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64a7628048
This PR upstreams the emission of the `cir.await` resume branch. Handling the case where the return value of `co_await` is not ignored is deferred to a future PR, which will be added once `co_return` is upstreamed. Additionally, the `forLValue` variable is always `false` in the current implementation. When support for emitting `coro_yield` is added, this variable will be set to `true`, so that work is also deferred to a future PR.
428 lines
16 KiB
C++
428 lines
16 KiB
C++
//===----- CGCoroutine.cpp - Emit CIR Code for C++ coroutines -------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This contains code dealing with C++ code generation of coroutines.
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//
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//===----------------------------------------------------------------------===//
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#include "CIRGenFunction.h"
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#include "mlir/Support/LLVM.h"
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#include "clang/AST/StmtCXX.h"
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#include "clang/AST/StmtVisitor.h"
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#include "clang/Basic/TargetInfo.h"
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#include "clang/CIR/Dialect/IR/CIRTypes.h"
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#include "clang/CIR/MissingFeatures.h"
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using namespace clang;
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using namespace clang::CIRGen;
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struct clang::CIRGen::CGCoroData {
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// What is the current await expression kind and how many
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// await/yield expressions were encountered so far.
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// These are used to generate pretty labels for await expressions in LLVM IR.
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cir::AwaitKind currentAwaitKind = cir::AwaitKind::Init;
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// Stores the __builtin_coro_id emitted in the function so that we can supply
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// it as the first argument to other builtins.
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cir::CallOp coroId = nullptr;
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// Stores the result of __builtin_coro_begin call.
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mlir::Value coroBegin = nullptr;
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// The promise type's 'unhandled_exception' handler, if it defines one.
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Stmt *exceptionHandler = nullptr;
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};
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// Defining these here allows to keep CGCoroData private to this file.
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CIRGenFunction::CGCoroInfo::CGCoroInfo() {}
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CIRGenFunction::CGCoroInfo::~CGCoroInfo() {}
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namespace {
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// FIXME: both GetParamRef and ParamReferenceReplacerRAII are good template
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// candidates to be shared among LLVM / CIR codegen.
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// Hunts for the parameter reference in the parameter copy/move declaration.
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struct GetParamRef : public StmtVisitor<GetParamRef> {
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public:
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DeclRefExpr *expr = nullptr;
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GetParamRef() {}
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void VisitDeclRefExpr(DeclRefExpr *e) {
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assert(expr == nullptr && "multilple declref in param move");
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expr = e;
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}
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void VisitStmt(Stmt *s) {
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for (Stmt *c : s->children()) {
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if (c)
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Visit(c);
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}
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}
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};
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// This class replaces references to parameters to their copies by changing
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// the addresses in CGF.LocalDeclMap and restoring back the original values in
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// its destructor.
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struct ParamReferenceReplacerRAII {
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CIRGenFunction::DeclMapTy savedLocals;
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CIRGenFunction::DeclMapTy &localDeclMap;
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ParamReferenceReplacerRAII(CIRGenFunction::DeclMapTy &localDeclMap)
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: localDeclMap(localDeclMap) {}
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void addCopy(const DeclStmt *pm) {
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// Figure out what param it refers to.
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assert(pm->isSingleDecl());
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const VarDecl *vd = static_cast<const VarDecl *>(pm->getSingleDecl());
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const Expr *initExpr = vd->getInit();
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GetParamRef visitor;
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visitor.Visit(const_cast<Expr *>(initExpr));
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assert(visitor.expr);
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DeclRefExpr *dreOrig = visitor.expr;
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auto *pd = dreOrig->getDecl();
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auto it = localDeclMap.find(pd);
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assert(it != localDeclMap.end() && "parameter is not found");
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savedLocals.insert({pd, it->second});
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auto copyIt = localDeclMap.find(vd);
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assert(copyIt != localDeclMap.end() && "parameter copy is not found");
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it->second = copyIt->getSecond();
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}
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~ParamReferenceReplacerRAII() {
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for (auto &&savedLocal : savedLocals) {
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localDeclMap.insert({savedLocal.first, savedLocal.second});
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}
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}
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};
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} // namespace
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RValue CIRGenFunction::emitCoroutineFrame() {
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if (curCoro.data && curCoro.data->coroBegin) {
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return RValue::get(curCoro.data->coroBegin);
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}
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cgm.errorNYI("NYI");
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return RValue();
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}
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static void createCoroData(CIRGenFunction &cgf,
