[coroutines] Refactor SuspendExpr to create just one OpaqueValue (almost NFC)

[GorNishanov]

Summary

Create only one OpaqueValue for await_ready/await_suspend/await_resume.
Store OpaqueValue used in the CoroutineSuspendExpr node, so that CodeGen does not have to hunt looking for it.

[EricWF]

This LGTM.

include/clang/AST/ExprCXX.h

 /// If the coroutine is not suspended, or when it is resumed, the 'resume'
 /// expression is evaluated, and its result is the result of the overall
 /// expression.
 class CoroutineSuspendExpr : public Expr {
   SourceLocation KeywordLoc;
 
   enum SubExpr { Common, Ready, Suspend, Resume, Count };
   Stmt *SubExprs[SubExpr::Count];
+  OpaqueValueExpr *OpaqueValue = nullptr;
 
   friend class ASTStmtReader;
 public:
   CoroutineSuspendExpr(StmtClass SC, SourceLocation KeywordLoc, Expr *Common,
-                       Expr *Ready, Expr *Suspend, Expr *Resume)
+                       Expr *Ready, Expr *Suspend, Expr *Resume,
+                       OpaqueValueExpr *OpaqueValue)
       : Expr(SC, Resume->getType(), Resume->getValueKind(),
              Resume->getObjectKind(), Resume->isTypeDependent(),
              Resume->isValueDependent(), Common->isInstantiationDependent(),
              Common->containsUnexpandedParameterPack()),
-        KeywordLoc(KeywordLoc) {
+        KeywordLoc(KeywordLoc), OpaqueValue(OpaqueValue) {
     SubExprs[SubExpr::Common] = Common;
     SubExprs[SubExpr::Ready] = Ready;
     SubExprs[SubExpr::Suspend] = Suspend;
     SubExprs[SubExpr::Resume] = Resume;
   }
   CoroutineSuspendExpr(StmtClass SC, SourceLocation KeywordLoc, QualType Ty,
                        Expr *Common)
       : Expr(SC, Ty, VK_RValue, OK_Ordinary, true, true, true,
CoroutineSuspendExpr(StmtClass SC, EmptyShell Empty) : Expr(SC, Empty) {
     SubExprs[SubExpr::Suspend] = nullptr;
     SubExprs[SubExpr::Resume] = nullptr;
   }
 
   SourceLocation getKeywordLoc() const { return KeywordLoc; }
   Expr *getCommonExpr() const {
     return static_cast<Expr*>(SubExprs[SubExpr::Common]);
   }
+  /// \brief getOpaqueValue - Return the opaque value placeholder.
+  OpaqueValueExpr *getOpaqueValue() const { return OpaqueValue; }
 
   Expr *getReadyExpr() const {
     return static_cast<Expr*>(SubExprs[SubExpr::Ready]);
   }
   Expr *getSuspendExpr() const {
     return static_cast<Expr*>(SubExprs[SubExpr::Suspend]);
   }
   Expr *getResumeExpr() const {
public:
   }
 };
 
 /// \brief Represents a 'co_await' expression.
 class CoawaitExpr : public CoroutineSuspendExpr {
   friend class ASTStmtReader;
 public:
   CoawaitExpr(SourceLocation CoawaitLoc, Expr *Operand, Expr *Ready,
-              Expr *Suspend, Expr *Resume, bool IsImplicit = false)
+              Expr *Suspend, Expr *Resume, OpaqueValueExpr *OpaqueValue,
+              bool IsImplicit = false)
       : CoroutineSuspendExpr(CoawaitExprClass, CoawaitLoc, Operand, Ready,
-                             Suspend, Resume) {
-      CoawaitBits.IsImplicit = IsImplicit;
+                             Suspend, Resume, OpaqueValue) {
   }
   CoawaitExpr(SourceLocation CoawaitLoc, QualType Ty, Expr *Operand,
               bool IsImplicit = false)
       : CoroutineSuspendExpr(CoawaitExprClass, CoawaitLoc, Ty, Operand) {
     CoawaitBits.IsImplicit = IsImplicit;
   }
   CoawaitExpr(EmptyShell Empty)
       : CoroutineSuspendExpr(CoawaitExprClass, Empty) {}
public:
   }
 };
 
