 +1843,8 @@ class CIR_CallOpBase<string mnemonic, list<Trait> extra_traits = []>
                       DeclareOpInterfaceMethods<SymbolUserOpInterface>])> {
   let extraClassDeclaration = [{
     /// Get the argument operands to the called function.
-    mlir::OperandRange getArgOperands() {
-      return getArgs();
-    }
-
-    mlir::MutableOperandRange getArgOperandsMutable() {
-      return getArgsMutable();
-    }
+    mlir::OperandRange getArgOperands();
+    mlir::MutableOperandRange getArgOperandsMutable();
 
     /// Return the callee of this operation
     mlir::CallInterfaceCallable getCallableForCallee() {
@@ -1871,8 +1866,17 @@ class CIR_CallOpBase<string mnemonic, list<Trait> extra_traits = []>
     ::mlir::Attribute removeArgAttrsAttr() { return {}; }
     ::mlir::Attribute removeResAttrsAttr() { return {}; }
 
+    bool isIndirect() { return !getCallee(); }
+    mlir::Value getIndirectCall();
+
     void setArg(unsigned index, mlir::Value value) {
-      setOperand(index, value);
+      if (!isIndirect()) {
+        setOperand(index, value);
+        return;
+      }
+
+      // For indirect call, the operand list is shifted by one.
+      setOperand(index + 1, value);
     }
   }];
 
@@ -1884,16 +1888,24 @@ class CIR_CallOpBase<string mnemonic, list<Trait> extra_traits = []>
   // the upstreaming process moves on. The verifiers is also missing for now,
   // will add in the future.
 
-  dag commonArgs = (ins FlatSymbolRefAttr:$callee,
-                        Variadic<CIR_AnyType>:$args);
+  dag commonArgs = (ins OptionalAttr<FlatSymbolRefAttr>:$callee,
+      Variadic<CIR_AnyType>:$args);
 }
 
 def CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
   let summary = "call a function";
   let description = [{
-    The `cir.call` operation represents a direct call to a function that is
-    within the same symbol scope as the call. The callee is encoded as a symbol
-    reference attribute named `callee`.
+    The `cir.call` operation represents a function call. It could represent
+    either a direct call or an indirect call.
+
+    If the operation represents a direct call, the callee should be defined
+    within the same symbol scope as the call. The `callee` attribute contains a
+    symbol reference to the callee function. All operands of this operation are
+    arguments to the callee function.
+
+    If the operation represents an indirect call, the `callee` attribute is
+    empty. The first operand of this operation must be a pointer to the callee
+    function. The rest operands are arguments to the callee function.
 
     Example:
 
@@ -1905,14 +1917,25 @@ def CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
   let results = (outs Optional<CIR_AnyType>:$result);
   let arguments = commonArgs;
 
-  let builders = [OpBuilder<(ins "mlir::SymbolRefAttr":$callee,
-                                 "mlir::Type":$resType,
-                                 "mlir::ValueRange":$operands), [{
+  let builders = [
+    // Build a call op for a direct call
+    OpBuilder<(ins "mlir::SymbolRefAttr":$callee, "mlir::Type":$resType,
+                   "mlir::ValueRange":$operands), [{
+      assert(callee && "callee attribute is required for direct call");
       $_state.addOperands(operands);
       $_state.addAttribute("callee", callee);
       if (resType && !isa<VoidType>(resType))
         $_state.addTypes(resType);
-    }]>];
+    }]>,
+    // Build a call op for an indirect call
+    OpBuilder<(ins "mlir::Value":$calleePtr, "mlir::Type":$resType,
+                   "mlir::ValueRange":$operands), [{
+      $_state.addOperands(calleePtr);
+      $_state.addOperands(operands);
+      if (resType && !isa<VoidType>(resType))
+        $_state.addTypes(resType);
+    }]>,
+  ];
 }
 