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CIRGenFunction::CGCoroInfo &curCoro,
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cir::CallOp coroId) {
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assert(!curCoro.data && "EmitCoroutineBodyStatement called twice?");
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curCoro.data = std::make_unique<CGCoroData>();
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curCoro.data->coroId = coroId;
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}
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cir::CallOp CIRGenFunction::emitCoroIDBuiltinCall(mlir::Location loc,
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mlir::Value nullPtr) {
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cir::IntType int32Ty = builder.getUInt32Ty();
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const TargetInfo &ti = cgm.getASTContext().getTargetInfo();
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unsigned newAlign = ti.getNewAlign() / ti.getCharWidth();
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mlir::Operation *builtin = cgm.getGlobalValue(cgm.builtinCoroId);
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cir::FuncOp fnOp;
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if (!builtin) {
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fnOp = cgm.createCIRBuiltinFunction(
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loc, cgm.builtinCoroId,
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cir::FuncType::get({int32Ty, voidPtrTy, voidPtrTy, voidPtrTy}, int32Ty),
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/*FD=*/nullptr);
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assert(fnOp && "should always succeed");
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} else {
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fnOp = cast<cir::FuncOp>(builtin);
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}
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return builder.createCallOp(loc, fnOp,
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mlir::ValueRange{builder.getUInt32(newAlign, loc),
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nullPtr, nullPtr, nullPtr});
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}
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cir::CallOp CIRGenFunction::emitCoroAllocBuiltinCall(mlir::Location loc) {
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cir::BoolType boolTy = builder.getBoolTy();
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mlir::Operation *builtin = cgm.getGlobalValue(cgm.builtinCoroAlloc);
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cir::FuncOp fnOp;
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if (!builtin) {
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fnOp = cgm.createCIRBuiltinFunction(loc, cgm.builtinCoroAlloc,
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cir::FuncType::get({uInt32Ty}, boolTy),
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/*fd=*/nullptr);
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assert(fnOp && "should always succeed");
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} else {
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fnOp = cast<cir::FuncOp>(builtin);
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}
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return builder.createCallOp(
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loc, fnOp, mlir::ValueRange{curCoro.data->coroId.getResult()});
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}
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cir::CallOp
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CIRGenFunction::emitCoroBeginBuiltinCall(mlir::Location loc,
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mlir::Value coroframeAddr) {
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mlir::Operation *builtin = cgm.getGlobalValue(cgm.builtinCoroBegin);
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cir::FuncOp fnOp;
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if (!builtin) {
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fnOp = cgm.createCIRBuiltinFunction(
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loc, cgm.builtinCoroBegin,
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cir::FuncType::get({uInt32Ty, voidPtrTy}, voidPtrTy),
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/*fd=*/nullptr);
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assert(fnOp && "should always succeed");
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} else {
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fnOp = cast<cir::FuncOp>(builtin);
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}
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return builder.createCallOp(
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loc, fnOp,
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mlir::ValueRange{curCoro.data->coroId.getResult(), coroframeAddr});
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}
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mlir::LogicalResult
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CIRGenFunction::emitCoroutineBody(const CoroutineBodyStmt &s) {
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mlir::Location openCurlyLoc = getLoc(s.getBeginLoc());
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cir::ConstantOp nullPtrCst = builder.getNullPtr(voidPtrTy, openCurlyLoc);
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auto fn = mlir::cast<cir::FuncOp>(curFn);
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fn.setCoroutine(true);
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cir::CallOp coroId = emitCoroIDBuiltinCall(openCurlyLoc, nullPtrCst);
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createCoroData(*this, curCoro, coroId);
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// Backend is allowed to elide memory allocations, to help it, emit
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// auto mem = coro.alloc() ? 0 : ... allocation code ...;
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cir::CallOp coroAlloc = emitCoroAllocBuiltinCall(openCurlyLoc);
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// Initialize address of coroutine frame to null
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CanQualType astVoidPtrTy = cgm.getASTContext().VoidPtrTy;
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mlir::Type allocaTy = convertTypeForMem(astVoidPtrTy);
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Address coroFrame =
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createTempAlloca(allocaTy, getContext().getTypeAlignInChars(astVoidPtrTy),
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openCurlyLoc, "__coro_frame_addr",
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/*ArraySize=*/nullptr);
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mlir::Value storeAddr = coroFrame.getPointer();
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builder.CIRBaseBuilderTy::createStore(openCurlyLoc, nullPtrCst, storeAddr);
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cir::IfOp::create(
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builder, openCurlyLoc, coroAlloc.getResult(),
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/*withElseRegion=*/false,
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/*thenBuilder=*/[&](mlir::OpBuilder &b, mlir::Location loc) {
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builder.CIRBaseBuilderTy::createStore(
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loc, emitScalarExpr(s.getAllocate()), storeAddr);
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cir::YieldOp::create(builder, loc);
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});
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curCoro.data->coroBegin =
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emitCoroBeginBuiltinCall(
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openCurlyLoc,
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cir::LoadOp::create(builder, openCurlyLoc, allocaTy, storeAddr))
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.getResult();
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// Handle allocation failure if 'ReturnStmtOnAllocFailure' was provided.
