[CIR] Upstream initial function call support (#134673)

This patch upstreams initial support for making function calls in CIR.
Function arguments and return values are not included to keep the patch
small for review.

Related to #132487

Author: Lancern

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

@@ -201,6 +201,19 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
     return create<cir::PtrStrideOp>(loc, base.getType(), base, stride);
   }
 
+  //===--------------------------------------------------------------------===//
+  // Call operators
+  //===--------------------------------------------------------------------===//
+
+  cir::CallOp createCallOp(mlir::Location loc, mlir::SymbolRefAttr callee) {
+    auto op = create<cir::CallOp>(loc, callee);
+    return op;
+  }
+
+  cir::CallOp createCallOp(mlir::Location loc, cir::FuncOp callee) {
+    return createCallOp(loc, mlir::SymbolRefAttr::get(callee));
+  }
+
   //===--------------------------------------------------------------------===//
   // Cast/Conversion Operators
   //===--------------------------------------------------------------------===//

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

@@ -1342,6 +1342,48 @@ def FuncOp : CIR_Op<"func", [
   let hasVerifier = 1;
 }
 
+//===----------------------------------------------------------------------===//
+// CallOp
+//===----------------------------------------------------------------------===//
+
+class CIR_CallOpBase<string mnemonic, list<Trait> extra_traits = []>
+    : Op<CIR_Dialect, mnemonic,
+         !listconcat(extra_traits,
+                     [DeclareOpInterfaceMethods<CIRCallOpInterface>,
+                      DeclareOpInterfaceMethods<SymbolUserOpInterface>])> {
+  let hasCustomAssemblyFormat = 1;
+  let skipDefaultBuilders = 1;
+  let hasVerifier = 0;
+
+  // TODO(cir): for now cir.call is just a tiny shell of what it will become.
+  // More attributes, arguments, and properties will be added in the future as
+  // the upstreaming process moves on. The verifiers is also missing for now,
+  // will add in the future.
+
+  dag commonArgs = (ins FlatSymbolRefAttr:$callee);
+}
+
+def CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
+  let summary = "call a function";
+  let description = [{
+    The `cir.call` operation represents a direct call to a function that is
+    within the same symbol scope as the call. The callee is encoded as a symbol
+    reference attribute named `callee`.
+
+    Example:
+
+    ```mlir
+    %0 = cir.call @foo()
+    ```
+  }];
+
+  let arguments = commonArgs;
+
+  let builders = [OpBuilder<(ins "mlir::SymbolRefAttr":$callee), [{
+      $_state.addAttribute("callee", callee);
+    }]>];
+}
+
 //===----------------------------------------------------------------------===//
 // UnreachableOp
 //===----------------------------------------------------------------------===//

clang/include/clang/CIR/Interfaces/CIROpInterfaces.td

@@ -15,8 +15,17 @@
 
 include "mlir/IR/OpBase.td"
 include "mlir/IR/SymbolInterfaces.td"
+include "mlir/Interfaces/CallInterfaces.td"
 
 let cppNamespace = "::cir" in {
+  // The CIRCallOpInterface must be used instead of CallOpInterface when looking
+  // at arguments and other bits of CallOp. This creates a level of abstraction
+  // that's useful for handling indirect calls and other details.
+  def CIRCallOpInterface : OpInterface<"CIRCallOpInterface", []> {
+    // Currently we don't have any methods defined in CIRCallOpInterface. We'll
+    // add more methods as the upstreaming proceeds.
+  }
+
   def CIRGlobalValueInterface
       : OpInterface<"CIRGlobalValueInterface", [Symbol]> {
 

clang/include/clang/CIR/MissingFeatures.h

@@ -72,6 +72,24 @@ struct MissingFeatures {
   static bool opFuncLinkage() { return false; }
   static bool opFuncVisibility() { return false; }
 
+  // CallOp handling
+  static bool opCallBuiltinFunc() { return false; }
+  static bool opCallPseudoDtor() { return false; }
+  static bool opCallArgs() { return false; }
+  static bool opCallReturn() { return false; }
+  static bool opCallArgEvaluationOrder() { return false; }
+  static bool opCallCallConv() { return false; }
+  static bool opCallSideEffect() { return false; }
+  static bool opCallChainCall() { 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; }
+  static bool opCallSurroundingTry() { return false; }
+  static bool opCallASTAttr() { return false; }
+
   // ScopeOp handling
   static bool opScopeCleanupRegion() { return false; }
 