 /// \brief Represents a 'co_yield' expression.
 class CoyieldExpr : public CoroutineSuspendExpr {
   friend class ASTStmtReader;
 public:
   CoyieldExpr(SourceLocation CoyieldLoc, Expr *Operand, Expr *Ready,
-              Expr *Suspend, Expr *Resume)
+              Expr *Suspend, Expr *Resume, OpaqueValueExpr *OpaqueValue)
       : CoroutineSuspendExpr(CoyieldExprClass, CoyieldLoc, Operand, Ready,
-                             Suspend, Resume) {}
+                             Suspend, Resume, OpaqueValue) {}
   CoyieldExpr(SourceLocation CoyieldLoc, QualType Ty, Expr *Operand)
       : CoroutineSuspendExpr(CoyieldExprClass, CoyieldLoc, Ty, Operand) {}
   CoyieldExpr(EmptyShell Empty)
       : CoroutineSuspendExpr(CoyieldExprClass, Empty) {}
 
   Expr *getOperand() const {
     // FIXME: Dig out the actual operand or store it.
     return getCommonExpr();

lib/Sema/SemaCoroutine.cpp

ExprResult FromAddr =
       S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
   if (FromAddr.isInvalid())
     return ExprError();
 
   return S.ActOnCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
 }
 
 struct ReadySuspendResumeResult {
-  bool IsInvalid;
   Expr *Results[3];
+  OpaqueValueExpr *OpaqueValue;
+  bool IsInvalid;
 };
 
 static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
                                   StringRef Name, MultiExprArg Args) {
   DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);
 
   // FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
   CXXScopeSpec SS;
   ExprResult Result = S.BuildMemberReferenceExpr(
       Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
       SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
       /*Scope=*/nullptr);
   if (Result.isInvalid())
     return ExprError();
 
   return S.ActOnCallExpr(nullptr, Result.get(), Loc, Args, Loc, nullptr);
 }
 
 /// Build calls to await_ready, await_suspend, and await_resume for a co_await
 /// expression.
 static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
                                                   SourceLocation Loc, Expr *E) {
+  OpaqueValueExpr *Operand = new (S.Context)
+      OpaqueValueExpr(Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
+
   // Assume invalid until we see otherwise.
-  ReadySuspendResumeResult Calls = {true, {}};
+  ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/true};
 
   ExprResult CoroHandleRes = buildCoroutineHandle(S, CoroPromise->getType(), Loc);
   if (CoroHandleRes.isInvalid())
     return Calls;
   Expr *CoroHandle = CoroHandleRes.get();
 
   const StringRef Funcs[] = {"await_ready", "await_suspend", "await_resume"};
   MultiExprArg Args[] = {None, CoroHandle, None};
   for (size_t I = 0, N = llvm::array_lengthof(Funcs); I != N; ++I) {
-    Expr *Operand = new (S.Context) OpaqueValueExpr(
-      Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
-
     ExprResult Result = buildMemberCall(S, Operand, Loc, Funcs[I], Args[I]);
     if (Result.isInvalid())
       return Calls;
     Calls.Results[I] = Result.get();
   }
 
   Calls.IsInvalid = false;
   return Calls;
if (E->getValueKind() == VK_RValue)
     E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
 
   // Build the await_ready, await_suspend, await_resume calls.
   ReadySuspendResumeResult RSS =
       buildCoawaitCalls(*this, Coroutine->CoroutinePromise, Loc, E);
   if (RSS.IsInvalid)
     return ExprError();
 
-  Expr *Res = new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
-                                        RSS.Results[2], IsImplicit);
+  Expr *Res =
+      new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
+                                RSS.Results[2], RSS.OpaqueValue, IsImplicit);
   if (!IsImplicit)
     Coroutine->CoroutineStmts.push_back(Res);
   return Res;
 }
 
 ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
   if (!actOnCoroutineBodyStart(*this, S, Loc, "co_yield")) {
     CorrectDelayedTyposInExpr(E);
ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
 
   // Build the await_ready, await_suspend, await_resume calls.
   ReadySuspendResumeResult RSS =
       buildCoawaitCalls(*this, Coroutine->CoroutinePromise, Loc, E);
   if (RSS.IsInvalid)
     return ExprError();
 
   Expr *Res = new (Context) CoyieldExpr(Loc, E, RSS.Results[0], RSS.Results[1],
-                                        RSS.Results[2]);
+                                        RSS.Results[2], RSS.OpaqueValue);
   Coroutine->CoroutineStmts.push_back(Res);
   return Res;
 }
 
 StmtResult Sema::ActOnCoreturnStmt(Scope *S, SourceLocation Loc, Expr *E) {
   if (!actOnCoroutineBodyStart(*this, S, Loc, "co_return")) {
     CorrectDelayedTyposInExpr(E);
     return StmtError();