[OpenACC] Sema changes for +*&|^ reduction combiner recipes (#162740)

As a followup to the previous AST changes, the next step is to generate
the proper expressions in Sema. This patch does so for +,*,&,|,^ by
modeling them as compound operators.

This also causes the legality of some expressions to change, as these
have to be legal operations, but were previously unchecked, so there are
some test changes.

This does not yet generate any CIR, that will happen in the next patch.

Author: erichkeane

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13665,6 +13665,11 @@ def warn_acc_var_referenced_lacks_op
               "reference has no effect">,
       InGroup<DiagGroup<"openacc-var-lacks-operation">>,
       DefaultError;
+def err_acc_reduction_recipe_no_op
+    : Error<"variable of type %0 referenced in OpenACC 'reduction' clause does "
+            "not have a valid operation available">;
+def note_acc_reduction_recipe_noop_field
+    : Note<"while forming combiner for compound type %0">;
 
 // AMDGCN builtins diagnostics
 def err_amdgcn_load_lds_size_invalid_value : Error<"invalid size value">;

clang/include/clang/Sema/SemaOpenACC.h

@@ -228,6 +228,11 @@ class SemaOpenACC : public SemaBase {
 
   bool DiagnoseAllowedClauses(OpenACCDirectiveKind DK, OpenACCClauseKind CK,
                               SourceLocation ClauseLoc);
+  bool CreateReductionCombinerRecipe(
+      SourceLocation loc, OpenACCReductionOperator ReductionOperator,
+      QualType VarTy,
+      llvm::SmallVectorImpl<OpenACCReductionRecipe::CombinerRecipe>
+          &CombinerRecipes);
 
 public:
   // Needed from the visitor, so should be public.

clang/lib/Sema/SemaOpenACC.cpp

@@ -2898,6 +2898,15 @@ OpenACCReductionRecipe SemaOpenACC::CreateReductionInitRecipe(
           dyn_cast<ArraySectionExpr>(VarExpr->IgnoreParenImpCasts()))
     VarTy = ASE->getElementType();
 