 //===----------------------------------------------------------------------===//

clang/include/clang/CIR/MissingFeatures.h

@@ -92,7 +92,6 @@ struct MissingFeatures {
   static bool opCallSideEffect() { return false; }
   static bool opCallNoPrototypeFunc() { return false; }
   static bool opCallMustTail() { return false; }
-  static bool opCallIndirect() { return false; }
   static bool opCallVirtual() { return false; }
   static bool opCallInAlloca() { return false; }
   static bool opCallAttrs() { return false; }

clang/lib/CIR/CodeGen/CIRGenCall.cpp

@@ -241,6 +241,7 @@ CIRGenTypes::arrangeFunctionDeclaration(const FunctionDecl *fd) {
 
 static cir::CIRCallOpInterface
 emitCallLikeOp(CIRGenFunction &cgf, mlir::Location callLoc,
+               cir::FuncType indirectFuncTy, mlir::Value indirectFuncVal,
                cir::FuncOp directFuncOp,
                const SmallVectorImpl<mlir::Value> &cirCallArgs) {
   CIRGenBuilderTy &builder = cgf.getBuilder();
@@ -249,7 +250,13 @@ emitCallLikeOp(CIRGenFunction &cgf, mlir::Location callLoc,
   assert(!cir::MissingFeatures::invokeOp());
 
   assert(builder.getInsertionBlock() && "expected valid basic block");
-  assert(!cir::MissingFeatures::opCallIndirect());
+
+  if (indirectFuncTy) {
+    // TODO(cir): Set calling convention for indirect calls.
+    assert(!cir::MissingFeatures::opCallCallConv());
+    return builder.createIndirectCallOp(callLoc, indirectFuncVal,
+                                        indirectFuncTy, cirCallArgs);
+  }
 
   return builder.createCallOp(callLoc, directFuncOp, cirCallArgs);
 }
@@ -275,6 +282,7 @@ RValue CIRGenFunction::emitCall(const CIRGenFunctionInfo &funcInfo,
                                 cir::CIRCallOpInterface *callOp,
                                 mlir::Location loc) {
   QualType retTy = funcInfo.getReturnType();
+  cir::FuncType cirFuncTy = getTypes().getFunctionType(funcInfo);
 
   SmallVector<mlir::Value, 16> cirCallArgs(args.size());
 
@@ -326,12 +334,27 @@ RValue CIRGenFunction::emitCall(const CIRGenFunctionInfo &funcInfo,
 
   assert(!cir::MissingFeatures::invokeOp());
 
-  auto directFuncOp = dyn_cast<cir::FuncOp>(calleePtr);
-  assert(!cir::MissingFeatures::opCallIndirect());
+  cir::FuncType indirectFuncTy;
+  mlir::Value indirectFuncVal;
+  cir::FuncOp directFuncOp;
+  if (auto fnOp = dyn_cast<cir::FuncOp>(calleePtr)) {
+    directFuncOp = fnOp;
+  } else {
+    [[maybe_unused]] mlir::ValueTypeRange<mlir::ResultRange> resultTypes =
+        calleePtr->getResultTypes();
+    [[maybe_unused]] auto funcPtrTy =
+        mlir::dyn_cast<cir::PointerType>(resultTypes.front());
+    assert(funcPtrTy && mlir::isa<cir::FuncType>(funcPtrTy.getPointee()) &&
+           "expected pointer to function");
+
+    indirectFuncTy = cirFuncTy;
+    indirectFuncVal = calleePtr->getResult(0);
+  }
+
   assert(!cir::MissingFeatures::opCallAttrs());
 
-  cir::CIRCallOpInterface theCall =
-      emitCallLikeOp(*this, loc, directFuncOp, cirCallArgs);
+  cir::CIRCallOpInterface theCall = emitCallLikeOp(
+      *this, loc, indirectFuncTy, indirectFuncVal, directFuncOp, cirCallArgs);
 
   if (callOp)
     *callOp = theCall;
@@ -431,7 +454,7 @@ void CIRGenFunction::emitCallArgs(
 
   auto maybeEmitImplicitObjectSize = [&](size_t i, const Expr *arg,
                                          RValue emittedArg) {
-    if (callee.hasFunctionDecl() || i >= callee.getNumParams())
+    if (!callee.hasFunctionDecl() || i >= callee.getNumParams())
       return;
     auto *ps = callee.getParamDecl(i)->getAttr<PassObjectSizeAttr>();
     if (!ps)

clang/lib/CIR/CodeGen/CIRGenCall.h

@@ -25,11 +25,20 @@ class CIRGenFunction;
 