@@ -90,7 +108,10 @@ struct MissingFeatures {
   static bool lowerModeOptLevel() { return false; }
   static bool opTBAA() { return false; }
   static bool objCLifetime() { return false; }
+  static bool objCBlocks() { return false; }
   static bool emitNullabilityCheck() { return false; }
+  static bool emitLValueAlignmentAssumption() { return false; }
+  static bool emitLifetimeMarkers() { return false; }
   static bool astVarDeclInterface() { return false; }
   static bool stackSaveOp() { return false; }
   static bool aggValueSlot() { return false; }
@@ -113,6 +134,8 @@ struct MissingFeatures {
   static bool incrementProfileCounter() { return false; }
   static bool insertBuiltinUnpredictable() { return false; }
   static bool objCGC() { return false; }
+  static bool weakRefReference() { return false; }
+  static bool hip() { return false; }
 
   // Missing types
   static bool dataMemberType() { return false; }
@@ -132,6 +155,7 @@ struct MissingFeatures {
   static bool complexImagOp() { return false; }
   static bool complexRealOp() { return false; }
   static bool ifOp() { return false; }
+  static bool invokeOp() { return false; }
   static bool labelOp() { return false; }
   static bool ptrDiffOp() { return false; }
   static bool ptrStrideOp() { return false; }

clang/lib/CIR/CodeGen/CIRGenCall.cpp

@@ -0,0 +1,95 @@
+//===--- CIRGenCall.cpp - Encapsulate calling convention details ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// These classes wrap the information about a call or function definition used
+// to handle ABI compliancy.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CIRGenCall.h"
+#include "CIRGenFunction.h"
+#include "clang/CIR/MissingFeatures.h"
+
+using namespace clang;
+using namespace clang::CIRGen;
+
+CIRGenFunctionInfo *CIRGenFunctionInfo::create() {
+  // For now we just create an empty CIRGenFunctionInfo.
+  CIRGenFunctionInfo *fi = new CIRGenFunctionInfo();
+  return fi;
+}
+
+CIRGenCallee CIRGenCallee::prepareConcreteCallee(CIRGenFunction &cgf) const {
+  assert(!cir::MissingFeatures::opCallVirtual());
+  return *this;
+}
+
+static const CIRGenFunctionInfo &arrangeFreeFunctionLikeCall(CIRGenTypes &cgt) {
+  assert(!cir::MissingFeatures::opCallArgs());
+  return cgt.arrangeCIRFunctionInfo();
+}
+
+const CIRGenFunctionInfo &CIRGenTypes::arrangeFreeFunctionCall() {
+  return arrangeFreeFunctionLikeCall(*this);
+}
+
+static cir::CIRCallOpInterface emitCallLikeOp(CIRGenFunction &cgf,
+                                              mlir::Location callLoc,
+                                              cir::FuncOp directFuncOp) {
+  CIRGenBuilderTy &builder = cgf.getBuilder();
+
+  assert(!cir::MissingFeatures::opCallSurroundingTry());
+  assert(!cir::MissingFeatures::invokeOp());
+
+  assert(builder.getInsertionBlock() && "expected valid basic block");
+  assert(!cir::MissingFeatures::opCallIndirect());
+
+  return builder.createCallOp(callLoc, directFuncOp);
+}
+
+RValue CIRGenFunction::emitCall(const CIRGenFunctionInfo &funcInfo,
+                                const CIRGenCallee &callee,
+                                cir::CIRCallOpInterface *callOp,
+                                mlir::Location loc) {
+  assert(!cir::MissingFeatures::opCallArgs());
+  assert(!cir::MissingFeatures::emitLifetimeMarkers());
+
+  const CIRGenCallee &concreteCallee = callee.prepareConcreteCallee(*this);
+  mlir::Operation *calleePtr = concreteCallee.getFunctionPointer();
+
+  assert(!cir::MissingFeatures::opCallInAlloca());
+
+  mlir::NamedAttrList attrs;
+  StringRef funcName;
+  if (auto calleeFuncOp = dyn_cast<cir::FuncOp>(calleePtr))
+    funcName = calleeFuncOp.getName();
+
+  assert(!cir::MissingFeatures::opCallCallConv());
+  assert(!cir::MissingFeatures::opCallSideEffect());
+  assert(!cir::MissingFeatures::opCallAttrs());
+
+  assert(!cir::MissingFeatures::invokeOp());
+
+  auto directFuncOp = dyn_cast<cir::FuncOp>(calleePtr);
+  assert(!cir::MissingFeatures::opCallIndirect());
+  assert(!cir::MissingFeatures::opCallAttrs());
+
+  cir::CIRCallOpInterface theCall = emitCallLikeOp(*this, loc, directFuncOp);
+
+  if (callOp)
+    *callOp = theCall;
+
+  assert(!cir::MissingFeatures::opCallMustTail());
+  assert(!cir::MissingFeatures::opCallReturn());
+
+  // For now we just return nothing because we don't have support for return
+  // values yet.
+  RValue ret = RValue::get(nullptr);
+
+  return ret;
+}