+  llvm::SmallVector<OpenACCReductionRecipe::CombinerRecipe, 1> CombinerRecipes;
+
+  // We use the 'set-ness' of the alloca-decl to determine whether the combiner
+  // is 'set' or not, so we can skip any attempts at it if we're going to fail
+  // at any of the combiners.
+  if (CreateReductionCombinerRecipe(VarExpr->getBeginLoc(), ReductionOperator,
+                                    VarTy, CombinerRecipes))
+    return OpenACCReductionRecipe::Empty();
+
   VarDecl *AllocaDecl = CreateAllocaDecl(
       getASTContext(), SemaRef.getCurContext(), VarExpr->getBeginLoc(),
       &getASTContext().Idents.get("openacc.reduction.init"), VarTy);
@@ -2946,5 +2955,163 @@ OpenACCReductionRecipe SemaOpenACC::CreateReductionInitRecipe(
     AllocaDecl->setInit(Init.get());
     AllocaDecl->setInitStyle(VarDecl::CallInit);
   }
-  return OpenACCReductionRecipe(AllocaDecl, {});
+
+  return OpenACCReductionRecipe(AllocaDecl, CombinerRecipes);
+}
+
+bool SemaOpenACC::CreateReductionCombinerRecipe(
+    SourceLocation Loc, OpenACCReductionOperator ReductionOperator,
+    QualType VarTy,
+    llvm::SmallVectorImpl<OpenACCReductionRecipe::CombinerRecipe>
+        &CombinerRecipes) {
+  // Now we can try to generate the 'combiner' recipe. This is a little
+  // complicated in that if the 'VarTy' is an array type, we want to take its
+  // element type so we can generate that.  Additionally, if this is a struct,
+  // we have two options: If there is overloaded operators, we want to take
+  // THOSE, else we want to do the individual elements.
+
+  BinaryOperatorKind BinOp;
+  switch (ReductionOperator) {
+  case OpenACCReductionOperator::Invalid:
+    // This can only happen when there is an error, and since these inits
+    // are used for code generation, we can just ignore/not bother doing any
+    // initialization here.
+    CombinerRecipes.push_back({nullptr, nullptr, nullptr});
+    return false;
+  case OpenACCReductionOperator::Addition:
+    BinOp = BinaryOperatorKind::BO_AddAssign;
+    break;
+  case OpenACCReductionOperator::Multiplication:
+    BinOp = BinaryOperatorKind::BO_MulAssign;
+    break;
+  case OpenACCReductionOperator::BitwiseAnd:
+    BinOp = BinaryOperatorKind::BO_AndAssign;
+    break;
+  case OpenACCReductionOperator::BitwiseOr:
+    BinOp = BinaryOperatorKind::BO_OrAssign;
+    break;
+  case OpenACCReductionOperator::BitwiseXOr:
+    BinOp = BinaryOperatorKind::BO_XorAssign;
+    break;
+
+  case OpenACCReductionOperator::Max:
+  case OpenACCReductionOperator::Min:
+  case OpenACCReductionOperator::And:
+  case OpenACCReductionOperator::Or:
+    // We just want a 'NYI' error in the backend, so leave an empty combiner
+    // recipe, and claim success.
+    CombinerRecipes.push_back({nullptr, nullptr, nullptr});
+    return false;
+  }
+
+  // If VarTy is an array type, at the top level only, we want to do our
+  // compares/decomp/etc at the element level.
+  if (auto *AT = getASTContext().getAsArrayType(VarTy))
+    VarTy = AT->getElementType();
+
+  assert(!VarTy->isArrayType() && "Only 1 level of array allowed");
+
+  auto tryCombiner = [&, this](DeclRefExpr *LHSDRE, DeclRefExpr *RHSDRE,
+                               bool IncludeTrap) {
+    // TODO: OpenACC: we have to figure out based on the bin-op how to do the
+    // ones that we can't just use compound operators for.  So &&, ||, max, and
+    // min aren't really clear what we could do here.
+    if (IncludeTrap) {
+      // Trap all of the errors here, we'll emit our own at the end.
+      Sema::TentativeAnalysisScope Trap{SemaRef};
+
+      return SemaRef.BuildBinOp(SemaRef.getCurScope(), Loc, BinOp, LHSDRE,
+                                RHSDRE,
+                                /*ForFoldExpr=*/false);
+    } else {
+      return SemaRef.BuildBinOp(SemaRef.getCurScope(), Loc, BinOp, LHSDRE,
+                                RHSDRE,
+                                /*ForFoldExpr=*/false);
+    }
+  };
+
+  struct CombinerAttemptTy {
+    VarDecl *LHS;
+    DeclRefExpr *LHSDRE;
+    VarDecl *RHS;
+    DeclRefExpr *RHSDRE;
+    Expr *Op;
+  };
+
+  auto formCombiner = [&, this](QualType Ty) -> CombinerAttemptTy {
+    VarDecl *LHSDecl = CreateAllocaDecl(
+        getASTContext(), SemaRef.getCurContext(), Loc,
+        &getASTContext().Idents.get("openacc.reduction.combiner.lhs"), Ty);
+    auto *LHSDRE = DeclRefExpr::Create(
+        getASTContext(), NestedNameSpecifierLoc{}, SourceLocation{}, LHSDecl,
+        /*ReferstoEnclosingVariableOrCapture=*/false,
+        DeclarationNameInfo{DeclarationName{LHSDecl->getDeclName()},
+                            LHSDecl->getBeginLoc()},
+        Ty, clang::VK_LValue, LHSDecl, nullptr, NOUR_None);
+    VarDecl *RHSDecl = CreateAllocaDecl(
+        getASTContext(), SemaRef.getCurContext(), Loc,
+        &getASTContext().Idents.get("openacc.reduction.combiner.lhs"), Ty);
+    auto *RHSDRE = DeclRefExpr::Create(
+        getASTContext(), NestedNameSpecifierLoc{}, SourceLocation{}, RHSDecl,
+        /*ReferstoEnclosingVariableOrCapture=*/false,
+        DeclarationNameInfo{DeclarationName{RHSDecl->getDeclName()},
+                            RHSDecl->getBeginLoc()},
+        Ty, clang::VK_LValue, RHSDecl, nullptr, NOUR_None);
+
+    ExprResult BinOpResult = tryCombiner(LHSDRE, RHSDRE, /*IncludeTrap=*/true);
+
+    return {LHSDecl, LHSDRE, RHSDecl, RHSDRE, BinOpResult.get()};
+  };
+
+  CombinerAttemptTy TopLevelCombinerInfo = formCombiner(VarTy);
+
+  if (TopLevelCombinerInfo.Op) {
+    if (!TopLevelCombinerInfo.Op->containsErrors() &&
+        TopLevelCombinerInfo.Op->isInstantiationDependent()) {
+      // If this is instantiation dependent, we're just going to 'give up' here
+      // and count on us to get it right during instantaition.
+      CombinerRecipes.push_back({nullptr, nullptr, nullptr});
+      return false;
+    } else if (!TopLevelCombinerInfo.Op->containsErrors()) {
+      // Else, we succeeded, we can just return this combiner.
+      CombinerRecipes.push_back({TopLevelCombinerInfo.LHS,
+                                 TopLevelCombinerInfo.RHS,
+                                 TopLevelCombinerInfo.Op});
+      return false;
+    }
+  }
+
+  // Since the 'root' level didn't fail, the only thing that could be successful
+  // is a struct that we decompose on its individual fields.
+
+  RecordDecl *RD = VarTy->getAsRecordDecl();
+  if (!RD) {
+    Diag(Loc, diag::err_acc_reduction_recipe_no_op) << VarTy;
+    tryCombiner(TopLevelCombinerInfo.LHSDRE, TopLevelCombinerInfo.RHSDRE,
+                /*IncludeTrap=*/false);
+    return true;
+  }
+
+  for (const FieldDecl *FD : RD->fields()) {
+    CombinerAttemptTy FieldCombinerInfo = formCombiner(FD->getType());
+
+    if (!FieldCombinerInfo.Op || FieldCombinerInfo.Op->containsErrors()) {
+      Diag(Loc, diag::err_acc_reduction_recipe_no_op) << FD->getType();
+      Diag(FD->getBeginLoc(), diag::note_acc_reduction_recipe_noop_field) << RD;
+      tryCombiner(FieldCombinerInfo.LHSDRE, FieldCombinerInfo.RHSDRE,
+                  /*IncludeTrap=*/false);
+      return true;
+    }
+
+    if (FieldCombinerInfo.Op->isInstantiationDependent()) {
+      // If this is instantiation dependent, we're just going to 'give up' here
+      // and count on us to get it right during instantaition.
+      CombinerRecipes.push_back({nullptr, nullptr, nullptr});
+    } else {
+      CombinerRecipes.push_back(
+          {FieldCombinerInfo.LHS, FieldCombinerInfo.RHS, FieldCombinerInfo.Op});
+    }
+  }
+
+  return false;
 }