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if (s.getReturnStmtOnAllocFailure())
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cgm.errorNYI("handle coroutine return alloc failure");
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{
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assert(!cir::MissingFeatures::generateDebugInfo());
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ParamReferenceReplacerRAII paramReplacer(localDeclMap);
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// Create mapping between parameters and copy-params for coroutine
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// function.
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llvm::ArrayRef<const Stmt *> paramMoves = s.getParamMoves();
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assert((paramMoves.size() == 0 || (paramMoves.size() == fnArgs.size())) &&
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"ParamMoves and FnArgs should be the same size for coroutine "
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"function");
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// For zipping the arg map into debug info.
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assert(!cir::MissingFeatures::generateDebugInfo());
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// Create parameter copies. We do it before creating a promise, since an
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// evolution of coroutine TS may allow promise constructor to observe
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// parameter copies.
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assert(!cir::MissingFeatures::coroOutsideFrameMD());
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for (auto *pm : paramMoves) {
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if (emitStmt(pm, /*useCurrentScope=*/true).failed())
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return mlir::failure();
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paramReplacer.addCopy(cast<DeclStmt>(pm));
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}
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if (emitStmt(s.getPromiseDeclStmt(), /*useCurrentScope=*/true).failed())
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return mlir::failure();
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// returnValue should be valid as long as the coroutine's return type
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// is not void. The assertion could help us to reduce the check later.
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assert(returnValue.isValid() == (bool)s.getReturnStmt());
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// Now we have the promise, initialize the GRO.
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// We need to emit `get_return_object` first. According to:
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// [dcl.fct.def.coroutine]p7
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// The call to get_return_object is sequenced before the call to
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// initial_suspend and is invoked at most once.
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//
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// So we couldn't emit return value when we emit return statment,
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// otherwise the call to get_return_object wouldn't be in front
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// of initial_suspend.
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if (returnValue.isValid())
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emitAnyExprToMem(s.getReturnValue(), returnValue,
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s.getReturnValue()->getType().getQualifiers(),
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/*isInit*/ true);
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assert(!cir::MissingFeatures::ehCleanupScope());
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// FIXME(cir): EHStack.pushCleanup<CallCoroEnd>(EHCleanup);
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curCoro.data->currentAwaitKind = cir::AwaitKind::Init;
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if (emitStmt(s.getInitSuspendStmt(), /*useCurrentScope=*/true).failed())
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return mlir::failure();
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assert(!cir::MissingFeatures::emitBodyAndFallthrough());
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}
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return mlir::success();
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}
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static bool memberCallExpressionCanThrow(const Expr *e) {
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if (const auto *ce = dyn_cast<CXXMemberCallExpr>(e))
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if (const auto *proto =
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ce->getMethodDecl()->getType()->getAs<FunctionProtoType>())
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if (isNoexceptExceptionSpec(proto->getExceptionSpecType()) &&
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proto->canThrow() == CT_Cannot)
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return false;
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return true;
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}
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// Given a suspend expression which roughly looks like:
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//
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// auto && x = CommonExpr();
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// if (!x.await_ready()) {
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// x.await_suspend(...); (*)
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// }
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// x.await_resume();
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//
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// where the result of the entire expression is the result of x.await_resume()
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//
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// (*) If x.await_suspend return type is bool, it allows to veto a suspend:
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// if (x.await_suspend(...))
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// llvm_coro_suspend();
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//
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// This is more higher level than LLVM codegen, for that one see llvm's
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// docs/Coroutines.rst for more details.