 /// Abstract information about a function or function prototype.
 class CIRGenCalleeInfo {
+  const clang::FunctionProtoType *calleeProtoTy;
   clang::GlobalDecl calleeDecl;
 
 public:
-  explicit CIRGenCalleeInfo() : calleeDecl() {}
+  explicit CIRGenCalleeInfo() : calleeProtoTy(nullptr), calleeDecl() {}
+  CIRGenCalleeInfo(const clang::FunctionProtoType *calleeProtoTy,
+                   clang::GlobalDecl calleeDecl)
+      : calleeProtoTy(calleeProtoTy), calleeDecl(calleeDecl) {}
   CIRGenCalleeInfo(clang::GlobalDecl calleeDecl) : calleeDecl(calleeDecl) {}
+
+  const clang::FunctionProtoType *getCalleeFunctionProtoType() const {
+    return calleeProtoTy;
+  }
+  clang::GlobalDecl getCalleeDecl() const { return calleeDecl; }
 };
 
 class CIRGenCallee {

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -931,14 +931,43 @@ CIRGenCallee CIRGenFunction::emitCallee(const clang::Expr *e) {
         implicitCast->getCastKind() == CK_BuiltinFnToFnPtr) {
       return emitCallee(implicitCast->getSubExpr());
     }
+    // When performing an indirect call through a function pointer lvalue, the
+    // function pointer lvalue is implicitly converted to an rvalue through an
+    // lvalue-to-rvalue conversion.
+    assert(implicitCast->getCastKind() == CK_LValueToRValue &&
+           "unexpected implicit cast on function pointers");
   } else if (const auto *declRef = dyn_cast<DeclRefExpr>(e)) {
     // Resolve direct calls.
-    if (const auto *funcDecl = dyn_cast<FunctionDecl>(declRef->getDecl()))
-      return emitDirectCallee(cgm, funcDecl);
+    const auto *funcDecl = cast<FunctionDecl>(declRef->getDecl());
+    return emitDirectCallee(cgm, funcDecl);
+  } else if (isa<MemberExpr>(e)) {
+    cgm.errorNYI(e->getSourceRange(),
+                 "emitCallee: call to member function is NYI");
+    return {};
   }
 
-  cgm.errorNYI(e->getSourceRange(), "Unsupported callee kind");
-  return {};
+  assert(!cir::MissingFeatures::opCallPseudoDtor());
+
+  // Otherwise, we have an indirect reference.
+  mlir::Value calleePtr;
+  QualType functionType;
+  if (const auto *ptrType = e->getType()->getAs<clang::PointerType>()) {
+    calleePtr = emitScalarExpr(e);
+    functionType = ptrType->getPointeeType();
+  } else {
+    functionType = e->getType();
+    calleePtr = emitLValue(e).getPointer();
+  }
+  assert(functionType->isFunctionType());
+
+  GlobalDecl gd;
+  if (const auto *vd =
+          dyn_cast_or_null<VarDecl>(e->getReferencedDeclOfCallee()))
+    gd = GlobalDecl(vd);
+
+  CIRGenCalleeInfo calleeInfo(functionType->getAs<FunctionProtoType>(), gd);
+  CIRGenCallee callee(calleeInfo, calleePtr.getDefiningOp());
+  return callee;
 }
 
 RValue CIRGenFunction::emitCallExpr(const clang::CallExpr *e,

clang/lib/CIR/CodeGen/CIRGenFunctionInfo.h

@@ -16,6 +16,7 @@
 #define LLVM_CLANG_CIR_CIRGENFUNCTIONINFO_H
 
 #include "clang/AST/CanonicalType.h"
+#include "clang/CIR/MissingFeatures.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/Support/TrailingObjects.h"
 

clang/lib/CIR/CodeGen/CIRGenTypes.h

@@ -68,7 +68,6 @@ class CIRGenTypes {
   /// types will be in this set.
   llvm::SmallPtrSet<const clang::Type *, 4> recordsBeingLaidOut;
 