clang/lib/CIR/CodeGen/CIRGenCall.h

@@ -14,15 +14,73 @@
 #ifndef CLANG_LIB_CODEGEN_CIRGENCALL_H
 #define CLANG_LIB_CODEGEN_CIRGENCALL_H
 
+#include "mlir/IR/Operation.h"
 #include "clang/AST/GlobalDecl.h"
 #include "llvm/ADT/SmallVector.h"
 
 namespace clang::CIRGen {
 
+class CIRGenFunction;
+
+/// Abstract information about a function or function prototype.
+class CIRGenCalleeInfo {
+  clang::GlobalDecl calleeDecl;
+
+public:
+  explicit CIRGenCalleeInfo() : calleeDecl() {}
+  CIRGenCalleeInfo(clang::GlobalDecl calleeDecl) : calleeDecl(calleeDecl) {}
+};
+
+class CIRGenCallee {
+  enum class SpecialKind : uintptr_t {
+    Invalid,
+
+    Last = Invalid,
+  };
+
+  SpecialKind kindOrFunctionPtr;
+
+  union {
+    CIRGenCalleeInfo abstractInfo;
+  };
+
+public:
+  CIRGenCallee() : kindOrFunctionPtr(SpecialKind::Invalid) {}
+
+  CIRGenCallee(const CIRGenCalleeInfo &abstractInfo, mlir::Operation *funcPtr)
+      : kindOrFunctionPtr(SpecialKind(reinterpret_cast<uintptr_t>(funcPtr))),
+        abstractInfo(abstractInfo) {
+    assert(funcPtr && "configuring callee without function pointer");
+  }
+
+  static CIRGenCallee
+  forDirect(mlir::Operation *funcPtr,
+            const CIRGenCalleeInfo &abstractInfo = CIRGenCalleeInfo()) {
+    return CIRGenCallee(abstractInfo, funcPtr);
+  }
+
+  bool isOrdinary() const {
+    return uintptr_t(kindOrFunctionPtr) > uintptr_t(SpecialKind::Last);
+  }
+
+  /// If this is a delayed callee computation of some sort, prepare a concrete
+  /// callee
+  CIRGenCallee prepareConcreteCallee(CIRGenFunction &cgf) const;
+
+  mlir::Operation *getFunctionPointer() const {
+    assert(isOrdinary());
+    return reinterpret_cast<mlir::Operation *>(kindOrFunctionPtr);
+  }
+};
+
 /// Type for representing both the decl and type of parameters to a function.
 /// The decl must be either a ParmVarDecl or ImplicitParamDecl.
 class FunctionArgList : public llvm::SmallVector<const clang::VarDecl *, 16> {};
 
+struct CallArg {};
+
+class CallArgList : public llvm::SmallVector<CallArg, 8> {};
+
 } // namespace clang::CIRGen
 
 #endif // CLANG_LIB_CODEGEN_CIRGENCALL_H