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namespace {
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struct LValueOrRValue {
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LValue lv;
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RValue rv;
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};
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} // namespace
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static LValueOrRValue
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emitSuspendExpression(CIRGenFunction &cgf, CGCoroData &coro,
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CoroutineSuspendExpr const &s, cir::AwaitKind kind,
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AggValueSlot aggSlot, bool ignoreResult,
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mlir::Block *scopeParentBlock,
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mlir::Value &tmpResumeRValAddr, bool forLValue) {
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[[maybe_unused]] mlir::LogicalResult awaitBuild = mlir::success();
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LValueOrRValue awaitRes;
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CIRGenFunction::OpaqueValueMapping binder =
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CIRGenFunction::OpaqueValueMapping(cgf, s.getOpaqueValue());
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CIRGenBuilderTy &builder = cgf.getBuilder();
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[[maybe_unused]] cir::AwaitOp awaitOp = cir::AwaitOp::create(
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builder, cgf.getLoc(s.getSourceRange()), kind,
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/*readyBuilder=*/
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[&](mlir::OpBuilder &b, mlir::Location loc) {
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Expr *condExpr = s.getReadyExpr()->IgnoreParens();
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builder.createCondition(cgf.evaluateExprAsBool(condExpr));
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},
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/*suspendBuilder=*/
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[&](mlir::OpBuilder &b, mlir::Location loc) {
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// Note that differently from LLVM codegen we do not emit coro.save
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// and coro.suspend here, that should be done as part of lowering this
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// to LLVM dialect (or some other MLIR dialect)
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// A invalid suspendRet indicates "void returning await_suspend"
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mlir::Value suspendRet = cgf.emitScalarExpr(s.getSuspendExpr());
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// Veto suspension if requested by bool returning await_suspend.
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if (suspendRet) {
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cgf.cgm.errorNYI("Veto await_suspend");
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}
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// Signals the parent that execution flows to next region.
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cir::YieldOp::create(builder, loc);
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},
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/*resumeBuilder=*/
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[&](mlir::OpBuilder &b, mlir::Location loc) {
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// Exception handling requires additional IR. If the 'await_resume'
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// function is marked as 'noexcept', we avoid generating this additional
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// IR.
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CXXTryStmt *tryStmt = nullptr;
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if (coro.exceptionHandler && kind == cir::AwaitKind::Init &&
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memberCallExpressionCanThrow(s.getResumeExpr()))
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cgf.cgm.errorNYI("Coro resume Exception");
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// FIXME(cir): the alloca for the resume expr should be placed in the
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// enclosing cir.scope instead.
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if (forLValue) {
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assert(!cir::MissingFeatures::coroCoYield());
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} else {
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awaitRes.rv =
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cgf.emitAnyExpr(s.getResumeExpr(), aggSlot, ignoreResult);
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if (!awaitRes.rv.isIgnored())
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// Create the alloca in the block before the scope wrapping
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// cir.await.
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assert(!cir::MissingFeatures::coroCoReturn());
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}
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if (tryStmt)
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cgf.cgm.errorNYI("Coro tryStmt");
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// Returns control back to parent.
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cir::YieldOp::create(builder, loc);
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});
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assert(awaitBuild.succeeded() && "Should know how to codegen");
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return awaitRes;
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}
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static RValue emitSuspendExpr(CIRGenFunction &cgf,
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const CoroutineSuspendExpr &e,
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cir::AwaitKind kind, AggValueSlot aggSlot,
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bool ignoreResult) {
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RValue rval;
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mlir::Location scopeLoc = cgf.getLoc(e.getSourceRange());
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// Since we model suspend / resume as an inner region, we must store
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// resume scalar results in a tmp alloca, and load it after we build the
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// suspend expression. An alternative way to do this would be to make
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// every region return a value when promise.return_value() is used, but
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// it's a bit awkward given that resume is the only region that actually
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// returns a value.
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mlir::Block *currEntryBlock = cgf.curLexScope->getEntryBlock();
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[[maybe_unused]] mlir::Value tmpResumeRValAddr;
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// No need to explicitly wrap this into a scope since the AST already uses a
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// ExprWithCleanups, which will wrap this into a cir.scope anyways.
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rval = emitSuspendExpression(cgf, *cgf.curCoro.data, e, kind, aggSlot,
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ignoreResult, currEntryBlock, tmpResumeRValAddr,
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/*forLValue*/ false)
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.rv;
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if (ignoreResult || rval.isIgnored())
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return rval;
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if (rval.isScalar()) {
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rval = RValue::get(cir::LoadOp::create(cgf.getBuilder(), scopeLoc,
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rval.getValue().getType(),
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tmpResumeRValAddr));
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} else if (rval.isAggregate()) {
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// This is probably already handled via AggSlot, remove this assertion
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// once we have a testcase and prove all pieces work.
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cgf.cgm.errorNYI("emitSuspendExpr Aggregate");
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} else { // complex
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cgf.cgm.errorNYI("emitSuspendExpr Complex");
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}
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return rval;
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}
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RValue CIRGenFunction::emitCoawaitExpr(const CoawaitExpr &e,
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AggValueSlot aggSlot,
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bool ignoreResult) {
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return emitSuspendExpr(*this, e, curCoro.data->currentAwaitKind, aggSlot,
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ignoreResult);
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}
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