-  llvm::SmallPtrSet<const CIRGenFunctionInfo *, 4> functionsBeingProcessed;
   /// Heper for convertType.
   mlir::Type convertFunctionTypeInternal(clang::QualType ft);
 

clang/lib/CIR/Dialect/IR/CIRDialect.cpp

@@ -465,15 +465,35 @@ OpFoldResult cir::CastOp::fold(FoldAdaptor adaptor) {
 // CallOp
 //===----------------------------------------------------------------------===//
 
+mlir::OperandRange cir::CallOp::getArgOperands() {
+  if (isIndirect())
+    return getArgs().drop_front(1);
+  return getArgs();
+}
+
+mlir::MutableOperandRange cir::CallOp::getArgOperandsMutable() {
+  mlir::MutableOperandRange args = getArgsMutable();
+  if (isIndirect())
+    return args.slice(1, args.size() - 1);
+  return args;
+}
+
+mlir::Value cir::CallOp::getIndirectCall() {
+  assert(isIndirect());
+  return getOperand(0);
+}
+
 /// Return the operand at index 'i'.
 Value cir::CallOp::getArgOperand(unsigned i) {
-  assert(!cir::MissingFeatures::opCallIndirect());
+  if (isIndirect())
+    ++i;
   return getOperand(i);
 }
 
 /// Return the number of operands.
 unsigned cir::CallOp::getNumArgOperands() {
-  assert(!cir::MissingFeatures::opCallIndirect());
+  if (isIndirect())
+    return this->getOperation()->getNumOperands() - 1;
   return this->getOperation()->getNumOperands();
 }
 
@@ -484,9 +504,15 @@ static mlir::ParseResult parseCallCommon(mlir::OpAsmParser &parser,
   mlir::FlatSymbolRefAttr calleeAttr;
   llvm::ArrayRef<mlir::Type> allResultTypes;
 
+  // If we cannot parse a string callee, it means this is an indirect call.
   if (!parser.parseOptionalAttribute(calleeAttr, "callee", result.attributes)
-           .has_value())
-    return mlir::failure();
+           .has_value()) {
+    OpAsmParser::UnresolvedOperand indirectVal;
+    // Do not resolve right now, since we need to figure out the type
+    if (parser.parseOperand(indirectVal).failed())
+      return failure();
+    ops.push_back(indirectVal);
+  }
 
   if (parser.parseLParen())
     return mlir::failure();
@@ -518,13 +544,21 @@ static mlir::ParseResult parseCallCommon(mlir::OpAsmParser &parser,
 
 static void printCallCommon(mlir::Operation *op,
                             mlir::FlatSymbolRefAttr calleeSym,
+                            mlir::Value indirectCallee,
                             mlir::OpAsmPrinter &printer) {
   printer << ' ';
 
   auto callLikeOp = mlir::cast<cir::CIRCallOpInterface>(op);
   auto ops = callLikeOp.getArgOperands();
 
-  printer.printAttributeWithoutType(calleeSym);
+  if (calleeSym) {
+    // Direct calls
+    printer.printAttributeWithoutType(calleeSym);
+  } else {
+    // Indirect calls
+    assert(indirectCallee);
+    printer << indirectCallee;
+  }
   printer << "(" << ops << ")";
 
   printer.printOptionalAttrDict(op->getAttrs(), {"callee"});
@@ -540,15 +574,18 @@ mlir::ParseResult cir::CallOp::parse(mlir::OpAsmParser &parser,
 }
 
 void cir::CallOp::print(mlir::OpAsmPrinter &p) {
-  printCallCommon(*this, getCalleeAttr(), p);
+  mlir::Value indirectCallee = isIndirect() ? getIndirectCall() : nullptr;
+  printCallCommon(*this, getCalleeAttr(), indirectCallee, p);
 }
 
 static LogicalResult
 verifyCallCommInSymbolUses(mlir::Operation *op,
                            SymbolTableCollection &symbolTable) {
   auto fnAttr = op->getAttrOfType<FlatSymbolRefAttr>("callee");
-  if (!fnAttr)
-    return mlir::failure();
+  if (!fnAttr) {
+    // This is an indirect call, thus we don't have to check the symbol uses.
+    return mlir::success();
+  }
 
   auto fn = symbolTable.lookupNearestSymbolFrom<cir::FuncOp>(op, fnAttr);
   if (!fn)